Language：English   Publishing type：Part of collection (book)   Publisher：Springer Singapore  

DOI： 10.1007/978-981-16-5763-4_7

Authorship：Last author   Language：English   Publishing type：Research paper (scientific journal)   Publisher：Springer Singapore  

DOI： 10.1007/978-981-15-9893-7_35

Publishing type：Research paper (scientific journal)   Publisher：Inderscience Publishers (IEL)  

Publishing type：Research paper (scientific journal)   Publisher：Carl Hanser Verlag  

Authorship：Last author   Publishing type：Research paper (scientific journal)  

Language：Japanese   Publishing type：Research paper (scientific journal)   Publisher：The Japan Society of Mechanical Engineers  

DOI： 10.1299/jsmemecj.2020.j02121

Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：SPRINGER-VERLAG SINGAPORE PTE LTD  

From the viewpoint of weight reduction in transportation equipment such as automobiles, the use of light metals is being promoted. Magnesium alloy is the lightest in practical metals, but it has the property that its strength is low. For improvement of fatigue strength, surface modification treatment such as shot peening is generally applied. Since the magnesium alloy has high reactivity with oxygen and may ignite, surface treatment in a dry environment like shot peening is difficult. In this study, we focused on wet blasting process with low probability of ignition and examined the influence of it on fatigue strength. The fatigue strength of wet blasting AZ31 showed higher results than untreated material. As this factor, improvement of hardness near the surface and application of compressive residual stress are conceivable. Also, the particles used in the wet blasting process are smaller than the particles used in the general shot peening process. Therefore, the fact that the surface roughness did not change significantly was also considered to be one factor. From the above results, we clarified that the wet blasting treatment can safely improve the fatigue strength of the magnesium alloy.

DOI： 10.1007/978-981-15-0054-1_3

Authorship：Last author   Publishing type：Research paper (international conference proceedings)  

Authorship：Last author   Publishing type：Research paper (scientific journal)   Publisher：Springer  

Authorship：Last author   Publishing type：Research paper (scientific journal)   Publisher：Scientific.Net  

Publishing type：Research paper (international conference proceedings)  

Publishing type：Research paper (international conference proceedings)  

Authorship：Last author   Publishing type：Research paper (international conference proceedings)  

Authorship：Last author   Publishing type：Research paper (international conference proceedings)  

Authorship：Last author   Publishing type：Research paper (scientific journal)   Publisher：Springer  

Authorship：Lead author   Publishing type：Research paper (international conference proceedings)  

Authorship：Lead author   Publishing type：Research paper (international conference proceedings)  

Authorship：Lead author   Publishing type：Research paper (international conference proceedings)   Publisher：IFHTSE  

Authorship：Last author   Publishing type：Research paper (international conference proceedings)  

Publishing type：Research paper (international conference proceedings)  

Publishing type：Research paper (scientific journal)  

Publishing type：Research paper (scientific journal)  

Publishing type：Research paper (international conference proceedings)  

Publishing type：Research paper (scientific journal)   Publisher：Foundry Journal Agency  

Publishing type：Research paper (scientific journal)   Publisher：Trans Tech Publications  

Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：Arbeitsgemeineschaft Warmebehandlung u. Werkstofftechnik  

Vacuum carburizing has the advantage, which can reduce the exhaust gas, so use of it has increased. However vacuum carburizing furnace needs the vacuum pomp and this method is little bit difficult to control the carbon potential. Direct carburizing in atmospheric pressure also can reduce the source gas and energy in comparison with the gas carburizing using the endothermic gas generator. However, it has been only slightly used in the surface heat treatment because it has many problems, for example, the difficulty of atmosphere control and the prevention of soot generation. Soot is generated from hydrocarbon gases. If soot deposition is occurred on the sensor, which controls the carbon potential, the sensor can't work correctly. Thus, the prevention of soot generation is important. In this study, the endothermic gas was not used for carrier gas, the hydrocarbon gas and moisture nitrogen, which prevent the soot generation, were introduced directly in carburizing furnace, and the following results were obtained. Addition of water in atmosphere inhibits the deposition of soot. By controlling the amount of water added, it is possible to prevent the internal oxidation during carburization. Addition of water does not affect the amount of carbon infiltration and it affected by the concentration of hydrocarbon.

Publishing type：Research paper (international conference proceedings)  

Language：English   Publishing type：Research paper (scientific journal)   Publisher：ELSEVIER SCIENCE SA  

Recently, a new nitriding process was proposed to produce the aluminum nitride on an aluminum surface using a barrel. After barrel nitriding, AlN nitride layer is formed on the aluminum surface and the surface hardness can be improved remarkably. In this study, barrel nitriding was performed to investigate the interface between aluminum substrate, with SUS304 austenitic stainless steel used for a physical catalyst. The barrel nitriding was carried out at 893 K for 18 ks, 25.2 ks and 36 ks, respectively with aluminum and aluminum-magnesium alloy powder. After barrel nitriding, aluminum nitride layer and Fe-Al intermetallic compound layers were formed at the interface between pure aluminum and austenitic stainless steel at the same time. The thickness of the aluminum nitride layer and intermetallic layer was increased by increasing the treatment time. (C) 2013 Elsevier B.V. All rights reserved.

DOI： 10.1016/j.porgcoat.2013.05.026

Language：English   Publishing type：Research paper (scientific journal)   Publisher：ELSEVIER SCIENCE SA  

Recently, much research has been carried out regarding techniques to improve the properties of steel surfaces, such as via ion-nitriding and gas nitriding. However, this needs a high vacuum rate or very expensive equipment and a long treatment time. In this study, a nitriding process is proposed which has a much shorter treatment time with very simple equipment by using plasma electrolytic treatment. To produce the plasma in the electrolyte, a JIS-SCM420 specimen was used as the cathode and a rolled punched stainless steel plate (SUS304) was used as the anode. Voltage was applied between the electrodes using a pulsed DC power supply. The pulsed power supply was used to prevent the discharge from concentrating on only one point. Urea (H2N)2C=O, which was added into distilled water as an electrolyte, was used as the supply source of nitrogen or carbon. In addition, potassium hydroxide (KOH) was added for adjusting the electrical conductivity. The treatment voltage was 600V, and experiments were conducted by varying the conditions, such as the treatment time and the concentration of the electrolyte. After the plasma electrolytic treatment, many fine discharge pores could be seen on the treated steel surface. In addition, a modified layer which has 1.9-2.7μm deep was formed on the steel surface within 5min of the start of the plasma electrolytic treatment. From the results of the XRD analysis, iron nitrides and chromium iron carbides were detected with α-Fe peaks, and the hardness of the modified-layer was found to be about 800HV. © 2013.

DOI： 10.1016/j.surfcoat.2013.05.010

Language：Japanese   Publishing type：Research paper (scientific journal)  

Publishing type：Research paper (scientific journal)  

Publishing type：Research paper (scientific journal)  

Publishing type：Research paper (scientific journal)  

Authorship：Last author   Publishing type：Research paper (international conference proceedings)  

Language：Japanese   Publishing type：Research paper (scientific journal)   Publisher：公益社団法人 日本鋳造工学会  

DOI： 10.11279/jfeskouen.162_98

Language：Japanese   Publishing type：Research paper (scientific journal)   Publisher：公益社団法人 日本鋳造工学会  

DOI： 10.11279/jfeskouen.162_108

Authorship：Last author   Publishing type：Research paper (international conference proceedings)  

Authorship：Last author   Publishing type：Research paper (international conference proceedings)  

Publishing type：Research paper (international conference proceedings)  

Publishing type：Research paper (international conference proceedings)  

Publishing type：Research paper (international conference proceedings)   Publisher：Wiley  

Authorship：Lead author   Publishing type：Research paper (international conference proceedings)  

Publishing type：Research paper (scientific journal)   Publisher：WILEY-VCH Verlag GmbH & Co. KGaA  

Authorship：Lead author   Publishing type：Research paper (international conference proceedings)  

Language：Japanese   Publishing type：Research paper (scientific journal)  

Authorship：Lead author   Publishing type：Research paper (international conference proceedings)  

Publishing type：Research paper (international conference proceedings)  

Authorship：Lead author   Publishing type：Research paper (international conference proceedings)  

Authorship：Lead author   Publishing type：Research paper (scientific journal)   Publisher：熱処理技術協会  

Publishing type：Research paper (international conference proceedings)  

Publishing type：Research paper (international conference proceedings)  

Language：Chinese   Publishing type：Research paper (scientific journal)  

The demand for high performance cast aluminum alloy components is often disturbed by increasing impurity elements, such as iron accumulated from recycled scraps. It is strongly required that coarse plate-like iron compounds of β-Al 5FeSi turn into harmless from without the need for applying refining additives or expensive virgin ingots. The microstructural modification of Al-7mass%Si alloy billets with different iron contents was examined by applying ultrasonic vibration during the solidification. Ultrasonically melt-treated billets were thixocast right after induction heating up to the semisolid temperature of 583°C, the microstructure and tensile properties were evaluated in the thixocast components. Globular primary α-Al is required to fill up a thin cavity in thixocasting, so that the microstructural modification by ultrasonic melt-treatment was firstly confirmed in the billets. With ultrasonic melt-treatment in temperature range of 630°C to 605°C, the primary α-Al transforms itself from dendrite into fine globular in morphology. The coarse plate-like β-Al 5FeSi compound become markedly finer compared with those in non-treated billets. Semisolid soaking up to 583°C, does not appreciably affect in size of β-Al 5FeSi compounds
however, it affects the solid primary α-Al morphology to be more globular, which is convenient for thixocasting. After thixocasting with preheated billets, eutectic silicon plates are extremely refined due to the rapid solidification arising from low casting temperature. The tensile strength of thixocast samples with different iron contents does not change much even at 2mass% of iron, when thixocast with ultrasonically melt-treated billets. However, thixocast Al-7mass%Si-2mass%Fe alloy with non-treated billets exhibits an inferior strength of 80 MPa, compared with 180 MPa with ultrasonically melt-treated billets. The elongation is also improved by about a factor of two in thixocastings with ultrasonically melt-treated billets for all iron contents of Al-7mass%Si alloys, for example, the elongation of 11% in thixocast of Al-7mass%Si-0.5mass% Fe alloy with ultrasonically melt-treated billets, 5% in that with non-treated billets.

Language：Japanese   Publishing type：Research paper (scientific journal)   Publisher：Japan Foundry Engineering Society  

Hypereutectic Al-Si alloys are promising candidates of light-weight wear resistant materials due to the hard primary silicon particles embedded in the eutectic matrix. These alloys are therefore expected to be applied to tribological components such as automotive cylinder liners. However, they do not exhibit sufficient performance heavy-duty tribological parts because coarse primary silicon grains reflect poor ductility and machinability. Both refinement and increase in the amount of primary silicon grains are required in order to use them as tribological components widely. Sono-solidification, in which ultrasound is radiated into molten metal during the solidification, improves the morphology of coarse primary silicon, as well as crystallizes non-equilibrium α-Al grains in hypereutectic Al-Si alloys. With sono-solidified Al-Si alloy billets, centrifugal thixocasting was examined for the segregation of refined globular primary silicon at an inner surface. The present study clarifies that the sono-solidification increases the amount of primary silicon in Al-18%Si alloy by 2.5 times more compared with that of equilibrium condition along with both refinement of globular primary silicon and crystallization of non-equilibrium α-Al grains. When sono-solidification billets are heated up to the semi-solid temperature, the α-Al grains are ready to disappear, but the refined primary silicon grains remain without coarsening their sizes. Centrifugal thixocasting causes segregated refined primary silicon grains at the inner surface of cylindrical castings within a short solidification period.

DOI： 10.11279/jfes.84.137

Language：Japanese   Publishing type：Research paper (scientific journal)   Publisher：Japan Foundry Engineering Society  

Recycling of aluminum alloy components plays a significant role in achieving sustainable society which requires superior performance of cast aluminum alloys containing high level of impurity elements such as iron. Since impurities of iron critically reduce both tensile strength and elongation of cast Al-Si alloys with iron content of over 1mass%, the morphological change in microstructure of Al-7mass%Si alloys with different iron contents was examined by applying ultrasonic vibration during the solidification, that is, the sono-solidification. The microstructure of conventionally solidified billets for thixocasting mainly composed of large plate-like β-Al₅FeSi compound and dendritic primary a-aluminum solid solution is eminently modified into a fine and globular shape through the sono-solidification. After induction heating of the billet up to the semi-solid temperature of 583℃, it was immediately thixocast to observe their microstructure and mechanical properties. In addition to the refinement of β-Al₅FeSi compound and primary α-aluminum in Al-Si-Fe alloy billets through the sono-solidification, eutectic silicon needles also become finer by thixocating, because of release of less latent heat compared with conventional castings solidified from their liquid state. This kind of characteristic microstructure generated by thixocasting with sono-solidified billets, exhibits not only high tensile strength, but also marked elongation even at high level of impurity iron. An increase in elongation of thixocast hypoeutectic Al-Si alloys with sono-solidified billets reflects major usage of recycled aluminum alloy ingots instead of virgin ones for the production of highly insured cast aluminum alloy components.

DOI： 10.11279/jfes.84.75

Authorship：Last author   Publishing type：Research paper (scientific journal)   Publisher：公益社団法人日本鋳造工学会  

Language：English   Publishing type：Research paper (scientific journal)   Publisher：SPRINGER SINGAPORE PTE LTD  

The demand for high performance cast aluminum alloy components is often disturbed by increasing impurity elements, such as iron accumulated from recycled scraps. It is strongly required that coarse plate-like iron compound of beta-Al5FeSi turns into harmless form without the need for applying refining additives or expensive virgin ingots. The microstructural modification of Al-7mass%Si alloy billets with different iron contents was examined by applying ultrasonic vibration during the solidification. Ultrasonically melt-treated billets were thixocast right after induction heating up to the semisolid temperature of 583 degrees C, the microstructure and tensile properties were evaluated in the thixocast components.Globular primary alpha-Al is required to fill up a thin cavity in thixocasting, so that the microstructural modification by ultrasonic melt-treatment was firstly confirmed in the billets. With ultrasonic melt-treatment in the temperature range of 630 degrees C to 605 degrees C, the primary alpha-Al transforms itself from dendrite into fine globular in morphology. The coarse plate-like beta-Al5FeSi compound becomes markedly finer compared with those in non-treated billets. Semisolid soaking up to 583 degrees C, does not appreciably affect the size of beta-Al5FeSi compounds; however, it affects the solid primary alpha-Al morphology to be more globular, which is convenient for thixocasting. After thixocasting with preheated billets, eutectic silicon plates are extremely refined due to the rapid solidification arising from low casting temperature. The tensile strength of thixocast samples with different iron contents does not change much even at 2mass% of iron, when thixocast with ultrasonically melt-treated billets. However, thixocast Al-7mass%Si-2mass%Fe alloy with non-treated billets exhibits an inferior strength of 80 MPa, compared with 180 MPa with ultrasonically melt-treated billets. The elongation is also improved by about a factor of two in thixocastings with ultrasonically melt-treated billets for all iron contents of Al-7mass%Si alloys, for example, the elongation of 11% in thixocast of Al-7mass%Si-0.5mass%Fe alloy with ultrasonically melt-treated billets, 5% in that with non-treated billets.

Publishing type：Research paper (scientific journal)   Publisher：公益社団法人日本鋳造工学会  

Publishing type：Research paper (international conference proceedings)  

Publishing type：Research paper (scientific journal)   Publisher：Foundry Institution of China Mechanical Engineering Society  

Publishing type：Research paper (scientific journal)  

Publishing type：Research paper (international conference proceedings)   Publisher：Foundry Institution of Chinese Mechanical Engineering Society  

Authorship：Last author   Publishing type：Research paper (international conference proceedings)  

Language：Japanese   Publishing type：Research paper (scientific journal)   Publisher：Japan Thermal Spray Society  

In suspension spraying, the vaporization of ethanol solvent causes the agglomeration of fine particles, which leads to form molten alloy droplets composed of hundreds of fine mixed particles during the flight. Intermetallic compound of NiAl was coated by reactive suspension plasma spraying with fine nickel and aluminum mixed powder. Highly concentrated suspension of ethanol solvent is preferred to form NiAl coatings without retained elemental powders, however, the coatings contain appreciable amount of Al₂O₃ due to engulfed air into the plume. The shroud was installed at the gun tip to prevent the oxidation, so that the coatings are composed of mainly NiAl with carbide. The carbide is formed based on the sooting reaction of ethanol pyrolysis, instead of its burning. Mixed solvent of ethanol and water was supplied to control the carbide formation, since the decrease in carbide is expected through the water-gas reaction. The soot formation is suppressed by ethanol and water mixed solvent, so nearly pure NiAl coatings are formed without containing residual nickel and aluminum, as well as oxides and carbides.

DOI： 10.11330/jtss.48.168

Authorship：Lead author   Publishing type：Research paper (international conference proceedings)  

Authorship：Last author   Publishing type：Research paper (scientific journal)   Publisher：日本溶射学会  

Authorship：Lead author   Publishing type：Research paper (international conference proceedings)  

Language：Japanese   Publishing type：Research paper (scientific journal)   Publisher：Japan Foundry Engineering Society  

Grain refinement of magnesium alloys is required for improving mechanical properties to expand their application fields. Ultrasonic vibration has been applied to a variety of liquid phase processes such as grain refinement and degassing in aluminum alloys. In the present study, ultrasonic radiation was applied to the continuous casting of magnesium alloy to refine its grain size. The microstructures of continuously cast billets was observed as a function of immersing depth of an ultrasonic horn into molten magnesium alloy, which is the distance between the solidification front and ultrasonic horn tip. Microstructures with grain size of 22μm were attained in the area with a small distance between the solidification front and horn tip. However, well refined regions were limited to the central area in the horizontal cross-section of the billets. In order to obtain refined grains over the whole billet, it was proposed that the ultrasonic horn be rotated around the center line to expand the area with a small distance between the solidification front and horn tip over the whole cross-section of the billet. By providing additional rotating motion to the ultrasonic horn, average grain size of 50μm was achieved in sono-solidified continuously cast billets. Furthermore, the effects of immersing depth of the ultrasonic horn on the microstructure were also examined from the viewpoint of acoustic cavitation by using luminol solution. The luminescent area was found to become much wider due to acoustic cavitation in continuous casting with a rotating ultrasonic horn compared to that with a fixed horn. Pressure measurements below the ultrasonic horn showed that the peak to peak pressure amplitude is strongly attenuated at one tenth of wave length, thereby limiting the generation of acoustic cavitation to the area with a short distance between the solidification front and horn tip.

DOI： 10.11279/jfes.83.93

Publishing type：Research paper (scientific journal)  

Language：Japanese   Publishing type：Research paper (scientific journal)  

Language：Japanese   Publishing type：Research paper (scientific journal)   Publisher：Japan Foundry Engineering Society  

Ultrasonic radiation during solidification is known to be an effective tool for achieving grain refinement in various kinds of alloys. Since the mechanism of grain refinement by ultrasonic vibration is not fully understood yet, it is not widely applied to practical casting processes. Through the observation of non-equilibrium α-Al grains appearing in sono-solidified hypereutectic Al-Si alloys, the authors have proposed the crystallizing mechanism of α-Al grains, in which the nucleation of α-Al grains arises from extremely high pressure generated by the collapse of acoustic cavitation in molten Al-Si alloys. However, the mechanism cannot explain the refinement of primary silicon in hypereutectic Al-Si alloys, because the liquidus temperature of primary silicon becomes lower with increasing pressure. In the present study, the refining mechanism of primary silicon was examined through their morphology observations after applying ultrasonic radiation to molten Al-Si alloy, during solidification and at constant temperatures. Fine primary silicon was recognized in Al-18mass%Si alloys quenched from above the liquidus temperature after ultrasonic radiation. It was also found that acoustic cavitation during the sono-solidification leads to the generation of inhomogeneous nuclei, that is, cavitation bubbles, so that a large number of inhomogeneous nuclei of cavitation bubbles causes the grain refinement of primary silicon even above the liquidus temperature.

DOI： 10.11279/jfes.82.618

Authorship：Last author   Publishing type：Research paper (scientific journal)  

Authorship：Last author   Language：English   Publishing type：Research paper (scientific journal)   Publisher：TRANS TECH PUBLICATIONS LTD  

Ultrasonic irradiation during the solidification of molten metals has an effect on grain refinement. However, the mechanism of grain refinement by ultrasonic vibration has not been fully understood yet, so that there exist difficulties to apply the ultrasonic grain refinement to industrial casting processes. In the present study, we propose the mechanism of ultrasonic grain refinement: the nucleation is based on the extremely high pressure generated by the collapse of acoustic cavitation in molten Al-Si alloys. The effect of ultrasonic irradiation into molten Al-Si alloy on the microstructure was firstly studied, that is, molten Al-12.6wt%Si alloy was rapidly cooled down from just above the eutectic temperature after the ultrasonic irradiation. The detailed microstructure observation exhibits that ultrasonic irradiation above the eutectic temperature causes crystalline alpha-Al and silicon to nucleate. Through the measurement of silicon content in alpha-Al nodules solidified with ultrasonic irradiation, the silicon content is higher than that in non-irradiated alpha-Al nodules. It is known that the collapse of acoustic cavitation generates extremely high pressure. At the highly pressurized sites, the eutectic temperature rises and the crystallized alpha-Al nodules contain higher amount of silicon compared with those solidified at ambient pressure. According to the fact that the alpha-Al nodules crystallized above the eutectic temperature contain higher amount of silicon, the irradiated microstructure of alpha-Al nodules is developed at the highly pressurized sites, that is, the collapse of acoustic cavitation induces nucleation and causes grain refinement.

DOI： 10.4028/www.scientific.net/AMR.89-91.190

Authorship：Last author   Publishing type：Research paper (scientific journal)  

Authorship：Last author   Publishing type：Research paper (scientific journal)  

Authorship：Last author   Publishing type：Research paper (scientific journal)  

Authorship：Last author   Publishing type：Research paper (international conference proceedings)  

Authorship：Last author   Publishing type：Research paper (international conference proceedings)   Publisher：World Foundry Organization  

Authorship：Last author   Publishing type：Research paper (scientific journal)  

Authorship：Last author   Publishing type：Research paper (scientific journal)  

Authorship：Last author   Publishing type：Research paper (scientific journal)  

Language：English   Publishing type：Research paper (international conference proceedings)  

Aluminum nitriding is effective process for making hard and high thermal conductivity layer. However, in the conventional process, nitriding of aluminum is very difficult because of the thin aluminum oxide layer, which prevents the infiltration of nitrogen, exists on the surface. We proposed a novel nitriding process, which is named barrel nitriding using the aluminum alloy and alumina powders for activating aluminum surface. By using this method, an aluminum nitride layer with a few hundreds of micrometers thickness can be formed within a matter of hours and the surface hardness can be controlled. In this study, we examined the effects of the process parameters on surface roughness of aluminum nitride layer and formation of deposited layer. If the magnesium powder is used for activating powder, the formation of deposited layer is prevented. If the fine alumina is used, the surface roughness is decreased. And if the compound powder, which is combined with fine and coarse alumina powders, is used, the surface roughness is the lowest. © 2010, Advanced Engineering Solutions.

Language：Japanese   Publishing type：Research paper (scientific journal)   Publisher：公益社団法人 日本鋳造工学会  

DOI： 10.11279/jfeskouen.156_61

Language：Japanese   Publishing type：Research paper (scientific journal)   Publisher：Japan Foundry Engineering Society  

Ultrasonic vibration is applied to various molten metal processes for such purposes as (1) improving wettability, (2) promoting liquid adhesion at vibrating surface and (3) promoting sono-solidification like grain refinement. The present study is focused on sono-solidification with acoustic cavitation in hypereutectic Al-18mass%Si alloy. An equilibrium microstructure composed of primary silicon and coupled eutectic α-Al/Si phases is generally observed in Al-18mass%Si alloy. However, non-equilibrium α-Al solid solution grains develop along with equilibrium phases in the sono-solidification. That is, during the sono-solidification of Al-18mass%Si alloy, non-equilibrium α-Al grains crystallize near the ultrasonic radiator before reaching the eutectic temperature of 577℃, in addition to the refined primary silicon grains. Ultrasound in molten Al-Si alloys exhibits two outstanding behaviors of cavitation bubbling and acoustic streaming, which cause the crystallization of α-Al grains in hypereutectic Al-Si alloy. It is known that high pressures of over 1GPa generated by collapse of cavitation bubbles lead not only to increase in the eutectic temperature, but also higher silicon content at the eutectic point in Al-Si alloy. With chemical analyses of EPMA, non-equilibrium α-Al grains are characterized by higher silicon content compared with that of primary α-Al grains in hypoeutectic Al-7masst%Si alloy. Consequently, non-equilibrium α-Al nuclei are crystallized at collapsed cavitation bubble sites before reaching the eutectic temperature and they are dispersed throughout the billet due to acoustic streaming.

DOI： 10.11279/jfes.81.469

Language：English   Publishing type：Research paper (scientific journal)   Publisher：ELSEVIER SCIENCE SA  

In the present study, mechanically alloyed Al-12Si, B2O3 and TiO2 powder was deposited onto an aluminum substrate using atmospheric plasma spraying (APS). The effects of mechanical alloying (MA) time and plasma parameters (arc current and primary/secondary/carrier gas flow rate) on in-situ reaction intensity and in-flight particle characteristics (temperature and velocity) have been investigated. It has been observed that MA time has a remarkable effect on powder morphology and relative amount of in-situ formed TiB2 and gamma-Al2O3, Inflight particle diagnostic measurements demonstrate that among the plasma parameters arc current has the strongest effect on in-flight particle velocity and temperature. Also, results indicate that in-flight particle velocity is more dominant than temperature on the relative amount of in-situ formed phases. (C) 2008 Elsevier B.V. All rights reserved.

DOI： 10.1016/j.surfcoat.2008.12.016

Language：Japanese   Publishing type：Research paper (scientific journal)   Publisher：JAPAN INST METALS  

Yield load and hardness on nanoscale have been reported using nanoindentation. However, the effect of crystallographic planes on the yield load and the hardness is not well understood. In order to investigate the effect of the crystallographic planes on the yield load and the hardness of the metals in nearly perfect crystal, nanoindentation test is performed on (111), (110) and (100) planes of aluminum single crystal with 99.9999% ultra-high purity. The yield load at a loading stage is found to be closely related to the crystallographic plane. The yielding behavior is also observed at an unloading stage under some conditions. In the loading stage, two kinds of yield processes, minor and major burst, are observed on (100) plane. The critical shear stress is estimated from the yield load in the loading curve. The estimated stress shows close agreement with the ideal strength of aluminum. The relationship between the hardness and the crystallographic plane is investigated by means of nanoindentation and micro-indentation. The hardness is strongly affected by crystallographic planes on the nano-scale, and the result is discussed from a viewpoint of the appearance of the slip line and the pile up around the indent.

DOI： 10.2320/jinstmet.73.95

Publishing type：Research paper (scientific journal)  

Authorship：Lead author   Language：English   Publishing type：Research paper (scientific journal)   Publisher：WILEY-V C H VERLAG GMBH  

In this study, a new nitriding process is proposed to produce the aluminum nitride on the aluminum surface. A process of combined barrel and plasma nitriding techniques was used. By using the barrel nitriding process, an aluminum nitride layer with high thickness can be formed within a matter of hours, and the surface hardness can be improved by using the plasma nitriding. It is suggested that a combined technique of the barrel nitriding and the plasma nitriding is one of the most promising surface treatments for the aluminum.

DOI： 10.1002/ppap.200930705

Authorship：Lead author   Publishing type：Research paper (international conference proceedings)   Publisher：Advanced Engineering Solutions  

Authorship：Last author   Publishing type：Research paper (international conference proceedings)   Publisher：Xi'an Jiaotong University  

Authorship：Last author   Publishing type：Research paper (scientific journal)  

Authorship：Last author   Publishing type：Research paper (scientific journal)  

Authorship：Last author   Publishing type：Research paper (international conference proceedings)  

Authorship：Last author   Publishing type：Research paper (scientific journal)  

Authorship：Last author   Publishing type：Research paper (scientific journal)  

Authorship：Lead author   Publishing type：Research paper (international conference proceedings)  

Language：English   Publishing type：Research paper (scientific journal)   Publisher：WILEY-V C H VERLAG GMBH  

Oxidation behavior of in-flight particle in plasma spray process significantly affects the coating properties and performance. Therefore, understanding the relationship between in-flight particle characteristics and oxidation phenomena is essential to improve the coating properties. This paper presents the oxidation behavior of in-flight aluminum particles and its relationship between in-flight particle temperature and velocity. Aluminum powder was injected into the plasma flame at different spray conditions and collected at different stand-off distances by using a specially designed equipment. It has been observed that in-flight particle velocity is the main parameter that affects the oxidation of aluminum particles.

DOI： 10.1002/ppap.200930602

Language：English   Publishing type：Research paper (scientific journal)   Publisher：WILEY-V C H VERLAG GMBH  

Aluminum nitride layers on aluminum are formed by the barrel nitriding in nitrogen gas, and duplex coatings are performed with the plasma nitriding in nitrogen and argon gas after the barrel nitriding. Aluminum nitride films with high thickness, high surface hardness, and good adhesion can be obtained on aluminum surfaces by using the above process. Hardness and Young's modulus of the AlN formed by the barrel nitriding is estimated by means of the rules of mixture. The microstructure of the AlN is proved to be composed of Al and AlN. it is suggested that the AlN formed by the barrel nitriding can play a role as the adhesion improvement of the AlN formed by the plasma nitriding. Furthermore, a microindentation test, which can obtain indentation load-penetration displacement curves, is performed in order to investigate the film fracture of the AlN.

DOI： 10.1002/ppap.200930104

Language：Japanese   Publishing type：Research paper (scientific journal)   Publisher：公益社団法人 日本鋳造工学会  

DOI： 10.11279/jfeskouen.155_116

Language：Japanese   Publishing type：Research paper (scientific journal)   Publisher：公益社団法人 日本鋳造工学会  

DOI： 10.11279/jfeskouen.155_117

Language：English   Publishing type：Research paper (scientific journal)   Publisher：ELSEVIER SCIENCE SA  

In the present study, mechanically alloyed Al-12Si and SiO(2) powder was deposited onto an aluminum substrate by atmospheric plasma spraying (APS) to obtain a hypereutectic Al-Si based in-situ alumina formed composite coating. The effect of process parameters (arc current, spray distance, nozzle type, oxygen gas support and substrate cooling) on in-flight particle characteristics (temperature and velocity) and in-situ alumina formation were investigated. It has been observed that while arc current and nozzle inner-diameter strongly affects the in-flight particle characteristics and in-situ alumina formation, the effect of oxygen gas support is insignificant. Also, the results show that the substrate cooling considerably hinders alumina formation. (C) 2008 Elsevier B.V. All rights reserved.

DOI： 10.1016/j.surfcoat.2008.08.057

Language：English   Publishing type：Research paper (scientific journal)   Publisher：ELSEVIER SCIENCE SA  

The joining behavior of solder on a Zr-based bulk metallic glass (BMG) surface without a soldering flux was studied under controlled ultrasonic cavitation in molten Sn-Cu-Ni solder at 528 K (open to air). Characteristic physical phenomenon appeared at the solder wetting interface when cavitation bubbles collapsed on the surface of the BMG substrate; this forced the wetting of the BMG surface with solder. The collapsing of the cavitation bubbles on the BMG surface-induced severe erosion. This cavitation erosion is effective in the immediate removal of passive film from the BMG substrate surface. The sono-capillary effect that is also induced by the ultrasonic vibration enhanced the adhesion property of the solder. Based on these results, an ultrasonic soldering method is proposed and its joining process is also investigated in detail. (c) 2007 Elsevier B.V. All rights reserved.

DOI： 10.1016/j.jmatprotec.2007.12.032

Language：English   Publishing type：Research paper (scientific journal)   Publisher：ELSEVIER SCIENCE SA  

In-situ plasma Spraying (IPS) is a promising process to fabricate composite coatings with in-situ formed thermodynamically stable phases. In the present study, mechanically alloyed Al-12Si, B2O3 and TiO2 powder was deposited onto an aluminum substrate using atmospheric plasma spraying (APS). It has been observed that, during the coating process, TiB2 and Al2O3 are in-situ formed through the reaction between starting powders and finely dispersed in hypereutectic Al-Si matrix alloy. Also, obtained results demonstrate that in-situ reaction intensity strongly depends on spray conditions. (C) 2008 Elsevier B.V. All rights reserved.

DOI： 10.1016/j.surfcoat.2008.03.012

Language：English   Publishing type：Research paper (scientific journal)   Publisher：ELSEVIER SCIENCE SA  

In-situ plasma spraying (IPS) is a promising process to fabricate composite coatings with in-situ formed thermodynamically stable phases. In the present study, mechanically alloyed Al-12Si and SiO2 powder was deposited onto an aluminum substrate by atmospheric plasma spraying (APS) to obtain a composite coating consisting of in-situ formed alumina reinforced hypereutectic Al-18Si matrix alloy. The effects of spray parameters (arc current and spray distance) and in-flight particle characteristics (temperature and velocity) on in-situ reaction intensity (alumina and silicon) have been investigated. The results show that, in-situ alumina formation and silicon intensity strongly depend on in-flight particle characteristics, spray distance and substrate temperature. (C) 2008 Elsevier B.V. All rights reserved.

DOI： 10.1016/j.surfcoat.2008.03.013

Authorship：Last author   Publishing type：Research paper (international conference proceedings)   Publisher：Japan Foundry Engineering Society  

Authorship：Last author   Publishing type：Research paper (international conference proceedings)  

Authorship：Last author   Publishing type：Research paper (scientific journal)  

Publishing type：Research paper (scientific journal)  

Publishing type：Research paper (scientific journal)  

Publishing type：Research paper (international conference proceedings)  

Authorship：Lead author   Publishing type：Research paper (international conference proceedings)  

Authorship：Last author   Publishing type：Research paper (international conference proceedings)  

Authorship：Last author   Publishing type：Research paper (international conference proceedings)   Publisher：German Welding Society(DVS)  

Authorship：Last author   Publishing type：Research paper (international conference proceedings)  

Authorship：Last author   Publishing type：Research paper (scientific journal)  

Authorship：Last author   Publishing type：Research paper (scientific journal)  

Publishing type：Research paper (scientific journal)  

Authorship：Last author   Publishing type：Research paper (scientific journal)  

Authorship：Last author   Language：English   Publishing type：Research paper (scientific journal)  

DOI： 10.2493/jjspe.74.287

Authorship：Last author   Publishing type：Research paper (scientific journal)  

Language：Japanese   Publishing type：Research paper (scientific journal)   Publisher：公益社団法人 日本鋳造工学会  

DOI： 10.11279/jfeskouen.152_73

Language：Japanese   Publishing type：Research paper (scientific journal)   Publisher：公益社団法人 日本鋳造工学会  

DOI： 10.11279/jfeskouen.153_24

Language：Japanese   Publishing type：Research paper (scientific journal)   Publisher：公益社団法人 日本鋳造工学会  

DOI： 10.11279/jfeskouen.152_74

Language：Japanese   Publishing type：Research paper (scientific journal)   Publisher：Japan Foundry Engineering Society  

&nbsp;&nbsp;In order to simplify the manufacturing process of complex structured slide-bearings used at the large ends of connecting rods in automotive engines, direct coating of bearing material mainly by thermal spraying is being examined. Newly substituted lead-free metals like aluminum-based alloys are appealing as slide-bearing material candidate. Hot-dip coatings practically employed in the manufacturing of zinc alloy coated steel sheets. However, it is difficult to coat aluminum alloy on bulky steel substrates without sufficient preheating, because a rapidly solidified layer containing gas babbles is formed on a substrate surface. A variety of iron-aluminides are also formed at the interface of steel and aluminum hot-dip coatings, which is the main reason for the difficulty in joining steel with aluminum. <br>&nbsp;&nbsp;Ultrasonic vibration was applied to a steel substrate during the hot-dip coating of aluminum alloy to suppress the rapidly solidified layer and a brittle reaction layer. Hot dipping of columnar steel substrates into molten aluminum alloy (Al-2.7mass%Si-4.6mass%Sn) was carried out through the use of a Langevin oscillator with a resonant frequency of 19.5kHz. The application of ultrasonic vibration is quite effective for removing rapidly solidified layers and surface oxide layers from the substrate surface by sonocapillary effects based on the cavitation phenomenon, so that intimate contact is achieved at the beginning of hot-dip coating. When the hot-dipped substrate surface is heated higher than liquid temperature, a brittle intermetallic reaction layer of Fe₂Al₅ grows at the interface. However, the application of ultrasonic vibration to hot-dipping is effective for controlling reaction layers less than 5μm in thickness. Impact test showed good adhesive strength of hot-dipped aluminum coatings with a thin reaction layer of approximately 5μm.

DOI： 10.11279/jfes.79.529

Authorship：Last author   Publishing type：Research paper (scientific journal)  

Language：Japanese   Publishing type：Research paper (scientific journal)   Publisher：Japan Foundry Engineering Society  

&nbsp;&nbsp;Ultrasound has been successfully applied to the grain refinement of various cast metals through frequent nucleation, as well as degassing, and inclusion removal from molten metals. In the present study, in order to broaden applications of semi-solid castings, grain refinement and formation of granular primary solid solution were examined by applying ultrasonic radiation to a molten aluminum alloy (AC4CH) surface during the solidification period, instead of inserting the ultrasonic radiator into molten metal. The ultrasound was radiated from a vibrating end surface with a vibration amplitude of 60μm and resonant frequency of 20kHz. Prior to the solidifying experiments of molten aluminum alloy, a transparent substance of succinonitrile was visibly solidified with ultrasonic radiation. According to successive observations, solid crystals generated near the heaved liquid surface were found to settle at the bottom by the forced convection due to the ultrasonic radiation, which is known as acoustic streaming. Primary aluminum solid solution vigorously nucleated right next to the vibrating surface, so that granular primary crystals accumulated at the mold bottom, instead of forming a dendrite structure. The granularity of primary solid solution depends on the irradiation period of ultrasound, that is, slow solidification rate is desired in the solid/liquid coexisting temperature zone. In the compressive shaping of semi-solid slurry, the form ability improves with the degree of primary crystal granularity.

DOI： 10.11279/jfes.79.95

Publishing type：Research paper (international conference proceedings)  

Authorship：Last author   Publishing type：Research paper (scientific journal)  

Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：International Federation for Heat Treatment and Surface Engineering, IFHTSE  

In quench hardening, it is important to determine the boiling states (film, nuclear and convection), in order to control the cooling process. However, it is difficult to understanding the each stage of boiling because of it changes by time and differs at each part of the specimen. In this study, a new method has been developed to discriminate the boiling states. In order to stabilise boiling states, a high-frequency induction heating (HFIH) method was applied and sound of boiling was monitored with aqua microphone. The obtained results evaluated by using Fast Fourier Transform (FFT). The results obtained by HFIH and quenching methods evaluated the states of boiling discriminated by matching the sound frequency of the sample. Consequently, we made possible to discriminate the boiling states by using the frequency observed in nuclear boiling state which has remarkable frequency band and high intensity compared to film and convection states.

Language：Japanese   Publishing type：Research paper (scientific journal)  

Authorship：Lead author   Publishing type：Research paper (scientific journal)  

Language：English   Publishing type：Research paper (scientific journal)   Publisher：INST PURE APPLIED PHYSICS  

Attractive force or repulsive force acts on solid objects facing an ultrasonically vibrating horn in liquid. Severe cavitation damage is observed on the surface of an aluminum plate adhereing to an ultrasonically vibrating horn in water. To elucidate the mechanisms of the generation of force acting on a solid object in a near ultrasonic field in water, the behavior of cavitation bubbles on the surfaces of an ultrasonically vibrating horn and a solid object was investigated. From the results of in situ observation, it was clarified that the force acting oil a solid object is controlled by bubble generation and collapse.

DOI： 10.1143/JJAP.45.2842

Authorship：Last author   Publishing type：Research paper (international conference proceedings)  

Authorship：Last author   Publishing type：Research paper (international conference proceedings)  

Authorship：Last author   Publishing type：Research paper (scientific journal)  

Authorship：Last author   Publishing type：Research paper (scientific journal)  

Authorship：Last author   Publishing type：Research paper (scientific journal)  

Authorship：Lead author   Language：English   Publishing type：Research paper (scientific journal)   Publisher：TRANS TECH PUBLICATIONS LTD  

In a previous study, an aluminum nitride (AlN) layer was formed below the melting point of aluminum (Al) on the surface of an Al substrate (JIS-A1050) in a barrel with alumina/aluminum-magnesium alloy powder which activates the substrate in the nitrogen atmosphere. In this study, the mechanism of formation of AIN in the barrel was examined. AN formation requires an incubation period. During the incubation period, a white region on the surface is observed by the optical microscopy. The Electron Probe Micro Analyzer (EPMA) show that this region contains magnesium (Mg). It seems that Mg penetrates and diffuses from the filled Al-Mg powder in the barrel. After that, the nitride is partially generated at the surface of the Al substrate, and it grows with the substrate surface. The AlN layer thickness increases proportionally with the square root of time, and it has good adhesion.

DOI： 10.4028/www.scientific.net/SSP.118.137

Publishing type：Research paper (international conference proceedings)  

Authorship：Last author   Publishing type：Research paper (scientific journal)  

Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：TRANS TECH PUBLICATIONS LTD  

Acetylene and ethylene are frequently used in vacuum carburizing in Japan. In this study the natural gas which is available from the lifeline is applied to vacuum carburizing. The gas composition inside the furnace was analyzed by the gas chromatography in order to examine the carbon infiltration mechanism. Unsaturated hydrocarbon gases (such as acetylene and ethylene) are generated from the natural gas. The effect of acetylene concentration in the furnace on the carbon infiltration rate was investigated. The carbon amount which infiltrates into the steel increases, as acetylene concentration in furnace increases. It is possible that carbon concentration of specimen surface increases to the cementite precipitation concentration in the short term, when natural gas flow rate increases in the initial carburizing stage. After that, carbon concentration of specimen surface does not decrease, even if the natural gas flow decreases, because carbon atoms which are consumed for diffusion to inside are sufficiently supplied. By using this method, inhibition of soot generation, reduction of process gas and shortening of the carburizing period are possible. The carbon concentration profile of the vacuum carburized specimen was compared with the simulation.

DOI： 10.4028/www.scientific.net/SSP.118.97

Language：Japanese   Publishing type：Research paper (scientific journal)   Publisher：Japan Foundry Engineering Society  

&nbsp;&nbsp;An ultrasonically vibrating end surface can retain large amount of liquid, the phenomenon of which has been newly discovered by author's group. Amount of adhering liquid linearly increases with vibration amplitude unless the cavitation occurs. At the same amount of adhering liquid, the droplet appearance becomes flatter to the vibrating end surface with an increase in vibration amplitude. The mechanism which allows large amount of liquid adhesion is discussed by focusing on the distribution of radiation pressure in an adhering droplet. The radiation pressure in a droplet exponentially decreases with distance from the horn end surface. A dynamic balance model regarding an adhering droplet was constructed through taking into consideration of the balance of liquid weight. intrinsic surface tension and radiation pressure. The calculated droplet appearance based on the model is good agreement with the experimentally observed one. With dipping and raising-up of an ultrasonically vibrated horn end to molten magnesium alloy, the maximum adhesion attains at 873 K, at which adhering metal is a semi-solid state approved by temperature measurement. Ultrasonic casting of magnesium alloy, in which the adhering molten or semi-solid metal is compressed by the counter molds, was carried out using a high powered ultrasonic transducer for shaping a thin saucer. Cast products are successfully manufactured without appreciable defects, because long molten metal flow is not necessary in the novel casing process.

DOI： 10.11279/jfes.77.752

Authorship：Last author   Publishing type：Research paper (scientific journal)  

Language：English   Publishing type：Research paper (scientific journal)   Publisher：ELSEVIER SCIENCE BV  

To investigate the synergistic effects of heat load and hydrogen irradiation, cyclic heat load tests with a hydrogen beam and a comparable electron beam were performed for high purity CVD-tungsten coatings. Surface modification was examined as a function of the peak temperature by changing the heat flux. Scanning Electron Microscopy analysis showed that the surface damage caused by the hydrogen beam was more severe than that by the electron beam. In the hydrogen beam case, cracking at the surface occurred at all peak temperatures examined from 300 degrees C to 1600 degrees C. These results indicate that the injected hydrogen induces embrittlement for the CVD-tungsten coating. (c) 2004 Elsevier B.V. All rights reserved.

DOI： 10.1016/j.jnucmat.2004.10.103

Publishing type：Research paper (scientific journal)  

Authorship：Last author   Publishing type：Research paper (scientific journal)  

Authorship：Last author   Publishing type：Research paper (international conference proceedings)  

Authorship：Last author   Publishing type：Research paper (scientific journal)  

Authorship：Last author   Publishing type：Research paper (international conference proceedings)   Publisher：Vietnam Foundry and Metallurgy Sci. and Tech. Association  

Authorship：Lead author   Publishing type：Research paper (scientific journal)  

Authorship：Lead author   Publishing type：Research paper (scientific journal)  

Language：Japanese   Publishing type：Research paper (scientific journal)   Publisher：公益社団法人 日本鋳造工学会  

DOI： 10.11279/jfeskouen.146_31

Language：Japanese   Publishing type：Research paper (scientific journal)   Publisher：公益社団法人 日本鋳造工学会  

DOI： 10.11279/jfeskouen.147_23

Language：Japanese   Publishing type：Research paper (scientific journal)   Publisher：公益社団法人 日本鋳造工学会  

DOI： 10.11279/jfeskouen.146_32

Authorship：Last author   Publishing type：Research paper (scientific journal)  

Publishing type：Research paper (scientific journal)  

Authorship：Last author   Publishing type：Research paper (international conference proceedings)  

Authorship：Last author   Publishing type：Research paper (international conference proceedings)  

Authorship：Last author   Publishing type：Research paper (scientific journal)  

Language：Japanese   Publishing type：Research paper (scientific journal)   Publisher：公益社団法人 日本鋳造工学会  

DOI： 10.11279/jfeskouen.145_82

Language：Japanese   Publishing type：Research paper (scientific journal)   Publisher：公益社団法人 日本鋳造工学会  

DOI： 10.11279/jfeskouen.145_80

Language：Japanese   Publishing type：Research paper (scientific journal)   Publisher：公益社団法人 日本鋳造工学会  

DOI： 10.11279/jfeskouen.145_83

Language：Japanese   Publishing type：Research paper (scientific journal)   Publisher：公益社団法人 日本鋳造工学会  

DOI： 10.11279/jfeskouen.145_81

Language：Japanese   Publishing type：Research paper (scientific journal)   Publisher：The Surface Finishing Society of Japan  

The gas carburizing atmosphere for surface treatment of steel can be regulated using the carbon potential, which is obtained by measuring the dew point, oxygen concentration or carbon dioxide concentration. The carbon potential which is calculated with carbon dioxide concentration is consistent with the carbon content of carburized steel foil. However, since a zirconium oxide oxygen sensor is easier to handle and its response is better than others, it is generally used for controlling the carbon potential, Methane is the main component of natural gas and it is stable at high temperature, so that the majority of tends to remain in the furnace. Since the retained methane decomposes on the oxygen sensor tip, the oxygen concentration around it decreases. Therefore the measurement of carbon potential with an oxygen sensor has been considered to be difficult when natural gas is used as the enriched gas. In this study, the carbon potential is regulated by taking account of the difference of the carbon potentials which are calculated with carbon dioxide concentration and with oxygen concentration; therefore the carbon potential can be controlled by the oxygen sensor, using natural gas for enriched gas. Target surface hardness and effective case depth are obtained when gas carburizing is carried out using this method, In addition, when the carrier gas is generated with natural gas and air, the carbon oxide concentration is 20.5 volume%, and the hydrogen concentration is 39.0 volume%; therefore the carburizing speed is higher than that when the carrier gas is generated with propane or butane.

DOI： 10.4139/sfj.54.1043

Authorship：Last author   Publishing type：Research paper (international conference proceedings)   Publisher：ASM International  

Publishing type：Research paper (international conference proceedings)  

Publishing type：Research paper (scientific journal)  

Publishing type：Research paper (scientific journal)  

Publishing type：Research paper (scientific journal)  

Authorship：Last author   Publishing type：Research paper (scientific journal)  

Authorship：Lead author   Publishing type：Research paper (scientific journal)  

Authorship：Lead author   Publishing type：Research paper (scientific journal)  

Authorship：Lead author   Publishing type：Research paper (scientific journal)  

Authorship：Last author   Publishing type：Research paper (international conference proceedings)   Publisher：ASM International  

Language：English   Publishing type：Research paper (international conference proceedings)  

Acetylene and ethylene are generally used in vacuum carburizing in Japan today. Available directly from the pipeline, natural gas was applied to vacuum carburizing as the carburizing gas, to study the effects that changes in process parameters would have on carbon infiltration. A specimen (JIS-SCr420) was carburized at 1203 K, increasing the variable carburizing period to 3.6 ks. The carburizing gas was supplied pulse and continuous flows. In continuous flow, the furnace pressure during the process of carburizing was kept constant. The gas composition inside the furnace was analyzed by the gas chromatography in order to examine the extent of the carbon infiltration. The carbon concentration profile of the cross-sectional carburized layer was estimated by EPMA, and the amount of infiltrated carbon was calculated, in order to establish its relationship to gas composition.

Language：Japanese   Publishing type：Research paper (scientific journal)  

Authorship：Lead author   Publishing type：Research paper (scientific journal)  

Language：Japanese   Publishing type：Research paper (scientific journal)   Publisher：Japan Foundry Engineering Society  

&nbsp;&nbsp;Selective incorporation of reinforcing particles in a specific portion of composite components is strongly desired for the machining and recycling of these components, as well as for reducing reinforcement and processing costs, This paper presents a selective incorporation method of composite slurry through an electromagnetic process, especially effects of the slurry diameter, solidification rate and particle size on the particle segregation are discussed, The non-conductive oxide particles of MgAl₂O₁ are forced to segregate to the outer periphery by the application of electromagnetic buoyancy during solidification of the in situ composite slurry prepared from a SiO₂, Al-Mg system. The particle segregation is mainly governed by two factors : (a) the solidifying period of the slurry must be longer than the electromagnetic migration time of particles, (b) the ratio of composite slurry diameter (2&gamma;₀) to the electromagnetic skin depth (&delta;), that is, 2&gamma;₀/&delta; must be around 3, because the optimum upward recirculating flow is necessary for preventing the particles from sedimentation. Furthermore, the volume fraction in segregated zones becomes larger towards the outer periphery, and larger with composite slurry containing large particles.

DOI： 10.11279/jfes.74.170

Language：Japanese   Publishing type：Research paper (scientific journal)  

Publishing type：Research paper (scientific journal)  

Authorship：Lead author   Publishing type：Research paper (international conference proceedings)   Publisher：ASM International  

Publishing type：Research paper (scientific journal)  

Publishing type：Research paper (scientific journal)  

Publishing type：Research paper (international conference proceedings)   Publisher：ASM International  

Authorship：Lead author   Publishing type：Research paper (international conference proceedings)  

Authorship：Lead author   Publishing type：Research paper (scientific journal)  

Language：Japanese   Publishing type：Research paper (scientific journal)  

Publishing type：Research paper (scientific journal)  

Language：English   Publishing type：Research paper (scientific journal)   Publisher：The Japan Institute of Metals and Materials  

In order to improve surface hardness, surface modification of die casting aluminum alloys was carried out by applying a new method called Electrical Discharge Alloying with ultrasonic vibrations, in which a conventional electrical discharge machine can be used. The layer deposited on the substrate consists of TiC and Ti₂AlC formed by the reaction between titanium contained in the green compact electrode, the aluminum in the electrode and the substrate and also the carbon decomposed from a working fluid. When the ultrasonic vibration is applied to the substrate, especially at a frequency of 94.2&thinsp;kHz, the discharged craters are bigger than those obtained when alloying without ultrasonic vibration. Also, for single discharge, the amount of deposited Ti and C increases near the edge of the crater. When the ultrasonic vibration is applied to the electrode for single discharge, many convex-shaped craters are generated on the substrate. The cross-sectional hardness of the alloyed area increases with increase in the concentration of carbon and titanium. The secondary elaboration using the cast Ti&ndash;36&thinsp;mass%Al solid electrode is effective for the improvement of surface roughness of the modified layer. When the green compact electrode is used in the primary Electrical Discharge Alloying and the cast solid electrode is used in the secondary elaboration, surface roughness is not so different between the process with and that without ultrasonic vibration. However, the modified layer&rsquo;s thickness obtained with ultrasonic vibration is thicker than that without ultrasonic vibration.

DOI： 10.2320/matertrans.42.1717

Authorship：Lead author   Publishing type：Research paper (scientific journal)  

Publishing type：Research paper (international conference proceedings)   Publisher：ASM International  

Publishing type：Research paper (international conference proceedings)   Publisher：ASM International  

Language：Japanese   Publishing type：Research paper (scientific journal)  

Language：Japanese   Publishing type：Research paper (scientific journal)   Publisher：The Surface Finishing Society of Japan  

This paper presents a novel pretreatment method required for aluminum alloy substrates prior to electroplating. An electrolytic jet containing coarse lumpy SiC particles is ejected on the substrate with a jet velocity of 16.5m/s for 60s. Jet electroplating is performed using the same electrolyte immediately after the pretreatment without water rinsing. With the inclined jet to the substrate pretreated at different collision angles, an optimum angle of 45&deg; produces the highest level of adhesive strength for the deposition. The inclined jet pretreatment with a substrate rotation provides higher adhesive strength. However, it is difficult to explain the increase in adhesive strength through the surface area of the substrates as measured by the AFM. The amount of aluminum transferred to the deposits after the peeling test is found to increase linearly with an increase in the interfacial area between the deposits and the substrate derived from the two directional interfacial lengths that include hook-shaped segments. Hence, an increase in adhesive strength is primarily due to the increase in the real interfacial area with the formation of hook-shaped segments.

DOI： 10.4139/sfj.51.75

Authorship：Last author   Publishing type：Research paper (scientific journal)  

Publishing type：Research paper (scientific journal)  

Language：Japanese   Publishing type：Research paper (scientific journal)   Publisher：The Japan Society of Mechanical Engineers  

In this study, natural gas was used as raw material and enriched gas of carrier gas, and the development of the system which shortened the carburization time was examined. The mechanical property of the sample which is treated by using this method was evaluated. The control of carbon potential by the oxygen concentration is possible, if enriched gas flow rate in which soot does not arise is chosen, even if the natural gas is used for enriched gas. And, the responsibility is better than carbon potential control by the carbon dioxide concentration. Using the difference between carbon potential calculated from carbon dioxide concentration and and it calculated from oxygen concentration, the system which foresaw the soot generation was developed. By controlling the carbon potential using this system and oxygen sensor, the carburization time was shortened, and retained methane quantity and using enriched gas quantity are drastically decreased.

DOI： 10.1299/jsmemecjo.2000.3.0_47

Language：Japanese   Publishing type：Research paper (scientific journal)  

Language：Japanese   Publishing type：Research paper (scientific journal)   Publisher：Japan Foundry Engineering Society  

&nbsp;&nbsp;This paper presents a novel cast joining method of aluminum matrix composite (AMC) made by molten aluminum alloy to aim at manufacturing of partially reinforced components. Ultrasonic vibration was applied to resolve the main difficulties of the process such as an oxide film formed on the molten aluminum surface and pores appeared adjacent to the solidified interface, which prevent the joining pair from its soundness. In order to eliminate an oxide film and pores at the interface during the process, the application of ultrasonic vibration is required until the full remelting of the initially solidified aluminum alloy region due to the direct contact of the AMC. Ultrasonic vibration makes not only to accelerate the remelting, but also to disappear the thermal contact resistance between the joined portion. Resultantly, sound interface with high strength is achieved. The effects of the vibrational amplitude and cooling rate during the process on the soundness of cast joining are also discussed.

DOI： 10.11279/jfes.71.691

Authorship：Last author   Publishing type：Research paper (scientific journal)  

Authorship：Lead author   Publishing type：Research paper (scientific journal)  

Publishing type：Research paper (scientific journal)  

Language：Japanese   Publishing type：Research paper (scientific journal)   Publisher：The Japan Institute of Metals and Materials  

This study is aimed at examining the influence of ultrasonic vibration on the in-situ formation of stable oxides, Al₂O₃ and MgAl₂O₄, from SiO₂ particles added as an oxygen source in melt stirring. The preheated SiO₂ particles were added on a molten Al or Al-Mg alloy surface and stirred at 1073 K in an Ar atmosphere. The ultrasonic vibration was then transmitted to molten metal through a ceramic plate. The SiO₂ particles are not transferred into the molten Al by melt stirring without ultrasonic vibration. With ultrasonic vibration, the SiO₂ particles, which have been transferred into the molten Al due to the improved wettability, change to stable Al₂O₃. The transferred SiO₂ particles into the molten Al-Mg alloy change to MgAl₂O₄ and Al₂O₃. The application of ultrasonic vibration to melt stirring makes not only the wettability improve, but also the cracks in the particles grow, which arise from the volumetric shrinkage accompanied with the change from SiO₂ to MgAl₂O₄ and Al₂O₃. The stable oxides are rapidly formed due to the fast diffusion of Al and Mg through the cracks. The exothermic reactions of MgAl₂O₄ and Al₂O₃ formation lead to a temperature rise in the molten Al-Mg alloy, in which the temperature rise of 99 K is approved by applying the ultrasonic vibration. Consequently, the in-situ reactions are promoted further. Gas defects disappear in the solidified Al alloy containing the stable oxides stirred with ultrasonic vibration, in which the particle distribution is also improved.

DOI： 10.2320/jinstmet1952.62.6_570

Language：Japanese   Publishing type：Research paper (scientific journal)   Publisher：The Japan Institute of Metals and Materials  

This paper presents a novel selective electroplating method that utilizes an electrolyte jet, instead of insulation masking on a substrate. The deposits have a convex shaped cross-section in the jet electroplating, so that the electrolyte jet is appropriately applied to selective electroplating. Even without masking process, a definite boundary between plated and non-plated area needs to be achieved in selective electroplating. The flat electroplated area, in which the current density distribution is nearly uniform, is deposited by using the nozzle with a center bar. However, the boundary becomes indistinct with this nozzle. The current density distribution on a cathode surface can be simulated by applying a finite element method based on the Laplace equation in steady state. The calculations suggest that the flat deposit area with a definite boundary will be created, if the electrolyte jet is limited to strike only on the projected nozzle area of a substrate. A modified nozzle with high velocity air holes adjacent to an electrolyte jet is designed, which successfully creates the flat deposit similar to the simulated cross-section profile.

DOI： 10.2320/jinstmet1952.62.4_377

Authorship：Last author   Publishing type：Research paper (international conference proceedings)  

Publishing type：Research paper (scientific journal)  

Publishing type：Research paper (scientific journal)  

Authorship：Last author   Publishing type：Research paper (international conference proceedings)  

Language：Japanese   Publishing type：Research paper (scientific journal)   Publisher：The Japan Institute of Metals and Materials  

This paper presents a novel pretreating method for electroplating on aluminum alloy substrates, in which an electrolyte jet containing coarse and fine SiC particles is ejected to the substrate surface prior to jet electroplating. The electrolyte jet with high velocity roughens the substrate surface due to the collision of coarse particles. The pretreatment with an inclined electrolyte jet is more effective to create a hooked substrate surface which is expected to reveal an anchoring effect in adhesion. Jet electroplated Ni-P deposits with a compositional gradient of fine SiC particles on the substrate, which has been pretreated by the inclined jet, show superior adhesive strength comparing with those done by a conventional double zincate pretreating method. The surfaces of electrodeposited nickel are plastically deformed by vigorous particle collision during the jet electroplating, so that there exists a compressive residual stress which increases with jet velocity increased. The vigorous particle collision also gives rise to harder deposits due to work hardening.

DOI： 10.2320/jinstmet1952.61.7_595

Publishing type：Research paper (scientific journal)  

Publishing type：Research paper (scientific journal)  

Publishing type：Research paper (scientific journal)  

Language：Japanese   Publishing type：Research paper (scientific journal)   Publisher：Japan Foundry Engineering Society  

&nbsp;&nbsp;This study is aimed at examining the influence of ultrasound-assisted exothermic reaction and improved wettability on the incorporation of Al₂O₃ particles into molten aluminum alloy in melt stirring. The Al₂O₃ particles with premixed nickel powder were added to molten Al-5mass%Mg alloy and stirred at a rotation speed of 16.7rps at 1023K in a nitrogen atmosphere. The ultrasound was then transmitted to the molten aluminum alloy with a ceramic plate. The application of ultrasonic vibration to melt stirring not only improves the apparent wettability, but also helps to dissolve the nickel powder thoroughly into molten aluminum alloy. The exothermic reaction of the nickel aluminide formation is promoted by ultrasonic vibration applied. This exothermic reaction leads to a local temperature rise of the molten aluminum alloy, which also improves the wettability. The ultrasound-assisted exothermic reaction of the nickel aluminide formation contributes to an increase in the engulfed Al₂O₃ particles and also the preparation of pore-free composite slurry.

DOI： 10.11279/jfes.69.578

Language：Japanese   Publishing type：Research paper (scientific journal)   Publisher：The Japan Institute of Metals and Materials  

The electrolyte jet containing ceramic particles not only greatly accelerates the deposition rate of the Ni-P matrix but also allows the volume fraction of particles and the phosphorus content in the deposit to be controlled by changing the jet velocity. Because of the forced nickel ion supply by the electrolyte jet, the deposition rate of the matrix becomes faster as far as the rate determining process is mass transfer. The volume fraction of Al₂O₃ particles is higher than that of SiC particles in the deposit when the jet velocity is high. The reverse takes place when it is slow. More nickel ions are adsorbed on Al₂O₃ particles with a larger specific surface, so that it is hard for Al₂O₃ particles to agglomerate in the electrolyte as compared with SiC particles. The phosphorus content in the matrix increases with jet velocity. The crystalline grain of the matrix becomes finer due to the hindered crystal growth of nickel by adsorbed phosphorus atoms.

DOI： 10.2320/jinstmet1952.61.5_437

Authorship：Last author   Publishing type：Research paper (scientific journal)  

Language：Japanese   Publishing type：Research paper (scientific journal)   Publisher：The Japan Institute of Metals and Materials  

Surface modification was carried out on aluminum substrates using pulsed electrical discharges in an air or nitrogen atmosphere. With an aluminum electrode and alumina powder applied on the substrate, formation of aluminum-oxinitride occurs on the substrate surface. The synthesized aluminum-oxinitride is composed of aluminum supplied from the electrode and substrate, oxygen from the alumina powder and nitrogen from the atmosphere. The thickness of deposition layers increases as discharged current, pulsed width or duty factor which is the ratio of pulse width to a total pulse period increases. With an electrode of iron, titanium or nickel composite layers mainly consisting of aluminum-oxinitride and aluminide intermetallic compounds are formed. In addition to the above constituents, when the electrode is aluminum or titanium, the modified layers also contain each nitride.

DOI： 10.2320/jinstmet1952.61.2_153

Publishing type：Research paper (international conference proceedings)  

Authorship：Lead author   Publishing type：Research paper (scientific journal)  

Publishing type：Research paper (scientific journal)  

Authorship：Last author   Publishing type：Research paper (scientific journal)  

Publishing type：Research paper (international conference proceedings)  

Language：English   Publishing type：Research paper (scientific journal)   Publisher：Japan Foundry Engineering Society  

&nbsp;&nbsp;This study is aimed at examining the influence of ultrasonic vibration on the incorporation of Al₂O₃ particles into molten aluminum by melt stirring. The preheated particles were added to a molten aluminum surface at 1023K in a nitrogen atmosphere. The ultrasonic vibration was then transmitted to the molten aluminum stirred at 5rps through a coated stainless steel plate. Ultrasonic vibration causes the composite slurry to change its rheological property in melt stirring. that is, the torque decreases at slow stirring speed and small amounts of engulfed particles. By contrast, the torque increases at fast stirring speed and large amounts of engulfed particles. With the application of ultrasonic vibration to a melt stirring process, the Al₂O₃ particles incorporated into the molten aluminum rapidly increase due to the improved apparent wettability within a given stirring period. Ultrasonic vibration also inhibits the agglomerate particles with atmospheric nitrogen generated in conventional melt stirring.

DOI： 10.11279/jfes.68.969

Language：Japanese   Publishing type：Research paper (scientific journal)   Publisher：The Japan Institute of Metals and Materials  

In the plasma carburizing process, the influence of electron temperature and electron density measured by a langmuir probe on carbon content was studied on low carbon steel foils of 0.25 mm in thickness. The increases in plasma current and plasma voltage cause the decreases in electron temperature. The carbon content decreases curvilinearly as the electron temperature increases. Generally the carbon content approximately 0.8 mass% is targeted to obtain an effective mechanical property. But the decreasing rate of carbon content to electron temperature at around 0.8 mass%C is large, so a highly accurate control with electron temperature is difficult. The increase in plasma current and plasma voltage cause the increases in electron density. The carbon content increases linearly as electron density increases. Negative charges balance with positive charges in plasma, so the density of positively charged carbon ions increases as the electron density increases, hence the carbon content increases. Even if the electron temperature or electron density is constant, the carbon content increases as the premixed methane ratio increases. Because the increase in premixed methane ratio causes the increased retained methane ratio and the increased carbon potential. Even if the plasma current or plasma voltage changes in plasma carburizing, the carbon content can be predicted and controlled by the electron density.

DOI： 10.2320/jinstmet1952.60.2_225

Publishing type：Research paper (scientific journal)  

Authorship：Lead author   Publishing type：Research paper (scientific journal)  

Publishing type：Research paper (scientific journal)  

Publishing type：Research paper (scientific journal)  

Publishing type：Research paper (scientific journal)   Publisher：Trans Tech Pub.  

Language：Japanese   Publishing type：Research paper (scientific journal)  

Publishing type：Research paper (international conference proceedings)  

Publishing type：Research paper (scientific journal)   Publisher：The Japan Institute of Metals and Materials  

Low crabon steel (S15CK) specimens were oxy-nitrided in nitrogen-ammonia-carbon dioxide mixed gas atmosphere. The microstructures of oxy-nitrided surface layers were examined by optical microscope, X-ray microanalysis and X-ray diffraction. Corrosion-resistance and wear-resistance of oxy-nitrided layers were also studied. The gas composition greatly affects the microstructure of oxy-nitrided surface layers, which is classified into white layer, gray layer with white layer and gray layer. The white nitride layer is composed of an &epsilon; phase, Fe₃N and &gamma;&prime; phase. The main constituent of the white layer containing higher nitrogen is &epsilon;, and that with lower nitrogen is &gamma;&prime;. The main constituent of the gray layer is found to be Fe₃O₄. The thickness of oxide layer increases as the premixed ammonia ratio decreases or the premixed carbon dioxide ratio increases through activated oxidation. With less than 45 vol% ammonia ratio and high carbon dioxide atmosphere, the oxy-nitrided layer is composed of only Fe₃O₄. The white nitride layer, &epsilon;, Fe₃N and &gamma;&prime; shows good corrosion resistance. The thickness of nitrided layer decreases as the premixed carbon dioxide ratio increases and the thin gray Fe₃O₄ layer formed on the nitride layer. These layers show bad corrosion resistance. But the thick gray Fe₃O₄ layer shows good corrosion resistance. Wear-resistance of oxy-nitrided steels is improved about fourfold compared with untreated specimens. The nitride layer shows good wear resistance and it slightly decreases as the thin gray Fe₃O₄ layer formed on the nitride layer.

DOI： 10.2320/jinstmet1952.59.2_177

Authorship：Lead author   Publishing type：Research paper (scientific journal)  

Publishing type：Research paper (scientific journal)  

Authorship：Lead author   Publishing type：Research paper (scientific journal)  

Authorship：Lead author   Publishing type：Research paper (scientific journal)  

Publishing type：Research paper (international conference proceedings)  

Publishing type：Research paper (scientific journal)  

Authorship：Lead author   Language：English   Publishing type：Research paper (scientific journal)   Publisher：The Japan Institute of Metals  

This work was initiated to study the influences of treatment time, plasma current and plasma voltage on the carbon content of specimens in a plasma carburizing process with propane as a carburizing gas. Low carbon steel foil with a thickness of 0.25 mm was used. The number of carbon atoms dissociated from the premixed propane by heat and plasma energy is about 2.5 times higher than that dissociated from the premixed methane. Thus, for the same treatment time, the carbon content of a specimen when using propane is 2.6 times higher than that in methane. The carbon content increases with increasing plasma current, plasma voltage and treatment time. For a 1.9&sim;7.4 vol% premixed propane ratio, however, the carbon content is saturated with 1.75&sim;1.90 mass%. Also, the increasing rate of carbon content in propane is higher than that in methane. But the carbon content of saturation when using propane is the same as that in methane. The carbon content is obtained using an equation containing the treatment time variable, the average obtained plasma voltage, the standard voltage and the plasma current. Using this equation, the carbon content can be predicted by the treatment parameters prior to the actual plasma carburizing process.

DOI： 10.2320/matertrans1989.35.351

Publishing type：Research paper (scientific journal)  

Publishing type：Research paper (scientific journal)  

Publishing type：Research paper (scientific journal)  

Language：Japanese   Publishing type：Research paper (scientific journal)   Publisher：Japan Foundry Engineering Society  

&nbsp;&nbsp;Wax pattern, plaster mold casting process for making magnesium alloy base composites reinforced by age hardening stainless steel, 17-7 PH, short fibers was studied. Steps of making composites are, 1st. fibers fill up in a plaster mold put in double magnetic field of AC, DC solenoid coils, 2nd. the mold with fibrous preforms is preheated, then, infiltrated molten magnesium alloy in vacuum casting system. Molten magnesium reacts upon plaster mold material, particularly high temperature preheated mold with fibrous preform inside. Some times, the mold is broken down by this reaction. Boron, and fluorine compounds are good inhibitors for this reaction. Near net shape composites castings of mechanical test specimen have fiber volume fraction of 39.3 %, and fiber alignment of 8.33&deg; in axis. Tensile strength is 462.3 MPa, and fatigue strength is 140 MPa. Automotive engine connecting rod was casted in this system. Fibers aligned along curve of the shape of connecting rod.

DOI： 10.11279/imono.66.4_263

Publishing type：Research paper (scientific journal)   Publisher：The Japan Institute of Metals and Materials  

Unidirectional alignment and high volume of fibers efficiently increase the strength of fiber reinforced MMC. However, it is very difficult in an ordinary process to get a high orientation and volume of short fibers in MMC. This research was done to solve these problem of short fibers. The apparatus, which has superimposed magnetic fields generated by A. C. solenoid coil in the upper part, D. C. solenoid in the lower part and iron core in D. C. solenoid, makes the orientation of ferromagnetic short fibers in uniaxis. The fibrous preform made by this apparatus has less than 10 degrees of fiber orientation angle and 0.35 to 0.45 or higher of volume fraction of fibers. Inorganic fibers coated with ferromagnetic materials also could be aligned in uniaxis by the apparatus with a rather high magnetic flux density of D. C. solenoid. Fine crystallized &alpha; alumina fibers, 18 &mu;m in diameter and 2 mm in length, which were coated with ferromagnetic nickel by electroless plating, were aligned uniaxaly in a casting mold. The molten magnesium alloy was sucked up and infiltrated into the mold under a low pressure of the vacuum pump. The Ni-B electroless plating process is effective in preventing the reaction between the nickel layer of fibers and molten magnesium. The thickness of the nickel plated layer needs to be 1 or 0.5 &mu;m. With increasing thickness of the nickel layer, the nickel content in the magnesium matrix increases, and a larger volume of the brittle structure of Mg₂Ni is formed. This decreases the strength of these composites. As an example of the strength of these composites, 1 &mu;m nickel-coated alumina fiber reinforced magnesium alloy composites display a bending strength of 570 MPa in 0.4 volume fraction and 8 degree orientation angle. This is about twice the strength of the matrix.

DOI： 10.2320/jinstmet1952.58.6_675

Publishing type：Research paper (scientific journal)  

Language：Japanese   Publishing type：Research paper (scientific journal)   Publisher：The Japan Institute of Light Metals  

Ultrasonic vibration is expected to improve the apparent wettability between reinforcements and molten metals and to achieve full infiltration with an extremely low applied pressure in the liquid processing of metal matrix composites. Non-infiltrated defects at contact points of reinforcements are, then, inhibited. In this work, ultrasonic vibration (resonant frequency=20.5kHz) was applied to alumina particle/molten aluminum as a model composite system at 1023K. The threshold infiltration pressure of 19.5kPa drops to zero by applying ultrasonic vibration with the power of 500kW/m². Therefore, full infiltration is achieved even with no applied pressure. Non-infiltrated defects are not formed at contact points of the particles in the pressure-less ultrasonic infiltration, while they are formed in the pressure infiltration without ultrasonic vibration. The infiltrated region with a semi-sphere was observed in the ultrasonic infiltration using particle preforms fixed by alumina sol. Ultrasonic vibration yields an ultrasonic pressure distributed radially throughout molten aluminum ahead of an ultrasonic horn. The ultrasonic pressure plays a vital role in the pressure-less infiltration as well as the hysteresis effect of contact angles at the interface between particle and molten aluminum does due to melt vibration.

DOI： 10.2464/jilm.43.14

Publishing type：Research paper (scientific journal)  

Publishing type：Research paper (scientific journal)  

Publishing type：Research paper (scientific journal)  

Publishing type：Research paper (scientific journal)  

Authorship：Lead author   Publishing type：Research paper (scientific journal)   Publisher：The Japan Institute of Metals and Materials  

In conventional gascarbonitriding, voids appeared in a surface layer right after the nitrogen content reached about 0.4 mass%, and then the nitrogen content decreases rapidly. The authors have established the novel method named a retained ammonia rising method that gives higher nitrogen contents without void formation. The influence of retained ammonia rising rate in the new gascarbonitriding process on the void formation and nitrogen content was studied using pure iron and low carbon steel foil with a thickness of 0.25 mm. Wear-resistance and fatigue limits for bulk specimens that were treated by the retained ammonia rising method were studied using medium carbon steel.<BR>The critical nitrogen contents for void formation in pure iron [C_Np] and in low carbon steel [C_Nl] were described by the logarithm equations with the variable treating times [t], respectively.<BR>(This article is not displayable. Please see full text pdf.) <BR>The rising rate of retained ammonia for void formation [R] was also described by the exponential equations with the variable C_Np or C_Nl.<BR>(This article is not displayable. Please see full text pdf.) <BR>For example, at the treating time of 1.8 ks, by the ammonia rising method, the critical nitrogen content of pure iron foil for void formation was 0.78 mass%, that was about 1.5 times that in conventional gascarbonitriding. The critical nitrogen content of low carbon steel foil for void formation was 0.81 mass%, that was about three times that in conventional gascarbonitriding.<BR>The wear resistance of medium carbon steel treated by the ammonia rising methed was about twice that in conventional gascarbonitriding. This is due to the improvement in resistance to temper softening and also to the increase in surface hardness through martensite transformation of the retained austenite during the wear test.<BR>Fatigue limits of medium carbon steel treated by the ammonia rising method did not differ from those in conventional gascarbonitriding. The retained austenite which prevented cracks from initiation and propagation was transformed into martensite during the fatigue test.

DOI： 10.2320/jinstmet1952.57.4_449

Publishing type：Research paper (scientific journal)  

Publishing type：Research paper (scientific journal)  

Language：Japanese   Publishing type：Research paper (scientific journal)   Publisher：Japan Foundry Engineering Society  

&nbsp;&nbsp;To realize full infiltration of non-wetted composite systems with a low applied pressure, the Al₂O₃ particle (mean diameter : 302 &mu;m) /molten Al system was studied as a model composite. Pressure infiltration was performed using an Al₂O₃ particle preform premixed with Ti powder in the temperature range of 1023 &sim; 1143 K. The threshold infiltration pressure is lowered from 19.5 kPa to 10.8 kPa at 1023 K by the premixing of 5.3 mass % Ti powder to Al₂O₃ particles. The size of non-infiltrated defects appeared at a contact point of two particles also becomes smaller by the same procedure, especially they disappear in the composites infiltrated at 1143 K with an applied pressure of 25 kPa. The wettability of Al₂O₃/Al system is improved by premixed Ti powder, which arises from the mixed surface consisted of non-wetted Al₂O₃ and wetted Ti, and also the exotherm due to formation of intermetallic TiAl₃. Hence, reinforcements premixed with Ti powder can be utilized to achieve full infiltration with a low applied pressure in liquid processing of non-wetted composite systems.

DOI： 10.11279/imono.65.2_106

Language：Japanese   Publishing type：Research paper (scientific journal)   Publisher：Japan Foundry Engineering Society  

&nbsp;&nbsp;This paper presents a new method of surface modification to diecast aluminum alloy by electrical discharge alloying. The process proceeds to deposit and alloy with titanium powder in electrode and with carbon decomposed from hydrocarbon working fluid on aluminum alloy. Electrical discharge alloying with an electrode of Ti/36 mass % Al premixed green compact synthesizes an in situ composite layer consisted of TiC and TiAl on an ADC 12 surface, since the substances between the electrode and substrate are transferred to the substrate surface by means of the electrical discharge process. The method makes it possible not only to form in situ composite layers with an average thickness of 100 &mu;m, but also to vary the TiC volume ratio in the layer by the process parameters. The TiC morphology shows extremely fine dendric precipitates due to rapid solidification during the process. The volume ratio of TiC decreases with a distance from the surface, which means the modified layers are composed of gradient constituents. The hardness close to the modified surface can be selected any value of HV 400-1200 by controlling the TiC ratio through the process parameters, such as pulse width and working time.

DOI： 10.11279/imono.65.10_783

Publishing type：Research paper (international conference proceedings)  

Publishing type：Research paper (scientific journal)  

Publishing type：Research paper (scientific journal)  

Authorship：Lead author   Publishing type：Research paper (scientific journal)   Publisher：The Japan Institute of Metals and Materials  

Influences of treating time, plasma current and plasma voltage in plasma-carburizing process on carbon content was studied using low carbon steel foils with a thickness of 0.25 mm. The increase in plasma current, plasma voltage and treating time caused the increased carbon content in specimens. Therefore, the quantitative prediction of carbon content which was varied with the treating parameters was done as follows.<BR>The carbon content C(t) was obtained by a linear equation with the variable treating times (t) at a constant plasma current (I_P),<BR>(This article is not displayable. Please see full text pdf.) <BR>the slopes of lines increased proportionally to I_P. At the higher I_P, however, the increasing rate of C(t) decreased gradually as t increased, and the carbon content was saturated with about 1.9 mass% (t>5.4 ks, I_P : 0.04 A).<BR>The carbon content C(V) was obtained by a linear equation with the variable plasma voltages at the constant I_P and t,<BR>(This article is not displayable. Please see full text pdf.) <BR>where V was defined as the average voltage of those measured at every 600 seconds in discharging at the constant I_P.<BR>Consequently, the carbon content [C(V, t)] at a given V and t was calculated as follows,<BR>(This article is not displayable. Please see full text pdf.) <BR>where V_O was the standard plasma voltage defined as an average value of all V at each I_P. Using the equations of C(V, t), the carbon content could be predicted by the treating parameters in advance of the practical plasma-carburizing process.

DOI： 10.2320/jinstmet1952.56.4_446

Publishing type：Research paper (scientific journal)  

Language：Japanese   Publishing type：Research paper (scientific journal)   Publisher：The Japan Institute of Light Metals  

Wettability of ceramic reinforcements with molten metals plays a vital role in the quality of metal matrix composites (MMCs) fabricated through liquid processing: the poor wettability causes non-infiltrated defects to remain in pressure cast MMCs with a low applied pressure. Threshold pressure for infiltration is one of the promising methods to evaluate wettability, since the reinforcement itself in MMCs can be utilized in this method. The mica-ceramic particles which had been classified into three sizes (L, M, S) were supplied to measure the threshold pressure for molten aluminum infiltration. Pressure infiltrations to the particle preforms were performed at 998K in vacuum or air atmosphere. The threshold pressures for molten aluminum infiltration were found to be 80.9 (L), 77.8 (M) and 159kPa (S) in vacuum, and 96.9 (L), 96.1 (M) and 162kPa (S) in air atmosphere. The lower threshold pressures in vacuum can be ascribed to the better wettability. Non-infiltrated defects with a meniscus configuration were observed in the vicinity of a contact point of two particles. However, flat defects appeared between quasi-tangential planes in MMCs using L-size particle preforms, and aggregate defects were observed in S-size preforms. Modelling the defect with a meniscus configuration to estimate the defect size, the relation between the threshold pressure and the wettability can be derived from the work done by an applied pressure balancing the interfacial energy changes. The contact angle of mica-ceramics with molten aluminum in vacuum is calculated to be approximately 2.39rad which is obtained from the threshold pressure into the M-size particle preforms with less flat or aggregate defects. Hence, the relation between the threshold pressure and the contact angle depends on a configuration of non-infiltrated defects.

DOI： 10.2464/jilm.42.92

Language：Japanese   Publishing type：Research paper (scientific journal)   Publisher：The Japan Institute of Light Metals  

Although fiber arrangement in preforms does not affect the interfacial energies nor contact angle in a given composite system, it affects the threshold pressure of infiltration into fiber preforms remarkably. The processing parameters, such as pressurizing rate, pressure holding at the maximum applied pressure and molten metal temperature, affect the apparent wettability, consequently they also affect the threshold pressure. In this study, &delta;-alumina fiber/molten aluminum composite system was selected to in vestigate the influence of such processing parameters on the threshold pressure of infiltration. Pressurizing rate in infiltrations was changed from 0.20kPa/s to 16kPa/s, pressure holding at the maximum applied pressure for 300s was also performed. The pressurizing rate and pressure holding at the maximum applied pressure do not affect the threshold pressure into alumina fiber preforms with quasi-planar random arrangement. It is experimentally approved that the threshold pressure obtained by extrapolation of infiltration distance and applied pressure agrees with the one obtained by the pressure drop based on Blake-Kozeny's equation. The influence of molten aluminum temperature on the threshold pressure which was obtained by the pressure drop, was studied with the pressurizing rate of 2.4kPa/s. The threshold pressure decreases from 259kPa to 162kPa with molten aluminum temperature increased in the range of 943K and 1163K.

DOI： 10.2464/jilm.41.576

Authorship：Lead author   Publishing type：Research paper (scientific journal)   Publisher：The Japan Institute of Metals and Materials  

The influences of the specimen size, treating time and retained methane content in the plasma-carburizing process on the carbon content and microstructures of specimens were studied. Case hardening steel (S15CK) foils with 0.25 mm thickness and low carbon steel foils with 0.06 mm thickness were used as specimens. When plasma-voltage was held constant, the plasma-current increased proportionally to the specimen surface area. Therefore the current density and carbon content could be kept constant. The time to reach the maximum carbon content decreased as the retained methane content increased. With increasing time in plasma-carburizing, the carbon content decreased slightly and a ferrite layer was formed near the surface. These specimens had definite carbon contents respectively regardless of both retained methane and treating time. The definite carbon content in S15CK was 1.1 mass%, and that in low carbon steel was 0.7 mass%. Since the thickness of the ferrite layer was not practically affected by the specimen thickness, the carbon content became lower in low carbon steel than that in S15CK. The decarburized ferrite layer was only observed in the sooted specimens. The potential gradient in the surface layer increased with the soot deposited, and the electrons emitted from the specimens increased. Hence, decarburization would occur due to the discharging of carbon atoms in the surface layer.

DOI： 10.2320/jinstmet1952.55.12_1353

Publishing type：Research paper (scientific journal)  

Publishing type：Research paper (scientific journal)  

Authorship：Lead author   Publishing type：Research paper (scientific journal)   Publisher：The Japan Institute of Metals and Materials  

Low-alloy steel (SCr42O) bulk specimens were plasma-carburized in methane/hydrogen mixed gas. The carburizing gas near a specimen was collected by a sampling cylinder and a piston system, and the retained methane in carburizing gas was measured by gas chromatography. The influences of treating temperature, plasma energy and vacumm-pumping speed on the retained methane were studied.<BR>The decomposing speed of methane being quite slow, the partial pressure of methane was extremely higher than the equilibrium partial pressure in plasma-carburizing. Since the methane was decomposed by heating, the retained methane decreased as treating temperature increased. It also decreased by plasma energy. As the retentive time of the carburizing gas in the furnace decreased with increasing pumping speed, the retained methane increased.<BR>The influences of the retained methane, treating temperature, pressure, time and pumping speed on the surface carbon content of specimen were also studied. The surface carbon content of the specimen was determined by the retained methane in the temperature range of 1203 and 1373 K. It increased as the retained methane increased. Under the stable glow discharge, it increased as the chamber pressure, pumping speed and treating time increased.<BR>The number of carbon atoms which were permeated into the specimen would agree with that of the dissociated carbon from the methane by plasma energy.

DOI： 10.2320/jinstmet1952.55.9_981

Publishing type：Research paper (scientific journal)  

Publishing type：Research paper (scientific journal)  

Language：Japanese   Publishing type：Research paper (scientific journal)   Publisher：The Japan Institute of Light Metals  

It is true that wettability plays an important role in fabrication of metal matrix composites: it decides an applied pressure in molten metal infiltration into fiber preforms. Infiltration occurs when the work done by the applied pressure balances the interfacial energy change due to the replacement of the solid/vapor interface by the solid/liquid interface. It has been experimentally and theoretically approved that fiber arrangement greatly influences the threshold pressure of infiltration in the alumina fiber/molten aluminum system. The threshold pressure of the uni-directional fiber array preforms is experimentally determined to be 425kPa, which is a little less than that calculated theoretically because of slight disarray in the fiber alignment. By contrast the experimentally observed threshold pressure of the quasi-planar random array is 245kPa. If the whole fiber surface is wetted, the wettability, &gamma;_la cos&theta;, where &gamma;_la: the molten aluminum/atmosphere interfacial energy and &theta;: the contact angle, is calculated to be-0.592Pa&bull;m. The relation between the threshold pressure and wettability is derived for infiltration with non-infiltrated defects at the intersection of non-wetted two fibers. According to this relationship, the threshold pressure of alumina fiber/molten aluminum system with defects is smaller than that without defects, and it decreases with decrease in intersection angle of two fibers because of increasing defects.

DOI： 10.2464/jilm.41.325

Authorship：Lead author   Publishing type：Research paper (scientific journal)   Publisher：The Japan Institute of Metals and Materials  

Pure iron and low-carbon steel (S15CK) foils were used as a specimen. Carbon and nitrogen contents in the furnace atmosphere of gas-carbonitriding were controlled by the dew point and retained ammonia, and the influence of temperature on the critical carbon and nitrogen contents for the formation of specific microstructures was studied. The specific microstructures were determined to be void, cementite, and graphite. The effects of the carbon and nitrogen contents on the mechanism of formation of the specific microstructures were discussed. In both kinds of specimen, the critical nitrogen content for formation of voids decreased with the treating temperature, and time. The critical carbon content for the formation of cementite or graphite increased with the treating temperature, but it was constant regardless of the treating time. The critical carbon content for the formation of cementite was practically unaffected by the nitrogen content. Under the same treating conditions, the critical carbon for the formation of cementite or graphite in pure iron and S15CK was nearly equal to each other. The critical nitrogen for the formation of void in pure iron was always lower than that in S15CK, because there were nonmetallic inclusions in S15CK and the austenite grain size was finer. In both specimens, graphite was formed only in the case of carbonitriding in which the nitrogen content was over about 0.1 mass%. Cementite existed whenever graphite was formed, and graphite existed mainly in and near cementite but sometimes at a distance. It appeared that nitrogen added to steels would afford the situation for formation of graphite in the solid phase and assist graphite formation.

DOI： 10.2320/jinstmet1952.54.2_208

Publishing type：Research paper (scientific journal)  

Publishing type：Research paper (scientific journal)  

Publishing type：Research paper (scientific journal)  

Publishing type：Research paper (scientific journal)  

Publishing type：Research paper (scientific journal)  

Publishing type：Research paper (scientific journal)  

Publishing type：Research paper (scientific journal)  

Publishing type：Research paper (scientific journal)  

Publishing type：Research paper (scientific journal)  

Publishing type：Research paper (scientific journal)  

Authorship：Last author   Publishing type：Research paper (scientific journal)   Publisher：The Japan Institute of Metals and Materials  

A new gas carburizing process which is capable of easily determining a suitable parameter has been developed using an explicit finite-difference method and a direct-search method of optimization. In this process, a weighting factor was introduced into this process for optimizing the carbon profile and time. Increasing the weighting factor made the difference between the calculated and target carbon profiles smaller but the treating time longer. Calculated carbon profiles of SCr420 steel were compared with experimental results by a atmosphere-control system using a zirconia oxygen-sensor. Agreement between the calculated and measured profiles was very good.<BR>The dependence of the diffusion coefficient on carbon concentration in SCr420 steel is expressed experimentally as follows:<BR>(This article is not displayable. Please see full text pdf.) <BR>\oindentwhere C was the carbon concentration (mass%).<BR>The influence of the carburizing parameter on a variety of the initial conditions in the calculation process was also discussed in relation to the carbon profiles.

DOI： 10.2320/jinstmet1952.52.5_495

Publishing type：Research paper (scientific journal)  

Language：Japanese   Publishing type：Research paper (scientific journal)   Publisher：The Japan Institute of Light Metals  

Aluminum matrix composite preforms containing silicon carbide whisker (SiCw) were directly fabricated by use of wire and powder flame spray guns. In the case of the wire flame spraying method, SiCw were supplied into the spray flame by suction pressure from a modified air cap. The suction pressure depended on the opening angle of the air cap at the top of the gun. Although a larger opening angle generated higher suction pressure, an excessive opening angle caused a separation of the spray flame and hence a heterogeneous piling-up of SiCw in the preform. In contrast, the powder flame spraying did not have a high flame velocity so that the suction pressure was quite low compared to that of the wire flame spraying. Consequently the air jet containing SiCw was blown into the spray flame which consisted of molten aluminum droplets and hot flame gases. After hot forging of the perform to align SiCw two-dimensinally, SiCw/Al composites were tensile-tested. The strength has been found to be improved with increasing volume fraction of SiCw.

DOI： 10.2464/jilm.38.581

Authorship：Lead author   Publishing type：Research paper (scientific journal)  

Publishing type：Research paper (scientific journal)  

Language：Japanese   Publishing type：Research paper (scientific journal)   Publisher：The Japan Institute of Light Metals  

&delta;-Al₂O₃/Al composites were fabricated by high pressure infiltration and extruded at high temperatures. The plastic flow in extruded matrices is classified into two types, namely a laminar flow in the surface region and a turbulent flow in the core. The wider the laminar flow region, the better the fiber alignment obtained. The laminer flow region extends at lower V_f and lower extruding temperatures. Surface defects, fir-tree-type cracks, easily grow at high V_f. The &delta;-Al₂O₃/Al alloy has tensile strength twice as much as that the matrix alloy extruded in the same way.

DOI： 10.2464/jilm.37.285

Language：Japanese  

Language：Japanese  

Language：Japanese  

Language：Japanese   Publisher：The Japan Society of Mechanical Engineers  

Recently, weight reduction of vehicles has been advanced to improve the fuel efficiency. It is necessary to use not only steel but also various kinds of materials in order to reduce weight. Therefore, we need to apply methods to join different materials. So, we focused on spot welding, which is the most frequently used joining method in automobile production lines. Strength analysis of dissimilar spot welding using stainless steel and copper is conducted. We use SUS304 and C1100 as test pieces. After spot welding, we observe the cross section using an optical microscope and scanning electron microscope. Also, the temperature distribution of the cross section is calculated using finite element simulation software "ANSYS". In addition, a tensile shear test is also conducted. Heat is mainly generated not in the contact surface but in the steel. Also, as the current is increased, the heat generation increases too. As the base material softens by the heat, the deformation by electrode force also increases. Some parts of the contact surface are melted. In addition, atomic diffusion can be observed under all current. Moreover, the strength improves and stabilizes as the current is increased. The reason of heat concentration in the steel is large electrical resistance of the steel. Also, as temperature becomes higher, base materials are easy to deform because of characteristics of Young's modulus. Dissimilar spot welding of SUS304 and C1100 can be joined by melting, diffusion and deformation on the contact surface.

DOI： 10.1299/jsmemm.2019.os1407

Language：Japanese   Publisher：公益社団法人 精密工学会  

<p>アルミニウムの表面に複合皮膜を形成することで、硬度や放熱性などの機能性を向上させることができ、使用範囲は広がると考えられる。前報では回転バレル窒化法を用いて、粒子分散型皮膜をアルミニウム表面に形成するための方法として回転バレル窒化法を提案した。本方法では粉末粒径が皮膜の形成機構に大きく影響を及ぼすと考えられる。そこで本報告では、皮膜形成に及ぼす粉末粒径の影響について検討した。</p>

DOI： 10.11522/pscjspe.2018A.0_708

Language：Japanese  

Language：Japanese  

Language：Japanese  

Language：Japanese   Publisher：メカニカル・テック社  

Language：Japanese   Publisher：特殊鋼倶楽部  

Language：Japanese   Publisher：日本工業炉協会  

Language：Japanese   Publisher：メカニカル・テック社  

Language：Japanese  

Language：Japanese  

Authorship：Lead author   Publishing type：Article, review, commentary, editorial, etc. (other)   Publisher：日本熱処理技術協会  

Authorship：Lead author   Publishing type：Article, review, commentary, editorial, etc. (other)   Publisher：日本熱処理技術協会  

Language：Japanese  

Authorship：Lead author   Publishing type：Article, review, commentary, editorial, etc. (other)   Publisher：日本熱処理技術協会  

Language：Japanese  

Language：Japanese   Publisher：The Japan Society of Mechanical Engineers  

Language：Japanese  

Language：Japanese  

Publisher：The Japan Society for Precision Engineering  

Nano-scale mechanical properties, such as hardness, yield load and Young's modulus, are obtained from nanoindentation test. However, the results of the test are considerably affected by sample surface condition, nose configuration of tip, and so on. In this study, the oxide layer thickness of 99.99% and 99.9999% aluminums exposed in air is measured using an X-ray photoelectron spectroscopy (XPS), and nanoindentation test is performed on the aluminums with the oxide layer of several thicknesses. The oxide layer thickness increases with the period exposed in air, and the layer of low purity aluminum is thicker than that of high purity aluminum. In nanoindentation test, it is revealed that the yield load and hardness are considerably affected by the oxide layer on sample surface.

DOI： 10.11522/pscjspe.2008S.0.907.0

Language：Japanese   Publisher：特殊鋼倶楽部  

Language：Japanese   Publisher：日本工業炉協会  

Language：Japanese   Publisher：The Japan Society of Mechanical Engineers  

In this study the natural gas which is available from the lifeline is applied to vacuum carburizing. The gas composition inside the furnace was analyzed by the gas chromatography in order to examine the carbon infiltration mechanism. Unsaturated hydrocarbon gases are generated from the natural gas. The effect of acetylene concentration in the furnace on the carbon infiltration rate was investigated. The carbon amount which infiltrates into the steel increases, as acetylene concentration in furnace increases. The carbon concentration of specimen surface does not decrease, even if the natural gas flow decreases, because carbon atoms which are consumed for diffusion to inside are sufficiently supplied. By using this method, inhibition of soot generation, reduction of process gas and shortening of the carburizing period are possible. The carbon concentration profile of the vacuum carburized specimen was compared with the simulation.

Language：English  

Language：Japanese   Publisher：日本工業炉協会  

Language：English  

Language：Japanese  

Language：Japanese   Publisher：The Japan Society of Mechanical Engineers  

Language：Japanese  

Language：Japanese  

Language：Japanese  

Language：Japanese  

Language：Japanese  

Language：Japanese  

Language：Japanese  

Language：Japanese  

Language：Japanese  

Language：English  

Language：Japanese  

Language：English  

Language：English  

Language：Japanese  

Language：Japanese  

Language：Japanese  

Language：Japanese  

Language：Japanese  

Presentation type：Oral presentation (general)  

Presentation type：Oral presentation (general)  

Presentation type：Oral presentation (general)  

Presentation type：Oral presentation (general)  

Presentation type：Oral presentation (general)  

Presentation type：Oral presentation (general)  

Presentation type：Oral presentation (general)  

Presentation type：Oral presentation (general)  

Presentation type：Oral presentation (general)  

Presentation type：Oral presentation (general)  

Presentation type：Oral presentation (general)  

Presentation type：Oral presentation (general)  

Presentation type：Oral presentation (general)  

Presentation type：Oral presentation (invited, special)  

Presentation type：Oral presentation (general)  

Presentation type：Oral presentation (general)  

Presentation type：Oral presentation (general)  

Presentation type：Oral presentation (general)  

Presentation type：Oral presentation (general)  

Presentation type：Oral presentation (general)  

Presentation type：Oral presentation (general)  

Session 4: Heat, cryogenic and surface treatments

Presentation type：Oral presentation (general)  

Session 4: Heat, cryogenic and surface treatments

Presentation type：Oral presentation (general)  

Presentation type：Oral presentation (general)  

Presentation type：Oral presentation (invited, special)  

Presentation type：Oral presentation (invited, special)  

Presentation type：Oral presentation (invited, special)  

Presentation type：Oral presentation (invited, special)  

Presentation type：Oral presentation (general)  

Presentation type：Oral presentation (general)  

Presentation type：Oral presentation (invited, special)  

Presentation type：Oral presentation (general)  

Presentation type：Oral presentation (general)  

Presentation type：Oral presentation (general)  

Presentation type：Oral presentation (general)  

Presentation type：Oral presentation (general)  

Presentation type：Oral presentation (general)  

Presentation type：Oral presentation (general)  

Presentation type：Oral presentation (general)  

Presentation type：Oral presentation (general)  

Presentation type：Oral presentation (general)  

Presentation type：Oral presentation (general)  

Presentation type：Oral presentation (general)  

Presentation type：Oral presentation (invited, special)  

Presentation type：Oral presentation (general)  

天然ガスを用いた直接浸炭における煤の低減法について発表を行った．

Presentation type：Oral presentation (general)  

プラズマを用いた新しいN-クエンチ法の特性について発表を行った．

Presentation type：Oral presentation (general)  

Presentation type：Oral presentation (general)  

Presentation type：Oral presentation (general)  

単層砥石作製の新たなプロセスとして放電プラズマ焼結の利用を提案し、アルミニウム合金を台金とする単層メタルボンド砥石の作製について検討した。結合材を予め台金に固定させて放電プラズマ焼結を行うことで、単層の砥粒層をもつ砥石が作製可能となった。結合材にCu-Sn合金粉末のみを用いて作製した場合は、結合材に十分な密度が得られなかったが、結合材にCu-Sn/Al混合粉末を用い、さらにメカニカルアロイング粉末とすることで結合材の高密度化を実現した。

Presentation type：Oral presentation (general)  

メタノール中で高周波誘導加熱を行い、気化したメタノールおよびメタノールの熱分解により生じた一酸化炭素・水素により浸炭を行い,その後高周波誘導加熱を停止してアルコール中にて焼入れを行った際の処理温度,処理時間が炭素濃度プロファイル等に及ぼす影響を検討した．保持時間5分で表面の炭素濃度は1.4wt％となり、短時間でオーステナイト中の炭素固溶限に到達した。プロセスパラメータの管理によって、表面炭素濃度の制御を可能とした。

Presentation type：Oral presentation (general)  

真空炉ではなく水中でプラズマを発生させることで、短時間で鋼の表面を改質することを検討した。これにより、装置の小型化、および前処理にかかる時間の短縮化を目指す。試料にSCM420を用い、電解液には蒸留水に窒素の供給源として尿素、導電性の調整用に水酸化カリウムを加え，水中プラズマを発生させた．プロセスパラメータの最適化により、表面に炭素・窒素が拡散した層を形成することを可能とした。

Presentation type：Oral presentation (general)  

グリースに導電性を付与し、静電気の除去によりグリースの分解の抑制を試みた。添加剤として極圧性および高温安定性に優れた固体潤滑剤として知られる二硫化タングステンを用いることで、過酷な使用環境に耐えうる導電性グリースを開発し、その性能評価を行った。二硫化タングステンを添加すると厚いグリース膜を維持する効果がある。タングステンを添加したグリースにおいては、表面に絶縁膜が形成されていることを電位差測定より明らかにした。

Presentation type：Oral presentation (general)  

Presentation type：Oral presentation (general)  

Presentation type：Oral presentation (general)  

Presentation type：Oral presentation (general)  

Presentation type：Oral presentation (general)  

Presentation type：Oral presentation (invited, special)  

Presentation type：Oral presentation (general)  

Presentation type：Oral presentation (general)  

Presentation type：Oral presentation (general)  

Presentation type：Oral presentation (general)  

Presentation type：Oral presentation (general)  

Presentation type：Oral presentation (general)  

Presentation type：Oral presentation (invited, special)  

Presentation type：Oral presentation (invited, special)  

Presentation type：Oral presentation (general)  

Presentation type：Oral presentation (invited, special)  

Presentation type：Oral presentation (invited, special)  

Presentation type：Oral presentation (general)  

Presentation type：Oral presentation (general)  

Presentation type：Oral presentation (general)  

Presentation type：Oral presentation (general)  

Presentation type：Oral presentation (general)