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76 巻, 7 号
選択された号の論文の9件中1～9を表示しています
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山本 尚嗣, 廖 金孫, 中田 一博2012 年 76 巻 7 号 p. 415-421
発行日: 2012年
公開日: 2012/07/01
ジャーナル フリーFiber laser and MIG arc hybrid weldability of Ni alloys was evaluated by changing welding parameters, such as laser power, welding current and welding speed. For the Inconel 601, a sound weld without inside defects was obtained under the conditions of welding speed 2-3 m/min and laser power 6-10 kW. For the Hastelloy C-276, however, a sound weld without hot crack was not obtained. Hardness at the center region of weld metal was slightly higher than that of base metal for both the Inconel 601 and Hastelloy C-276. Transverse tensile strength of hybrid welded joints of Inconel 601 and Hastelloy C-276 was almost identical with that of their base metals.
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福岡 隆弘, 菊池 将一, 小茂鳥 潤, 深沢 剣吾, 三阪 佳孝, 川嵜 一博2012 年 76 巻 7 号 p. 422-428
発行日: 2012年
公開日: 2012/07/01
ジャーナル フリーIn this study, in order to increase surface hardness of S45C steel, hybrid surface modification treatment which is a combination of atmospheric-controlled induction-heating fine particle peening (AIH-FPP) and gaseous nitriding, were developed. Surface microstructures of gaseous nitrided specimens pre-treated with AIH-FPP were characterized by a scanning electron microscope (SEM), an energy dispersive X-ray spectrometer (EDX), X-ray diffraction analysis (XRD) and X-ray photoelectron spectroscopy (XPS). In the case of the AIH-FPP treated specimens with a Cr transferred layer, the nitrided layer was not formed. This was because diffusion of nitrogen into the surface of the specimens was disturbed by chromium oxide in the transferred layer. On the other hand, the nitrided layer was formed at the surface of the specimen with Cr diffused layer induced by pre-AIH-FPP, and this nitrided layer showed higher hardness than that of the specimen without AIH-FPP. However, the surface hardness decreased near the surface. In order to suppress decreasing of the surface hardness, the specimens with different Cr concentrations were prepared. It was clarified that the surface hardness was affected by Cr concentration in the Cr diffused layer; the lower the Cr concentration, the higher the surface hardness. It was assumed that the pore formation during nitriding process was inhibited by decreasing Cr concentration. These results suggest that surface hardness of S45C steel remarkably increases by hybrid surface treatments of AIH-FPP and gaseous nitriding.
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越智 達朗, 宮西 慶, 戸田 正弘, 加田 修2012 年 76 巻 7 号 p. 429-436
発行日: 2012年
公開日: 2012/07/01
ジャーナル フリーThe purpose of this study is to clarify the optimum approach to obtain high tensile strength after warm working, without increasing warm deformation resistance during warm working of medium carbon steel. Increase in warm deformation resistance during warm working by addition of Cr is small. On the other hand, Cr has the effect of suppressing the annihilation of dislocations in the air cooling process after warm working. Thus, by adding Cr, the tensile strength after warm working is effectively improved, without increasing warm deformation resistance during warm working. Increasing of Si is effective as a method to obtain high tensile strength after warm working, without increasing warm deformation resistance during warm working, too. Si has an effect of the solid solution hardening. This effect by increasing Si is due to the large temperature dependence of solid solution hardening effect. The control of microstructural factors, that are pearlite fraction and cementite spacing, is not effective as a method to obtain high tensile strength after warm working, without increasing warm deformation resistance during warm working.
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澤田 俊之, 柳谷 彰彦2012 年 76 巻 7 号 p. 437-442
発行日: 2012年
公開日: 2012/07/01
ジャーナル フリーMicro shot peening, using fine media with mean particle diameter of approximately 100 μm, is widely applied for various parts with high strength. Recently, micro shot peening by fine media with particle diameter of under approximately 50 μm is also researched. As mentioned above, it is required to use finer media to obtain more effective result. In order to meet this requirement, the effect of particle diameter on properties of Fe-Cr-B media with high hardness was investigated.
Fe-Cr-B media with various Cr and B contents were manufactured by gas atomization, followed by sieving in various particle sizes. Microstructures of these media were observed by field emission scanning electron microscopy and transmission electron microscopy. Crystal structures of boride were examined by XRD and Vickers hardness was also measured.
Fe-8%Cr-x%B (x=6-9.5) media were consisted of only stable phases of αFe, Fe2B and FeB. On the other hand, Fe-4%B and Fe-8%Cr-4%B media contained meta-stable borides of Fe3B and Fe23B6. The structure of boride varied from Fe2B to Fe3B and from Fe3B to Fe23B6 with decrease of particle diameter in both Fe-4%B and Fe-8%Cr-4%B media. In addition, these media with the minimum particle diameter of under 25 μm in this study had nanolayer consisted of αFe and Fe23B6. Vickers hardness of Fe-4%B and Fe-8%Cr-4%B media changed by these variations of boride form and microstructure with decrease of particle diameter.
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中野 博昭, 荒川 真吾, 高田 裕也, 大上 悟, 小林 繁夫2012 年 76 巻 7 号 p. 443-448
発行日: 2012年
公開日: 2012/07/01
ジャーナル フリーElectrodeposition behavior of Zn-Ni alloys was investigated at current densities of 10 to 500 A•m−2 and at amount of charge of 5×104 C•m−2 in unagitated zincate solution containing triethanolamine to form a stable complex with Ni2+ ions at 308 K. At low current densities, the deposition of Zn-Ni alloy showed a normal type codeposition, in which electrochemically more noble Ni deposited preferentially, while at high current densities, it showed an anomalous codeposition, in which less noble Zn deposited preferentially. The Ni deposition and H2 evolution were significantly suppressed in the region of anomalous codeposition at high current densities, showing the formation of inhibitor of deposition resulting from Zn ions in the cathode layer. In the region of normal codeposition at low current densities, the underpotential deposition of Zn apparently occurred with Ni. Because the Zn-Ni alloys are composed of stable intermetallic compound of Ni5Zn21, the activity coefficient of Zn in deposit seems to decrease remarkably.
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竹元 嘉利, 越智 昌宏, 瀬沼 武秀, 高田 潤, 清水 一郎, 松木 一弘2012 年 76 巻 7 号 p. 449-455
発行日: 2012年
公開日: 2012/07/01
ジャーナル フリーUnprecedented phenomena were discovered by tempering the Ti-4Fe-7Al alloy quenched from the β (bcc) field. The alloy became very hard when it was tempered at 450℃ for several minutes, and severely rugged surface was generated. The inverse shape recovery phenomenon was also discovered when a quenched specimen that had been bent at room temperature was heated. The tempered microstructure showed almost β grains and some of the usual martensitic acicular structure areas. However, electron back scattering pattern (EBSP) measurements showed that the β-like grain was not the bcc structure but was the hcp or orthorhombic structure. X-ray diffraction (XRD) measurements clarified that an orthorhombic α″ structure (a=0.2995 nm, b=0.4913 nm, c=0.4659 nm) was formed from the β phase by tempering. Moreover, this α″ structure was confirmed to be a type of martensitic transformation because no concentration distribution was detected in scanning transmission electron microscopy-energy dispersive spectroscopy (STEM-EDS) analysis of the microstructure. It was suggested that the essential Ms point of the alloy should be higher than room temperature; however, the martensite transformation could not operate by fast quenching.
The newly-discovered α″ martensite is formed without atomic diffusion by heating. When the β grain transforms into the single α″-variant, a very huge lattice strain is generated, resulting in the severely rugged surface or the inverse shape recovery phenomenon.
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道山 泰宏, 出水 敬2012 年 76 巻 7 号 p. 456-461
発行日: 2012年
公開日: 2012/07/01
ジャーナル フリーThis paper describes the creation of a surface-hardened layer with a minimum thickness of 1.0 mm on a titanium alloy. Two layers, a soft layer and a thick surface-hardened layer, were created on titanium alloy specimens by using different age-hardening speeds caused by different conditions of solution treatment. The solution treatment involved furnace and laser heating. After the solution treatment, we performed an accelerated aging treatment at 300℃ for aging times in the range 86.4-432.0 ks. Changes in the titanium alloy specimens after the aging treatment were examined by hardness and wear tests and microstructure observations.
The results revealed that the laser-heated part hardened at an early stage during aging. Because of the difference in the hardening speed, a hardened layer was formed. Except for the case of furnace heating at 700℃, the grain diameter of the laser-heated specimens barely changed after furnace heating. The wear amount of the titanium alloy specimens decreased with hardness; this decrease was remarkable especially at 450 HV and higher. For the specimens that were both furnace- and laser-heated and had the same hardness, the wear amounts were the same. The specimen that was laser-heated for 259.2 ks after furnace heating at 800℃ had an effective hardened layer with hardness in the range 490-500 HV, ranging from the surface to a thickness of about 1.0 mm. The hardness of the internal unhardened layer for this specimen was 260 HV.
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小口 かなえ, 澁田 靖, 鈴木 俊夫2012 年 76 巻 7 号 p. 462-467
発行日: 2012年
公開日: 2012/07/01
ジャーナル フリーCalculation efficiency of molecular dynamics simulation performed on GPU and CPU is discussed focusing on methodology of neighboring atom search such as book keeping and domain decomposition methods. The CUDA architecture is employed to develop a source code of the molecular dynamics simulation on the GPU consisting of the many-body potential for metals. It is confirmed from the calculation on relaxation of bcc crystal of iron that the order of calculation cost is about one for the domain decomposition method, whereas it depends on the temperature in the case of book keeping method. Performance of the relaxation calculation on the GPU achieves about 10 times the speed of a single CPU.
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野山 義裕, 三浦 拓也, 石本 卓也, 池尾 直子, 新家 光雄, 中野 貴由2012 年 76 巻 7 号 p. 468-473
発行日: 2012年
公開日: 2012/07/01
ジャーナル フリーThe present work was aimed at understanding the stress-shielding caused by hip-joint implantation into a femur by using a human cadaver with a cementless hip implant. In particular, bone quality was assessed from the standpoint of preferential c-axis orientation of biological apatite (BAp). Comparing the implanted side to the non-implanted side, a finite element analysis (FEA) indicated that artificial hip-joint implantation had a significant stress-shielding on the femur. The results also showed a remarkable decrease in the degree of preferential BAp orientation as well as bone loss in Haversial canal in the medial-proximal femur. This is the first report showing a reduction in the degree of preferential BAp orientation due to a stress-shielding after artificial hip-joint implantation. Since preferential BAp orientation is an important parameter for determining bone mechanical function, these findings should be taken into account in future artificial hip-joint designs, especially those involving the stem component.
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