Designing, Processing and Properties of Advanced Engineering Materials

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作者: Hiroyuki Toda, Toshiro Kobayashi
摘要: Cutting chip is, generally, remelted for recycling solely as raw materials. In terms of microstructures, however, the cutting chip may be identified utilizable due to highly accumulated strain during its formation. In this study, aluminium chipsareconsolidated by cold severe plastic deformation so that their highly deformed microstructure is utilized for strengthening. After a preliminary investigation in which a variety of cutting processes and conditions are examined to find the optimum one for the present purpose, the aluminium chips have been successfully consolidated by a combination of pressing and swaging. The consolidated chips exhibit superior strength to a wrought alloy together with finer microstructure when compared at a same applied strain. In addition, a simple method is demonstrated effective to eliminate the undesirable effects of oxide film on the surface of the chips, which inevitably causes debonding during loading.
作者: Lei Wang, Tong Cui, Jun Ying Lü, Hong Cai Yang, Guang Pu Zhao
摘要: Low-cycle fatigue property of superalloy GH4586 was investigated using a stress amplitude-controlled mode at 1023K. Fracture surface was examined with a scanning electronic microscopy. It was found that the cyclic life can be illustrated by Manson-Coffin at all strain levels. The fatigue cracks initiate primarily on the surface of the specimen. The plastic strain amplitude responded to the cyclic loading shows higher sensitivity than that of the elastic strain amplitude. It was demonstrated that the failure of the present alloy is in a manner of creep-fatigue feature.
作者: Atsushi Yamamoto, Harushige Tsubakino, Masami Ando, Lie Liu, Mititaka Terasawa, Tohru Mitamura
摘要: Ion-implantation on high purity iron substrates with nitrogen ions were carried out by using a Cockcroft Walton type accelerator under an accelerating voltage of 150 kV. Hardness measurements on the implanted surfaces showed that hardness effectively increased in the cold rolled specimens by ion-implantation in comparison with in an annealed specimen. Iron nitride, Fe16N2, was formed in the ion-implanted specimens. In the annealed specimen, relatively large particles of Fe16N2 were formed with low number density, while in the deformed specimens, dislocation substructures due to cold rolling were disappeared by ion-implantation and fine particles were densely formed. Strain field around dislocations induced by deformation provides nucleation sites for Fe16N2 particles.
作者: Y. Harada, Kazuya Mori, Seijiro Maki, Lei Wang
摘要: Shot peening process of inner surface of machine parts in which rebound shots collide with the inner surface was investigated. The jig used for rebound shot peening has the surface with a slope to the inner surface of machine parts, and the collision direction of shots was vertical to the inner surface. In this process, a compressed air type shot peening machine was employed. The influence of processing conditions was evaluated by the distributions of hardness, residual stress and surface roughness in the test pieces of pipes and coiled springs. The effect of shot peening increases with the increase of shots collision energy. A stress peening process for inner surface of coiled springs using rebound shots was also performed. The coiled spring was provided higher compressive residual stresses. The results of a fatigue test showed that the fatigue life of the spring was improved. The compressive residual stress reduces the tensile stress of coiled spring. It was found that the present process was suitable for improving the inner surface of machine parts.
作者: Yoshinori Murata, Masahiko Morinaga, Ryokichi Hashizume
摘要: In order to elucidate the Re effect on oxidation resistance, a high-temperature oxidation test was conducted with two groups of Ni-based superalloys. One group of alloys was characterized by 10mol%Al content (10-Al series). The other group of alloys was characterized by 15mol%Al content (15-Al series). The oxidation resistance decreased clearly with increasing Re content in the 10-Al series alloys, but did not in the 15-Al series alloys.
作者: Hyoun Woo Kim
摘要: The usage of barium strontium titanate (BST) capacitor have recently been considered in the fabrication of dynamic random access memory (DRAM) device. In this study, in order to avoid the difficulties of high aspect ratio etching of bottom electrode in the conventional stack-typecapacitor structure, we suggest to introduce a concave-type capacitor structure. The fabrication procedure of the two kinds of the concave capacitor cells, Pt/BST/Pt and Ru/BST/Ru are explained. We have studied on the metal electrode etching in the concave structure and have discussed the patterning issues in fabricating the capacitor structures.
作者: Hyoun Woo Kim
摘要: In this study, the etching characteristics of ruthenium (Ru) electrode using O2/Cl2 helicon plasmas were investigated. The variation of Ru etch rate, Ru to SiO2 etch selectivity and Ru etching slope with varied process variables were scrutinized. Not only the gas chemistry affected the Ru etching, but also the higher bias power and argon (Ar) bombardment helped to faciliate the Ru etching.
作者: H.B. Kang, J.K. Choi, J.W. Lee, Cheol Woong Yang
摘要: We have investigated the oxidation behavior of epi-Si0.7Ge0.3 films in dry oxygen ambient. Epi- Si0.7Ge0.3 films about 500Å in thickness were deposited on (100) Si wafers by UHV-CVD system. Oxidation was carried out in a conventional tube furnace at 800 °C . In this study, it was found that Ge piles up at the oxide/substrate interface, forming a Ge-rich layer. Because of the large difference in the heat of formation between SiO2(-730.4KJ/mol at 1000K) and GeO2(-387.07 at 1000K) [1], the Si is to be more reactive than Ge to oxygen. The oxidation rate of SiGe in a dry oxygen environment is found to be essentially the same as that of pure Si.
作者: Shigeru Okada, Kunio Kudou, T. Mori, Takaaki Shishido, I. Higashi, Naoki Kamegashira, Kazuo Nakajima, T. Lundström
摘要: Single crystals of AlMgB 14 and AlMgB 22 were grown from a high-temperature aluminum metal flux in an Ar atmosphere. The optimum conditions for growing AlMgB 22 and AlMgB 14 were established using the starting mixtures of B/Mg=0.5-1.0 and B/Mg=2.0-6.0. The AlMgB 14 and AlMgB 22 crystals obtained have well-developed {001} and {100} faces, and were black with a metallic luster. The maximum dimensions of these crystals were about 5.2 mm and 4.6 mm, respectively. The values of micro-Vickers hardness of the AlMgB 14 and AlMgB 22 crystals are in the ranges of 23.9±0.6-27.6±0.6 GPa. The oxidation process of AlMgB 14 and AlMgB 22 crystals were studied up to 1473 K by TG-DTA method. The susceptibility of AlMgB14 with an increase at low temperatures does not show any particular features, being indicative of a paramagnetic contribution, which is likely due to impurities. The susceptibility of the AlMgB 22 sample shows no apparent contribution from impurities and also does not have any anomalous behavior.
作者: W.S. Chung, W.Y. Yoon, Kwang Jin Kim
摘要: Magnesium powders having inactive surface layer have been processed easily and intentionally by DET under fluoride, chromate, and bromide salt. The modified surfaces play an important role in preventing contact with active environments to improve corrosion resistance of Magnesium powders; the image of the surface modified powders was observed using SEM. The composition distribution and characteristics was determined and analyzed by using XRD, XPS, and EIS. Compared with bare Magnesium, the Magnesium having chromate modified surface layer showed a more passive behavior such as smaller current density and nobler potential in 4wt% NaCl solution.