Papers by Author: Yasuhiro Morizono

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Authors: Yasuhiro Morizono, Seiichiro Nakatsukasa, Minoru Nishida
Abstract: Ti-Sn binary alloys (Ti-5 to 20 mol% Sn) were diffusion-bonded to high carbon steel between 1073 and 1273 K for 3.6 ks in a vacuum to investigate the influence of the alloy composition on the interfacial microstructures. Ti-5 and 10 mol% Sn alloys were attached firmly to the steel at a bonding temperature of 1273 K. A continuous TiC layer was formed along the interface, while voids were observed between the TiC layer and the steel. Although the joints with Ti-15 and 20 mol% Sn alloys were also prepared at 1273 K, these joints separated near the interface after the bonding treatment. The TiC layer was formed in the separated surface of Ti-Sn alloy, and Fe in the steel diffused into the Ti-Sn alloy. This indicates that the Ti-15 and 20 mol% Sn alloys established contact with the steel at elevated temperatures until just before the separation. The specimens bonded at 1173 K also denoted the same tendency. However, the Ti-15 mol% Sn/steel joint bonded at 1073 K showed a shear strength of more than 50 MPa. The mechanism and the application of the interface separation are discussed on the basis of the microstructural observations.
Authors: Seiichiro Ii, N. Matsuzaki, Yasuhiro Morizono, Minoru Nishida
Authors: Minoru Nishida, Takao Yamamuro, M. Nagano, Yasuhiro Morizono, Yoshihito Kawamura
Authors: Akira Chiba, Minoru Nishida, Yasuhiro Morizono
Authors: Y. Shirakawa, Yasuhiro Morizono, Minoru Nishida
Authors: Akira Chiba, K. Ooyabu, Yasuhiro Morizono, Tomoyuki Maeda, Shinya Sugimoto, T. Kozuka, E. Kakimoto, Koichi Kawahara, T. Watanabe
Abstract: Sm2Fe17Nx compound is a prospective candidate as a material for high performance permanent magnets because of its good intrinsic magnetic properties with a Curie temperature of 747K, a room-temperature anisotropy field of 14T and a room-temperature saturation magnetization of 1.5T. However, Sm2Fe17Nx compound decomposes to -Fe and Sm nitride above 873K and conventional powder metallurgy processing techniques fail to meet the processing requirements. Shock consolidation is a viable alternative to process this compound. Fully dense Sm2Fe17Nx bulk materials were fabricated by cylindrical explosive consolidation technique using water as a pressure transmitting medium. Explosive consolidation is performed under cold state and fully dense materials can be obtained without any degradation of the characteristics of the powder states. Sound compacts were obtained without any cracks or teas, and the value of (BH)max of Sm2Fe17Nx compact is 23.8 MGOe.
Authors: Yasuhiro Morizono, Minoru Nishida, Yoshikazu Kodama, Takateru Yamamuro, Yasuhide Ohno
Abstract: Diffusion bonding of Ti and Ti-Al (Ti-10, 20 and 40 mol%Al) alloys to high carbon steel was carried out at 1073 and 1273 K for 3.6 ks in a vacuum. It has been found that the joint with Ti-20 mol%Al alloy is separated in the vicinity of the interface promptly after the bonding treatment at 1273 K. Such a phenomenon could not be observed in other Ti-Al alloy/steel joints, and the Ti-20 mol%Al alloy/steel joint bonded at 1073 K showed a high strength of about 170 MPa. Therefore, this phenomenon depends on the bonding temperature and the composition of the Ti-Al alloys. From the observation results of the interface, it is thought that the diffusion of constituent elements across the interface is part of the reason for the separation phenomenon. The separated surface of the Ti-20 mol%Al alloy side showed diffraction peaks of TiC phase by XRD. Its Vickers hardness was about 1200 and approximately 4 times higher than that before the bonding treatment. It is expected that the separation phenomenon at the Ti-20 mol%Al alloy/steel interface serves surface modification of titanium materials, which show poor wear resistance.
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