Papers by Author: Nobuhiro Fujita

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Authors: Hiromi Miura, Haruka Hamaji, Taku Sakai, Nobuhiro Fujita, Naoki Yoshinaga
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Authors: M. Azuma, Nobuhiro Fujita, M. Takahashi, Thierry Iung
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Authors: Kenji Murakami, Nobuhiro Fujita, S. Adachi, Hideo Nakajima, H. Miyake
Abstract: Copper, iron and a nickel-chromium alloy were thermal sprayed onto a mild steel substrate in air and the structures of the sprayed particles that were collected during flying and those of the coatings are examined. The coatings consist of metal layers and metal oxide layers, and the minor phase layers become disintegrated and granulated on annealing. This morphology change is caused by the balance of the boundary energies.
1301
Authors: Hiromi Miura, Taku Sakai, Takanori Ueno, Nobuhiro Fujita, Naoki Yoshinaga
Abstract: A Ni-30 mass% Fe alloy with dispersed coarse oxide particles, ranging from 1 to 3 μm in diameter, was multi-directionally forged (MDF) at temperatures between 773 K and 873 K at a true strain rate of 1 x 10-3 s-1 in vacuum. For comparison, a particle-free Ni-Fe alloy was also prepared and MDFed. At 873 K, an obvious flow softening occurred during MDF especially in the alloy with dispersed particles, while work hardening followed by steady-state flow appeared at 773 K in both alloys. With increasing cumulative strain, the average grain size became gradually finer. However, the evolved microstructure was quite different depending on temperature and dispersion of particles. At 873 K, in the alloy with particles, equi-axed fine grains of about 1.3 μm in average was uniformly evolved at a cumulative strain of Σε = 2.4, while at 773 K the microstructure was still inhomogeneous. The above experimental results suggest important role of coarse particles to stimulate grain refinement.
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