Masao Ono1,, Takahiro Kinoshita2, Xinsheng Huang3, Yusuke Iguchi2,, Satoru Okayasu1 and Tsutomu Mashimo1,2,
1Advanced Science Research Center, Japan Atomic Energy Agency (JAEA), Tokai, Ibaraki 319-1195
Ultracentrifuge experiments were performed on a miscible In-Pb alloy to study sedimentation of constitutional atoms under a strong gravitational field (maximum acceleration: 106 g level, temperature: below melting point (solid), starting state: intermediate α-phase (f.c.t., c0/a0<1), time duration: 30-150 h). The Graded structures were formed in all centrifuged samples, in which, the Pb content continuously increased, and the In content decreased in the direction of gravitational field. For the centrifuged sample of 100 h in time duration, Pb-rich phase (f.c.c.) and In-rich phase (f.c.t., c0/a0>1) appeared at the highest- and lowest-gravitational field sides of the sample, respectively. These observation results showed that the graded structure was continuous in atomic scale, and was formed by sedimentation of constitutional atoms (substitutional atoms). It was also found that the composition change reached steady state within 60 hours. Based on a simulation of sedimentation process, the diffusion coefficient for sedimentation was estimated to be about 8 times larger than that for usual diffusion.
sedimentation, constitutional atoms, ultracentrifuge, diffusion, indium-lead system, graded structure, phase transformation, acceleration field
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