Shinichiro Fujikawa1 and Ken-ichi Hirano1
1Department of Materials Science, Faculty of Engineering, Tohoku University, Sendai
Solid solubility of Au in Al was determined by measuring the electrical resistivity at 77°K of Al-Au alloys air-cooled after annealing at various temperatures for sufficient times to complete the precipitation of the equilibrium phase (AuAl2), and the following results were obtained:
(1) The solid solubility of Au in Al was determined to be 0.35 wt%(0.048 at%) at 640°C; 0.30(0.041) at 630°C; 0.25(0.034) at 615°C; 0.20(0.027) at 600°C; 0.18(0.024) at 590°C; 0.11(0.015) at 560°C; 0.075(0.010) at 530°C; 0.043(0.0058) at 500°C and 0.025(0.0034) at 470°C.
(2) From the temperature dependence of the solid solubility the excess entropy ( Δ s) and the (excess) heat of mixing ( Δ h) associated with solid solution of Au in Al were calculated to be 3.8 k and 0.9 eV, respectively. Δ s and Δ h for other solute elements in Al were also calculated using the available data on the temperature dependence of the solid solubility and compared with the present results.
(3) The resistivity increment caused by Au atoms in solution was found to be linearly proportional to the concentration of Au.
The impurity resistivity per atomic percentage of the impurity for Au in Al was estimated to be 2 μ \varOmega⋅cm/at% which was considerably larger than those for other elements including other noble metals in Al.
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