Effects of silicon content on electrical resistivity and thermal conductivity of Al-Si binary alloys

Thermal conductivity is useful to improve performance and manufacturing process for various products. In this study, thermal conductivity was measured for solution-treated Al-Si alloys, and the influence of solute Si on thermal conductivity was studied. For quantification of metallurgical structure, electrical resistivity was measured. Ingots of Al-Si alloys were prepared with Si content between 0.5 and 10mass%. Thermal conductivity was measured at room temperature (294～300K), λ, after heat treatment at 843K showed a good proportional relation to Si content up to 1.4%. The specimens of Si content above 5% showed negative deviations from the proportional relation, suggesting incomplete dissolution of silicon. Contribution per unit concentration of solute Si to the λ‒1 was 0.856×10‒3 W‒1 m · K · mass%‒1. Electrical resistivity was measured at room temperature (298K) and 77K. Electrical resistivity also showed a good proportional relation to Si content up to 1.4%. Contributions per unit concentration of solute Si to the resistivity at 77K and at 298K were 5.65 nΩm·mass%‒1 and 5.71 nΩm·mass%‒1, respectively. For specimens of Si content above 5%, volume fractions of Si particles were calculated from the measured values of thermal conductivity and electrical resistivity, respectively. Both of volume fractions were larger than calculated value from the concentration of solute Si.