Achieving High Thermal Conductivity of Al-50si Alloy Through Heat Treatment and its Microstructural Evolution

Abstract

Al-50Si alloys were prepared by powder extrusion and characterized for electronic packaging. The optimization of powder size, extrusion temperature, and heat treatment parameters was performed to enhance the microstructure and thermo-physical properties. The alloy exhibits a high relative density >99%, a low coefficient of thermal expansion (CTE) <10×10-6/K, and a good thermal conductivity (TC) ~117 Wm-1K-1 achieved by employing a large size powder and high extrusion temperature during the extrusion process. Subsequent heat treatment of the optimized alloy at 550 °C for various time reveals a fluctuating increasing trend in TC during the heat treatment process. The TC values exhibit periodic fluctuations as they alternate between increments and decrements, primarily resulting from the recrystallization and secondary recrystallization of Al grains during heat treatment process. Notably, the maximum TC value (~159.1 Wm-1K-1) at room temperature is obtained after heating the alloy to 550 °C for 26 h. Compared to the as-extruded alloy, the TC of heat-treated alloy increases by approximately 36%, which can be attributed to the elimination of eutectic Si and growth of Si and Al grains within the alloy. The study may shed light on the mechanism underlying the improvement in thermal conductivity of Al-50Si alloy by microstructural evolution.

Keywords: Al-50Si alloy, Hot extrusion, Heat treatment, Microstructure, Thermal property