Microstructure and Properties of Semi-solid Die Casting of High Silicon Aluminum Alloy with High Thermal Conductivity

Electronic components, such as package substrate, need materials having high thermal conductivity and low expansion at the same time. The effect of semi-solid rheo-diecasting on microstructure, mechanical properties and thermal physical properties of high-silicon content aluminum alloy (Al-20Si-Cu-Fe-Mg) with high thermal conductivity and low thermal expansion, was investigated. The results show that compared with gravity casting, eutectic silicon in alloys made with semi-solid rheo-diecasting was refined, and the microstructure of the alloy was more homogeneous. There were few internal defects in castings and the tensile strength in as-cast cast state was increased to 192.4 MPa. At 25–150 °C range, the average thermal expansion coefficient was 17.05 × 10−6 ℃−1, which decreased by about 3.54%, and the average thermal conductivity was elevated to 146 W/(m · K), which increased about 17.5%.