The Effect of Heat Treatment on the Thermal Conductivity of Squeeze Casting A356 Al Alloy and A356/SiC Composite

摘要

The purpose of this study is to investigate the improvement of thermal conductivity in A356 Al alloy and Al/SiC composites by using heat treatment. The materials used include a squeeze casting A356 Al alloy and an Al/SiC composite made by high pressure infiltration of A356 Al melt into 80 vol% SiC perform in a squeeze casting machine. The heat treatment was carried out at temperatures ranging from 200 to 600°C for a fixed time period of 30 min. After heat treatment, the microstructures and the lattice constant of A356 Al alloy were analyzed by OM and XRD, respectively. And the effects of heat treatment on density, electrical conductivity and thermal conductivity of A356 Al alloy and Al/SiC composite were evaluated. The results show that, among the various heat treatment conditions studied, the 580°C/0.5h heat treatment significantly increased the density of as cast A356 A1 alloy. While the 350°C/0.5 h heat treatment effectively depleted the solutes content in the Pri-α matrix of A356 A1 alloy, which results in a remarkable increase of thermal conductivity. By using a 2-step heat treatment of 580°C/0.5 h+350°C/0.5 h, the thermal conductivity of as cast A356 Al alloy was found increased from 127.2 W/(m·K) to 155.3 W/(m·K). But for the Al/SiC composite, it was found that the 2-step heat treatment has little effect on both density and thermal conductivity of the Al/SiC composite.