Effect of Heat Treatment on the Microstructure and Mechanical Properties of a Composite Made of Al-Si-Cu-Mg Aluminum Alloy Reinforced with SiC Particles

In this paper, the effect of heat treatment (solution treatment and artificial aging) on the microstructure and properties of as-cast Al5Si1Cu0.5Mg aluminum alloy and its composite reinforced with 1.5 wt.% SiC particles was studied. The results showed that at 520 °C the optimal solution time for the aluminum alloy and its composite is 9 h and 6 h, respectively. After solution treatment, the microstructure of these two materials consists of a uniform distribution of nearly spherical eutectic Si and skeletal γ phase, furthermore, the composite eutectic Si phase is smaller and γ phase is more dispersed. After artificial aging at 175 °C for 6 h, the microstructure of the composite is more dispersed and finer than that of the aluminum alloy on the whole and Al2Cu is precipitated. After heat treatment, the microhardness, ultimate tensile strength, and elongation of the aluminum alloy and its composite are higher than those of the as-casts. At the same time, the morphology of tensile fracture surface changes very much from a large area of cleavage plane to a large number of dimples and the tearing ridges become thicker for both the aluminum alloy and its composite.