Aging Behavior and Tensile Properties of Squeeze Cast AL 6061/SIC Metal Matrix Composites

Abstract

In this work, the production and properties of Al 6061/SiC composites, made using a squeeze casting method, were investigated. SiC preforms were manufactured by mixing SiC powder, having a 16 and 22 mu m particle size, with colloidal silica as a binder. 6061 Al melt was squeeze cast into the pores of the SiC preform to manufacture a DRA composite containing 30v/o reinforcement. The aging behavior, tensile properties and fracture mechanism of the cast material were studied. The results show that higher hardness, yield strength, tensile strength and Young's modulus can be obtained by the addition of SiC particles to 6061 Al alloy, whereas tensile elongation decreases. This is mainly caused by a thermal mismatch between the metal matrix and the reinforcement, which leads to a lower grain size of the matrix with more dislocation density. It was also found that the precipitation kinetics of GP zones in the composite material was accelerated, owing to the heterogeneous nucleation capability of metastable phases on the SiC particles. Decreasing the SiC particle size resulted in better mechanical properties and a faster aging response. Nevertheless, the decohesion of the interface between the metal matrix and SiC particles led to the formation of voids which, subsequently, coalesced to generate the ductile rupture of the metal matrix.