EFFECT OF HEAT TREATMENT ON MICROSTRUCTURE AND MECHANICAL PROPERTIES OF EXTRUDED SiC/6061 COMPOSITE

Abstract

The effect of heat treatment on microstructure and mechanical properties of extruded SiC/6061 aluminium alloy matrix composite was investigated. The heat treatment (annealing at 540 °C for 1.5 hours, water quenching and artificial aging at 170 °C for 7 hours) caused dissolution of Mg2Si particles and decomposition of small SiC particles. The 0.2 % yield strength and the ultimate tensile strength of extruded composite were increased by application of heat treatment due to precipitation of β´´ phase particles. On the other hand, the ductility of composite was decreased. The fracture surface of as-extruded composite was consisted of numerous dimples. It was a result of micro voids nucleation at interface between matrix and SiC particles and second-phase particles. The fracture of heat treated composite was similar, micro voids were nucleated mainly on SiC particles, which were cracked during tensile test.