The Effect of Thermal Cycling and Isothermal Exposure on the Mechanical Properties of SiC Particle Reinforced Al Composites

Abstract

Influences of thermal cycling (100 cycles between 200 and 300°C) and isothermal exposure (80 h at 300°C) on tensile strength, micro Vickers hardness and fracture mechanism of T6-SiCp/Al6061 composites (SiCp/Al) and base metal of T6-Al6061 alloy(AA6061) were studied under the condition of the same hardness of the base metal for isothermal exposure and thermal cycling. Both thermal cycling and isothermal exposure reduced 0.2% proof stress, tensile strength and micro Vickers hardness to one third through a half of those of the original SiCp/Al6061 composites and mainly due to the softening of the matrix. In addition, the thermal cycling caused interfacial debonding between coarse particles and matrix in the SiCp/Al, which was confirmed from the observation of fracture morphology. The reduction in 0.2% proof stress and tensile strength increased with increasing SiC particle volume fraction. It was shown empirically that 0.2% proof stress and tensile strength of thermally degraded composites can be described as a linear function of hardness, which provides a useful tool for further study since 0.2% proof stress and ultimate tensile strength can be inferred by this relation without tensile test.