Mechanical Properties of As-Exposed Al-SiCp Composite Fabricated by Powder Injection Moulding

This research investigated mechanical degradation of powder injection moulded SiCp-reinforced aluminium composite subjected to moderate temperature exposures. Aluminium composite of 20 vol.% SiCp reinforcement was produced by powder injection moulding and sintering at 680°C, followed by 500°C solution treatment plus 150°C for 6 hours artificial aging, and subsequent exposures at 100, 200 and 300°C for 10 and 100 hours. It was found that short-term exposure for 10 hours provided increasing hardness with increasing exposure temperature, while long-term exposure for 100 hours led to an opposite result. The maximum micro Vickers hardness was obtained at 182.2 Hv for Al-SiCp composite exposed at 300°C for 10 hours. Tensile strength was however found deleterious with increasing both exposure temperature and time. The maximum tensile strength was achieved at 191.2 MPa for Al-SiCp composite exposed at 100°C for 100 hours. The formations of AlN, Mg2Si and Al2Cu were observed in both age-hardened and as-exposed conditions. Furthermore, the highest temperature exposure at 300°C and extended exposure time at 100 hours resulted in the lowest hardness and tensile properties due possibly to the loss of coherency of precipitates. SiCp clusters were the main cause of the tensile failure.