Creep behavior of spray-deposited AlLi/SiCp composite

The effect of T6 heat treatment on the creep behavior of Al8090/SiCp composite fabricated by spray-deposition is studied. Creep tests were performed in air at temperatures of 250, 300, 350 and 400 °C, with applied stresses ranging from 15 to 50 MPa. The as-received Al8090/SiCp composite contained a majority of large spherical phases rich in Mg and Cu. After T6 ageing, the grains of the specimen contained well-developed δ (Al3Li) and S (Al2CuMg) precipitates. Tensile and creep properties of the T6-aged sample were significantly improved, due to the solution of the coarse second phases and the strengthening effect from the fine precipitates. Inter-particle spacing of the SiCp and second phases in the Al matrix exerts an important role in creep resistance. The measured values of power-law stress exponent (n) and activation energy (Q) of the spray-deposited 8090 composite (T6-aged and non-aged) were much lower than those reported for Al alloys and composites (e.g. 2124, 6061, 7005 and 8090) fabricated by powder metallurgy (PM) and liquid metallurgy (LM) routes. Further, there was no obvious threshold stress (σth) in the spray-deposited 8090 Al composite, due to the free oxide content in the spray-deposited Al composites.