Effect of thermal exposure on microstructure and high-temperature fatigue life of Al-Si piston alloys

A very effective approach is proposed here to increase the high-temperature fatigue life of an Al-Si piston alloy. Compared with traditional T6 heat treatment, the high-temperature fatigue life can be improved by three times of magnitude with thermal exposure treatment, which reduces the negative effects of gradually decreasing high-temperature fatigue life due to over-aging of piston durability. Specimens heat-treated by various processes have been tested in a rotating bending test machine under conditions of 50 MPa, 350 °C, and 80 Hz to observe the effects of thermal exposure on microstructure and high-temperature fatigue life. The thermal exposure treatment provides an effective method to optimize Si and the thermally stable phases of δ-Al3CuNi and γ-Al7Cu4Ni. It is one of the most important methods for improving the high- temperature fatigue life of an Al-Si piston alloy.