Low cycle thermal fatigue and microstructural change of AC2B-T6 aluminum alloy

Low cycle thermal fatigue tests were conducted using an aluminum alloy AC2B-T6, which is widely used in diesel engines, especially, in cylinder heads. Specimens made of the AC2B-T6 alloy were subjected to thermal fatigue with thermo-mechanical loadings over several temperature ranges, symmetric and asymmetric strain amplitudes, and cycle periods. These test conditions are chosen considering realistic running conditions of diesel engines. A method to predict time to fatigue failure under the test conditions is proposed. The specimens were also observed by transmission electron microscope (TEM) to clarify the effects of temperature, strain amplitude, and cycle period on microstructural changes such as precipitates. Finally, the relationship between the microstructural changes and the low cycle thermal fatigue is discussed.