Effect of Mo on Elevated-Temperature Low-Cycle Fatigue Behavior of Al-Si 356 Cast Alloy

Components of diesel engines are often subjected to cyclic loading at elevated temperature during operation, which may cause their fatal fatigue failure. In this study, elevated-temperature low-cycle fatigue (LCF) tests were conducted at 300 °C on Al-Si 356 cast alloys with Mo addition. Various strain amplitudes of 0.1, 0.2, 0.4 and 0.6% was applied. Results showed that a high volume of finer dispersoids formed with addition of Mo. Compared with the base alloy free of Mo, a higher fatigue strength but reduced plastic strain at all studied strain amplitudes was obtained in the alloy containing Mo. Smaller fatigue striation spacing was observed in Mo-containing alloy, indicating its better fatigue crack propagation resistance. However, the total LCF cycle at 300 °C in the alloy with Mo was moderately decreased due to the fast growth of crack to the final rupture. Fatigue parameters were calculated from test data for fatigue life estimation.