Influence of Si Content on Fatigue Life for Heat Treated Cast Al-Si-mg Alloy Using Different Quenching Technique

Al-Si-Mg aluminum alloy samples were subjected to solution heat treatment at the temperature of 520 °C for 2 h to attain T42 condition. The heat-treated samples were quenched further in air and water mediums. After quenching, the fatigue life was analyzed with the total strain amplitude (TSA) of 0.4% at the cyclic frequency of 0.3 Hz using a low cycle fatigue testing machine. Air quenched sample has higher life with 1286 cycles than heat-treated and water quenched sample, which were having a fatigue life of 836 cycles and 708 cycles. Tensile mean stress was observed in all samples due to residual stress. Due to fatigue striation, ripple formation was observed in the air quenched sample, and the ripple having the size of 2-3 μm observed under SEM fractography. XRD peaks of Mg2Si and Al3Fe precipitates confirm the proper dispersion during the solution heat treatment.