Softening response of cast Al-Si-Cu samples tested under low-cycle-fatigue and fatigue-creep regime and elevated temperate: Experimental and analysis

In this paper, the strain-controlled low-cycle-fatigue (LCF) test and low-cycle-fatigue-creep (LCFC) test of a cast Al-Si-Cu alloy at 350 degrees C were investigated. A significant softening behavior can be observed in the tests, the strain amplitude has an effect on softening speed, and the dwell time has an effect on both softening ratio and softening speed. Microscopic observation indicated that the compressive load of creep could result in a significant amount of plastic deformation and lead to the eutectic silicon particles rupture and the propagation of dimples, causing the softening behavior and the decrease of failure life of Al-Si-Cu alloy. Based on the experiment data, a modified visco-plasticity model combining Chaboche model and theta-projection model was proposed to capture the cyclic stress response. The modified model could simulate the softening behavior and hysteresis loop for LCF test and LCFC test of Al-Si-Cu alloy accurately.