Variability in the impact properties of A356 aluminum alloy on microporosity variation

This study aimed to investigate the effects of variations in the microporosity of a low-pressure die-cast A356 alloy on the impact properties of the alloy and the maximum impact value achievable in the defect-free condition. The study also aimed to determine the optimal T6-treatment conditions to minimize the effect of micro-voids on impact properties. The impact properties of as-cast and T6-treated specimens were evaluated using a conventional Charpy test, and the microporosity was described with a fractographic porosity term measured through SEM observation of the fractured surface. The effect of variation in microporosity on the absorbed impact energy can be described as an inverse power relationship in terms of the exponent of defect susceptibility and the maximum impact energy that can be achieved in the defect-free condition. The defect susceptibility of the absorbed impact energy to microporosity variation was remarkably improved by T6 treatment compared to the as-cast condition. Although the defect susceptibility has little influence on the solutionizing time over a range of conventional solutionizing temperatures, the maximum impact energy achievable in the defect-free condition depends strongly on the holding time. The defect susceptibility gradually decreases with the decreasing aging time from solution treatment, and the maximum value of the impact energy decreases abruptly after 16 h of aging.