The effect of heat treatment and copper on the tensile properties and quality index of Al-7Si-0.35Mg-xFe alloys

In this study, the effect of Cu addition (0.5, 1.0 and 1.5 wt%) and T6 heat treatment on the tensile properties and quality index of A356 alloy containing different amount of iron (0.5-1.5 wt%) was investigated. According to the results in as-cast condition, the addition of copper to the iron bearing alloys increased the tensile strength by about 25% while substantially decreased the percent elongation (by almost 80%). After heat treatment, however, the tensile strength and the quality index of the alloy containing 1 wt% copper and 1.5 wt% iron were found to be increased by about 100 and 35% as compared to the base alloy, respectively. The improvement in the quality index was attributed to the precipitation hardening effect of Al2Cu and Mg2Si precipitates as well as thermal modification of eutectic silicon and iron-rich platelets, which increase the tensile strength, and ductility of the alloy.