Effects of Cu content on microstructure and mechanical properties of Al–14.5Si–0.5Mg alloy

This study elucidates how Cu content affects the microstructure and mechanical properties of Al–14.5Si–0.5Mg alloy, by adding 4.65 wt.% and 0.52 wt.% Cu. Different Fe-bearing phases were found in the two alloys. The acicular β-Al5FeSi was found only in the high-Cu alloy. In the low-Cu alloy, Al8Mg3FeSi6 was the Fe-bearing phase. Tensile testing indicated that the low-Cu alloy containing Al8Mg3FeSi6 had higher UTS and elongation than the high-Cu alloy containing the acicular β-Al5FeSi. It is believed that the presence of the acicular β-Al5FeSi in the high-Cu alloy increased the number of crack initiators and brittleness of the alloy. Increasing Cu content in the Al–14.5Si–0.5Mg alloy also promoted solution hardening and precipitation hardening under as-quenched and aging conditions, respectively. The hardness of the high-Cu alloy therefore exceeded that of low-Cu alloy.