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 Al₈Mg ₃FeSi₆ 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.