Magnesium inclusion effect on Al-Zn-Cu alloys: A study on microstructure and mechanical properties

Abstract

The microstructure and mechanical properties of Al-Zn-Cu alloy with magnesium inclusion varying between 0.5 and 1.5 wt% were explored in this investigation. Al-Zn-Cu-Mg alloy was prepared by sand casting. Heat-treatment was done on the cast alloy samples at 460 °C for 2 h, which was then water-quenched. The samples at 160 °C were age-hardened for 5 h. Mechanical tests were done on both the heat-treated and as-cast alloy samples. Optical and scanning electron microscopy were used for the surface morphology of the samples. The maximum tensile strength (178.04 N/mm2) and hardness value (42.49 HB) were obtained from the Al-Zn-Cu-Mg alloy samples with 0.33 wt% Mg and 0.001 wt% Mg, respectively. In the as-cast samples, the reinforcing intermetallic phases present was coarse in nature while the precipitation hardened samples showed well-distributed reinforcing intermetallic phases which are fine grain size. Hence, the tensile strength of the cast Al-Zn-Cu-Mg alloy was positively influenced with the addition of magnesium while precipitation hardening eliminates micro segregations, thus, Al-Zn-Cu-Mg alloy mechanical properties were improved. Thus, the Al-Zn-Cu-Mg alloy can be useful in automobile industry.