The effect of Cu and Al on the mechanical properties of gravity-east hyper-eutectic Zn-Al-based alloys

Abstract

A series of Zn-Al-based alloys, one group with 1 % Cu and the other without Cu, was produced by using gravity casting. The effect of Al content on hardness, ultimate tensile strength (UTS), impact strength, and tensile creep behaviour at 120 degreesC and an applied stress of 40 MPa has been investigated. It has been found that the hardness and UTS of the alloys considerably increased with increasing Al content, but the creep strength decreased. The impact strength of the alloys improved with increasing Al content up to 7.5 % and then reduced gradually with further increase in Al content. In addition, the effect of 1 % Cu addition on the mentioned properties has been determined. While the addition of 1 % Cu had a profound effect on increasing the hardness, UTS, and creep strength, it did not have a significant effect on the impact strength of the alloys. Metallographic examinations showed that an increasing Al content of the alloys increased the volume fraction of the Al-rich beta dendrites in expense of a decreased volume fraction of the eutectic, which is in principle responsible for the change in mechanical properties of the alloys depending on the Al content.