The Effect of Ti–B and Sr on the mechanical behaviour of the Zinc–Aluminum-based ZA-12 alloy produced by gravity casting

Abstract

Abstract In this study, the effect of Ti –B (0.05 – 0.7 wt.% Ti, 0.01 – 0.13 wt.% B) and Sr additions (0.05 – 0.7 wt.%) on the hardness, ultimate tensile strength (UTS), strain and fatigue properties of the gravity cast Zn – Al-based ZA-12 alloy was investigated. While the Ti –B additions had no significant effect on the hardness of the alloys, the Sr additions lowered the hardness by a small amount. UTS and fatigue resistance of the ZA-12 alloy increased with 0.05 wt.% Ti, but the addition of 0.05 wt.% Sr to the standard alloy did not change these properties significantly. In excess of 0.05 wt.% Ti and Sr, the UTS and fatigue resistance of the alloys decreased and reached a lower value than that of the standard alloy. The failure strain only increased for the ZA-12 alloy containing 0.05 wt.% Ti, then decreased with further increase in Ti content. The failure strain values of the alloys decreased with addition of Sr. Metallographic examination indicated that the addition of Ti –B strongly modified the microstructure of the standard ZA-12 alloy, but Sr did not. Ti and Sr have also formed complexshaped intermetallic compounds, which were identified as Al5Ti2Zn and Zn5Al3Sr by X-ray diffraction and EDS analyses. It can be suggested that these particles cause a decrease in UTS, fatigue resistance, and strain to failure of the ZA-12 alloy.