Effect of zirconium on the microstructure and mechanical properties of Zn-4%Al hypoeutectic alloy

The effect of additional Zr in the range of 0-0.3 wt.% on the microstructure and mechanical properties of ZnAl4 alloy was studied. Microstructure and compositions of experimental alloys were analyzed by scanning electron microscopy and energy dispersive spectroscopy. The results show that the morphology of primary η-Zn phase as well as eutectic structure, with different Zr content in ZnAl4 alloys, are considerably distinct, resulting in the remarkable evolution of mechanical properties. Along with the increase of Zr content, the tensile strength of ZnAl4 alloys increases, peaking at 231 MPa with 0.1 wt.% Zr, followed by a decrease thereafter. The elongation, impact toughness and HB hardness show similar evolution character, peaking at 4.80%, 70.37 J/cm2 and 85.19 kgf/mm2, respectively. The most optimized additive content of Zr to ZnAl4 alloy may be 0.1 wt.%, which contributes to abundant eutectic structure and fine η-Zn phase, thereby improved mechanical properties.