Effect of Al on the Microstructure and Mechanical Properties of Mg-6Zn Alloy

Abstract

In this work, the effect of trace Al on the microstructure and mechanical properties of Mg-6Zn alloy was studied. The results show that the as-cast ZM60 alloy consists of α-Mg phase and Mg51Zn20 phase. After the addition of Al, fine Al8Mn5 phase increases in the microstructure of the experimental alloy, and the number of the second phase increases. Dynamic recrystallization occurred in all the experimental alloys during extrusion deformation, the grain size of Al alloy is significantly smaller than that of ZM60 alloy, and the average grain size of ZAM610 alloy is the smallest, which is 5.6µm. ZAM610 alloy has the best mechanical properties, with tensile strength, yield strength, elongation after fracture, U-notch impact work and non-notch impact work of 302.7MPa, 216MPa, 19.7%, 10.0 J/cm2 and 56.0 J/cm2, respectively. The fracture of the impact sample shows that there are many tearing edges in the ZM60 alloy, which shows the characteristics of quasi-cleavage fracture. The ZAM600 and ZAM610 alloys have a large number of dimples, which are characterized by dimple fracture. The improved properties of magnesium alloys after microalloying can be attributed to the formation of fine Al8Mn5 phase, which has good Zener blocking effect, refines the dynamic recrystallized grains, and improves the strength and impact toughness of the alloy.