Microstructural Evolution and Mechanical Properties of Mg Added ZA-12 Alloy

A ZA-12 Zinc-based alloy was melted in an induction melting furnace, and cast in a graphite mold. Different amount of Mg was added for examining the microstructural evolution and mechanical properties of ZA-12 alloy. All alloys were annealed at 350oC for 22 hours to research the effect of heat treatment on the properties of ZA-12 alloy. The microstructure examinations revealed that while ZA-12 alloy has a dendritic microstructure with fine grains, with the Mg addition the distance between dendrite arms was getting larger. The hardness of alloys was increased with an increase in Mg content. The hardness of all alloys was increased slightly with the annealing also. Compression tests were performed to determine the mechanical properties. These tests showed that the yield strength and elongation are increased with increasing Mg amount for as casted alloys. The annealing heat treatment decreased the yield strength of alloys. A brittleness was observed for as-cast alloys containing more than 2.0wt.% Mg. The brittleness was still existing after heat treatment for alloy including 4.0 wt.% Mg while the alloy containing 2.0 wt.% of Mg became ductile.