Microstructures and mechanical properties of as-cast and as-extruded Mg-4.50Zn-1.13Ca (wt%) alloys

A large Mg-4.50Zn-1.13Ca (wt%) alloy ingot 350 mm in diameter and 1730 mm long was successfully fabricated by semi-continuous casting. The microstructures and mechanical properties of the as-cast and as-extruded alloys were investigated. The as-cast alloy exhibits uniform chemical composition and microstructure from the centre to the surface of the ingot and mainly consists of α-Mg and Ca2Mg6Zn3. The coarse grains and network-like second phases that are distributed at the grain boundaries result in poor mechanical properties for the as-cast alloy. The mechanical properties of the as-extruded alloys are significantly enhanced. The high yield strengths of the as-extruded alloys mainly result from the fine DRXed grain and the stronger basal texture.