Microstructure, mechanical properties and corrosion resistance of as‐cast and as‐extruded Mg–4Zn–1La magnesium alloy

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Microstructure, mechanical properties and corrosion resistance of as‐cast and as‐extruded Mg–4 wt% Zn–1 wt% La magnesium alloys were investigated. The alloys were produced by low‐pressure die casting method and extruded at 350 °C after homogenization at 400 °C for 24 h. The results show that the as‐cast alloy mainly consists of primary α‐Mg matrix and Mg–Zn–La ternary second phases (also called T‐Phase) along grain boundaries and isolated spherical particles inside the grains. After extrusion at 350 °C, the average grain size decreases by 81% due to dynamic recrystallization mechanism and T‐phase particles are distributed along the extrusion direction. The elongation, yield strength and tensile strength of the as‐cast Mg–4Zn–1La alloy increase by 179%, 90% and 40%, respectively, as a result of the extrusion process. The as‐extruded Mg–4Zn–1La alloy shows better corrosion resistance than the as‐cast alloy due to increased grain boundaries and decreased content of T‐phase.