The influence of hot extrusion deformation on microstructure evolution, tensile properties and corrosion behavior of Mg–3Al–0.5Mn–0.5Sr alloy

A novel microalloyed Mg–3Al–0.5Mn–0.5Sr (AMJ300) alloy was designed and prepared. Then the original structure of as-cast alloy was optimized by hot extrusion. The influence of extrusion on microstructure, corrosion and tensile properties of as-cast AMJ300 alloy were studied by OM, SEM, EDS, XRD, TEM, electrochemical workstation and tensile tests. The results indicated that α-Mg, Al₈Mn₅ and Al₄Sr phases constitute the AMJ300 alloy. Furthermore, the microstructure of alloy was further refined after extrusion, which indicates that the microstructural evolution during extrusion was governed by dynamic recrystallization. The fine and close of structure and the morphology change of intermetallic compounds greatly improved the corrosion resistance of AMJ300 alloy. The results of corrosion rate, corrosion current and corrosion morphology showed that the corrosion resistance of as-cast alloy could be significantly improved by extrusion. The main corrosion products of AMJ300 alloy in 3.5 wt.% NaCl solution was Mg(OH)₂. After extrusion, the tensile properties of AMJ300 alloy was significantly improved. The tensile strength reached 349 MPa, the yield strength reached 229 MPa, and the elongation reached 13.2%. Compared with the as-cast alloy, the tensile strength, the yield strength and the elongation increased by 218.1%, 248.9% and 173.7% respectively