Microstructures and Tensile Properties of AZ91 Magnesium Alloys with Ca, Sm, and La Elements Additions

Microstructures and tensile properties of as‐cast and as‐extruded AZ91 magnesium alloys with individual and combined additions of Ca, Sm, and La elements are investigated. The results show that Al₂Ca, Al₂Sm, and Al₁₁La₃ new phases form after adding Ca, Sm, La elements, decreasing the amount of Mg₁₇Al₁₂ phases and refining the microstructures. Microstructures of as‐cast and as‐extruded alloys with combined additions are significant refined. The Al₂Ca and Al₁₁La₃ intermetallic compounds are crushed into granules because of severe deformation during hot extrusion, while the Al₂Sm intermetallic compounds are not. Tensile tests results at room temperature indicate that individual additions of Ca, Sm, and La elements could increase the elongation of as‐extruded alloys, and tensile tests results at 150 °C indicate that individual additions of Sm and La elements could increase the ultimate tensile strength and yield strength of as‐extruded alloys. AZ91–0.3La alloy exhibits the best comprehensive tensile properties both at room temperature and 150 °C. However, combined additions in AZ91 alloys leads to coarseness and aggregation of Al₂Sm phases, resulting in slightly decline of tensile properties both at room temperature and 150 °C.