Effects of Sn on Microstructures and Mechanical Properties of As-Extruded Mg−6Al−1Ca−0.5Mn Magnesium Alloy

Effects of Sn on microstructures and mechanical properties of Mg–6Al–Ca–0.5Mn magnesium alloy were investigated. With Sn addition, the grain size of Mg–6Al–Ca–0.5Mn–xSn alloy decreases and the volume fraction of Mg₂Sn phase increases. The minimum average grain size of Mg–6Al–Ca–0.5Mn–xSn alloy is 15 μm. The distribution of the phase is more dispersive in the Mg matrix. Sn content plays a key role for the inhibition of β-Mg₁₇Al₁₂ phase and the promotion of Mg₂Sn phase. However, excessive Sn addition results in the decline of strength and elongation. Tensile results show that the Mg–6Al–Ca–0.5Mn–3Sn alloy exhibits the best mechanical properties, and the ultimate tensile strength, yield strength and elongation of the alloy are 335.9 MPa, 261.1 MPa and 10.9%, respectively. The improved tensile properties are mainly related to grain refinement, solid solution strengthening of Sn and precipitation strengthening of Mg₂Sn phase. Fractographic analysis demonstrates that quasi-cleavage fracture is the dominant mechanism of these alloys.