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 mu m. The distribution of the phase is more dispersive in the Mg matrix. Sn content plays a key role for the inhibition of beta-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.