Effect of Al addition on microstructure and mechanical properties of Mg-Zn-Sn-Mn alloy
The microstructure and properties of the as-cast, as-homogenized and as-extruded Mg-6Zn-4Sn-1Mn (ZTM641) alloy with various Al contents (0, 0.5, 1, 2, 3 and 4 wt.％) were investigated by OM, XRD, DSC, SEM, TEM and uniaxial tensile tests. The results show that when the Al content is not higher than 0.5％, the alloys are mainly composed of α-Mg, Mg2Sn, Al8Mn5 and Mg7Zn3 phases. When the Al content is higher than 0.5％, the alloys mainly consist of α-Mg, Mg2Sn, MgZn, Mg32(Al,Zn)49, Al2Mg5Zn2, Al11Mn4 and Al8Mn5 phases. A small amount of Al (≤1％) can increase the proportion of fine dynamic recrystallized (DRXed) grains during hot-extrusion process. The room- temperature tensile test results show that the ZTM641-1Al alloy has the best comprehensive mechanical properties, in which the ultimate tensile strength is 332 MPa, yield strength is 221 MPa and the elongation is 15％. Elevated- temperature tensile test results at 150 and 200 ℃ show that ZTM641-2Al alloy has the best comprehensive mechanical properties.
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