Microstructure and Mechanical Properties of Extruded Mg-7Sn-5Zn-xAl (x = 0, 1, 2 and 3 wt.%) Alloy

Microstructure and mechanical properties of extruded Mg-7Sn-5Zn-xAl (x = 0, 1, 2 and 3 wt.%) alloy were investigated. The as-cast Mg-7Sn-5Zn alloy mainly comprised α-Mg dendrites, Mg2Sn and nanosized Mg-Zn phases in a Mg matrix, whereas the quasicrystal (icosahedral (I)) phase precipitated with the addition of Al. After extrusion, the grain size decreased due to dynamic recrystallization and the resulting particles were crushed and distributed along the extrusion direction. The highest tensile strength was exhibited by the extruded Mg-7Sn-5Zn-2Al alloy, which had a yield strength, ultimate tensile strength and elongation to failure of 198, 343 MPa and 18.7%, respectively. The high tensile strength was mainly attributed to grain refinement and precipitation strengthening of the Mg2Sn and icosahedral phases.