Microstructure and enhanced mechanical properties of Mg-3Sn alloy with Mn addition

Abstract

The effects of Mn content on the microstructure and mechanical properties of the extruded Mg-3Sn-xMn (x = 0, 0.5, 1.5, 2.5) alloys was systematically investigated in this study. More importantly, the relationship between microstructure and mechanical properties of Mg-Sn-Mn alloy was revealed in detail by calculating the various strength contribution value. The microstructure and mechanical properties of the alloys were characterized by X-ray diffraction (XRD), scanning electron microscope (SEM), electron backscatter diffraction (EBSD) and universal testing machine. The results revealed that the average grain size (AGS) decreased from 21.45 μm to 10.51 μm and then increased to 13.41 μm with increasing Mn content. It was observed that the second phases are dispersed in Mg-Sn-Mn alloys, namely the granular Mg2Sn phase and the rod-shaped α-Mn. Furthermore, the Mg-3Sn-1.5Mn alloy exhibits the optimal comprehensive mechanical properties with ultimate tensile strength (UTS), yield strength (YS), and elongation to fracture (EL) of 249.5 MPa, 203.3 MPa, and 19.3 %, respectively. The YS of Mg-3Sn-1.5Mn alloy was significantly enhanced by 42.5MPa than that of Mg-3Sn alloy, accompanied by a moderately improved elongation from 15.4% to 19.3%. The higher strength of the Mg-3Sn-1.5Mn alloy was attributed to grain refinement (25.2～28.8 MPa) and second phase strengthening (17.097～17.147 MPa), while the enhanced plasticity of the alloy is due to the weakening of the basal texture, and the higher SF of the prismatic <a> slip.