Exploring the evolution of microstructure and mechanical property of low-alloyed Mg-Zn-Mn alloy with Sm addition

High strength low-alloyed Mg-1Zn-0.3Mn (ZM) alloys with different of Sm contents (0, 1 and 2wt%) were fabricated via hot extrusion. The evolution of microstructure and mechanical property of these alloys were investigated. The results showed that the incorporation of Sm altered the grain structure and secondary phase precipitation behavior of the alloys, resulting in exceptional tensile yield strength (∼383 MPa) coupled with a fracture elongation of 4.2% in the extruded Mg-1Zn-0.3Mn-2Sm (ZMS2) alloy. As the increase of Sm content, the volume fraction of second phases increased both in as-cast and extruded alloys. Meanwhile, the recrystallization ratio in extruded alloy decreased from nearly 100% in ZM alloy to 69.4% and 61.4% in ZMS1 and ZMS2, respectively. Moreover, the grain size in dynamical regions decreased from 1.92 µm (ZM) to 0.69 µm (ZMS2). Further analysis revealed that the large number of (Mg,Zn)₃Sm phases in Sm containing alloy, fine grains and dislocation strengthening contributed the high strength of ZMS alloys.