Significance of segregation on grain refinement and property improvement in extruded Mg-Al-Mn alloy with moderate Al content

Two Mg-5Al-Mn (mass%, AM50) alloys having different microstructures were extruded, and the tension/ compression properties were investigated. One was a lab-scale material, which had dense segregation of Al element, while the other was a commercial casting ingot with sparce segregation of Al element. The dense segregation led to significant grain refinement. The average recrystallized grain size was 5.0 mu m, which resulted in the high proof stresses of 252 MPa, 211 MPa, and 178 MPa for the tension along the extrusion direction (ED), compression along the ED, and compression along the radical direction, respectively. When the extrusion was performed after homogenization, grain coarsening was apparent, leading to the significant decrease in strengths for the tension and compression, and both the lab-scale and commercial cast ingot exhibited similar properties despite the difference in the initial grain size.