Optimizing microstructure and mechanical properties of biomedical Mg–Y–Zn–Mn alloy with LPSO phases by solution treatment plus equal-channel angular pressing

Long-period stacked ordered (LPSO) Mg–Y–Zn alloys have shown great medical prospects. To explore the impact of LPSO phase evolution on mechanical properties, a new biomedical Mg-2.2Y-1.1Zn-0.4Mn (wt.%) alloy prepared by solution treatment plus equal-channel angular pressing (ECAP) was systematically investigated. The results indicate that massive 18R LPSO networks along α-Mg grain boundaries are disintegrated during solution treatment of the as-cast alloy, whereas 14H lamellas are precipitated in α-Mg grains. Following a similar dispersion of 14H precipitated phases, the remnant 18R network phase was gradually extended, broken, and refined throughout the subsequent multi-pass ECAP process. The refined LPSO phases promote dynamic recrystallization (DRX) during the severe deformation process and improve mechanical properties of the obtained fine-grained alloy. After 773K solution treatment for 10h plus 693K ECAP for 12 passes, the biomedical alloy with co-existing 18R and 14H LSPO phases shows excellent mechanical properties with an ultimate tensile strength of 326.6 MPa and elongation of 14.5 percent.