Microstructure and mechanical properties of Mg–9RY–4Cu alloy with long period stacking ordered phase

The microstructure and mechanical properties of Mg–9RY (RY: Y-rich misch metal)–4Cu (wt%) alloys have been investigated. In as-cast state, the LPSO phase presents lamellar structure at grain boundaries or in the interdendritic regions and fine lamellae in Mg grains. After hot extrusion, the LPSO phase presents bent long-strip-shape distributed along the extrusion direction. The as-cast and as-extruded alloys exhibit excellent compression properties and strong work hardening responses. The high mechanical properties of as-cast alloy are mainly attributed to the hard LPSO skeleton and high-density LPSO lamellae. In as-extruded state, besides the hard LPSO phase itself serve as a strengthening phase, multiple strengthen mechanism contributes to the high mechanical properties, including the well aligned long-strip-shape morphology of LPSO phase, kinked LPSO phase and fine dynamic recrystallized (DRX) grains with fine lamellae phase. The kinking of the LPSO phase during plastic deformation is beneficial to the obvious work hardening for both as-cast and as-extruded alloys.