Realizing ultra-high strength and excellent ductility in a low-alloyed biomedical Mg-Zn-Ca-MgO composite

An ultra-fine grained (UFG) Mg-1Zn-0.2Ca-1.0MgO composite with an average grain size of 0.49 µm as well as an excellent combination of yield strength (379 MPa) and ductility (10.1%) was produced by one-step extrusion. Subsequent heat treatment at 200 ℃ for 30 min further improved its yield strength to 420 MPa and elongation to 12.1% with a slight grain growth to 0.76 µm. Microstructure observations revealed that the precipitation of high number density of Ca₂Mg₆Zn₃ phase was the main reason for the enhanced strength after ageing treatment. Grain coarsening and recovery of dislocations during ageing improved the work-hardening capability of the extruded sample, leading to improved ductility. Our work provides a pathway for the mass production of strong and ductile Mg-based materials without excessive addition of alloying elements.