Effect of rotary forging on the gradient microstructure and mechanical properties of a biodegradable Mg-0.2Ca-0.2Ce-4Y alloy

Magnesium alloys are promising biodegradable materials for load-bearing implants, yet their clinical application is hindered by insufficient yield strength. In this study, high-strength Mg-0.2Ca-0.2Ce-4Y alloy bars were fabricated via rotary forging. A pronounced radial gradient microstructure was developed, characterized by refined grains, dense dislocations, and heterogeneous distribution of precipitates, which was attributed to the strain gradient during processing. Consequently, the ultimate tensile strength increased from 188 MPa in the as-cast state to 240 MPa at the center and 298 MPa at the periphery of the forged bar, accompanied by a hardness increase of 15–20 HV. Microstructural analysis revealed that {10-12} tensile twins dominated the deformation structure. Extensive cross-twinning in the late forging stage promoted further grain subdivision and intensified work hardening.