Annealing-induced precipitation strengthening and thermal stability of an ultrafine-grained bioresorbable Zn–Li–Mn–Mg alloy processed by rapid solidification

Biodegradable Zn alloys require improved strength and thermal stability to meet the demands of load-bearing biomedical, bioresorbable implants. In this study, a Zn–0.33Li–0.44Mn–0.45Mg (wt.%) alloy was processed by rapid solidification (RS) followed by high-pressure torsion (HPT), producing a uniform ultrafine-grained matrix (∼140 nm) with a homogeneous dispersion of nanometric Mg₂Zn₁₁ precipitates. These precipitates effectively stabilized grain boundaries and provided precipitation strengthening. Post-deformation annealing up to 300 °C resulted in gradual grain growth without abrupt coarsening, confirming the enhanced thermal stability imparted by Mg₂Zn₁₁. The RS–HPT condition annealed at 250 °C for 15 min achieved an ultimate tensile strength of ∼507 MPa and a yield strength of ∼391 MPa, with a UTS/YS ratio of ∼1.3 and measurable strain hardening. Strain-rate sensitivity remained high in the ultrafine state and decreased only after significant grain growth, consistent with grain boundary-mediated deformation. These results demonstrate that combining RS, HPT, and tailored Mg content provides a controllable processing pathway to thermally stable, high-strength Zn alloys, offering strong potential for bioresorbable load-bearing applications.