Microstructure Regulation and Strength–Ductility Enhancement of Zn-0.5Mn-0.2Mg Alloy via Equal-Channel Angular Pressing

Zn-Mn-based alloys represent promising material candidates for biodegradable orthopedic implants. Nevertheless, their real-world clinical deployment is severely hampered by unsatisfactory mechanical properties. In this research, a Zn-0.5Mn-0.2Mg (wt.%) alloy was subjected to equal-channel angular pressing (ECAP) with 4, 8 and 12 passes, to systematically explore the influence of ECAP on microstructural evolution and tensile properties. Grain refinement proceeds gradually with additional ECAP passes. The average grain size declines from 1.94 μm (4 passes) to 1.09 μm (8 passes) and further decreases to 0.78 μm (12 passes). While the tilted basal texture remains strong and stable (approximately 15.1–15.2 multiples of uniform distribution, MUD) after 4 and 8 passes, a dramatic drop in texture intensity to 6.7 MUD is detected for the 12-pass sample. Yield strength (YS) and ultimate tensile strength (UTS) increase monotonically with pass number from 279 MPa and 311 MPa (4 passes) to 287 MPa and 323 MPa (8 passes), and further to 298 MPa and 348 MPa (12 passes). Grain boundary strengthening serves as the dominant strengthening mechanism, and dislocation hardening provides supplementary strength contributions. Elongation (EL) also shows a pronounced improvement, increasing from 12% (4 passes) and 17% (8 passes) to a high value of 41% (12 passes). The excellent ductility achieved after 12 passes stems from the combined effects of significant texture weakening and refined second-phase particles. Benefiting from the excellent strength and superior ductility, the 12-pass alloy satisfies the mechanical benchmark for load-bearing orthopedic implantation.