Enhancing the Hardness–Corrosion Balance in Lean Mg–Ca Alloys via Post-Extrusion Thermomechanical Processing

Lean magnesium–calcium (Mg–Ca) alloys are promising for biodegradable orthopedic implants because their limited alloying content suppresses corrosion while maintaining biocompatibility. The key challenge is achieving high strength without sacrificing corrosion resistance. Conventional extrusion at elevated temperatures prevents cracking but delivers only modest grain refinement. With the minimal precipitation hardening available from dilute Ca additions, the resulting mechanical performance remains inadequate. To overcome this, we systematically investigate post-extrusion thermomechanical processing routes, including equal channel angular pressing (ECAP), rolling, and heat treatments, to optimize microstructure, hardness, and degradation response. Among the pathways explored, extrusion followed by ECAP, rolling, and annealing offers the most effective balance of hardness and corrosion resistance. These results demonstrate that process design can overcome the limited strengthening capacity of lean Mg–Ca alloys and advance their viability as next-generation biodegradable implant materials.