Breakthrough and Challenges for Biodegradable Zn Alloys: Grain Coarsening as a Strategy for Superior Strength and Creep Resistance

• • Coarse-grained Zn-0.2Mg (47 μm) exhibits higher yield strength than fine-grained (11 μm) counterparts, contradicting the Hall-Petch relationship; this enables compressive yield strengths exceeding 400 MPa in multi-component alloys (Zn-0.2Mg-0.1Cu-0.2Mn) with grain sizes of 10–50 μm, directly addressing the strength ceiling that limits Mg alloys in medium-load-bearing implants. • • Zn-Mn alloys demonstrate 143% room-temperature elongation via surface-roughness-induced plasticity, providing a ductility benchmark that mitigates the brittle fracture risk associated with fine-grained Zn alloys under physiological loading. • • In vivo degradation rates of Zn-based devices match tissue healing periods: 3–6 months for vascular healing and 2–3 months for bone healing, as validated by a 6-week in vivo study, ensuring implant integrity during critical healing phases without premature loss of mechanical support. • • Fine-grained Zn alloys exhibit reduced creep resistance at body temperature (approximately 0.45 homologous temperature), whereas coarse-grained variants show significantly improved creep resistance, extending implant durability under sustained physiological loads.