A High-Performance Biodegradable Mg-Zn- Ca-Sn Alloy with Synergistic Improvement of yield strength and corrosion rate achieved by precise control of Extrusion and Microstructural Design.

Abstract

Magnesium alloys are emerging as promising candidates for biomedical applications due to their biodegradability, biocompatibility, and appropriate mechanical properties. However, achieving a balance between high strength and corrosion resistance remains a critical challenge. This study presents the development of a low-alloy Mg-1.2Zn-0.32Ca-0.25Sn (ZXT100) alloy aimed at overcoming the trade-off between high strength and high corrosion resistance. Comprehensive microstructural, mechanical, and electrochemical analyses were performed to elucidate the alloy's performance and underlying mechanisms. The ZXT100 alloy demonstrates the promising tensile yield strength (∼345 ± 13 MPa) and degradation rate (∼0.209 ± 0.012 mm/y), surpassing most commercially available and recently reported medical magnesium alloys. Grain boundary strengthening was found to be the primary mechanism for the improved yield strength, contributing approximately 65.8%. The modification of heterogeneous fiber structure facilitates balance between elasticity and strength. In vitro cytocompatibility and osteogenic differentiation assays confirmed favorable biocompatibility and enhanced cell migration compared to high-purity Mg. In vivo studies in rats and rabbits demonstrated controlled degradation, minimal gas formation, and favorable osteointegration with no systemic toxicity. This work provides a feasible strategy for designing high-performance biodegradable Mg alloys for load-bearing orthopedic implants. STATEMENT OF SIGNIFICANCE: Biodegradable magnesium alloys offer a promising alternative to permanent metallic implants, eliminating the need for secondary removal surgery. However, achieving both high strength and controlled degradation-essential for load-bearing orthopedic applications-remains a major challenge. Building on our previous compositional optimization, this study demonstrates that precise control of extrusion temperature enables microstructural design that simultaneously achieves exceptional yield strength (349  ± 13 MPa) and a low degradation rate (0.209  ± 0.012 mm/y) in a low-alloyed Mg-Zn-Ca-Sn system. The alloy also exhibits favorable biocompatibility in vitro and in vivo, positioning it as a strong candidate for next-generation biodegradable orthopedic implants.