Effect of laser shock peening on the thermomechanically processed ZRE10 novel Mg alloy: Tailoring the biodegradable orthopedic implant material's behaviour

Third-generation biodegradable magnesium (Mg) alloys are emerging as promising candidates for orthopedic implants. However, challenges persist regarding their mechanical integrity and bio-corrosion behaviour. Thus, there is a need to develop suitable processing techniques to address these challenges. The combined effect of thermomechanical processing followed by laser shock peening (LSP) surface treatment on a novel Mg-1Zn-0.5Sc (ZRE10) alloy exhibited improved mechanical integrity and bio-corrosion resistance. During thermomechanical processing at 250°C and 350°C, the microstructure and texture evolution of the hot extruded (350°C) alloy (E350) exhibited complete dynamic recrystallization, resulting in better grain refinement with even dispersion of ScZn second-phase particles. Moreover, texture evolved to strong basal plane orientation, influencing an increased strength of 142 MPa, reduced ductility of 10%, and improved corrosion resistance. Further processing through LSP on this extruded alloy (ELSP-3P) surface leads to further recrystallizations owing to the effect of developed compressive residual stress near the peened surface, resulting in large grain formation. Also, favourable texture evolution of basal and non-basal planes due to this LSP-induced plastic strain with significant improvement in strength and ductility to 230 MPa and 16%, respectively. Biocompatibility analysis shows that both E350 and ELSP-3P possess a uniform bio-friendly hydroxyapatite layer and exhibit good cell viability after 72 h of incubation. In-vitro studies have demonstrated that LSP-treated extruded ZRE10 Mg alloy exhibits improved strength, a controlled degradation rate, and excellent cytocompatibility, making it a promising candidate material for orthopaedic implants, and can be harmonized with tissue regeneration and gradual degradation of the implant within the body.