A study on a high-strength and corrosion-resistant extruded Mg-2Sr alloy: mechanochemical coupled experiments and finite-element phase-field simulation

Developing biomedical magnesium (Mg) alloys with synchronized mechanical integrity and controllable degradation is crucial for temporary orthopedic implants. In this study, an extruded Mg-2Sr alloy was prepared, and its mechanical and corrosion resistance performance were characterized. A suture anchor with an outer diameter of 4.5 mm was fabricated, and its torsional resistance, pull-out strength, and stress corrosion resistance were comprehensively evaluated by combining experiments and finite-element (FE) simulations: (1) Attributed to the elongated grain structure and dispersed precipitates induced by the extrusion process, the yield strength and ultimate tensile strength of the Mg-2Sr alloy reach 242.3±11.5 MPa and 296±0.7 MPa, respectively, which are 3.7 times and 1.6 times those of 99.92% pure Mg, respectively; Its hydrogen evolution rate in Hank’s balanced salt solution (HBSS) is 0.35±0.05 mm∙y -1 , demonstrating excellent corrosion resistance. (2) FE simulations show that Mg-2Sr suture anchor possesses excellent torsional stiffness, pull-out stiffness, and strength, ensuring superior initial fixation strength and structural stability within cancellous bone. (3) For long-term physiological service, stress corrosion coupled damage (SCCD) experiment of Mg-2Sr reveal a brittle-ductile combination characteristic. A non-conservative phase-field model, incorporating contributions of hydrostatic stress and cumulative plastic strain to corrosion rate, was implemented to analyze the anchor’s SCCD behavior in HBSS. Simulations indicate that hydrostatic stress dominates the brittle damage path of SCCD, while cumulative plastic strain accelerates anodic dissolution in equivalent stress concentration areas. The Mg-2Sr alloy prepared in this study meets the high requirements of orthopedic implants for stiffness, strength and corrosion resistance.