Correlative investigation of microstructure, localized corrosion behavior and mechanical properties in hot rolled Mg-Zn-Ca-xEr (x = 0.75, 2, 5, 8 wt%) biodegradable alloys for orthopedic applications

Magnesium alloys hold immense potential for biodegradable orthopedic implants, yet their rapid degradation, coarse microstructure, and limited ductility hinder clinical translation. This study investigates a novel Mg–1.5Zn–0.5Ca alloy system modified with varying rare earth Erbium (Er) additions (0.75, 2, 5, 8 wt%) and processed through a sequential route of casting, homogenization, and symmetric hot rolling to simultaneously enhance mechanical performance, corrosion resistance, and cytocompatibility. Comprehensive characterization using SEM, EDS, XRD, and EBSD, revealed that 2 wt% Er produced the most refined microstructure, weakened basal texture and uniform W-phase dispersion. In addition, rolling significantly improved grain morphology and suppressed galvanic intermetallic networks, correlating with superior tensile properties (UTS ≈ 236 MPa, elongation ≈ 29 %) and minimized corrosion activity, as confirmed by electrochemical and immersion analyses. Moreover, SECM technique was introduced that demonstrated the lowest localized electrochemical current in 2 wt% Er alloy in rolled state, indicating stable degradation behavior. In addition cytocompatibility assessment using MC3T3-E1 cells validated cell viability above 70 %, meeting ISO 10,993–5 and USFDA standards. This integrated processing–composition approach establishes the rolled Er alloy as a promising candidate for next-generation biodegradable Mg implants, offering an optimal balance of mechanical integrity, corrosion control, and biological safety.