Microwave sintered multifunctional Fe–30Mn–xCu biomedical alloys: microstructure, mechanical properties, MRI compatibility, biodegradation, antibacterial activity, cytocompatibility, and osteogenic differentiation

Abstract

Fe–Mn–Cu alloys show promise for temporary bone implants due to Fe's biodegradability, Mn's enhanced antiferromagnetism, and Cu's antibacterial properties. Microwave sintering is a prevalent metal processing technique, offering unique volumetric heating that can enhance physicomechanical properties. However, its application to Fe–Mn–Cu alloys remains underexplored. This work systematically investigates physicomechanical and biological properties of microwave sintered Fe–30Mn–xCu alloys (x = 0, 1, 4, 8). Cu content played a crucial role in performance. Incorporation of Cu stabilizes the γ-austenite phase, homogenizes the microstructure with increasing Cu content, and induces precipitation of excess Cu. Yield strength and Vickers hardness initially decrease and then increase with Cu content, reaching minima at 3 wt% Cu. Notably, the alloys exhibit excellent ductility, with elastic moduli approaching that of human bone. Biodegradation rates exceed those of compositionally equivalent alloys prepared via conventional sintering or casting, peaking at 4 wt% Cu. The hysteresis loop area decreases with Cu content; ≥4 wt% Cu exhibit narrow loops and low magnetic susceptibility, satisfying Class I MRI compatibility requirements. ≥4 wt% Cu achieve >99% antibacterial efficacy against E. coli and S. aureus. The alloys also demonstrate good cytocompatibility and osteogenic differentiation of MC3T3-E1 cells. This study advances the design of structure–performance–function–integrated multifunctional Fe–Mn–Cu alloys for biomedical applications.