Selective laser melted Fe-30Mn-6Cu alloy: A multifunctional candidate for orthopedic implants with MRI compatibility, biodegradation, antibacterial efficacy, and biocompatibility

Orthopedic applications for biodegradable Fe-Mn-Cu alloys are currently not well-defined, necessitating comprehensive studies on their mechanical strength, wear resistance, MRI compatibility, biodegradation rate, antibacterial efficacy, cytocompatibility, and osteogenic differentiation potential. This work systematically addressed these gaps by integrating microstructural characterization, mechanical testing, and biological evaluations of Fe-30Mn-6Cu alloy fabricated via selective laser melting (SLM). For comparison, Cu-free Fe-30Mn was fabricated via SLM under the same conditions. The incorporation of 6 wt.% Cu to Fe-30Mn stabilized the γ-austenite phase, enhanced yield strength, improved wear resistance, accelerated electrochemical biodegradation rate, and imparted excellent antibacterial activity. The SLMed Fe-30Mn-6Cu (i) consisted of a complete γ-austenite phase microstructure with fine equiaxed grains (~7 μm) containing Cu-enriched intergranular second-phase particles; (ii) had a yield strength of ~230 MPa reflecting a ~24% increase, an improved tribological performance, a smaller hysteresis loop area indicating very low saturation magnetization and magnetic susceptibility, and a biodegradation rate three times higher compared to the SLMed Fe-30Mn; and (iii) presented a bacteriostatic rate over 99% against E. coli and S. aureus, as well as excellent cytocompatibility and osteogenic differentiation capability of MC3T3-E1 cells. This work provides insights into the structure-performance-function integrated multifunctional Fe-Mn-Cu alloys for orthopedic applications.