Antimicrobial Titanium–Copper Alloys: The Role of Microstructure in Arc‐Melted Compositions

Copper‐containing alloys have attracted global attention in response to rising rates of orthopedic implant infections and antimicrobial resistance. Two theories have emerged for the antimicrobial mechanisms of titanium–copper alloys: ion release and contact sterilization. While previous studies have focused on the overall effect of intermetallic Ti₂Cu phases, this research digs deeper, unpicking the influence of precipitate size and morphology. Herein, heat treatment (950 °C and 760/820 °C) of cast Ti‐11.5Cu and Ti‐33Cu (wt%) alloys may be used as a tool to tune antimicrobial potency through microstructural refinement. Specifically, it is shown that nanoscale precipitates (≈30 nm) of Ti₂Cu exhibit limited in vitro efficacy against Staphylococcus aureus. While larger (≈5 μm), rounded precipitates exhibit superior action due to increased surface contact. Contrary to the literature, this study shows no detectable Cu²⁺ ion release in 0.9% NaCl over 7 days, measured by inductively coupled plasma optical emission spectroscopy, suggesting that under these manufacturing conditions, the antimicrobial mechanism is solely contact dependent. In vitro studies indicate that while Ti₂Cu phases contribute to antimicrobial properties, a balance in Cu content and precipitate size is critical for both bacterial and native bone cell cytotoxicity. Overall, this study demonstrates a significant link between phase size, morphology, and desirable antimicrobial properties of exploratory cast Ti–Cu alloys.