Enhancement of Antibacterial and Osteogenic Properties in Novel Ti‐Mo‐Hf‐Cu Medium Entropy Alloys

To enhance the success rate and osseointegration of medical implants, it is crucial to develop multifunctional titanium alloys with antibacterial and osteogenic properties. Novel medium entropy alloys (MEAs) are developed by introducing hafnium (Hf) and copper (Cu) into non-equiatomic MEAs (TiMoHfCu_x, x = 0, 5, 10), guided by d-electron alloy design theory and phase diagram calculations. Due to the sluggish diffusion effect in MEAs, nanoscale acicular (Ti, Hf)₂Cu precipitates with a coherent interface are observed in TiMoHfCu₅ and TiMoHfCu₁₀, alongside a β phase. Elastic modulus values decrease by 39, 31, and 20 GPa, respectively, for x = 0, 5, 10, compared to CP-Ti, as Hf mitigates the adverse effects of Cu. TiMoHfCu₅ exhibits superior corrosion resistance and hydrophilicity. With an increase in Cu content to 10 at.%, the MEA demonstrates a 97% antibacterial rate against Escherichia coli, and superior osteogenesis in rat femoral condyles. (Ti, Hf)₂Cu exhibits excellent antibacterial properties. Additionally, antibacterial and osteogenic properties are associated with the micro-area potential difference (MAPD). By modifying the morphology of (Ti, Hf)₂Cu through the combined addition of Hf and Cu, TiMoHfCu₁₀ leads to a combination of desirable mechanical properties, antibacterial characteristics, and osteogenic properties, highlighting its potential for biomedical applications.