Antibacterial Ti-35Nb-7Zr-xCu alloy with excellent mechanical properties generated with a spark plasma sintering method for biological applications

Highlights: • Antibacterial Ti-35Nb-7Zr-xCu alloys were successfully prepared using SPS. • The effects of the Cu content on the properties of Ti-Nb-Zr-based alloys were discussed. • The optimal Cu content (10 wt%) for clinical implants was determined. • The antibacterial mechanism of the Ti-Nb-Zr-Cu alloy was revealed. -- Abstract: Given the biomechanical properties (including the elastic modulus and strength) of complex human service environment requirements for implants, Ti alloy-based implants must exhibit excellent mechanical properties and antibacterial self-healing ability. In this paper, the density, microstructure, mechanical properties, and antibacterial properties of Ti-35Nb-7Zr-xCu (x = 4, 7, 10, and 13 wt%) alloys prepared using Spark plasma sintering (SPS) were studied. The results showed that the Ti-35Nb-7Zr-xCu alloys with densities greater than 96% were composed mainly of β-Ti, α-Ti, Nb, Ti₂Cu and Cu_xZr_y phases. The precipitated Cu_xZr_y phases were concentrated mainly near the grain boundaries, and the Ti₂Cu phase exhibited a eutectoid lamellar morphology. With increasing Cu content, the amount of precipitated Cu_xZr_y phase increased, inducing grain refinement. The Ti-35Nb-7Zr-xCu alloys exhibited excellent yield strengths (1061–1469 MPa), with the maximum value corresponding to the alloy containing 10 wt% Cu. In addition, these alloys have elastic moduli (57–79 GPa) that are close to that of human bone. Tests of the antibacterial properties indicated that the antibacterial rate for the Ti-35Nb-7Zr-xCu alloy against E. coli and S. aureus reached 99.99% when the Cu content was greater than or equal to 10 wt%, indicating its excellent antibacterial properties. The Cu ion release capacity indicated that the amount of Cu ions released was correlated with Cu content and immersion time. The Cu ion release rate increased with increasing Cu content but decreased with increasing number of immersion days. Therefore, the Ti-35Nb-7Zr-10Cu alloy prepared by SPS has excellent mechanical properties and antibacterial properties, all of which meet the requirements of human hard tissue replacements.