Effect of Phase Distribution on the Antibacterial Property and Cytotoxicity of Ti-5Al-2.5Cu Alloy after Heat Treatment at Various Temperatures

Abstract

Titanium alloys are widely employed for the fabrication of biomedical devices. In this study, we designed and developed a Ti-5Al-2.5Cu alloy, which exhibited antibacterial properties. Microstructure and elemental analyses were performed using X-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDS), and transmission electron microscopy (TEM). We evaluated the alloy’s antibacterial properties using Escherichia coli in the plate-count method. The cytotoxicity was examined using the MG-63 cell response by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide (MTT) and lactate dehydrogenase (LDH) assays. Microstructural analysis revealed that Ti-5Al-2.5Cu exhibited an equiaxed α’ martensite structure after short-term annealing. The heterogeneous and homogeneous α → α + Ti2Cu phase transitions occurred at ~840 and 920 °C, respectively. The antibacterial property for Ti-5Al-2.5Cu was varied by volume fraction in the Ti2Cu and Cu-rich phase, which was obtained using different heat treatments. The high volume fraction of the Ti2Cu and Cu-rich phase was observed after long-term annealing at 720–840 °C and thus exhibited a higher antibacterial rate. The relationship between phase distribution and the antibacterial property could be satisfied by a positive linear regression equation. Cytotoxicity results showed that heat treatments at different temperatures for Ti-5Al-2.5Cu alloys had no effect on cell viability. The optimal heat treatment for Ti-5Al-2.5Cu alloy was annealing at 760 °C for 24 h. After, the alloy exhibited both promising antibacterial performance and good cytocompatibility.

Keywords

• Ti-5Al-2.5Cu alloy
• Ti₂Cu phase
• phase distribution
• antibacterial property
• cytotoxicity