Novel low modulus beta-type Ti–Nb alloys by gallium and copper minor additions for antibacterial implant applications

Abstract

This study aims to develop novel low-modulus, corrosion-resistant Ti-based alloys with enhanced antimicrobial properties for bone-related implant applications. Novel β-type (Ti–45Nb)-based alloys with minor additions of the antibacterial elements Ga and/or Cu (up to 4 wt.%) were produced by a two-step casting process followed by homogenization treatment. Three nominal compositions (Ti–45Nb)96-4 Ga, (Ti–45Nb)96–4Cu and (Ti–45Nb)96-2 Ga–2Cu (wt.%) were prepared based on alloy design approach using [Mo]eq and electron per atom (e/a) ratio. The influence of Ga and/or Cu addition on the phase constitution, mechanical response and corrosion characteristics in simulated body fluids (PBS, 37.5 °C) has been investigated. X-ray diffraction studies displayed a single β phase structure for all alloys, with an observed lattice contraction evidenced by the reduction of lattice parameters during Rietveld analysis. Homogenous equiaxed microstructures with grain sizes ranging from 55 μm up to 323 μm were observed for (Ti–45Nb)96-4 Ga, (Ti–45Nb)96-2 Ga–2Cu and (Ti–45Nb)96–4Cu alloys. The alloys displayed excellent plasticity with no cracking, or fracturing during compression tests. Their tensile strength, Young's modulus, maximum tensile strain and elastic energy were measured in the ranges of 544–681 MPa, 73–78 GPa, 17–28% and 2.5–3.7 MJ/m3, in the order (Ti–45Nb)96-4 Ga > (Ti–45Nb)96-2 Ga–2Cu > (Ti–45Nb)96–4Cu. In addition, it has been observed that micro-alloying Ti–Nb alloy with Ga and/or Cu posed no deleterious effect on the corrosion resistance in simulated body fluid conditions. The improvement in strength of the developed alloys has been discussed based on grain boundary and solid-solution strengthening, whereas the improved plasticity is attributed to work hardening.