Studying the effect of composition on the in vitro wear behavior and elastic modulus of titanium-niobium-based alloys for biomedical implants

Abstract

The fabrication of titanium-based biocompatible alloys with good wear resistance and a low elastic modulus remains a challenge for researchers. In the present study, titanium niobium alloys with compositions of Ti-35Nb-4Sn, Ti-29Nb-13Ta-7Zr and Ti-24Nb-4Zr-8Sn were fabricated using vacuum arc re-melting. The alloys were solution-annealed, then their microstructure was characterized using field emission scanning electron microscopy, their hardness determined by microhardness measurements, their phase determined using x-ray diffraction analysis and their elastic modulus determined by nano-hardness measurements. Subsequently, the wear resistance of the samples was determined by in vitro testing with a pin-on-disc wear-testing machine using 500 g, 1000 g and 1500 g loads in Ringer's solution. The results reveal an increase in the wear resistance of the alloys by one order of magnitude as compared to conventional Ti-based alloys. The improvement in wear resistance is due to (a) the synergistic effect of the volume fraction ratio of the β versus α phases, (b) the variation in the composition and hardness of the individual α and β phases and (c) the variation in the size, morphology and distribution of the α and β phases for each of the alloys. The elastic modulus of the fabricated alloys was much lower than conventionally used alloys and matched well with the modulus of human bone.