Elastic properties of as-solidified Ti-Zr binary alloys for biomedical applications

Young's modulus (E), shear modulus (G), bulk modulus (K) and Poisson's ratio (ν) of Ti-Zr binary alloys containing 20, 40, 50, 60, 70 and 80 at% Zr and component pure metals (Ti, Zr) prepared by arc-melting followed by solidification process were determined precisely by ultrasonic sound velocity measurements. X-ray diffraction analysis showed that all the as-solidified alloys and pure metals were with a single-phase structure of the hexagonal close-packed lattice (martensitically formed α'-phase). The alloying addition of Zr to Ti effectively decreased both E and G values with their minimum values of 89.5± 1.0 GPa and 33.3±0.4 GPa, respectively, being recorded at the same composition Ti-60 at% Zr. On the other hand, K values decreased slightly when the concentration of Zr was increased from 20 to nearly 50 at% and further increases in Zr concentration did not change K values greatly. The observed variations of Young's modulus with Zr concentration in the entire range of composition were well interpreted in terms of density (ρ), Debye temperature (θ_D) and concentration of atoms (n) in each alloy. The quantity ρθ_D²n^-2/3 was revealed to be a good measure in predicting the tendency of variations of Young's modulus with composition in this binary system.