Formation of Structural-Phase State and Elastic and Durometric Properties of Biocompatible Cold-Rolled Titanium Ti–Nb–Zr-Based Alloys during Aging

Abstract—The methods of scanning electron microscopy, X-ray diffraction analysis, and microindentation are used to study the effect of alloying with zirconium (within 3 to 6 at %) and complex Zr + Sn and Zr + Sn + Ta additions on the evolution of the structure, phase composition, and properties (effective modulus of elasticity, hardness, and wear-resistance parameters) of quenched biocompatible β-titanium (at %) Ti–26% Nb–3% Zr, Ti–26% Nb–5% Zr, Ti–26% Nb–6% Zr, Ti–26% Nb–3% Zr–1% Sn, and Ti–26% Nb–3% Zr–1% Sn–0.7Ta alloys during aging (at 400°C for 4, 16, and 64 h) after multipass cold rolling with a total degree of strain of 85%. As compared to the quenching, the cold rolling of the studied Ti–Nb–Zr alloys is shown to suppress the occurrence of the β → ω transformation in the course of aging and to favor the acceleration of the decomposition of β solid solution with the formation of nonequilibrium α_l phase in the course of aging. The increase in the zirconium content from 3 to 6 at % in the cold-rolled ternary Ti–26% Nb – х% Zr alloys and introduction of complex Zr + Sn and Zr + Sn + Ta additions to the Ti–26% Nb alloy instead of only zirconium addition hinder the decomposition processes of the β phase during aging; this impacts the intensity of variations of the effective modulus of elasticity and microhardness. The aging of the cold-rolled alloys under study was found to allows us to obtain the higher values of the parameters H/E_r and \({{{{H}^{3}}} \mathord{\left/ {\vphantom {{{{H}^{3}}} {E_{{\text{r}}}^{2}}}} \right. \kern-0em} {E_{{\text{r}}}^{2}}}\) (Н is the hardness and E_r is the resolved modulus of elasticity) associated with the wear resistance as compared to those for the widely used medical Ti–6Al–4V alloy. The compositions of the alloys and conditions of their treatment are determined, which allow us to obtain the combination of the highest-level properties.