Mechanisms of tensile strengthening and oxygen solid solution in single β-phase Ti-35 at.%Ta+O alloys

Single β phase titanium alloys are used for fabricating biomedical devices, and it is desirable to improve the strength of these alloys. In this study, the tensile strength of Ti-35 at.% Ta alloys with a single β phase was improved using oxygen solid solution and the strengthening mechanism was also investigated. The lattice constants of these alloys calculated from X-ray diffraction data increased with an increase in the oxygen content. This result suggests that oxygen atoms formed solutes in the alloys, which was supported by results obtained from first-principles calculations. Microstructural analyses of the alloys indicate that Ti, Ta, and O were homogeneously distributed. Tensile tests were conducted for the alloys, and the 0.2%YS increased with the increase in the O content of the alloy. The increments of 0.2%YS which was determined experimentally correspond well with the theoretically determined trend, and this observation is a result of the effect of the change in grain size and O solid solution. The contribution of the grain refinement was negligibly small compared with that of the O solid solution, and the latter is the major reason for the observed increase in the 0.2%YS of the Ti-35 at.% Ta alloys.