Elastic moduli of titanium-hydrogen alloys in the temperature range 20 °C to 1100 °C

Abstract: The elastic properties of a series of polycrystalline titanium-hydrogen alloys (containing up to 25 at. pct H) were measured over the temperature range 20 C to 1100 C. The latter limits permitted investigation of adjacent parts of the α+δ, α, and β phase fields. A laser ultrasonic technique was employed to measure the temperature and hydrogen-concentration dependencies of the elastic constants. The room-temperature elastic properties of the alloys depended only slightly on hydrogen concentration, remaining almost independent of the volume fraction of the δ hydride phase. In the α phase field, the addition of hydrogen decreased the shear and Young’s moduli and increased the bulk modulus, Lam constant, and Poisson’s ratio. The Young’s and shear moduli decreased more rapidly with increasing temperature than in cubic phases. By contrast, Poisson’s ratio increased with temperature. In the β phase field, the temperature dependence of the elastic constants was weak. However, alloying with hydrogen increased the shear and Young’s moduli, decreased Poisson’s ratio, but did not appreciably affect the bulk modulus and Lam constant. The different effects of hydrogen on the elastic constants of alpha and beta titanium are interpreted in terms of the influence of dissolved hydrogen on the stability of the hexagonal close-packed (hcp) and body-centered cubic (bcc) lattices in the vicinity of the α-to-β transformation. The present results are also used to help account for the effect of hydrogen concentration on the mechanical properties of Ti-H alloys.