Thermally activated flow of beta-titanium and beta-titanium-hydrogen alloys

The hardening of beta -titanium due to the presence of hydrogen in solid so lution was investigated. The steady-state flow of a series of beta -Ti-H al loys containing up to 31at.% of dissolved hydrogen was analysed using the t heory of thermally activated glide. This approach permitted the stress and temperature dependences of the strain rate to be separated into that part r elating to the preexponential Factor and that to the Gibbs free energy. At a given flow stress, the pre-exponential factor decreased and the Gibbs fre e energy increased when the hydrogen concentration was increased owing to t he strengthening effect of hydrogen on the elastic moduli. It is concluded that the steady-state flow of beta -Ti-H alloys is controlled by a single t hermally activated mechanism and that the observed hydrogen-induced hardeni ng is largely caused by the stiffening effect of hydrogen on the shear modu lus.