Thermally activated flow of β-titanium and β-titaniumhydrogen alloys

Abstract

The hardening of β-titanium due to the presence of hydrogen in solid solution was investigated. The steady-state flow of a series of β-Ti–H alloys containing up to 31 at.% of dissolved hydrogen was analysed using the theory of thermally activated glide. This approach permitted the stress and temperature dependences of the strain rate to be separated into that part relating to the pre-exponential factor and that to the Gibbs free energy. At a given flow stress, the pre-exponential factor decreased and the Gibbs free energy increased when the hydrogen concentration was increased owing to the strengthening effect of hydrogen on the elastic moduli. It is concluded that the steady-state flow of β-Ti–H alloys is controlled by a single thermally activated mechanism and that the observed hydrogen-induced hardening is largely caused by the stiffening effect of hydrogen on the shear modulus.