Hydrogen absorption and desorption in a B2 single-phase Ti–22Al–27Nb alloy before and after deformation

Abstract

The effects of deformation on the hydrogen absorption/desorption behavior of a B2 single-phase Ti–22Al–27Nb (at.%) alloy were investigated mainly by measuring the static pressure–composition ( P– C) isotherms from room temperature to 100°C for specimens quenched from 1200°C and deformed to 5–∼90% in compression or by cold-rolling. β hydride is formed at a very low hydrogen pressure similarly to bcc hydrogen absorbing alloys. In as-quenched specimens, further absorption to γ hydride is sluggish and there is no obviously reverse γ→β hydride transformation. Both the β→γ and reverse γ→β hydride transformations are promoted by deformation. The best hydrogen absorption/desorption properties are attained in specimens deformed to 5–10%, the deformation structure of which consists of well-aligned and uniformly distributed <111> screw dislocations. The beneficial effects of deformation on the hydrogen absorption/desorption behavior of the alloy are interpreted in terms of similarities between atomic displacements around straight screw dislocations and those taking place during the β–γ hydride transformation.