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

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 degreesC for specimens quenched from 1200 degreesC and deformed to 5-similar to 90% in compression or by cold-rolling. beta hydride is formed at a very low hydrogen pressure similarly to bcc hydrogen absorbing alloys. In as-quenched specimens; further absorption to gamma hydride is sluggish and there is no obviously reverse gamma --> beta hydride transformation. Both the beta --> gamma and reverse gamma -->beta 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 beta-gamma hydride transformation. (C) 2001 Acta Materialia Inc. Published by Elsevier Science Ltd. All rights reserved.