Effects of cold-rolling on the hydrogen absorption/desorption behaviour of Ti–22Al–27Nb alloys

Abstract

B2 single-phase alloys with a composition of Ti–22Al–27Nb (at.%) were deformed by compression or rolling to 5, 10.5 and 80% reduction in thickness at room temperature and the effects of deformation on their hydrogen absorption/desorption behaviour were investigated. P–C isotherm measurements were made at 50 and 100 °C. Similar to bcc hydrogen absorbing alloys, Ti–22Al–27Nb alloys with the B2 structure form β (bcc) hydride at a very low hydrogen pressure. However, the β hydride in undeformed specimens does not easily transform to γ (bct) hydride. In contrast, the β hydride in mildly deformed specimens transforms to the γ hydride with increasing hydrogen concentration and the γ hydride transforms back to the β hydride with decreasing hydrogen pressure. Heavy deformation does not show such beneficial effects. The strain field around dislocation is believed to be a kind of assistance to β–γ hydride transformation.