Effect of prior processing on the decomposition of the β phase in Ti–Nb alloys during intermediate heat treatments

Abstract

Metastable β-Ti alloys exhibit multiple decomposition pathways during isothermal ageing. Ages at intermediate temperatures below the α/β transus result in the formation of α or isothermal ω. The effect of prior processing on these pathways remains largely unexplored within the literature. Therefore, the role of processing on a Ti–Nb alloy was investigated in cold rolled and solutioned conditions. The solutioned sample showed evidence of recrystallisation, with shear bands remnant from the prior cold rolling that exhibited a greater degree of texture than the surrounding material. During isothermal ageing ωiso was observed outside of these bands whilst α phase precipitated within the bands and throughout the cold rolled sample. This shows that the remnant strain from the rolling process facilitated α nucleation over ωiso due to accommodation of the α/β interface. Additionally, it was seen that the magnitude of internal strains had a marked effect on the α morphology observed.