Processing and microstructure control of (α2+B2+O) alloy sheet in Ti–Al–Nb system

Abstract Rolling processing and microstructure evolution during rolling and heat treatment for two typical α 2 +B2+O alloys, Ti–24Al–14Nb–3V and Ti–23Al–17Nb (at%), were investigated. The experimental results showed that the alloys have good workability for rolling at temperatures both in the α 2 +B2 and in α 2 +B2+O fields. The thickness reduction up to 99% was obtained for the sheets rolled above 900°C in a quasi-isothermal condition without cracking. A typical duplex microstructure of the α 2 +B2+O phases formed when the sheets were rolled and then solution treated at temperatures in the α 2 +B2 phase field plus aging in the O+B2 field. Such duplex microstructure was proved to have good mechanical properties both in room and elevated temperatures. A microstructure of fine equiaxed α 2 and O phases distributed in B2 matrix was obtained for the sheets rolled and then solution treated at the temperatures in the α 2 +B2+O phase field, which possess excellent room temperature ductility and superplasticity in temperatures of 900∼1000°C. An advanced cold rolling processing plus a proper vacuum heat-treatment used for the production of high-quality foils of Ti–24Al–14Nb–3V (at%) alloy are also reported.