High strain rate superplasticity in ultrafine-grained Ti-4.5Al–3V–2Mo–2Fe alloy

High strain rate superplasticity (≥1 × 10 −2 s −1 ) has been widely reported in low-melting-point materials such as aluminum and magnesium alloys, but remains underdeveloped in high-melting-point materials, particularly titanium alloys. This work developed an ultrafine-grained Ti-4.5Al–3V–2Mo–2Fe alloy with a micro-network β phase by double side-friction stir processing and the alloy achieved excellent high strain rate superplasticity. Especially at 700 °C and 9 × 10 −2 s −1 , the superplastic elongation reached 3800 %, which due to the micro-network β phase pinned the ultrafine-grained α grains, facilitating the dislocation slip-coordinated grain boundary sliding process. This work offered great application potential in high strain rate superplastic forming for the alloy.