Characterization of hot deformation behavior of Ti–3Al–5Mo–4.5V alloy with a martensitic starting microstructure

The hot deformation behavior of Ti–3Al–5Mo–4.5V alloy with an α′′ martensitic microstructure was studied in the temperature range of 700–1000∘C and strain rates range of 0.001–1s−1 up to a height reduction of 50%. The results show that an ultrafine equiaxed microstructure with an average grain size of 0.45μm were successfully produced through thermomechanical processing of a martensitic starting microstructure. A processing map was successfully constructed and provides appropriate processing parameters for hot deformation which are located in the temperature range of 700–800∘C and the low strain rate range of 0.001–0.01s−1. The instability domain mainly occurs at the strain rate higher than 0.05s−1 for the whole deformation temperature, which should be avoided during practice. The flow softening mechanism of the alloy is determined to be continuous dynamic recrystallization and the unstable flow is caused by the macro-fracture and flow localization.