Superplastic deformation behaviors of powder-metallurgical Ti–6Al–4V

Powder-metallurgical (PM) Ti–6Al–4V with an average grain size of 22.3 μm was prepared via cold isostatic pressing and vacuum sintering. The superplastic deformation behaviors of PM Ti–6Al–4V in the temperature range of 800–1000 °C and strain rate range of 0.01–0.001 s −1 were investigated in terms of microstructural evolution, kinetics, and superplasticity mechanisms. The dominant microstructural evolution mechanisms of PM Ti–6Al–4V samples at 950 and 1000 °C were continuous dynamic recrystallization (CDRX) and CDRX with a dynamic recovery of β, respectively. The increase in β-coordinated deformation restrained cavitation and promoted superplasticity. The dominant superplastic deformation mechanism of PM Ti–6Al–4V was Rachinger sliding. The dislocation creep in β, with the stress-induced phase transformation of α → β, accommodated the Rachinger sliding at 1000 °C. The intersection of the flow stress is considered to be the transition point of dynamic recrystallization → superplasticity.