Superplastic deformation behavior of ultra-fine-grained Ti-1V-4Al-3Mo alloy: constitutive modeling and processing map

This paper studies the superplasticity of conventional sheets of Ti-1V-4Al-3Mo (α+β) alloy. The flow behavior was investigated in a temperature range of 775 °C–900 °C and a constant strain rate range of 2×10⁻⁴–5×10⁻³ s−1 via uniaxial tensile tests. The microstructure evolution during the superplastic deformation was analyzed. The results revealed that, the flow behavior of Ti-1V-4Al- 3Mo (α+β) alloy is characterized by strain softening phenomena. The experimental stress-strain data were used to build a power law constitutive model. A processing map, which shows the safe and unsafe regions of deformation, was also constructed for the studied alloy. The optimal deformation regime was attained at a temperature of 875 °C and strain rate of 1×10⁻³ s⁻¹ which provided a β phase fraction of 52%. Equiaxed fine-grained α and β structure with size of 2–3 μm as well as dislocation activity inside the α-grains were identified in the optimum deformation regime.