Constitutive modeling and the effects of strain-rate and temperature on the formability of Ti–6Al–4V alloy sheet

• The constitutive model considering strain-rate and temperature is established.
• The forming limit prediction model with strain-rate and temperature is established.
• The limit strain of Ti–6Al–4V alloy decreases with strain-rate increasing.
• The limit strain of Ti–6Al–4V alloy increases with temperature increasing.
• The forming limit prediction model is accurate at the right side of FLD.

The constitutive model considering the strain-rate and temperature effects was presented by fitting the true stress–strain curves of Ti–6Al–4V alloy over a wide range of strain-rates (0.0005–0.05 s−1) and temperatures (923–1023 K). The Forming Limit Curve (FLC) of Ti–6Al–4V alloy at 973 K was measured by conducting the hemispherical dome test with specimens of different widths. The forming limit prediction model of Ti–6Al–4V alloy, which takes strain-rate and temperature sensitivity into account, was predicted based on Marciniak and Kuczynski (M–K) theory along with Von Mises yield criterion. The comparison shows that the limit strain decreases with temperature lowering but strain-rate increasing. The comparison between theoretical analysis and experiment of FLC verifies the accuracy and reliability of the proposed methodology, which considers the strain-rate and temperature effects, to predict limit strains in the positive minor strain region of Forming Limit Diagram (FLD).