Effect of the strain on the deformation behavior of isothermally compressed Ti-6Al-4V alloy

The deformation behavior of isothermally compressed Ti-6Al-4V alloy in the deformation temperature range from 1093 K to 1303 K, the strain rate range from 0.001 s−1 to 10.0 s−1 and the height reduction range from 20% to 60% has been investigated in depth. Effect of the strain on the flow stress, the grain size and the apparent activation energy for deformation of isothermally compressed Ti-6Al-4V alloy is analyzed. The results show that the apparent activation energy for deformation and the grain size of isothermally compressed Ti-6Al-4V alloy in the α + β two-phase region vary slightly with strain: the activation energy increases with strain after an early drop as the primary α grain size varies with strain. On the other hand, the apparent activation energy for deformation of isothermally compressed Ti-6Al-4V alloy in the β single-phase region increases firstly with the increasing of strain and then does that slightly in the strain range from 0.3 to 0.7. A processing map of the isothermally compressed Ti-6Al-4V alloy is constructed at a strain of 0.6. The processing map of isothermally compressed Ti-6Al-4V alloy exhibits that the optimal processing parameters are the deformation temperature of 1143 K and the strain rate of 0.001 s−1. Meanwhile, two instability domains in the processing map of isothermally compressed Ti-6Al-4V alloy are as follows: one is in the deformation temperature range from 1093 K to 1183 K and the strain rate range from 0.011 s−1 to 2.02 s−1, and another is in the deformation temperature range from 1243 K to 1303 K and the strain rate range from 1.0 s−1 to 10.0 s−1.