High temperature deformation and creep behavior of Ti-5Al-5Mo-5V-1Fe-1Cr alloy

The hot compression testing of Ti-5Al-5Mo-5V-1Fe-1Cr alloy was performed by a thermal simulation machine Gleeble 1500 in the temperature range of 700-950 °C with the strain rate range of 0.001-10 s−1. The stress-strain behavior showed flow softening in α+β phase region, whereas in β phase region temperature range and strain rate higher than 0.1 s−1, discontinuous yield behavior was also observed. The average activation energy is about 137 kJ/mol and 288 kJ/mol in β phase and α+β phase region, respectively. The alloy exhibits flow instability under the deformation conditions of strain rates about 0.01 s−1 and temperature range 700-810 °C, which should be avoided during hot working. In addition, the instability area enlarged in processing map with the increasing of true strain. In the α+β phase region the morphology of α phase was bent and intended to globularization, and dynamic recrystallization occurred in β phase region. Based on the stress exponent and microstructure features, dislocation slip controls the creep process of alloy under the conditions of 400 °C and all applied stresses. The isothermal ω phase precipitated during creep at 400 °C but was not observed at 500 °C. The creep process was controlled by dislocation climb under the conditions of 500 °C and higher stress.