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 degrees C with the strain rate range of 0.001-10 s(-1) The stress-strain behavior showed flow softening in alpha+beta phase region, whereas in beta 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 beta phase and alpha+beta 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 degrees 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 alpha+beta phase region the morphology of alpha phase was bent and intended to globularization, and dynamic recrystallization occurred in beta phase region. Based on the stress exponent and microstructure features, dislocation slip controls the creep process of alloy under the conditions of 400 degrees C and all applied stresses. The isothermal omega phase precipitated during creep at 400 degrees C but was not observed at 500 degrees C. The creep process was controlled by dislocation climb under the conditions of 500 degrees C and higher stress. (c) 2014 Elsevier B.V. All rights reserved.