Study on high-temperature deformation mechanical behavior and dynamic recrystallization kinetics model of Ti-47.5Al-2.5V-1.0Cr-0.2Zr alloy

Abstract

The high-temperature deformation mechanical behavior and dynamic recrystallization(DRX) kinetics model of Ti-47.5Al-2.5 V-1.0Cr-0.2Zr alloy were studied by thermal compression tests on a Gleeble thermal simulator. The influences of deformation heat and friction on rheologic stress were calculated and corrected. The results show that the rheologic stress corrected by friction is less than the experimental stress value. This shows that the existence of interface friction has a negative effect on stress. The influence of deformation heat on the stress is significant at lower temperatures and higher strain rates. The stress-strain curve shows the peak stress at low strain, and then descends with increasing of strain. Based on the curve of the work hardening rate versus stress (dσ⁄dε versus σ) the characteristic strain of the alloy was determined, containing the critical strain of DRX and peak strain, and the expression between the critical stress of DRX, the peak stress and the Z parameters was established. To describe the variation law of the DRX volume fraction, DRX kinetics were examined. The Avrami index values of the alloy were all less than 2 within the parameters of this experiment. The smaller Avrami index of this alloy indicates that the recrystallization rate is lower than that of ordinary alloy. The fraction of DRX rises with increasing of strain. That is, the higher the thermal deformation strain is, the higher the external input energy and the greater the degree of DRX. At the same strain rate, the peak value of the DRX growth rate increases with the increasing of temperature, which reflects the effect of the thermal activation energy on the DRX dynamics.