反应堆耐压壳体用Ti-5Al-3V-3Zr-0.7Cr合金的热变形行为

The isothermal hot compression experiment of Ti-5Al-3V-3Zr-0.7Cr alloy melted by VAR melting three times was performed by Gleeble-3800 thermo-simulation machine. High-temperature deformation and recrystallization behaviors of the as-cast alloy were studied over a wide range of strain rate (0.001 to 1.0 s^-1) and temperature (750 to 900℃). The results show that the flow curves for the current alloy firstly exhibits sharp peaks at low strain levels revealing pronounced work hardening, and then drops rapidly after peak stress presenting the soft characteristics. The flow stress decreases with decreasing the strain rate or increasing the temperature. Dynamic recrystallization (DRX) is the major softening mechanism. The relationship between the critical strain and the peak strain of DRX is linear. Based on the conventional recrystallized fraction curves, the recrystallized volume fraction grows as an "S" shape with the increasing the deformation temperature and the true strain. Processing maps were established under different deformation conditions, and the optimal condition for hot work on this material was determined to be 750℃/0.001~0.01 s^-1 and 850~900℃/0.01~0.1 s^-1.