Deformation behavior and microstructure evolution of TZM alloy with 1.0 wt%ZrO2 under high temperature compression

Abstract

The hot deformation behavior of TZM-1.0 wt% ZrO2 alloy in the temperature range of 1000–1600 °C and strain rate range of 0.005–1 s−1 was studied by hot compression method. The constitutive equation and hot working diagram were established, and the microstructure evolution was emphatically analyzed by SEM and EBSD. The results indicate that the flow stress decreases with the increase of temperature and the decrease of strain rate, and ZrO2 particles can improve the stability of TZM alloy in rate-control during hot deformation. The constitutive equation accurately predicted the correlation coefficient as high as 0.9685, calculated the average activation energy Q = 426 kJ mol−1, and obtained the best process parameters of 1150 °C–1250 °C /0.01–0.05 s−1 under 0.7 strain. The unstable zone was mainly composed of a small number of coarse grains and a large number of fine grains. The main reason for flow instability was the disharmonious deformation between coarse and fine grains during compression. The optimum hot working zone consists of more uniform equiaxed grains. However, EBSD observed that at a strain rate of 1 s−1, the recrystallization fraction at 1600 °C was lower than 1200 °C, and the dynamic recrystallization (DRX) and texture evolution trends at 1200 °C and 1600 °C were completely different. The abnormal changes in recrystallization fraction and texture evolution at 1600 °C were due to the competition between deformed grain growth and DRX on energy storage consumption, and the effect of deformed grain growth on energy storage consumption was greater than that of DRX. At 1600 °C/1 s−1, the growth of deformed grains was dominant, exhibiting strong texture components in the [001] direction, with〈100〉fibers as the main component and the highest peak texture strength. As the strain rate decreases, DRX dominates and weakens the texture strength, resulting in a significant decrease in<100>fibers.