Microstructure evolution and dynamic recrystallization mechanism of tantalum-tungsten alloys under hot compression

Ta-W alloys exhibit outstanding comprehensive properties at high temperatures, allowing them to have great application prospects in the high-temperature field. High-temperature compression tests (1573–1873K) were conducted to evaluate the high-temperature mechanical properties of Ta-12W alloy, and the strain-compensated Arrhenius-Type model and hot processing map were developed to predict the optimal processing window. The microstructure evolution and distributions of strain during hot compression were systematically investigated, and the results demonstrated that the flow stress of Ta-12W alloy presented apparent negative temperature sensitivity and positive strain rate sensitivity. Based on the thermal processing diagrams and microstructural analysis, the low deformation temperature and high strain rate would introduce stress concentration and deformation instability in the Ta-12W alloy. The optimized processing temperature and strain rate are predicted as 1800 -1873K,0.001 s^-1-0.05 s^-1, and the microstructure at 1873K, 0.001 s^-1 is more uniform and exhibits a low residual stress level. As the temperature increases, dynamic recovery and dynamic recrystallization cause significant softening effects, and continuous dynamic recrystallization dominates the high-temperature deformation behavior. Moreover, multiple continuous dynamic recrystallizations occur simultaneously, including sub-grain nucleation inside large grains, sub-grain nucleation at grain boundaries, and grain fragmentation accompanied by grain rotation. This study revealed the mechanisms of microstructural evolution during hot deformation of Ta-12W alloy, providing important guidance for optimizing the thermomechanical processing parameters.