Effect of hydrogen on thermal deformation behavior and microstructure evolution of MoNbHfZrTi refractory high-entropy alloy

The study examined the thermal-deformation behavior of an MoNbHfZrTi refractory high-entropy alloy (RHEA), which were hydrogenated using a liquid hydrogenation method and then subjected to high-temperature uniaxial compression in the deformation temperature range of 1100-1250 degrees C and strain rate range of 0.5-10- 3 s-1. Test results showed that: (1) When the deformation temperature was between 1100 and 1250 degrees C, hydrogen addition led to increased high-temperature peak stress of the alloy at higher strain rates of 0.5 and 10-1 s- 1. At a low strain rate of -10-2 s- 1, the addition of hydrogen causes a decrease in the high-temperature peak stress. However, at a lower strain rate of -10-3 s-1, hydrogen addition has insignificant effects on the high-temperature peak stress. (2) At a higher strain rate of -0.5 s-1, the major reasons for hydrogen-induced hardening of the peak stress were solution strengthening and dislocation pinning. (3) At a low strain rate of 10-2 s- 1, the reason for decrease of the peak stress was that the hydrogen addition promoted the formation of precipitated phases, thereby facilitating dynamic recrystallization (DRX), and making the microstructure more uniform at high temperatures.