Effect of 0.2% H on high temperature tensile deformation behavior of Ti₂AlNb based alloy plate

In order to understand the effect of thermo hydrogen treatment (THT) on high temperature tensile behavior of a Ti₂AlNb based alloy plate, high temperature tensile tests of Ti-22Al-25Nb alloy plates without and with 0.2%H (mass fraction) charging were conducted with strain rate of 2.5×10^-2 s^-1 at 870, 900, 930 and 990°C respectively. It was found that 0.2%H charging could reduce the high temperature flow stress and enhance the tensile elongation. When deformed at 930°C, the peak stress of the hydrogen charged Ti-22Al-25Nb alloy decreased by approximately 36%, and the elongation increased by approximately 53% in comparison with the bare alloy. Hydrogen-induced softening and plasticity might mainly be attributed to the hydrogen promoted the dynamic recrystallization of α₂ phase, the dislocation movement and the dynamic recovery of β/B2 phase as well as increased the amount of β/B2 phase.