Mechanism of significant plasticity improvement via dual assistance with electric current and hydrogen in the Ti-22Al-25Nb alloy

This study proposes a dual-assisted forming method using electric current and hydrogen to address the challenges of poor plasticity and high deformation temperatures induced by brittle cracking in the Ti-22Al-25Nb alloy. The optimal parameters for this novel technology were identified as a current density of 7.5 A/mm² and hydrogen content of 0.1 wt.%. These conditions enabled a reduction in the forming temperature to 750 °C. At this temperature, the ultimate tensile stress decreased by 51.4%, reaching 518 MPa, whereas the elongation reached 32.4%. This significant improvement in plasticity is attributed to two primary mechanisms. First, the decomposition of the O phase during deformation generated fine O-phase particles on the nanometer scale, dispersed within the B2/β phase. This dispersion inhibited the deformation-induced cracking in the O phase and facilitated the activation of a significant amount of (001)_O-basal slip. Second, a fully dynamic recrystallized (DRX) microstructure developed in the necking region.