Vibration-enhanced hot workability of TiAl alloy induced by the motion of 1/2 < 112] superdislocations

The limited hot workability of TiAl alloys significantly restricts their widespread application. This study presents a cost-effective approach to increase the formability of TiAl alloys through vibration-assisted forming. By applying low-frequency vibration at 1.5 Hz during the vibration-assisted tensile tests (VT), the elongation of the as-cast TiAl alloy increased to 82 %, representing an improvement of nearly 110 % compared to the 39 % achieved in normal tensile tests (NT). Microstructural observations indicate that, under vibration conditions, the primary deformation mechanism of the TiAl alloy shifts from 1/2 < 110] ordinary dislocation glide to 1/2 < 112] superdislocation glide and twinning. Furthermore, 1/2 < 112] superdislocations were observed directly crossing the α₂/γ phase interface. These results revealed that vibration promotes the massive activation of 1/2 < 112] superdislocations and the formation of twins, facilitating the cross-slip of 1/2 < 112] superdislocations and allowing them to overcome external particle pinning. This mechanism allows the alloy to accommodate greater plastic deformation and achieve a greater proportion of recrystallized grains. Our study revealed a novel deformation mechanism in TiAl alloys induced by vibration, offering a new approach to address the challenges associated with the thermoplastic formation of these alloys.