Improved low-stress thermoplastic forming of TiAl alloys via dislocation behavior under mechanical vibration

Abstract

Despite their lightweight and high-temperature advantages, TiAl alloys have limited thermoplastic forming capacity, which considerably restricts their use in complex structural components for aerospace applications. To improve their thermoplastic forming ability while preserving performance, this study introduced a mechanical vibration-assisted forming technology and independently developed a mechanical vibration tensile test platform. In a vibration-assisted tensile test (VT), a low-frequency vibration of 1.5 Hz was applied, resulting in a peak stress of 194 MPa for the specimen, which was nearly 21% lower than the 242 MPa in the non-vibration-assisted tensile tests (NT). This study demonstrates, for the first time, that mechanical vibration–assisted forming technology can considerably reduce molding stress in TiAl alloys. Subsequent characterization results showed that vibration improved the long-range slip capacity of dislocations and promoted their rearrangement and annihilation, resulting in a substantially improved dynamic recrystallization (DRX) capacity. Furthermore，active dislocation movement and dissociation in the α₂ and γ phases provided nucleation sites for the formation of metastable phase Ti₂Al and promoted twinning, this was accompanied by considerable dislocation consumption. Vibration also promoted the uniform deformation of the α₂ and γ phases and reduced the strain gradients at the phase interfaces, thereby weakening back-stress strengthening to reduce deformation resistance. These findings provide an effective pathway for overcoming the intrinsic brittleness of TiAl alloys and are expected to extend to other hard-to-deform metals, offering transformative potential in precision forming technologies.