Promoted phase transformation of α₂ to O in Ti₂AlNb alloy with improved mechanical performance via laser shock peening

Phase transformation and microstructure change are important ways for the mechanical property improvement of Ti₂AlNb alloys, such as ductility, tensile strength, and fracture toughness. However, the brittle α₂ phase is stable, and phase transformation is difficult to be introduced at a lower temperature. This seriously affects the mechanical properties of Ti₂AlNb alloy. Here, we propose a new method to promote phase transformation in Ti₂AlNb alloy by deformation-induced defects through laser shock peening (LSP). The results show that after LSP, high-density defects were observed in the α₂ phase, such as dislocations and stacking faults (SFs). After heat treatment at 600 ℃, the phase transformation from α₂ phase to O phase was observed in the Ti₂AlNb alloy treated by LSP, forming twinned and chessboard-like morphologies with nanoscale grain size. High-density defects induced by LSP reduced the thermodynamic barrier of phase transformation from α₂ phase to O phase. LSP promoted the lattice distortion and Nb element diffusion in Ti₂AlNb alloy at high temperatures. This work provides a new method to promote phase transformation in Ti₂AlNb alloy, which may be used to improve other materials' mechanical properties.