Promoted phase transformation of a2 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 a2 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 a2 phase, such as dislocations and stacking faults (SFs). After heat treatment at 600 & DEG;C, the phase transformation from a2 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 a2 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. & COPY; 2023 The Authors. Published by Elsevier Ltd. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/).