Strength Optimization of Diffusion-Bonded Ti2AlNb Alloy by Post-Heat Treatment

Abstract

Diffusion-bonded Ti₂AlNb-based alloys commonly present a low strength compared with the deformed or aged ones. In this study, the post heat treatment including solution and aging treatments is proposed to optimize the microstructure, contributing to strength improvement and appropriate ductility sacrifice. An available method by the introduction of fine size (both 20–100 nm) and a high fraction (59.7% and 13.7%) of O and α₂ phases using both solution at 1000 °C for 1 h and aging at 750 °C for 5 h can result in excellent tensile strength (992 MPa and 858 MPa) at room temperature and 650 °C, respectively, which increases 5.3% and 44.5% than that of as-received sample. The aging treatment can contribute to lamellar O and α₂ grains precipitated from the B2 parent, which results in limited dislocation slip systems and slip spaces to resist plastic deformation. Moreover, the crack propagation and fracture surfaces are also comparatively analyzed to reveal the fracture behaviors in the samples with high and low strength. This study can provide a new method for the mechanical property optimization of the welded Ti₂AlNb alloys.