Thermal Stability and Lattice Strain Evolution of High‐Nb‐Containing TiAl Alloy under Low‐Cycle‐Fatigue Loading

Abstract

The micromechanical behavior and the effect of temperature on the micromechanical mechanism of high‐Nb‐containing TiAl alloy during low‐cycle fatigue still remain uncertain. Herein, in situ and ex situ synchrotron‐based high‐energy X‐ray (HEXRD) experiment results reveal that the γ and ωo phases suffer compressive lattice strains but the lattice strain in the α2 phase evolves from tensile to compressive during low‐cycle fatigue at 900 °C. In addition, the three phases suffer compressive lattice strains during cooling to room temperature, which could result in larger compressive lattice strains in γ and ωo phases and the change of the lattice strain state in the α2 phase. The peak‐broadening results show γ recrystallization is dominant in the interrupted low‐cycle‐fatigue samples, whereas inhomogeneous deformation occurs in the failed low‐cycle‐fatigue samples. The performed synchrotron diffraction experiments offer a deeper insight into the phase transformations and micromechanism of TiAl alloy during low‐cycle fatigue.