In-situ synchrotron high energy X-ray diffraction study on the compressive creep behavior of an extruded Ti-45Al-8Nb-0.2C alloy

Wrought high Nb containing (high Nb-TiAl) alloys are potential materials for low pressure turbine blades in aeroengines. The performance and microstructure evolution under high temperature creep condition is of importance to the service stability of these materials. In this study, the internal strain and FWHM evolution of an extruded TNB-based high Nb-TiAl alloy during compressive creep are characterized by in-situ high energy X-ray diffraction (HEXRD) technique for the first time. The compressive creep test was conducted under a constant load of 300 MPa at 900 degrees C for 10 h in vacuum. The final creep strain is approximately 1.72 %. The microstructure and phase constitution after creep shows little difference from that before creep. Lattice strain analysis shows that gamma phase is plastically deformed while the alpha 2 phase deforms elastically due to the low creep strain. The lattice strain of alpha 2 grains is dependent upon the deformation of surrounding gamma grains. Creep induces dynamic recovery, exerting a softening effect. A high number of dislocations are visible in the gamma lamellae while almost no dislocations exist within the alpha 2 lamellae. alpha 2 lamellae are partially decomposed and refined via the alpha 2-*gamma transformation.