Herein, we present a significant breakthrough in processing TiAl alloys by demonstrating that a large-ratio hot extrusion process alone, without any subsequent heat treatment or surface treatment, can yield an exceptional strength-ductility, superior creep and fatigue resistance. The as-extruded TiAl alloy exhibits remarkably high fatigue strength of 700 MPa at room temperature and 648 MPa at 700°C, with a minimal performance gap between these temperatures indicating outstanding microstructural stability. Contrary to conventional wisdom, the absence of post-processing treatment did not compromise performance; instead, the finely tuned as-extruded microstructure provided superior resistance to thermal–mechanical degradation. The results showed that surface and subsurface crack nucleation failures were identified as two competing mechanisms that influenced the fatigue life of TiAl alloys. When failure was dominated by the subsurface cracks, the TiAl alloys exhibited a significantly longer fatigue life compared to failures initiated by surface cracks. The deformation mechanisms of dislocations and intersecting nanotwins in the γ phase were observed to play crucial roles in the fatigue fracture process. Concurrently, dislocations and antiphase domains within equiaxed α2 grains were found to provide additional deformation capacity. There was a sharp drop in fatigue limit in high-temperature high-cycle fatigue. Transmission electron microscopy analysis revealed that this scatter primarily correlates with the degradation of the α2 laths and the transformation of the ω0 phase, when the critical stress value was exceeded.
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