Abstract:Near-α TA33 alloy has been successfully employed in integrally bladed disks of advanced aeroengines due to its outstanding high-temperature performance and favorable room-temperature fatigue strength. Nevertheless, accurately understanding fatigue crack initiation at the microscale is still a major challenge in engineering, which mainly stems from the inherent sensitivity of the crack initiation process to the microstructure. Therefore, the fatigue life and dwell fatigue sensitivity of TA33 alloys with different microtexture region (MTR) characteristics were systematically investigated. Results show that MTR significantly aggravates dwell-fatigue sensitivity and gives rise to a larger crack initiation area, which is closely associated with dislocation slip and crack transmission within MTR. After removing MTR, the crack initiation zone in the no-MTR alloy is confined to 2~3 grains, and the area of the crack source region is remarkably reduced. Meanwhile, the dispersed grain orientations and multi-site nucleation decrease the dwell-fatigue sensitivity of the alloy to 2.86. These initiation characteristics are closely related to basal slip in the [0001] orientation domain. Crack initiation occurs not only on basal planes of hard grains with low Schmid factor (SF) but also in the high SF range, both exhibiting a pronounced near-basal orientation dependence.