Effects of Crystallographic Texture on Subsurface Fatigue Crack Generation in Ti–Fe–O Alloy at Low Temperature

Subsurface microcracks developed in a groove-rolled and cold-swaged Ti–Fe–O alloy were characterized to clarify the generation of subsurface fatigue crack. In addition, the effects of crystallographic texture on subsurface crack initiation and growth were discussed. A considerable number of microcracks were detected in the β grains, α grains, and at the α-β interface. The microcracks in the β grains grew negligibly into the neighboring α grains along the basal plane. This was because these grains were oriented with their c-axis almost perpendicular to the loading axis. The {1010}α fiber texture prevents the formation of basal facet and its growth on the basal plane. The stress concentration around the microcrack in the β grains could assist the growth of the microcrack into neighboring α grains along the prismatic plane (which is inclined to the loading axis at a suitable angle) or occasionally at a {1010}α twist boundary. The {1010}α fiber texture assisted microcrack growth, and thereby, formed aligned facets and yield longer microcrack length. The combination of the shear stress and opening stress on {1010}α results in a Mode II or III microcrack and causes microcrack growth on the prismatic plane in the neighboring grain.