Effects of crystallographic texture on subsurface fatigue crack generation in Ti-Fe-O alloy at low temperature

Abstract

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 beta grains, alpha grains, and at the alpha-beta interface. The microcracks in the beta grains grew negligibly into the neighboring alpha grains along the basal plane. This was because these grains were oriented with their c-axis almost perpendicular to the loading axis. The {10 (1) over bar0}(alpha) fiber texture prevents the formation of basal facet and its growth on the basal plane. The stress concentration around the microcrack in the beta grains could assist the growth of the microcrack into neighboring alpha grains along the prismatic plane (which is inclined to the loading axis at a suitable angle) or occasionally at a {10 (1) over bar0}(alpha) twist boundary. The {10 (1) over bar0}(alpha) 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 {10 (1) over bar0}(alpha) results in a Mode II or III microcrack and causes microcrack growth on the prismatic plane in the neighboring grain.