Temperature Independences of Fatigue Crack Growth in Ti–0.49 mass%O

Abstract

The temperature dependence of fatigue crack growth in stage IIb was investigated in Ti–0.49 mass%O with an alpha single phase. It was found that the fatigue crack growth rate in stage IIb was temperature independent at temperatures above 300 K. EBSD maps beside the fatigue crack showed that prismatic slips with 〈a〉 dislocations were dominantly activated during the fatigue crack growth. The reason why the prismatic slips were dominantly activated is discussed with numerical crystal plasticity analysis. It was shown that the local strain rate at the notch tip was higher than the macroscopic strain rate, which leads to the suppression of non-prismatic slips at the fatigue crack tip.

(a) and (b) are the experimental results. (c), (d) and (e) are the numerical result using crystal plasticity analysis. (a) Orientation map along the wake of a fatigue crack. The crack extended toward the x direction. (b) Colour map showing the deviation of the [0001] direction from the average orientation of [0001] in each grain. The colour key is shown at the middle-right corner. (c) and (d) are maps of the local strain rate at the notch tip. (c) At the nominal strain of 0.00004. (d) At the nominal strain 0.001. (e) Evolution of strain rate at the notch tip versus nominal strain.