金属間化合物TiAlにおける切欠き底微小疲労き裂の伝ぱ挙動

抄録

Single-edge-notched specimens of an intermetallic compound TiAl were fatigued under cyclic axial tension compression. The effect of microstructure on the propagation behavior of short fatigue cracks formed at the notch root was investigated. The crack length was measured with the AC potential method and the development of crack closure with crack extension was measured through the compliance method. The crack path is tortuous in lamellagrains, while straight in gamma-grains. When compared at the same non-propagating crack length, the crack opening stress intensity factor at the threshold increases with increasing lamella volume fraction. The relation between the crack propagation rate and the effective stress intensity range for short cracks was identical to that for long cracks. The resistance-curve method was used to predict the fatigue strength of notched specimens. The predicted values of the fatigue limits for crack initiation and for fracture, and the non-propagating crack length agreed well with the experimental results.