Fracture behavior and toughness of PST crystals of TiAl have been investigated through three-point bend tests of specimens which are notched, fatigue-precracked and side-grooved. Bend tests have been conducted in air at room temperature. Fracture surface morphology and toughness of notched PST crystals of TiAl strongly depend on their notch orientation with respect to the lamellar boundaries and crystal orientation of γ lamellae. In this study, we have tested specimens with five different notch orientations, i.e. types I-<110>, I-<112>, II-<110>, II-<112> and III, where I, II and Ill are crack arrester, crack divider and crack delamination orientations, respectively, and (hkl) indicates the direction normal to the notch plane, which is given with respect to crystal orientation of γlamellae.
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