Microtension behaviour of TiAl polysynthetically twinned crystals with 0°- and 90°-oriented lamellae

Microtension testing was conducted upon TiAl polysynthetically twinned crystals containing single domains with 0°- and 90°-oriented lamellae. The orientation-dependent deformability of the Ti3Al phase plays an important role in the microtension deformation behaviour. Small-scale delaminations due to TiAl/Ti3Al interlamellar cracking enhance the ductility of the 0°-oriented crystal. In the 90°-oriented crystal, the high degree of strength due to the size effect on the scale of a few tens of micrometres may be attributed to the reduced probability of the weakest link.