High Speed Dynamic Deformation of Polysynthetic Twinned Titanium Aluminide Intermetallic Compound

Impact deformed TiAI polysynthetic twinned crystal was investigated by scanning and transmission electron microscopy including aberration-corrected scanning transmission electron microscopy. Shear bands, deformation twins and dislocations were observed in gamma-TiAI phase. Deformation twins were identified on both primary (11 (1) over bar) and secondary (1 (11) over bar) twin planes, and dislocation structures were resolved on the coherent [111] twin boundaries. Among them, 1/6 < 211] pseudo-twin dislocations were observed on the coherent twin boundaries co-existing with 1/2 < 101] super-partial dislocations. Two types of shear bands were identified, one was composed of (11 (1) over bar) twin lamellae inclined to the propagation direction of shear bands, while the other was composed of curved (1 (11) over bar) twin lamellae and its propagation is nearly parallel to the (1 (11) over bar) twin plane. (C) 2018 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.