High-resolution electron microscopy of [gamma]-TiAl irradiated with 15 keV helium ions at room temperature

γ-TiAl intermetallic alloy was irradiated with 15 keV He ⁺ to a dose of 8.6 × 10 ²⁰ ions m ^-2 (4.4 dpa) in a high-voltage transmission electron microscope (HVTEM) at room temperature, and the evolution of irradiation defects was observed during and after irradiation with HVTEM and high-resolution transmission electron microscopy (HRTEM). Induced defect clusters in γ-TiAl became visible with HVTEM to an irradiation dose of 4.7 × 10 ¹⁹ ions m ^-2 (2.4 × 10 ^-1dpa). They are mainly planar defects and have a character of domain structures with the edges parallel to {1 1 1) of the matrix and several nanometers in size. Cavities (He bubbles) with irregular shapes were observed in γ-TiAl after He ⁺ irradiation of 5.7 × 10 ²⁰ ions m ^-2 (2.9 dpa). Post-irradiation annealing at 673 K for 1800 s enhanced the growth of the domain structure. The analysis of HRTEM images and selected area diffraction (SAD) patterns suggests the formation of rotated domain (RD) which has the same structure as the matrix but in orientations rotating 90° to the matrix. The mechanism of formation of the RD in γ-TiAl crystals is discussed.