Irradiation-induced structural transitions in Ti2AlC

In this study, 1 MeV Au ions were used to irradiate Ti2AlC at room temperature with fluences ranging from 1 x 10(14) to 2 x 10(16) cm(-2). The structural transformation and the evolutions of defects induced by Au irradiation were investigated by means of Grazing incidence X-ray diffraction (GIXRD) and transmission electron microscopy (TEM). GIXRD analyses show serious structural disorder and phase transitions, which are consistent with the selected area electron diffraction (SAED) results and high-resolution TEM images. TEM observations reveal that the nanolayered structures are partially disturbed at the lowest fluence of 1 x 10(14) cm(-2), with the phase transition from original hexagonal-close-packed (hcp) structure to gamma-Ti2AlC phase structure. With the fluence increasing, more extended defects lead to the symmetry variation and the transformation of a possible delta-phase structure. At the highest fluence of 2 x 10(16) cm(-2), some face-centered-cubic (fcc) structures are formed from the original hcp structures without amorphization, indicating a great tolerance of irradiation-induced amorphization of Ti2AlC. Based on the phase contrast images and EDPs simulation of the microstructures of the transformed structures, a mechanism for the phase transitions of Ti2AlC is proposed. (C) 2015 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.