The structural transitions of Ti3AlC2 induced by ion irradiation

The structural transitions of Ti3AlC2 induced by ion irradiation were investigated over a wide fluence range by transmission electron microscopy. No amorphization occurs even at the highest dose of 31 dpa, indicating a great tolerance to irradiation-induced amorphization. Dynamic electron diffraction simulations and high-resolution observations indicate that the nanolamellar structure of Ti3AlC2 is readily destroyed through the formation of antisite defects and a phase transformation from α-Ti3AlC2 to β-Ti3AlC2 occurs at 2.61 dpa. A great number of stacking faults in basal planes are formed with increasing fluence, leading to the formation of nano Ti3AlC2 grains with different stacking sequences at 10.45 dpa. Serious structural damage and polygonization are observed at the highest dose of 31 dpa. Due to the similar structural transition process with some complex oxides (pyrochlore and murataite), it is assumed that the great irradiation tolerance of Ti3AlC2 results from the low formation energy of antisite defects. These findings first clarify the structural transition mechanism of Ti3AlC2 under ion irradiation and its relationship with irradiation tolerance, which is of vital importance in understanding the irradiation response of MAX phases and provides a clue in searching for materials with higher irradiation tolerance from MAX phases.