Effect of neutron irradiation on defect evolution in Ti3SiC2 and Ti2AlC

Abstract Herein we report on the characterization of defects formed in polycrystalline Ti 3 SiC 2 and Ti 2 AlC samples exposed to neutron irradiation – up to 0.1 displacements per atom (dpa) at 350 ± 40 °C or 695 ± 25 °C, and up to 0.4 dpa at 350 ± 40 °C. Black spots are observed in both Ti 3 SiC 2 and Ti 2 AlC after irradiation to both 0.1 and 0.4 dpa at 350 °C. After irradiation to 0.1 dpa at 695 °C, small basal dislocation loops, with a Burgers vector of b  = 1/2 [0001] are observed in both materials. At 9 ± 3 and 10 ± 5 nm, the loop diameters in the Ti 3 SiC 2 and Ti 2 AlC samples, respectively, were comparable. At 1 × 10 23  loops/m 3 , the dislocation loop density in Ti 2 AlC was ≈1.5 orders of magnitude greater than in Ti 3 SiC 2 , at 3 × 10 21  loops/m 3 . After irradiation at 350 °C, extensive microcracking was observed in Ti 2 AlC, but not in Ti 3 SiC 2 . The room temperature electrical resistivities increased as a function of neutron dose for all samples tested, and appear to saturate in the case of Ti 3 SiC 2 . The MAX phases are unequivocally more neutron radiation tolerant than the impurity phases TiC and Al 2 O 3 . Based on these results, Ti 3 SiC 2 appears to be a more promising MAX phase candidate for high temperature nuclear applications than Ti 2 AlC.