In situ transmission electron microscopy study and molecular dynamics simulation of dislocation loop evolution in FeCrAl alloys under Fe+ irradiation

Abstract FeCrAl alloys with excellent comprehensive properties are the most promising candidates to replace zirconium alloy fuel claddings. In our study, the dislocation loop evolution including initiation, migration, merging, growth, annihilation, and reaction in a FeCrAl alloy was investigated by using in situ transmission electron microscopy during 400 keV Fe + irradiation. The mechanism induced the growth of dislocation loops including the absorption of high-mobility point defects and defect clusters and the merging of two or more dislocation loops of different sizes. In the initial stage of irradiation, the loop density was relatively stable and the loop size increased rapidly with the increase in irradiation dose; however, owing to the formation of dislocation networks, the loop density decreased significantly in the later stage of irradiation. Both b = 1/2 and b  =  dislocation loops were formed in the FeCrAl alloy. The ratio of loops was 49% after irradiation with 0.14 dpa at 723 K. Molecular dynamics simulations displayed the reaction of dislocation loops with different Burgers vectors and sizes. Although the presence of alloying elements (Cr and Al) would prohibit or delay the interaction process, loop merging continued owing to the atomic rearrangement of dislocation loops.