Role of refractory inclusions in the radiation-induced microstructure of APMT

Kanthal APMT is a promising FeCrAl-based alloy for accident-tolerant fuel cladding because of its excellent high-temperature oxidation resistance. In this study, powder metallurgy Kanthal APMT alloy, neutron irradiated to 1.8 dpa at nominally 382 °C, was characterized. On-zone STEM imaging revealed that radiation-induced dislocation loops with Burgers vectors of a/2〈111〉 or a〈100〉 and black dots tended to agglomerate in the vicinity of refractory inclusions. The densities and sizes of these loops decreased with distance from the inclusion-matrix interfaces. In addition, high-resolution energy-dispersive X-ray spectroscopy mapping was used to determine the inclusions to be either yttrium- or silicon-rich, as well as to detect the radial distribution of radiation-enhanced α′ phase near these inclusions. A high density of randomly distributed Cr-rich α′ phase was found, regardless of the presence of inclusions. Results from this study provide insights into how microstructural features can locally tailor the radiation-induced defects in FeCrAl-based alloys.