PNNL

Abstract

This report summaries TEM characterization of 14YWT and 12YWT, ODS ferritic alloys with 14 and 12 wt % of Cr respectively, to compare the effect of neutron irradiation with and without concurrent He injection using ISHI. The density and average size of /{100} type dislocation loops are always larger than those of 1/2/{111} type, but this difference is significantly affected by He implantation. The density of dislocation loops of both types ranges from ~1 to 4x1021 m-3 with average size ranging from 5~20 nm. 14YWT has lower density but larger size dislocation loops than 12YWT, while the line dislocation density of 14YWT is 3 times lower than that of 12YWT. Helium bubble densities of both 14YWT and 12YWT are 1.9x1023 m-3, the average He bubbles size of 14YWT and 12YWT are 1.4 and 1.2 nm, respectively. 14YWT exhibits a-a’ phase separation, Y-rich particles and uniformly distributed W. In addition to those features, 12YWT exhibits Y-Ti-O particles (not Y-O rich) and elongated Cr-rich phases.