Tem studies of radiation-induced stress changes IN low-activation CWC

Low activation cemented tungsten carbides (cWCs) have attracted considerable attention as compact refractory nuclear shielding with a particular focus on compact spherical tokamaks (cSTs). This work presents non-ambient study of stress-depth profiles in irradiated low-activation cWC as investigated by electron backscatter diffraction (EBSD), transmission electron microscopy (TEM) and microhardness indents near the incident faces of samples. Proton beam irradiation used 1.5 MeV protons at 410 K and 823 K with γ-irradiation using ⁶⁰Co radiation at 77 K and 293 K for 90 kGy and 10 MGY respectively. Radiation-induced changes were observed in WC grains via TEM and EBSD. Initial radiation response resulted in an increase in hardness from dislocation-induced pinning and formation of linear defects preferentially aligned along the 〈0001〉 direction in the WC basal plane confirmed by a shift in preferred orientation of dislocation alignment from EBSD inverse pole figure maps. Observed changes correlate well with total energy deposited into sample with respect to TEM and EBSD data with dislocation clusters showing a more significant shift to <0001> with more deposited energy. This work shows evidence for the first time that cWCs have some self-annealing properties at temperatures ≥823 K in radioactive environments with implications for fusion reactor design.