Microstructures and Hardening Effects of Refractory High Entropy Alloys Irradiated by Proton & He Ion Dual Beam

This research revealed the irradiation hardening mechanism in two novel NbZrTiV and VNbMoTaWTi refractory high entropy alloys (RHEAs). The RHEA sample irradiated by a dual-beam of 0.5 MeV protons and 2 MeV He ions at 300 K. Irradiation-induced defects were characterized by transmission electron microscope (TEM). It was discovered that the defect clusters were mostly consisted of nano-sized dislocation loops and bubbles. The density of defects was higher in the peak region than in the plateau region for both irradiated samples. The effects of irradiation-induced defects on hardening were evaluated by the nanoindentation test and dispersed barrier hardening (DBH) model. The results show that the peak region contributes more to the hardening than the plateau region in both irradiated alloys. The DBH hardness increments agree well with those measured by nanoindentation. Dual-beam irradiation led to -14% hardening for NbZrTiV and - 18% for VNbMoTaWTi. The effects of the chemical disorder and lattice distortion induced by compositional complexity on defect formation and hardening were discussed. The excellent irradiation resistance makes RHEAs to be potential candidate materials used as core component in advanced nuclear reactors.