NiCoCr-based medium-entropy alloys with superior resistance to radiation hardening and helium cavity growth

In this work, three NiCoCr-based medium-entropy alloys (MEAs), i.e., NiCoCr, NiCoCrW_0.1 and NiCoCrTi_0.1, were irradiated with helium (He) ions at 400 ℃ and 700 ℃ to study the radiation hardening and He-induced cavity growth behavior. The typical quaternary FeCoNiCr alloy was irradiated similarly and evaluated for comparison. Using transmission electron microscopy and nanoindentation measurements, He-induced microstructural evolution and mechanical changes were systematically investigated. Here we show that mitigated radiation hardening at 400 ℃ and cavity growth behavior at 700 ℃ were exhibited in the NiCoCr-based MEAs, in contrast to significant radiation hardening and He cavity growth of FeCoNiCr. Among the studied alloys, NiCoCrW_0.1 displayed the best radiation hardening resistance, while NiCoCrTi_0.1 presented the strongest tolerance in terms of He cavity growth. The underlying reasons were carefully analyzed based on the observed microstructures. Our results demonstrate the great potential of NiCoCr-based MEAs to function as critical nuclear structural components at relatively low and high temperatures.