Diminished Role of Grain Boundaries in Mitigating Irradiation Damage in Multi-Principal Element Alloys

Grain boundaries (GBs) in metallic materials are commonly recognized as effective defect sinks. For this reason, extensive efforts have been made to engineer GB structures and densities to design highly irradiation-resistant structural materials over the past decades. Here we show that GBs in multi-principal element alloys (MPEAs), which represent a novel material design strategy, are no longer strong defect sinks. Our conclusions are derived from integrated efforts involving simulations at different time and spatial scales as well as experimental characterizations. We demonstrate that chemical disorder and local segregation ordering around GBs greatly weaken the interactions between GBs and irradiation-induced defects at both the thermodynamic and dynamic levels. The absence of a denuded zone in the GB vicinity suggests that defects are almost not influenced by the appearance of GBs in MPEAs. Our results indicate that the normally adopted approaches, such as GB engineering for material design in conventional materials, may not be well-suited for enhancing the irradiation resistance of MPEAs.