Heterogeneous atomic environments destabilize defect clustering to enable a radiation-tolerant alloy

Designing structural materials capable of tolerating high irradiation doses at elevated temperatures remains a grand challenge, with profound implications for the next-generation nuclear technologies. In conventional alloys, irradiation-generated point defects (vacancy or interstitial) tend to aggregate spontaneously to minimize energy, leading to progressive damage accumulation that eventually undermines material integrity. Here we demonstrate that this detrimental defect evolution is disrupted in a NbZrTi refractory multi-principal element alloy (MPEA) characterized by pronounced atomic-level chemical heterogeneity. The diverse atomic bonding environments inherent to such chemical disorder produce broad variations in defect cluster formation and binding energies, as revealed through atomistic simulations. For migrating defect clusters, the probability of their dissociation becomes comparable to that of growth, effectively stagnating coarsening and preventing the accumulation of defect clusters. Consequently, voids and dislocation loops are effectively suppressed, as demonstrated in heavy-ion irradiation experiments up to 127 dpa at 873 K and 1023 K. These findings establish a paradigm shift in designing irradiation-resistant alloys—one that alters defect thermodynamic stability rather than merely recombination kinetics, exploiting intrinsic atomic-scale variability instead of relying on microstructural sinks—to achieve robust irradiation resistance for advanced nuclear applications.