Mechanistic insights into spinodal L1₂ nanostructures in mitigating radiation defect growth in Al_0.5Cr_0.9FeNi_2.5V_0.2 high-entropy alloys

High-entropy alloys with high-content L1₂ nanoprecipitates formed through phase separation have recently demonstrated outstanding mechanical properties across a wide temperature range, making them suitable structural materials for advanced nuclear systems. This study investigates the irradiation response of a high-entropy alloy composed of Al_0.5Cr_0.9FeNi_2.5V_0.2 with varying volumes of L1₂ nanostructures. High-temperature He ion irradiation was performed, and its effects on defect evolution were analyzed using transmission electron microscopy and nanoindentation. The results show that the spinodal order-disorder L1₂ network structure effectively suppresses irradiation-induced defects, as evidenced by reduced dislocation loop size, lower He bubble swelling, and decreased irradiation hardening in alloys with higher L1₂ volume fractions. This is primarily because the L1₂ structure, with its low-misfit coherent interface, undergoes the reversible order-disorder transition that reduces early irradiation point defects and suppresses defect nucleation and growth. Furthermore, the spinodal order-disorder L1₂ nanostructure impedes defect cluster movement by providing diffuse obstacles and forming antiphase boundaries, thereby slowing the growth of defects and He bubbles. This work provides an alloy design strategy to improve irradiation tolerance by exploiting the self-healing and structural complexity of the L1₂ structure.