Irradiation-induced solute trapping by preexisting nanoprecipitates in high-strength low-alloy steel

In the present study, a nanoprecipitate-strengthened high-strength low-alloy steel was irradiated by high-energy Au²⁺ ions with a peak dose of ∼70 displacements per atom (dpa) at room temperature. The formation of nanoprecipitates, dislocation loops, elemental segregation and mechanical properties before and after irradiation were carefully characterized using atom probe tomography (APT), transmission electron microscopy (TEM) and nanoindentation. The mechanism of precipitation and coarsening of these nanoprecipitates and the effect of the dose on irradiation-induced solute capture were studied. The results show that, different from a simple aging-induced precipitation of Cu-rich nanoprecipitates, coprecipitation of Cu/Ni nanoprecipitates occurred under irradiation. With increasing dose, the nanoprecipitates coarsened. Although irradiation induced the formation of small dislocation loops together with new nanoprecipitates, the abnormal softening that occurred after irradiation can be attributed to the coarsening of the preexisting nanoprecipitates. These studies and discoveries are expected to provide unique and important information for the design of new structural alloys with enhanced radiation resistances.