Revealing nanoscale strain mechanisms in ion-irradiated multilayers

Tailoring of interfaces is a powerful way of reducing the accumulation of radiation defects. Understanding strain evolution induced by ions bombardment in nuclear materials with high interface density is crucial for next-generation reactors since induced defects are responsible for volumetric swelling and catastrophic failure. X-ray and SADPs measurements reveal that, after Cu implantation, a relatively high out-of-plane strain is created in thin Zr/Nb 6 multilayers, while the thick Zr/Nb 96 is barely distorted. The absence of the layer deformation in Zr/Nb 96 is explained by Astar strain mapping showing the presence of two oppositely distorted regions (inner and interface-affected regions) within one layer producing only a small overall strain, whereas the whole individual layers of Zr/Nb 6 are affected by the interface manifesting high strain. Using MD simulations, the type of defects responsible for layer distortion is identified. The opposite distortion within the layer is attributed to the inequality of the defect flux from the inner to interface-affected region due to the difference in migration energy barriers of the point defects. Moreover, the interface sink efficiency (defect annihilation) is determined for Zr/Nb as an illustration which provides a strategy for designing new derivate structures of multilayers with high radiation damage resistance.