Interface-controlled mechanical properties and irradiation hardening in nanostructured Cr/Zr multilayers

Interface as an effective defect-absorbing trap can reduce the accumulation of irradiation damage by promoting the recombination of point defects. As an efficient strategy for designing radiation resistant materials, nanostructured multilayers have attracted extensive interests due to their controllable structure and density of heterogeneous interface. In this work, Cr/Zr nanostructured metallic multilayers (NMMs) were prepared with equal individual layer thickness h spanning from 5 to 75 nm, and then subjected to He+ implantation with a total fluence of 1 × 1017 ions cm−2 at room temperature. With decreasing h, the Cr/Zr NMMs exhibited the size-driven strengthening to softening behavior at the critical h = 25 nm. This phenomenon can be quantitatively described via the dislocation mechanism models at different length scale. The size effect of hardness closely matches the evolution of back stress, which can be elucidated by the probability of interfacial absorption of dislocations. Moreover, the radiation hardening behavior of irradiated Cr/Zr NMMs is very strong due to the interaction between He bubbles and dislocations at large h, and the synergistic effect of bubble hardening and back stress hardening at small h.