Interface-controlled mechanical properties and irradiation hardening in nanostructured Cr75Al25/Zr multilayers.

As an efficient strategy to design accident-tolerant fuel (ATF) materials, nanostructured metallic multilayers (NMMs) have attracted significant research interest. In this work, Cr 75 Al 25 /Zr (CA/Zr) NMMs were prepared with equal individual layer thickness h spanning from 5 to 75 nm, and subjected to He+ implantation with a total fluence of 1 × 1017 ions cm−2 at room temperature. With decreasing h , the interface changed from crystalline/crystalline to crystalline/amorphous along with size-driven strengthening to softening behavior of CA/Zr NMMs at the critical thickness h = 25 nm. The size-dependent hardness consists well with the evolution of the back stress with respect to h , which is elucidated by the statistical dislocation absorption propensity by the interface. Moreover, notable irradiation hardening emerges in the CA/Zr NMMs, which is caused by He bubble-dislocation interactions at large h and by the cooperation of He bubble hardening and increased back-stress hardening at small h. The hardness of both as-deposited and irradiated CA/Zr NMMs was quantitatively explained by dislocation models operative at different length scales. [ABSTRACT FROM AUTHOR]