Deformation profile and interface-mediated defect interaction in Cu/CuZr nanolaminates: An effective-temperature description

Abstract

Both simulations and experiments have suggested that Cu/CuZr nanolaminates are stronger and more ductile than their individual constituents due to interface-mediated interactions between plasticity carriers. In this work, we use the effective-temperature theories of dislocation and amorphous shear-transformation-zone (STZ) plasticity to study amorphous-crystalline interface (ACI)-mediated plasticity in Cu/CuZr nanolaminates under mechanical straining. The model is shown to capture reasonably well the measured deformation response when strained either in tension parallel to or in compression normal to the amorphous-crystalline interface. Our analysis indicates that increasing CuZr or decreasing Cu layer thickness increases the maximum flow stress for both perpendicular and parallel loading cases. For the cases of parallel and perpendicular loading, the maximum flow stress values are 3.4 and $2.5\phantom{\rule{0.16em}{0ex}}\mathrm{GPa}$, respectively. Furthermore, increasing the strain rate for the parallel loading case decreases the slip strain in the amorphous and crystalline layers. For the perpendicular loading case, an increase in strain rate decreases the amorphous layer slip but increases the crystalline layer slip. In all slip strain analyses, maximum slip strain occurs at the ACI, thus indicating that plasticity carriers accumulate at the interface and are absorbed there. These findings indicate a significant anisotropy in strength with greater sensitivity to layer thickness for the case of tensile loading parallel to the ACI. Further findings signify that slip strain is more sensitive when the nanolaminate is compressed perpendicular to the ACI.