3D interfaces enhance nanolaminate strength and deformability in multiple loading orientations

Abstract

3D interfaces are a new type of interface containing nanoscale crystallographic, structural, and chemical heterogeneities in all spatial dimensions. Recently, 3D interfaces have been shown to enhance strength and deformability simultaneously by frustrating shear instability under layer-normal micropillar compression in Cu/Nb nanolaminates. However, quantification of deformed microstructure and effects of loading orientation were not explored in that work. Here, we address these shortcomings by performing post mortem TEM characterization of micropillars compressed at normal and 45° inclination to layers. We find high strength and deformability in both loading geometries and show that 3D interfaces enhance mechanical behavior under multiple loading orientations. In layer-normal compression, post mortem characterization allows for quantification of key quantities correlating well to the severity of shear localization across nanolaminates with different layer thickness and interface type. In 45° compression, TEM results demonstrated no strong plastic instability. This motivated analytical computation of Schmid factors and simulation of slip system activity via crystal plasticity finite element modeling (CPFE). The CPFE model demonstrates that most slip activity occurs non-parallel to layers, indicating that dislocation-3D interface interactions must mediate the observed mechanical behavior of micropillars. This work lays the foundation for further study of 3D interface-driven deformation physics in nanostructured alloys.