Fig. 1. High-throughput compression tests of CuZr/Cu nanopillars with a ~600 nm diameter: (a) SEM images of nanopillars with different views; (b) stress-displacement curves of the tested samples at a strain rate of 1 × 10-3 s-1. The top and side views of the nanopillars before compression are presented in the first row of (a) while the side views of nanopillars after compression are listed in the other rows.

Fig. 2. Microstructures of the CuZr/Cu nanolaminates before and after micro-compression: (a, b) TEM images of the multilayers of the as-fabricated CuZr/Cu nanolaminates; (c-e) High-resolution TEM images and composition mapping of the sample after micro-compression. The CuZr/Cu NLs consist of 100-nm amorphous CuZr and 10-nm nanocrystalline Cu layers. The ellipses in c highlight the ordering clusters in the amorphous CuZr layer.

Fig. 3. Configurational transformation dominated serrations of CuZr/Cu NLs under strain rate of 1 × 108 s-1: (a) hydrostatic stress versus axial strain along the z direction of the polycrystalline Cu, amorphous CuZr, and the CuZr/Cu NLs; (b) Von-Mises shear-strain distributions for the CuZr/Cu NLs calculated by MD simulations. The three independent structures/supercells shown are different in their Cu polycrystalline structures since only one amorphous CuZr layer from ab initio MD calculations are utilized here. The BGR gradient colors in (b) correspond to various levels of Von-Mises shear strains.

Fig. 4. Snapshots of configurations corresponding to the stress-strain curve of the CuZr/Cu NLs under a strain rate of 1 × 108 s-1. The HCP-type structures that are produced to create a deformation fault (2 layers combined together) and twin boundaries (the isolated single layer), BCC-type ordering at grain boundaries of Cu, and amorphous CuZr, and atoms constructing the Voronoi polyhedra of CuZr are selected through deleting the FCC matrix of the polycrystalline Cu and disordered structures of the amorphous CuZr. The BGR gradient colors are utilized to identify the atomic spatial coordinates.

Fig. 5. Various views of the configurational transformations of the CuZr/Cu NLs under strain rates of 1 × 108 s-1 and 1 × 109 s-1: (a) the resultant HCP-type structure for deformation faults (2 layers combined together) and twin boundaries (the isolated single layer) in red, BCC-type ordering at Cu grain boundaries and the amorphous CuZr in blue, and atoms constructing the Voronoi polyhedra of CuZr in green; (b) an enlarged region of the nanocrystalline Cu shown in (a); (c) the evolution of the disordered structures in the nanocrystalline Cu, trailing the edge of the stacking faults and the (partial) dislocations shown with the BGR gradient; (d) BGR view of the HCP and BCC regions, and the Voronoi polyhedra discussed in (a).