Fig. 5: As-processed and post-deformed microstructures beneath the surface of a representative nanoindentation impression and a microprojectile impact impression in NC Cu 3-Ta alloys.

a, d, g represent the low magnification STEM BF images of the nanocrystalline grains for as-processed, nanoindentation, and impact samples, respectively; b, e, h represent the higher magnification STEM HAADF images of the high density of Ta-based clusters residing in the lattice as well as along the grain boundaries of the Cu-based matrix for as-processed, nanoindentation and impact sample, respectively; c, f and i show the magnified STEM BF images of a limited number of dislocations surrounding the Ta nanoclusters for as-processed, and been pinned by Ta nanoclusters for nanoindentation and impact samples, respectively. The red arrows in c, f and i highlight some exemplar dislocations.