Effect of growth twins on strength and microstructural evolution of nanocrystalline aluminum

YQ Shi and I Szlufarska, JOURNAL OF MATERIALS SCIENCE, 56, 14587-14597 (2021).

DOI: 10.1007/s10853-021-06220-6

The effect of growth-twins on friction, wear, and microstructural evolution of nanocrystalline (NC) aluminum is investigated using molecular dynamics simulations. NC Al with growth-twins has been previously synthesized experimentally, but the role of twins in deformation of this material has remained unknown. We find that twins increase strength and wear resistance of NC Al. The main reason is the anisotropy of plastic deformation since dislocations preferentially propagate along twin boundaries and therefore it is more difficult to nucleate dislocations in twinned sample with randomly oriented grains. The strengthening that comes from the increased stress required to nucleate dislocations in twinned samples can be off-set by the lower rate of strain hardening associated with the reduced dislocation densities. The balance of these effects is expected to depend on the grain size and twin spacing. Finally, our simulations reveal that dislocations in the neighboring twin layers move together, leading to a concerted confined layer slip.

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