Suppression of shear localization in nanocrystalline Al-Ni-Ce via segregation engineering

Shear localization in nanocrystalline metals is a severely limiting factor precluding their use as practical engineering materials. While several strategies exist to enhance the thermal and mechanical behavior of these materials, there are still many outstanding questions regarding the effects of chemical segregation on shear localization in FCC nanocrystalline materials. In this paper we investigate the mechanical response of a ternary aluminum alloy with a sub-10 nm nanocrystalline microstructure subject to various thermal treatments. Contrary to previous observations, our results suggest that annealing up to 0.7 T-m reduces the propensity for shear localization and increases strength, as demonstrated by a transition in deformation morphology from pronounced strain localization to more homogeneous deformation during indentation. This behavior coincides with the formation of an amorphous intergranular film during annealing, causing intragranular dislocation plasticity to be favored over other grain boundary dominated deformation mechanisms, in turn resulting in a lower propensity for long range plastic localization. (C) 2020 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.