Thicker amorphous grain boundary complexions reduce plastic strain localization in nanocrystalline Cu-Zr

TL;DR

This study shows that increasing the thickness of amorphous grain boundary complexions in nanocrystalline Cu-Zr enhances plasticity homogeneity and damage tolerance, reducing strain localization and failure.

Contribution

It provides experimental evidence that thicker amorphous complexions improve plastic flow stability and suppress localization in nanocrystalline alloys.

Findings

Thicker complexions lead to more homogeneous plastic deformation.

Thicker complexions increase resistance to strain localization.

Samples with thicker complexions show higher damage tolerance.

Abstract

Amorphous grain boundary complexions have been shown to increase the plasticity of nanocrystalline alloys as compared to ordered grain boundaries. Here, the effect of an important structural descriptor, amorphous complexion thickness, on the plasticity and failure modes of nanocrystalline Cu-Zr is studied with in-situ compression testing, with over 50 micropillars tested. Two model materials were created that differ only in their complexion thickness, with one having a thicker complexion population than the other. The sample with thinner complexions was more likely to experience non-uniform plastic deformation in the form of localized plastic flow or shear banding. In contrast, the sample with thicker complexions displayed more homogeneous plasticity and higher damage tolerance; thicker amorphous complexions suppress localization by absorbing defects. This work demonstrates that increasing complexion thickness can be beneficial for stable plastic flow in nanocrystalline alloys, by improving resistance to strain localization and premature failure.