Amorphous complexions alter the tensile failure of nanocrystalline Cu-Zr alloys

TL;DR

This study demonstrates that amorphous intergranular films at grain boundaries enhance the ductility and delay failure in nanocrystalline Cu-Zr alloys, offering insights into boundary engineering for improved material performance.

Contribution

It provides the first direct experimental evidence that amorphous complexion structures at grain boundaries improve ductility in nanocrystalline metals.

Findings

Failure is significantly retarded with amorphous films.

Increased cross-sectional area reduction observed.

Reduced shear-dominated failure and strain localization.

Abstract

Grain boundary-based mechanisms are known to control the plastic deformation and failure of nanocrystalline metals, with manipulation of the boundary structure a promising path for tuning this response. In this study, the role of interfacial structural disorder on plasticity and failure of nanocrystalline Cu-Zr alloys is investigated with in situ scanning electron microscopy tensile deformation experiments. Two model materials are created, one with only the typical ordered grain boundaries and another with amorphous intergranular films interspersed into the boundary network, while the microstructures are otherwise identical. Hence, the importance of complexion type on plasticity and failure is isolated by only varying complexion structure. The tensile experiments show that failure of the samples containing amorphous films is significantly retarded, as evidenced by an increase in the cross-sectional area reduction, a decrease in the occurrence of shear-dominated failure, a decrease in strain localization, and fracture surfaces with more elongated dimple features. As a whole, this study provides direct evidence that structural disorder at the grain boundaries can be beneficial for improving the ductility of nanocrystalline metals.