Origin of anomalous inverse notch effect in bulk metallic glasses

Understanding notch-related failure is crucial for the design of reliable engineering structures. However, substantial controversies exist in the literature on the notch effect in bulk metallic glasses (BMGs), and the underlying physical mechanism responsible for the apparent confusion is still poor...

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Bibliographic Details
Published in:Journal of the mechanics and physics of solids 2015-11, Vol.84, p.85-94
Main Authors: Pan, J., Zhou, H.F., Wang, Z.T., Li, Y., Gao, H.J.
Format: Article
Language:English
Subjects:
Amorphous materials
Bulk metallic glasses
Cavitation
Failure mechanisms
Inverse
Metallic glasses
Notch
Notch sensitivity
Notches
Origins
Shear band
Strength
Zirconium base alloys
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Summary:Understanding notch-related failure is crucial for the design of reliable engineering structures. However, substantial controversies exist in the literature on the notch effect in bulk metallic glasses (BMGs), and the underlying physical mechanism responsible for the apparent confusion is still poorly understood. Here we investigate the physical origin of an inverse notch effect in a Zr-based metallic glass, where the tensile strength of the material is dramatically enhanced, rather than decreased (as expected from the stress concentration point of view), by introduction of a notch. Our experiments and molecular dynamics simulations show that the seemingly anomalous inverse notch effect is in fact caused by a transition in failure mechanism from shear banding at the notch tip to cavitation and void coalescence. Based on our theoretical analysis, the transition occurs as the stress triaxiality in the notched sample exceeds a material-dependent threshold value. Our results fill the gap in the current understanding of BMG strength and failure mechanism by resolving the conflicts on notch effects and may inspire re-interpretation of previous reports on BMG fracture toughness where pre-existing notches were routinely adopted.
ISSN:0022-5096
DOI:10.1016/j.jmps.2015.07.006