Wavelike fracture pattern in a metallic glass: a Kelvin–Helmholtz flow instability

Abstract

We report a wavelike fracture pattern in a Zr-based bulk metallic glass that has been deformed under quasi-static uniaxial tensions between room temperature (300 K) and liquid nitrogen temperature (77 K). We attribute this wavelike pattern to a Kelvin–Helmholtz flow instability that occurs at certain interfaces between local cracking/softening regions. The instability criterion for the pattern formation is achieved via a hydrodynamic perturbation analysis, and furthermore, an instability map is built which demonstrates that the shear velocity difference on both sides of the interface is the main destabilizing factor. Finally, the characteristic instability time (the inverse of the instability growth rate) is explored by seeking the dispersion relation in the dominant (fastest) instability mode. The results increase the understanding of the flow and fracture of metallic glasses as well as the nature of their liquid structures.

Keywords:

• metallic glass
• fracture pattern
• Kelvin–Helmholtz instability

Acknowledgements

M.Q.J. gratefully acknowledges the Alexander von Humboldt Foundation for the support with a research fellowship. G.W. acknowledges the support by DFG. L.H.D. acknowledges the CAS/SAFEA International Partnership Program for Creative Research Teams.

Additional information

Funding

Funding. Financial support is from the NSFC [grants number 11372315], [grants number 11132011], [grants number 11023001], [grants number 51171138] and the National Key Research Program of China [grants number 2012CB937500].