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Variability of Poisson's Ratio and Enhanced Ductility in Amorphous Metal


  • This work was enabled through the ANSTO Senior Research Fellowship Program entitled Modern Diffraction Methods for The Investigation of Thermo-Mechanical Processes. The synchrotron beam time at APS was granted and travel supported through the Australian Synchrotron Research Program, funded by the Commonwealth of Australia under the National Collaborative Research Infrastructure Strategy. Use of the APS was supported by the US Department of Energy under contract DE-AC02-06CH11357. Special thanks goes to Jonathan Almer and the beamline staff for experimental set-up and help at the APS. We acknowledge support from Jun Shen and his group at the Harbin Institute of Technology for sample preparation by W. Zheng and X.S. Wei, and financial support of DDQ, enabled by the National Natural Science Foundation of China under the grant No. 51025415.


Ductile bulk metallic glass of composition 53.0Zr–18.7Cu–12.0Ni–16.3Al (at%) is plastically deformed under uniaxial compression and observed in situ by synchrotron high-energy X-ray diffraction. The diffraction patterns reveal the induced atomic strain is orientation dependent. At the onset of plastic deformation, the atomic strain in the compression direction saturates to a close-nearest-neighbor distance while atoms relax in the transverse direction. The ever increasing transverse atomic strain expresses in an augmentation of the apparent Poisson's ratio up to ν = 0.5, which is consistent with volume conservation. Contradicting phenomena from linear mechanics, such as the non-vanishing shear modulus at ν = 0.5 can be explained by the non-affine character of the deformation, giving rise to characteristics of a localized martensitic phase transformation. The findings explain the often-reported phenomena such as, the high Poisson's ratio values found in metallic glasses, the partially liquid character of the structure, the free volume increase and the Bauschinger effect.