Microalloying and the mechanical properties of amorphous solids

Abstract

The mechanical properties of amorphous solids like metallic glasses can be dramatically changed by adding small concentrations (as low as 0.1%) of foreign elements. The glass-forming-ability, the ductility, the yield stress and the elastic moduli can all be greatly effected. This paper presents theoretical considerations with the aim of explaining the magnitude of these changes in light of the small concentrations involved. The theory is built around the experimental evidence that the microalloying elements organise around them a neighbourhood that differs from both the crystalline and the glassy phases of the material in the absence of the additional elements. These regions act as isotropic defects that in unstressed systems modify the shear moduli. When strained, these defects interact with the incipient plastic responses which are quadrupolar in nature. It will be shown that this interaction interferes with the creation of system-spanning shear bands and increases the yield strain. We offer experimentally testable estimates of the lengths of nano-shear bands in the presence of the additional elements.

Keywords:

• Plasticity
• amorphous solids
• defects
• geometry

Acknowledgements

M.M. is grateful to Prof. Raz Kupferman and to Prof. Eran Sharon for their support and useful discussions.

Notes

No potential conflict of interest was reported by the authors.

Additional information

Funding

This work had been supported in part by and ERC ‘ideas’ grant STANPAS. M.M. was supported by the Israel-US Binational Foundation [grant number 2010129]; Israel Science Foundation [grant number 661/13].