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Transition from a strong-yet-brittle to a stronger-and-ductile state by size reduction of metallic glasses


Amorphous metallic alloys, or metallic glasses, are lucrative engineering materials owing to their superior mechanical properties such as high strength and large elastic strain. However, their main drawback is their propensity for highly catastrophic failure through rapid shear banding, significantly undercutting their structural applications. Here, we show that when reduced to 100 nm, Zr-based metallic glass nanopillars attain ceramic-like strengths (2.25 GPa) and metal-like ductility (25%) simultaneously. We report separate and distinct critical sizes for maximum strength and for the brittle-to-ductile transition, thereby demonstrating that strength and ability to carry plasticity are decoupled at the nanoscale. A phenomenological model for size dependence and brittle-to-homogeneous deformation is provided.

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Figure 1: Nanotension results for the specimen larger than 200 nm in diameter.
Figure 2: Monotonic nanotension results for the 100-nm-diameter specimen.
Figure 3: Multiple-loading nanotension results for the 100-nm-diameter specimen.
Figure 4: Tensile yield strength as a function of sample diameter.
Figure 5: Schematic representation of the applied stresses required to initiate shear-band propagation versus homogeneous deformation as a function of sample diameter, d.


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The authors gratefully acknowledge the financial support of the National Science Foundation through MRSEC (DMR-0520565) at Caltech and of the Office of Naval Research (grant no. N000140910883), as well as Kavli Nanoscience Institute at Caltech and W. L. Johnson and M. D. Demetriou for providing the bulk sample and for useful discussions.

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D.J. and J.R.G. designed the research and J.R.G. supervised the project. D.J. carried out the experiments. D.J. and J.R.G. contributed to the interpretation of the results and to the writing of the paper.

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Correspondence to Dongchan Jang.

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The authors declare no competing financial interests.

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Jang, D., Greer, J. Transition from a strong-yet-brittle to a stronger-and-ductile state by size reduction of metallic glasses. Nature Mater 9, 215–219 (2010).

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