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Elastostatic Reversibility in Thermally Formed Bulk Metallic Glass: Nanobeam Diffraction Fluctuation Electron Microscopy

Abstract

The unparalleled shaping capability of bulk metallic glasses can revolutionize the commercial products having multi-length scale features in several minutes of processing time. Despite widespread shaping capability of these polymer-like multicomponent alloys, thermoplastic forming (TPF) can severely degrade the intrinsic properties, particularly when complex stress states are activated. Present work places an importance on elastostatic loading (ESL) which not only fully reverses deteriorated room temperature plasticity originated from TPF or post-cryostatic conditions, but also activates a rejuvenation mechanism by rendering an extended resistance against strain softening. Furthermore, the drop in the supercooled liquid region and crystallization enthalpy measured by differential scanning calorimeter are found to be temporary, and can be fully reversed to its initial condition. HRTEM imaging of the samples are performed with an imaging spherical aberration corrector. Individual nanobeam diffraction patterns taken by the fluctuation electron microscopy (FEM) measurements are acquired with a probe size of 1.2 nm from a 10x10 raster, yielding 100 diffraction patterns in a scanning transmission electron microscope. The normalized variance of a series of nanodiffraction patterns of the post-elastostatically loaded sample reveals height decrease in the first broad peak of normalized intensity variance V(k) suggesting the modifications in the medium-range structural order which in turn dramatically restores the mechanical and thermal properties. Overall, the combination of TPF and post-ESL treatment in advanced glassy metals can open a new avenue for ultra-high mechanical and thermal performance micro- and nanomechanical devices for biosensors, MOSFETs, and robotics.

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Publication details

The article was received on 15 Sep 2017, accepted on 01 Dec 2017 and first published on 04 Dec 2017


Article type: Paper
DOI: 10.1039/C7NR06891C
Citation: Nanoscale, 2017, Accepted Manuscript
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    Elastostatic Reversibility in Thermally Formed Bulk Metallic Glass: Nanobeam Diffraction Fluctuation Electron Microscopy

    B. Sarac, C. Gammer, L. Deng, E. Park, Y. Yokoyama, M. Stoica and J. Eckert, Nanoscale, 2017, Accepted Manuscript , DOI: 10.1039/C7NR06891C

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