A S Argon | PubMed Health

PubMed2004

High-density liquidlike component facilitates plastic flow in a model amorphous silicon system.

Molecular dynamics simulations show that plastic deformation of amorphous Si modeled by the Stillinger-Weber potential is very sensitive to the density of the initial unstressed state. Low-density systems exhibit a pronounced yield phenomenon, strain softening, and a dramatic drop in pressure during deformation at a constant volume. This behavior is explained by the presence in every system of a certain concentration of solidlike and liquidlike components, the latter being denser and more amenable to plastic flow.

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PubMed2002

Nanocrystallization during nanoindentation of a bulk amorphous metal alloy at room temperature.

It is known that nanocrystallites can form in shear bands produced during severe bending or high-energy ball milling of thin ribbons of a metallic glass. We present direct experimental evidence that highly confined and controlled local contact at the ultrafine scale in the form of quasi-static nanoindentation of a bulk glassy metal alloy at room temperature can also cause nanocrystallization. Atomic force microscopy and transmission electron microscopy show that nanocrystallites nucleate in and around shear bands produced near indents and that they are the same as crystallites formed during annealing without deformation at 783 kelvin. Analogous to results from recent experiments with glassy polymers, our results are reasoned to be a consequence of flow dilatation inside the bands and of the attendant, radically enhanced, atomic diffusional mobility inside actively deforming shear bands.

Journal Article↗