When 3:00 PM - 5:00 PM Dec 09, 2011
Where 1670 CSE
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Phase Selection in Systems driven Far from Equilibrium

Matthew Kramer
Ames Laboratory

Rapid solidification processes, such as melt spinning, are common means to produce non-equilibrium metal alloys, yet little is understood about the phase selection and nanoscale structural dynamics in such systems driven far from equilibrium.  Effective exploitation of highly driven phase transformations for new materials with novel properties requires that we attain better understanding and control of the competitive mechanisms underlying the transition dynamics. The kinetic suppression of liquid dynamics during rapid cooling may give rise to phase transition pathways that involve departure from the equilibrium “equation of state” for the liquid before or during the formation of stable or metastable crystalline phases, which themselves may be far from equilibrium in terms of structure and chemistry. These non-equilibrium liquid structures and glassy phase dynamics may contribute to or even dominate the structural transitions in systems driven far from equilibrium. In this way, noncrystalline forms of structural/chemical ordering may play an important role in establishing viable kinetic pathways which strongly influence transition dynamics. To try to understand these kinetic effects, at Ames Laboratory, we have assembled a group of researchers with expertise in the critical areas of first-principles investigations of material behavior, classical potentials and molecular dynamics simulations, X-ray scattering and e-beam microanalysis, solution thermodynamics, solid-liquid interfaces, and solidification/transformation dynamics to work together on a common set of model alloy systems.  I will present specific examples where atomistic simulations combined with critical experiments have begun to unravel the complexity of the chemical and topological ordering of the liquid structure undergoes during glass formation and subsequent effect on phase selection during devtification.

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