Structural Ordering and Vitrification of Multicomponent Metallic Liquids

George Mason University, Fairfax VA

Investigators

Abstract

This Award is funded under the American Recovery and Reinvestment Act of 2009 (Public Law 111-5). TECHNICAL SUMMARY Many metallic liquids can be supercooled to a great extent without crystallizing, and have a tendency to form metallic glasses with technological importance. Fundamental understandings of the atomic arrangements in supercooled metallic liquids have been lacking. In order to fill this knowledge gap, the proposed project aims to use computational methods, coupled with synchrotron x-ray scattering experiments, to reveal the details of atomic-level structural evolution in multicomponent metallic liquids. This work will advance our understanding of the structural underpinnings of the vitrification process of supercooled metallic liquids. Specific research objectives in this proposal include: (1) identifying different types of topological structural ordering in supercooled liquids; (2) monitoring hierarchical structural ordering of supercooled liquids, temporally and spatially; and (3) uncovering the correlations between atomic packing schemes and the vitrification physics (i.e., dynamic slowing-down, liquid fragility, glass forming ability, etc.) of supercooled liquids. To this end, the principal investigator will develop high-fidelity interatomic potentials for a realistic system by fitting to extensive first-principles calculations. Both ab initio molecular dynamics and large-scale classical molecular dynamics will be performed to study the atomic-level structure and dynamics of the supercooled multicomponent liquid. Theoretical results will be validated within experimental capabilities. To further complement theoretical investigations and address the issues of atomic-level structure and glass forming ability, in situ high-pressure high-temperature synchrotron x-ray scattering experiments are proposed to test the possibility of controlling the glass forming ability and fragility of multicomponent metallic systems by tuning atomic packing. NON-TECHNICAL SUMMARY What the internal structure looks like in complex metallic liquids remains something of a mystery. The proposed project aims to use state-of-the-art computational and experimental techniques to deal with this difficult topic. Insight into the structural arrangement of supercooled metallic liquids will provide much-needed information critical to understanding the formation of metallic glasses. The knowledge gained will broaden our perspectives on this state of matter, and should have an impact on existing theories about the structure, formation and evolution of supercooled liquids and glasses. As an integral part of the proposal, the training of graduate students will be carried out through cutting-edge scientific research. The program involves the full participation of graduate students, promotes the participation of local high-school students, and produces new course development for a possibly new materials curriculum. On a broader horizon, the proposed project promotes collaborations between various institutions, including international laboratories and universities. Its collaborative nature will provide students a broader exposure to multidisciplinary scientific research modes, contributing to an excellent preparation for a scientific career.