Amorphous Steels: Atomic Structure Characterization via Experiment and Modeling

University Of Virginia Main Campus, Charlottesville VA

Investigators

Abstract

TECHNICAL: A key issue in materials science and condensed matter physics is to understand the reasons for bulk glass formation that occurs in some alloys and not in others. The time is now right to expand on the fundamental study of metallic alloys as recent discoveries of bulk amorphous metals have opened up the possibilities for new industrial applications. The objective of this project is twofold: 1) Combine experimental structural characterization and molecular dynamics (MD) simulation- Measurement and modeling of amorphous metals to determine the atomic and nanoscale structures; and 2) Understand structure-property relationships - Relate results from modeling to thermodynamic properties; investigate brittle-ductile properties to structural features observed in the amorphous phase. For example, the amount of free volume in the amorphous structure may determine the ductility of the amorphous metal. The goal is to define the essential features of the driving mechanism of the glass forming ability and to understand the competing mechanisms among the thermodynamic, kinetic and structural processes that take place at a local level. Through an integrated research and educational program, the project will be realized by involving the active participation of students in implementing theoretical modeling and experimental tools to understanding glass forming ability in new amorphous alloys. The bulk glass capabilities of these alloys will potentially lead to new technological applications that make use of their properties that far exceed those of pure metals, conventional metallic glasses and crystals. Representative amorphous metals of Fe-based alloys that exhibit different glass forming abilities and crystallization behaviors will be investigated by scattering techniques to obtain their local topological arrangement. These will be combined with ab-initio quantum mechanical calculations addressing fundamental issues that can lead to important revelations about glass formation ability and predictions of new bulk metallic glass compositions. NON-TECHNICAL: Scientifically, the study of novel amorphous metals could accelerate the development of a new approach to modeling complex alloys. Additionally, it could also lead to new predictions of glass forming ability and structure-property relationships for guiding as well as stimulating the design of new structural materials. The nature of the program is interdisciplinary and collaborative. It involves sample characterization through the use of neutron/x-ray probes for the investigation of atomic structures that will allow students to understand structure-property relationships. The project also involves ab-initio modeling and simulation that includes collaboration with another university. Project goal is to bridge the gap between large-scale modeling and experiment by constructing a foundation for direct validation of models from the experimental output. The combination of both approaches will provide valuable training and research experience for undergraduates and graduate students. This project will become the PhD thesis of at least one graduate student. The long term plans include expanding the collaboration with other groups from other universities that work on similar systems to develop a program where the local structure-modeling capabilities of amorphous materials become widely available.