Connecting Interface Structure to Interface-Defect Interactions in Metals

This CAREER project aims to increase the understanding of interfaces in metals through theory and computer modeling. Interfaces are locations where two different crystals meet and are ubiquitous in engineering alloys such as steel, aluminum, titanium, and many others. Although interfaces typically comprise less than 0.01% of the volume of such materials, they play a decisive role in determining their mechanical, electrical, thermal, and diffusion properties. Textbooks often portray them schematically as two-dimensional and abrupt. This simplification is convenient and often necessary, but fundamentally false: interface structure is inherently three dimensional, often complex, and occasionally quite beautiful. Thus, much remains to be understood about the structure and properties of interfaces.

An improved understanding of interfaces may provide a path to making better engineering alloys. The performance envelope of materials limits much of what technology can accomplish, for example in energy applications: from steam generators and batteries to high-voltage power lines and nuclear reactors, better materials translate into cleaner, safer, and cheaper energy. Materials performance in these applications is often controlled by crystal defects, such as vacancies, dislocations, and cracks. Tailoring the interactions of interfaces with such defects is one path to expanding the performance envelope of materials.

This project has three objectives. The first is to develop models that capture the full complexity of interface structure with enough precision to make quantitative predictions. The second is to discover how interfaces with different structures interact with defects that control materials performance and to develop the capability to predict these interface-defect interactions from interface structure. Finally, the third objective is to validate the interface structure and defect interaction models described above. All models make simplifying assumptions. A major goal of this work is to develop strategies for validating models of interface structure and defects interactions using both theory and experiments.

Because there is an infinite number of possible interfaces, this project has to focus on a selected subset of them. The specific types of interfaces to be studied have therefore been downselected based on criteria that give the highest likelihood of making rapid progress towards achieving the goals of this project. Similarly, interactions of interfaces with only three types of defects will be considered: point defects, dislocations, and cracks. There are, however, no fundamental physical limitations that prevent broadening the scope of future work to interfaces, interactions, and defect types other than those initially downselected.