Quantification of the Devitrification Process of Metallic Glasses through Simulation and Experiment

George Mason University, Fairfax VA

Investigators

Abstract

NON-TECHNICAL SUMMARY Metallic glasses are novel engineering alloys in which the structure is disordered, with the atoms occupying more-or-less random positions. Metallic glasses are important in many applications, because they can be relatively resistant to fracture. The PI proposes a practical approach to quantifying the glass-forming ability of metallic materials, which has been a grand challenge in computational physics and materials science. This work will study how metallic glasses are developed, paving the way to new approaches toward quantitative metallurgy. The knowledge gained through this project will greatly advance our understanding building on existing theories on nucleation, glass transition, and the structure of glasses in general. The proposed project provides an excellent platform for integrating education, research, and outreach activities, and will help promote close collaborations among multiple academic institutions in the greater Washington D.C. area. TECHNICAL SUMMARY The glass formation ability (GFA) of metallic liquids concerns how new metallic glasses can be developed. Fundamental theories about nucleation and growth, alloy formation, and to a greater extent, glass transition, are currently insufficient to provide a parameter-free prediction of the devitrification process of metallic liquids. The precise assessment of GFA thus remains an unresolved problem in metals research. We are now positioned to address this important problem through advanced computational modeling in conjunction with state-of-the-art transmission electron microscopy experiments for validation. The ultimate goal of this project is to provide reliable parameter-free time-temperature-transformation curves for gauging the GFA ab initio, which has hitherto been impossible. This will be achieved by integrating computational approaches on multiple scales to simulate the nucleation and crystal growth during the devitrification process of realistic metallic liquids while addressing several key issues that are of scientific importance and have practical implications, including the crystallization pathway, incipient metastable phase, and critical cooling rate. Unique to this proposal is the integration of new TEM techniques (ultrafast cooling and heating conditions by passing nanosecond pulsed electric current) that create glass formation (devitrification) conditions truly commensurate with computer simulation, enabling a useful validation tool to examine the reliability of simulation. By capitalizing on powerful and unique TEM characterization capabilities, the PI will shed new light on the underlying mechanism of nucleation on the atomic level so as to establish effective and accurate simulation protocols for GFA prediction.