Changes in short- and medium-range order in metallic liquids during undercooling

Abstract

It has been widely speculated that dominant motifs, such as short-range icosahedral order, can influence glass formation and the properties of glasses. Experimental data on both fragile and strong undercooled liquids show corresponding changes in their thermophysical properties consistent with increasing development of a network of interconnect motifs based on molecular dynamics. Describing these regions of local order, how they connect, and how they are related to property changes have been challenging issues, both computationally and experimentally. Yet the consensus is that metallic liquids develop interconnected medium-range order consisting of some regions with lower mobility with deeper undercooling. Less well understood is how these motifs (or “crystal genes”) in the liquid can inhibit nucleation in the deeply undercooled liquid or influence phase selection upon devitrification. These motifs tend to have local packing unlike stable compounds with icosahedral order tending to dominate the best glass formers. The underlying kinetic and thermodynamic forces that guide the formation of these motifs and how they interconnect during undercooling remain open questions.

Appendix

Matthew Kramer is the director of the Materials Science and Engineering Division at the US Department of Energy Ames Laboratory. He is also an adjunct professor of materials science and engineering at Iowa State University. His expertise is in materials characterization using advanced electron beam and synchrotron x-ray methods connecting synthesis to advanced modeling through in situ and in operando studies. Materials systems experience includes amorphous, liquid and nanocrystalline metals and alloys, functional materials (permanent magnets, thermal electrics) and high-temperature alloys. He has published more than 400 peer-reviewed papers and is a recipient of a number of awards from the US Department of Energy as well as a R&D 100 Award. Kramer can be reached by email at mjkramer@ameslab.gov.

Mo Li is a professor at the Georgia Institute of Technology. He received his PhD degree in applied physics in 1994 from the California Institute of Technology (Caltech). He was a postdoctoral fellow at Caltech and Argonne National Laboratory, and then joined Morgan Stanley and Co. From 1998 to 2001, he was an assistant professor at Johns Hopkins University. Li’s research includes the understanding of fundamental properties and processes of materials, and predicting material behaviors. His research focuses on algorithm development, simulation, and theoretical analysis. Li can be reached by email at mo.li@mse.gatech.edu.