Understanding and Prediction of Glass Formation from Composition-Dependent Atomic Structures in Bulk Metallic Glasses

Bulk metallic glasses (BMGs), a new emerging class of metallic materials, have attracted extensive interest because of their unique mechanical and physical properties, including extremely high strength, large elastic strain limit, good corrosion resistance, and superior magnetic properties. In spite of these promising properties, their widespread applications are limited primarily due to their limited glass-forming ability (GFA) and high production cost, which are the major obstacles to the economic manufacture of these materials for industrial applications at present. For the past decade, considerable effort has been devoted to exploring the GFA of BMGs; however, most of approaches are mainly from thermodynamic and kinetic aspects in macroscopic scales. As a result, none of them are capable of predicting GFA from given alloy compositions. This proposed research aims at developing computational methodology and experimental techniques to resolve this issue from an atomic structure perspective. We intend to develop a scientific scheme to quantitatively correlate the GFA with atomic structures in the Zr-Ni-Al model system (see Fig. 1). Based on this correlation, the ultimate goal is to understand glass formation from the atomic-scale structure and alloy composition, and then to provide scientific principles to design novel BMGs with superior GFA.First-principles ab initio molecular dynamics (AIMD), classical MD and reverse Monte Carlo simulations will be used to investigate the atomic-level structures and assess the glass formation and GFA. The structural features of atomic clusters and free volume, including their hierarchical orderings, energy states and percolations, will be quantitatively measured in MD simulations as a function of alloy composition. A systematic variation of alloy compositions will be used to reveal the composition dependence of GFA. Base on these results, the quantitative correlation between atomic structure and GFA will be developed by carefully analyzing their atomic-scale structural features in different alloy compositions. To verify the simulation results, the state-of the- art techniques, including high resolution transmission electron microscopy, synchrotron extended X-ray absorption fine structure and neutron diffraction, will be conducted. Based on this systematic investigation, we will be in a position to understand how atomic clusters and short-range orders existing in the amorphous and supercooled liquid states affect glass formation and then to assess GFA from an atomic structure perspective.The implementation of this proposed research will lead to the understanding of atomic structures and glass formation of BMGs, and the development of innovative BMGs with vast industrial potentials for high-tech applications in Hong Kong.