Abstract
A realistic interatomic potential of Mg–Ca–Ag system is constructed under a proposed modified tight-binding scheme with the aid of ab initio calculations. Then, the favored and optimized compositions for forming Mg–Ca–Ag metallic glasses are investigated by means of the potential-based molecular dynamics simulations of atomistic modeling. The calculation shows that the Mg–Ca–Ag ternary system is liable to form amorphous alloys and the favored compositions for metallic glass formation locate at a sub-region, where the amorphization driving force is greater than that of other regions. Notably, we improve the conventional method of removing the facets in the amorphous structure analysis, and we introduce K-means clustering to eliminate the facets of the Voronoi polyhedra, which allows more reasonable description of various geometries of the different central atoms and their neighboring atoms. Then, both the Voronoi tessellation method and the Honeycutt–Andersen pair analysis are used to describe the disordered structure in Mg50Ca30Ag20 metallic glass based on the result of K-means clustering. Our work provides good guidance for composing the Mg–Ca–Ag metallic glasses, and further verifies the microstructure of the amorphous alloys.
Highlights
Metallic glasses (MGs), namely the amorphous alloys, refer to the long-range disordered arrangement of atoms in materials
The issue related to predicting the GFR of the Mg–Ca–Ag system in our study could be converted into an issue of comparing the relative stability of the solid solution versus its amorphous counterpart as a function of alloy composition, by applying the solid solution model
A solid solution model is established within the entire composition region based on the interaction potential between atoms, and the GFR in the system is predicted by molecular dynamics (MD) simulations
Summary
Metallic glasses (MGs), namely the amorphous alloys, refer to the long-range disordered arrangement of atoms in materials. They have attracted intensive attention since their first compositions. The GFR (glass formation region) and GFA are critical and fundamental scientific issues in Mg–Ca–Ag MGs. In this paper, a realistic atomic potential of an Mg–Ca–Ag system is constructed based on the long-range smoothed second-moment approximation of tight-binding (TB-SMA).. The skeleton, connected by 1551 bond pairs in the MGs, provides the extension of fivefold symmetry from short range to medium range and beyond, which appears to be a striking feature in many categories of MGs. Our studies provide a microscopic picture and shed light on the relationship among the formation mechanism of amorphous alloys, the nature of the glass transition process, and the atomic structure
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