The molecular dynamics simulation studies of nanoscale mechanical deformation behaviors and mechanisms in metallic glasses
Date of Issue2017-02-28
School of Mechanical and Aerospace Engineering
As a new class of materials, metallic glasses (MGs) appear to have great potential for engineering applications, due to their superior properties including high strength, good corrosion resistance, thermoformability etc. Despite several attractive traits of MGs, the main drawback lies in their limited ductility at room temperature. Typically, the topological and chemical short-to-medium range structure is believed to be intimately linked with the physical and mechanical properties of MGs, and hence becomes one of the fundamental interests in this endeavor. In this regard, the main objective of this PhD project is to examine the structure-property relationships in MGs by using molecular dynamics (MD) simulations. The thesis comprises three simulation studies. The first study probes the correlations between atomic level stress and local dynamic/mechanical properties in Cu-Zr MGs. Atoms with excessive shear stress are proven to be unstable under external stimuli, and thus can be regarded as structural defects. The second study examines medium-range structures of Cu-Zr-Al glasses. The formation of medium-range networks is fundamentally determined by the local fivefold symmetry of atoms. According to the connectivity of atoms, two types of medium-range networks (solid and liquid-like) are respectively characterized. The third study investigates the chemical short range order in Cu-Zr-Ag glasses. Development of chemical short range order are found to be attributed to the local energetic stability. Correlations between chemical short range order and local dynamic/mechanical properties are also examined.