Understanding Structure-Property Correlation in Metallic Glasses by Energy Landscape-Augmented Atomistic Modeling
Creators: name: Liu, Chaoyi
Publisher: name: My University
Year: 2022
Subjects: subject: Computational materials
subject: Metallic glasses
subject: Energy landscape
subject: Ageing Phenomenon
subject: Stress-Accelerated dynamics
subject: Materials Science and Engineering
subject: Mechanical Engineering
subject: FOS: Mechanical engineering
subject: Engineering

description: The need for high-performance materials in complex environments continues to increase. Various scenarios require materials to operate in high-stress environments, at extreme temperatures, under irradiations, and in other work environments far from equilibrium. In these conditions, amorphous materials such as metallic glasses outperform many other traditional materials because of their high yield strength, high hardness, corrosion resistance, and excellent conductivity. With these properties, metallic glasses have a wide range of applications such as biomedical equipment, membranes of Micro Electromechanical System (MEMS), hydrogen sensors in fuel cell vehicles, and machinery parts. However, there are also disadvantages associated with metallic glasses such as low ductility. Overcoming these disadvantages is essential to further enhance their performance. With these significant properties and drawbacks, in this work, we try to understand the structures of metallic glasses and their responses to external stimuli. Numerous critical mechanical properties such as strength, ductility, and failure are determined by the structure-property relationship. In crystalline materials, the featured structures are naturally defined by topological defects, for example, dislocations, interstitials, vacancies, etc. As a result, the structural evolution under different environments can be directly observed and quantified, such as the well-known Taylor equation that correlates the dislocation density to the strength of the system. Metallic glasses and other amorphous solids, however, due to the disordered atomic nature and disappearance of lattice periodicity, the structure-property relationships can hardly be explicitly defined as in their crystalline counterparts. Yet given many similarities between the two systems such as the glass rheology and crystal plasticity, it is widely believed that there exist some universal deformation units in amorphous materials, although details are subject to a large variety of concepts, such as free volume, shear transformation zone, flow unit, etc. Recent experiments and modeling also support such a picture that the properties of individual deformation units are invariant, while the densities and distributions of such units are closely related to the processing histories and relaxation levels of the glasses. However, quantification of the structural variations in response to surrounding environments has been hindered by the aforementioned difficulties in analyzing the disordered atomic packing in glasses. In this work, we depict the structure-property correlations of metallic glasses using Molecular Dynamics simulation methods. We develop multiple means to overcome the above challenges and successfully provide an analytical model to explain changes in properties under various thermomechanical conditions.