Irradiation-induced ductilization in the Zr-based metallic glasses

Crystalline metals in the nuclear energy system often suffer from the radiation-induced embrittlement which is resulted from the interaction between dislocation motions and the irradiation-induced changes in microstructures. This transition to the brittle failure may lower the mechanical stability of the irradiated components, posing significant threats to the operation and security of the entire mechanical system. In contrast to the crystalline metals, amorphous alloys, often called metallic glasses, have a different plasticity mechanism that does not involve the dislocation motion and hence are expected to exhibit the different irradiation effects on the mechanical from their crystalline counterparts. In this study, we investigated the mechanical properties of the Zr57Nb5Al10Cu15.4Ni12.6 metallic glass specimens irradiated by the protons through compression experiments on the nanopillars with 200 nm and 400 nm diameters at various strain rates. The energies of the protons were properly chosen between 30 keV and 200 keV to ensure the nearly uniform radiation damage depth profile to ~1.5 micron. The experimental results were also corroborated by the molecular dynamic simulation to fully understand the atomic level processes associated with the proton irradiation and mechanical behavior in the metallic glasses

Micromechanics-Based Homogenization of the Effective Physical Properties of Composites With an Anisotropic Matrix and Interfacial Imperfections

Micromechanics-based homogenization has been employed extensively to predict the effective properties of technologically important composites. In this review article, we address its application to various physical phenomena, including elasticity, thermal and electrical conduction, electric, and magnetic polarization, as well as multi-physics phenomena governed by coupled equations such as piezoelectricity and thermoelectricity. Especially, for this special issue, we introduce several research works published recently from our research group that consider the anisotropy of the matrix and interfacial imperfections in obtaining various effective physical properties. We begin with a brief review of the concept of the Eshelby tensor with regard to the elasticity and mean-field homogenization of the effective stiffness tensor of a composite with a perfect interface between the matrix and inclusions. We then discuss the extension of the theory in two aspects. First, we discuss the mathematical analogy among steady-state equations describing the aforementioned physical phenomena and explain how the Eshelby tensor can be used to obtain various effective properties. Afterwards, we describe how the anisotropy of the matrix and interfacial imperfections, which exist in actual composites, can be accounted for. In the last section, we provide a summary and outlook considering future challenges