Creep Behavior of Core (Metal)–Shell (Metallic Glass) Structure: a Molecular Dynamics Simulation Study

Core–shell structures have gained importance due to the multifunctional nature achieved by the combined properties of the core and shell. In the present study, the creep behavior of the Cu (core)–Cu50Zr50 metallic glass (shell) structure has been investigated using molecular dynamic simulations. Embedded atom method potential is used to model the interactions between Cu and Zr atoms. Model size of 100 Å diameter × 800 Å length is used for the study (integration timestep = 1 fs). The tensile-creep simulations are carried at a constant temperature of 300 K, subjecting to different stresses (800 MPa, 1000 MPa, and 1200 MPa). Also, the temperature effect (300 K, 400 K, 500 K) is investigated at a constant stress of 1000 MPa. The creep curves show short primary, long-steady-state regions after instantaneous strain upon loading. The structures do not show any tertiary creep even after a simulation time of 3000 ps indicating good creep life. The strain rates in the steady-state region increase with stress and are found to be 3.43 × 106 s−1, 4.42 × 106 s−1, and 11.37 × 106 s−1, respectively. Also, as the temperatures increase, the strain rates increase, i.e., 7.4 × 106 s−1 at 400 K and 8.31 × 106 s−1 at 500 K. Activation energy (Q) and stress exponent (n) has been calculated, and the values obtained are: Q = 4.157 kJ/mol and n≈2\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$\approx 2$$\end{document}. Voronoi polyhedra analysis is performed to study the atomic structure of metallic glass shell. The fraction of Cu-centered icosahedral with index (0 0 12 0), the key structural motif, has slightly increased. An increase in the fraction value indicates that there are newborn icosahedral during creep deformation.