Indentation Behavior of Zr-Based Metallic-Glass Films via Molecular-Dynamics Simulations

Abstract

Molecular dynamics (MD) models of the Zr-based metallic-glass film (Zr 47 Cu 31 Al 13 Ni 9 , in atomic percent) were constructed by simulating sputter depositions on the titanium substrate. The as-deposited films were used as initial structures for subsequent nanoindentation simulations. For the deposition simulations, a many-body, tight-binding (TB) potential was adopted for interatomic interactions among the multiple species of atoms. The interactions between the metallic atoms and working gas (Ar + ) were modeled with the pairwise Moliere potential. The TB potential parameters for unlike atoms were chosen to be the algebraic average of those for like ones, and hence, the MD simulations provide qualitative information. The deposition simulations revealed an amorphous morphology in the as-deposited films. Indentation simulations with a right-angle conical indenter tip showed a homogeneous flow to form pileups on the surface of the metallic glass around the indent. The pileup index calculated from MD is consistent with that obtained from the experiment. Moreover, our MD results show that the pileup index exhibits anomalies, which are defined as unusual changes in the values of the pileup index, around the experimentally found glass-transformation temperature through in situ indentation simulations at elevated temperatures. From indentation load-displacement curves at various temperatures, indentation modulus and hardness obtained from MD simulations were in qualitative agreement with experimental findings in terms of their decreasing rates with respect to the temperature. Three-dimensional atomic-strain calculations revealed strain localization and propagation of shear bands under the indenter tip at their initial evolution stages after the formation of shear transformation zones. In addition, higher loading rates decrease hardness, cause larger disturbed regions under the indent, and enlarge shear-banding patterns.

Metallic glass matrix composites

“…Coating is a typical approach to constrain the shear-band propagation and, thus, promote the proliferation of shear bands [532]. The detailed mechanism responsible for the coating effects can be well understood through computational studies, such as finite-element modeling [178,[533][534][535] and molecular-dynamic (MD) simulation [515,536].…”

“…[148]. Moreover, Wang et al [536] In the MD-simulations of deposition and indentation process, interatomic potentials were adopted to probe the interactions among the three species of atoms forming the metallic glass. The interatomic potentials are expressed as:…”

Indentation properties of Cu–Zr–Al metallic-glass thin films at elevated temperatures via molecular dynamics simulation

“…For the interaction between the working argon gas and film atoms, the pair-wise Moliére potential is adopted [27,28], and the functional form of the potential is as follows:…”

“…Hardness and modulus of the films are inferred from indentation load-displacement curves by the Oliver-Pharr method [30]. The pile-up index calculations follow the method reported in [28], and region-by-region elastic anisotropy calculation procedure is similar to [3], which adopts LAMMPS to calculate all elastic constant C ijkl with PBC on all surfaces of a selected cube by a strain perturbation method.…”

The Definition Method and Optimization of Atomic Strain Tensors for Nuclear Power Engineering Materials

“…Many engineering problems involving physical phenomena need to calculate strain tensors at atomic scale. Wang et al [2] pointed that it was important to analyze the atomic-level strain distribution and get the atomic stress-strain curve while studying the mechanical behavior of Zr-based metallic glass under indentation. Hirth et al [3] considered that the computation of the deformation gradient and strain tensors made the approach useful for evaluation of continuum models, development of microstructure and mechanical property relationships, and identification of dislocations and disclinations, as well as for quantification of plastic spin and strain gradients.…”