A molecular dynamics technique for determining energy landscapes as a dislocation percolates through a field of solutes

E Antillon and C Woodward and SI Rao and B Akdim and TA Parthasarathy, ACTA MATERIALIA, 166, 658-676 (2019).

DOI: 10.1016/j.actamat.2018.12.037

Current alloy development efforts in High Entropy Alloys call for a better understanding of solution hardening in high-concentration chemically-complex alloys. Here we propose a general scheme for assessing the overall solute-dislocation interaction, independent of concentration, stress, and temperature. While significant progress has been made in including solute-dislocation interactions in FCC metals (Leyson et al) there are open questions as to how to model more complex (solute-solute-dislocation) chemical interactions that arise in high concentration solid solutions. A method similar to Olmsted et al, is developed to quantify representative energy landscapes as a dislocation percolates through a field of solutes. This approach uses molecular dynamics under stress in order to estimate the strengthening parameters for a system over a wide range of solute concentrations and a moderate range of temperatures. While MD introduces additional complications to the simulation, due to coupling of temperature with the potential energy of the system, it also provides significant flexibility in terms of avoiding local minimum, assessing the effects of dislocation bowing and the effects of stress and temperature. Also, by avoiding the direct assessment of solute-solute bonding very complex systems can be evaluated efficiently. As proof of concept the method is applied to Al solutes in FCC Ni, where the system is known to be dominated by strong Al solute-solute interactions at high solute concentrations. Self- consistency of the method is shown by computing various strengthening parameters near critical percolation stress states at various system sizes, concentrations, and temperatures. We propose an extension to current solute-dislocation hardening models (i.e. Leyson et al.) to include solute-solute bonding and compare the scaling prediction and temperature dependence of solid solution models to the molecular dynamics results. (C) 2018 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

Return to Publications page