Atomistic modeling of dislocations to support an ICME framework
Abstract
The realization of an ICME framework is a critical step in providing support for agile, time efficient, and deployable alloy development capability for various process routes that support U.S. Naval mission objectives. In turn, atomistic modeling is an underpinning predictive computational modeling and simulation platform that can support critical understanding of deformation and strengthening mechanisms of new and improved alloy systems. Predictive methods in computational materials science are at the core of alloy design and development, providing support for decision-making in selection of alloy composition and microstructure. Atomistic simulations are complementary to the role of solid state thermodynamics regarding phase stability and properties related to evolution of defects in the ICME paradigm. Simulations of dislocations in crystals are critical to informing fundamental properties such as initial yield strength and rate of work hardening of metals and alloys, as these are controlled by dislocation-obstacle reactions of various types, or example point defects, precipitates, dispersed phases, and interfaces (grain or phase boundaries). Moreover, the kinetics of such unit dislocation processes are critical to understanding material stability and temperature dependence of material response under applied stress; atomistic modeling provides direct pathways to estimate kinetics. The Georgia Tech team, consisting of Professors David McDowell and Ting Zhu, will provide expertise to the configuration of a model chain in several distinct areas of atomistic modeling of dislocations as part of a broader ICME framework to provide decision-support for alloy design and development. Atomistic modeling methods based on molecular statics (MS), molecular dynamics (MD), and the Nudged Elastic Band (NEB) method will be employed to simulate stable or metastable structures and to access reaction pathways during microstructure reconstruction associated with evolution of dislocations in unit processes, for example dislocation interactions with obstacles, cross-slip, and other mechanisms. The computed activation enthalpies from NEB can be employed with transition state theory to provide estimates of temperature- and stressdependent kinetics for various operative mechanisms. Other important properties relate to mobility of dislocations and their interaction with solute atoms or obstacle fields, in addition to extended dislocation reactions with grain and phase interfaces. Larger scale configurations involving energy minimization of structure or extended dislocation interactions can be accessed using recently developed coarse-grained atomistic models developed in part by the Georgia Tech team. In this three-year research program, the Georgia Tech research effort will configure that atomistic modeling effort to interact with “top-down” inquiries regarding desired responses or properties arising from characterization of processed materials or thermodynamics and phase field simulations of accessible strengthening obstacles and spatial distributions, as well as interfaces. Results from atomistic simulations will be used to inform upscale models such as discrete dislocation dynamics and crystal plasticity regarding nanostructure-property relations that involve dislocation reactions in alloys of interest. The Georgia Tech team will seek to address the accuracy of interatomic potentials to serve either purposes of parametric trend studies (requiring lower accuracy) to comparative quantitative property predictions (requiring higher accuracy); both of these purposes support ICME objectives by providing decision support for upscale material modelers and alloy developers. Data, codes and computational atomistic modeling workflows supporting the ICME Foundational Engineering Problems (FEPs) will be made available on-line and to the broader ICME framework developed by Naval Research Laboratory.
Document Details
- Document Type
- DoD Grant Award
- Publication Date
- Sep 19, 2018
- Source ID
- N000141812784
Entities
People
- David Mcdowell
Organizations
- Georgia Tech Research Corporation
- Office of Naval Research
- United States Navy