Computational Framework for Assessing Grain Boundary Structure-Property Relationships at Nanoscale

Transcription

1 Computational Framework for Assessing Grain Boundary Structure-Property Relationships at Nanoscale M.A. Tschopp, M.F. Horstemeyer Center for Advanced Vehicular Systems (CAVS), Mississippi State University 1

2 Introduction CAVS: Multiscale Models of Mechanical Behavior Where do grain boundaries enter into multiscale models? 2

3 Outline Grain boundary structure-property relationships Electronic Principles (DFT) Interatomic Potential Development Molecular dynamics GB structure database GB properties database Potts Model Phase Field Dislocation Dynamics Mesoscale models Continuum models Molecular Continuum 3

4 Integration Driver Tschopp et al. MSMSE (2009), Wilks et al. MSEA (2010) Genetic Algorithm Spline Fitting Neural Network Image Processing Optimization Parallel Processing Toolboxes Tschopp et al. ScrMater (2010) GUI MATLAB External Programs Data Management *.mat datafiles Write to Excel Output images Generate LaTex reports Write to *.ppt *.fig graphs DYNAMO VASP LaTex LAMMPS GNUPLOT ABAQUS VPSC 4

5 Interatomic Potential Development Introduction CAVS - Interatomic Potential Development Aluminum Al-Mg, Al-Si, Al-Cu, Al-Fe, etc. Magnesium Mg-Al, etc. Steel Fe-V, Fe-C, etc. Nuclear Applications Polymer/composites New research areas Still needs some work Needs to be efficient!!! Optimization techniques what methodology works best? Ease of transferability to new potentials Addition of new response variables (e.g., stacking fault energy) 5

6 Interatomic Potential Development Simulation Methodology Interatomic Potential Design Methodology Fe-He potential Design Space Evaluation MA Tschopp, KN Solanki, MI Baskes, F Gao, X Sun, M Khaleel 6

7 Interatomic Potential Development Simulation Methodology Interatomic Potential Design Methodology Fe-He potential Sensitivity Analysis MA Tschopp, KN Solanki, MI Baskes, F Gao, X Sun, M Khaleel 7

8 Interatomic Potential Development Simulation Methodology Interatomic Potential Design Methodology Fe-He potential Design Space Evaluation MA Tschopp, KN Solanki, MI Baskes, F Gao, X Sun, M Khaleel 8

9 Interatomic Potential Development Simulation Methodology Interatomic Potential Design Methodology Fe-He potential Design Space Evaluation MA Tschopp, KN Solanki, MI Baskes, F Gao, X Sun, M Khaleel 9

10 Interatomic Potential Development Fe-He Results E sub (ev) E tetra (ev) E octa (ev) E He2V (ev) E He2 (ev) E He3V (ev) W i 1/3 1/3 1/ VASP RSM DYNAMO Ran for 1 starting point Advantage of optimization on response surface is that 100 s of different starting points, weighting factors, can be ran quickly. How well does the response surface model (RSM) capture the atomistic results? MA Tschopp, KN Solanki, MI Baskes, F Gao, X Sun, M Khaleel 10

11 Outline Electronic Principles (DFT) Interatomic Potential Development Molecular dynamics GB structure database GB properties database Potts Model Phase Field Dislocation Dynamics Mesoscale models Continuum models Molecular Continuum 11

12 Grain Boundary Structure Database GB Energy Results Symmetric Tilt Grain Boundary Asymmetric Tilt Grain Boundary FCC Cu/Al 12

13 Grain Boundary Structure Database GB Energy Results Symmetric Tilt Grain Boundary Asymmetric Tilt Grain Boundary BCC Fe 13

14 Grain Boundary Structure Database GB Energy Results Symmetric Tilt Grain Boundary Asymmetric Tilt Grain Boundary HCP Mg 14

15 Grain Boundary Structure Database GB Structure Results [ 558 ] [ 445 ] SITB CTB D C D D D D D D D D D D D D C [ 774 ] [ 227 ] Cu Fe 4, 4,11 11,11, 8 SITB CTB Mg C C D C C C D D D D D D [ 223 ] [ 334 ] Cu 15

16 Grain Boundary Structure Database GB Structure Results The structure, energy and free volume of symmetric and asymmetric tilt grain boundaries can provide insight into interfacial properties, such as dislocation nucleation. Grain boundary structures of a few Σ3 asymmetric boundaries in Cu compared to HRTEM images in Ag (Ernst et al. 1992). Tschopp, Spearot, McDowell, Dislocations in Solids, Chapter 82, (2008). 16

17 Grain Boundary Properties Grain boundary dislocation nucleation No apparent correlation with GB ENERGY MISORIENTATION ANGLE SIGMA VALUE FREE VOLUME 17

18 Grain Boundary Properties Point defect formation energy results Normalized point defect formation energies Interstitial formation energies vs GB energy Site binding energies for vacancies & interstitials SIA vacancy 1 0 Influence of grain boundary character on point defect formation energies 18

19 Grain boundary hierarchical strategy Mechanical Properties Diffusivity Elastic Properties Segregation Energies SIA Formation Energies Do correlations exist that allow us to predict the properties for a wide range of GB character? Vacancy Formation Energies Free Volume Energy STGB Increasing GB size Increasing CPUs needed ATGB STwistGB ATwistGB 19

20 Cyberinfrastructure CAVS: Cyberinfrastructure ccg.hpc.msstate.edu IT technologies (hidden from the engineer) Conceptual design process (user-friendly interfaces) Engineering tools (CAD, CAE, etc.) 20

21 Thank you! QUESTIONS? 21