QUANTITATIVE EVALUATION OF TOPOLOGICAL MEASURES FROM GRAIN STRUCTURES GENERATED BY LARGE-SCALE PHASE-FIELD SIMULATIONS OF GRAIN GROWTH

Open Access
Author:
Chang, Kunok
Graduate Program:
Materials Science and Engineering
Degree:
Doctor of Philosophy
Document Type:
Dissertation
Date of Defense:
August 10, 2011
Committee Members:
  • Long Qing Chen, Dissertation Advisor
  • Long Qing Chen, Committee Chair
  • Qiang Du, Committee Member
  • Christopher Muhlstein, Committee Member
  • Gary Lynn Messing, Committee Member
Keywords:
  • Phase-field
  • Grain growth
  • Zener pinning
  • Topological measures
Abstract:
The macroscopic properties of materials are predicted from the microstructure using the topological measures. In this thesis, we measured various types of topological measures in both the transient and steady state regimes. We evaluated the steady state distributions of grain size, the number of faces, the number edges and the number vertices per grain from two different types of phase-field grain growth models proposed by Kim et al. and Chen et al. The large-scale three dimensional grain growth simulations were performed using parallel computing technique. We invented the novel methods to measure the integrated mean curvature of the grain surface, the triple line length and the dihedral angle between adjacent grain faces. These methods are applicable for grain structure described by a voxel-based microstructure representation (VBMR), such as those generated by phase-field simulations, Monte Carlo Potts models, or three-dimensional reconstructions of experimentally measured grain structures. We measured those characteristics and proposed analytic expressions that allow the prediction of mean width and triple line length with respect to the normalized grain size from the normalized grain size. Additionally, the MacPherson-Srolovitz relation was examined using the evaluated mean curvature and triple line length values. The grain boundary pinning force applied by a second-phase particle was precisely measured from the grain boundary morphology in a three-dimensional system. The dragging forces exerted by spherical and ellipsoidal second-phase particle were examined using the forces estimated from the grain boundary geometry. The particle pinning forces applied by cuboidal particles were evaluated and compared with the pinning forces that were estimated from the derived expression. In addition, the effect of the second-phase particle morphology on two-dimensional grain growth kinetics was examined.