Understanding the evolution of grain microstructures is one of the central problems of materials science. This paper provides an overview of some recent efforts to use molecular dynamics simulation methods to obtain some of the fundamental interfacial properties that drive the evolution and also to directly examine grain evolution. The interfacial properties include the energy and free energy of the boundaries as well as the interfacial mobility. The reliability of the energy predictions is assessed by comparisons to recent determinations of grain boundary energy distributions and grain boundary character distributions. Finally, the direct simulation of the annealing of a nanocrystalline grain structure provides insights into the kinetics of nanocrystalline grain growth and suggests an explanation of grain growth stagnation.

The orientation dependence on recovery have been studied in polycrystalline high-purity aluminum (99.99 wt\%). After cold-rolling to

High-energy X-ray diffraction microscopy is a non-destructive materials characterization technique that is capable of tracking the evolution of three-dimensional microstructures as they respond to external stimuli. We present measurements of the annealing response of high-purity aluminum using the near-field variant of this technique. The data are analyzed with the forward modeling method which produces orientation maps that exhibit complex intragranular structures. Analysis and verification of results use both reconstructed sample space maps and detector space intensity patterns. Sensitivity to the ordering of the microstructure through both recovery and recrystallization is demonstrated. Sharpening of diffraction peaks and a corresponding reduction in intragranular orientation variations signal recovery processes. The emergence of a new bulk grain (recrystallization) is observed in a disordered region of the microstructure; the new grain has an orientation with no obvious relation to those of grains surrounding the disordered region. (c) 2012

Various degrees of rolling reductions account for diverse recrystallization mechanisms and thus different microstructural and texture features. The development of deformation and recrystallization textures is discussed based on experimental data and results of finite element and crystal plasticity simulations. A recrystallization model is presented that incorporates the microstructural heterogeneities and changes in local stored energy. The experimental observations and results of crystal plasticity calculations testify that orientation selection during recrystallization is controlled by low stored energy nucleation which is incorporated in the recrystallization model. Results of texture simulations show that the evolution of \100\<130> and \011\<233> components is related to a particle stimulated nucleation mechanism.

We examine the relationship between local gradients in orientation, which are quantified with the Kernel Average Misorientation, and the grain boundary network in an interstitial-free steel sheet, before and after 12\% tensile strain. A portion of the unstrained microstructure is used as input to a full-field spectral viscoplastic code that simulates the same deformation. The orientation gradients are concentrated near grain boundaries in both experiments and simulation. Mapping out stress gradients in the simulation suggests that the development of orientation gradients is strongly correlated with such gradients.

A model is proposed for post-recrystallization grain size. The model is based on the coarsening of subgrain networks as present after deformation and recovery. It is shown that the orientation spread in the subgrain network is the key variable in predicting the density of abnormal subgrains and, hence, the recrystallized grain size. The model explains the strong dependence of the post-recrystallization grain size on prior strain and the lack of a dependence on the annealing temperature. (C) 2011 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.