The role of orientation pinning by neighboring grains oil migrating boundaries in a statically recrystallized oxygen-free high-conductivity (OFHC copper was investigated. Two specimens of heavily drawn OFHC copper wires deformed to true strains of 2.31 and 3.56 were, annealed at 170degreesC and local orientations were mapped by means of the automated electron backscattered diffraction technique. Inverse pole figures, misorientation distribution functions. and grain boundary misorientations were calculated from local orientation data. In spite of annealing, the nucrostrucrure of the low-strain specimen was characterized by elongated grains, similar to the as-deformed structure, whereas the microstructure of the high-strain specimen showed a high fraction of well-defined recrystallized grains. The recrystallized grains consisted of type A grains. which mostly grew laterally with hkl< 100 > orientations and type B grains, which generally grew axially with hkl < 100 > orientations. Type A grains were larger and of higher frequency than type B grains. The large size of Type A grains was attributed to the high frequency of the mobile boundaries with misorientations in the 40 to 50 deg range. Boundaries that were rnisoriented at 60 deg < 111 > (Sigma3) were found to exert the greatest pinning effect on the groqing grains. This caused recrystallized grains to grow either laterally or axially, and sometime led to branching. A detailed analysis of the influence of the next neighbor misorientations in the perimeter of the recrystallized grains is presented.

The intensities of texture components are modeled by Gaussian distribution functions in Euler space. The multiplicities depend on the relation between the texture component and the crystal and sample symmetry elements. Higher multiplicities are associated with higher maximum values in the orientation distribution function (ODF). The ODF generated by Gaussian function shows that the S component has a multiplicity of 1, the brass and copper components, 2, and the Goss and cube components, 4 in the cubic crystal and orthorhombic sample symmetry. Typical texture components were modeled using standard distributions in Euler space to calculate a discrete ODF, and their volume fractions were collected and verified against the volume used to generate the ODE The volume fraction of a texture component that has a standard spherical distribution can be collected using the misorientation approach. The misorientation approach means integrating the volume-weighted intensity that is located within a specified cut-off misorientation angle from the ideal orientation. The volume fraction of a sharply peaked texture component can be collected exactly with a small cut-off value, but textures with broad distributions (large full-width at half-maximum (FWHM)) need a larger cut-off value. Larger cut-off values require Euler space to be partitioned between texture components in order to avoid overlapping regions. The misorientation approach can be used for texture s volume in Euler space in a general manner. Fiber texture is also modeled with Gaussian distribution, and it is produced by rotation of a crystal located at g(0), around a sample axis. The volume of fiber texture in wire drawing or extrusion also can be calculated easily in the unit triangle with the angle distance approach.

Mesoscale surface-roughening evolution in 6022-T4 Al sheets was investigated using plane-strain tension. The formation of grain-scale hills and valleys and their relation to the morphologies and corresponding orientations of surface grains after deformation were examined experimentally. These observations were analyzed using various approaches based on the Schmid and Taylor crystal plasticity models. It was observed that surface grains with and without slip bands tend to form valleys and hills, respectively, wherever these two types of grains are adjacent to each other along the plane-strain tension direction. When the sample was pulled along the transverse direction, the formation of hills and valleys by unbanded and banded grains was more lineally organized in the plane-strain (rolling) direction than in the sample that was pulled along the rolling direction (RD). Slip banding and valley formation were principally observed in the surface grains with either very few (1 to 2) slip systems of high Schmid factors or with low Taylor factors, in contrast to nonslip-banded and hill-forming surface grains. Quantitative analysis using correlation coefficients showed that the Schmid factor provided slightly better agreement than the Taylor factor in predicting the slip-banding (and valley-forming) and nonslip-banding (and hill-forming) behaviors of surface grains. In addition, measures that quantify the image qualities of electron backscattered diffraction (EBSD) patterns for selected surface grains suggested that the slip-banded and valley-forming grains contain less lattice distortion than the nonslip-banded and hill-forming grains, despite the larger strains experienced by these grains. This indicates that dislocations in the slip-banded grains move out of the surface to create deformation without lattice distortion. Plastic interactions between specific neighboring grains are central to the formation of mesoscale surface roughening.

We present a new analysis of the relative rate of growth or shrinkage of grains in a two-dimensional network, based on the classical von Neumann-Mullins (VN-M) analysis. We find that an analysis of the stability of the grain shape during shrinkage or growth shows that any change in the regular 2D grain leads to changes in the shape. We also re-examine a recent analysis that claims to have invalidated the VN-M relationship, but find that it is still valid, and that the cited analysis, in fact, confused a second order correction with a first order problem, partly because their derivation was in error. The erroneous magnitude of the discrepancy led them to use unphysical issues to explain the discrepancy. The way in which the curvature is distributed along the perimeter of a grain only gives rise only to second order corrections to the rate of change of area as a function of grain topology (number of sides).

Through simulations with the moving finite element program GRAIN3D, we have studied the effect of anisotropic grain boundary energy on the distribution of boundary types in a polycrystal during normal grain growth. An energy function similar to that hypothesized for magnesia was used, and the simulated grain boundary distributions were found to agree well with measured distributions. The simulated results suggest that initially random microstructures develop nearly steady state grain boundary distributions that have local maxima and minima corresponding to local minima and maxima, respectively, of the energy function.

Through simulations with the moving finite element program GRAIN3D, we have studied the effect of anisotropic grain boundary energy on the distribution of boundary types in a polycrystal during normal grain growth. An energy function similar to that hypothesized for magnesia was used, and the simulated grain boundary distributions were found to agree well with measured distributions. The simulated results suggest that initially random microstructures develop nearly steady state grain boundary distributions that have local maxima and minima corresponding to local minima and maxima, respectively, of the energy function.

Simulation is becoming an increasingly important tool, not only in materials science in a general way, but in the study of grain growth in particular. Here we exhibit a consistent variational approach to the mesoscale simulation of large systems of grain boundaries subject to Mullins Equation of curvature driven growth. Simulations must be accurate and at a scale large enough to have statistical significance. Moreover, they must be sufficiently flexible to use very general energies and mobilities. We introduce this theory and its discretization as a dissipative system in two and three dimensions. The approach has several interesting features. It consists in solving very large systems of nonlinear evolution equations with nonlinear boundary conditions at triple points or on triple lines. Critical events, the disappearance of grains and and the disappearance or exhange of edges, must be accomodated. The data structure is curves in two dimensions and surfaces in three dimensions. We discuss some consequences and challenges, including some ideas about coarse graining the simulation.

Measurements of the grain boundary character distribution in MgAl2O4 (spinel) as a function of lattice misorientation and boundary plane orientation show that at all misorientations, grain boundaries are most frequently terminated on 111 planes. Boundaries with 111 orientations are observed 2.5 times more frequently than boundaries with 100 orientations. Furthermore, the most common boundary type is the twist boundary formed by a 60$\,^\circ$ rotation about the [111] axis. 111 planes also dominate the external form of spinel crystals found in natural settings and this suggests that they are low energy and/or slow growing planes. The mechanisms that might lead to a high population of these planes during solid state crystal growth are discussed.