The selective abnormal grain growth (AGO) of Goss grains in Fe-3\% Si steel was investigated using a parallel Monte Carlo (MC) simulation based on the concept of sub-boundary-enhanced solid-state wetting. Goss grains that contain low angle sub-boundaries will induce solid-state wetting against grain boundaries in the matrix that exhibit a moderate variation in grain boundary energy, as expected from the variation in boundary type. AGG generates a sharp Goss texture provided that only Goss-oriented grains have the required sub-grain structure to grow selectively by sub-boundary-induced wetting and that other orientations lack the required content of low angle boundaries. This behavior is shown in three-dimensional MC simulations of microstructure evolution with textures and grain boundary distributions matched to experimental data.

Three-dimensional electron backscatter diffraction data, obtained by serial sectioning a nickel base superalloy, has been analysed to measure the geometric arrangement of grain boundary planes at triple junctions. This information has been used to calculate the grain boundary character distribution (GBCD) and the grain boundary energy distribution (GBED). The twin content from the three-dimensional GBCD calculation compares favourably with the twin content estimated by stereology. Important factors in the analysis are the alignment of the parallel layers, the ratio of the out-of-plane to in-plane spacing of the discrete orientation data and the discretisation of the domain of grain boundary types. The results show that grain boundaries comprised of (111) planes occur most frequently and that these grain boundaries have a relatively low energy. The GBCD and GBED are inversely correlated.

Recent experimental and computational studies have produced two large grain boundary energy data sets for Ni. Using these results, we perform the first large-scale comparison between measured and computed grain boundary energies. While the overall correlation between experimental and computed energies is minimal, there is excellent agreement for the data in which we have the most confidence, particularly the experimentally prevalent Sigma 3 and Sigma 9 boundary types. Other CSL boundaries are infrequently observed in the experimental system and show little correlation with computed boundary energies. Because they do not depend on observation frequency, computed grain boundary energies are more reliable than the experimental energies for low population boundary types. Conversely, experiments can characterize high population boundaries that are not included in the computational study. Together the experimental and computational data provide a comprehensive catalog of grain boundary energies in Ni that can be used with confidence by microstructural scientists.

The viscoplastic deformation of polycrystals under uniaxial loading is investigated to determine the relationship between hot spots in stress and their location in relation to the microstructure. A 3D full-field formulation based on fast Fourier transforms for the prediction of the viscoplastic deformation of poly-crystals is used with rate-sensitive crystal plasticity. Two measured polycrystalline structures are used to instantiate the simulations, as well as a fully periodic synthetic polycrystal adapted from a simulation of grain growth. Application of (Euclidean) distance maps shows that hot spots in stress tend to occur close to grain boundaries. It is also found that low stress regions lie close to boundaries. The radial distribution function of the hot spots indicates clustering. Despite the lack of texture in the polycrystals, the hot spots are strongly concentrated in < 1 1 0 > orientations, which can account for the observed clustering. All three microstructures yield similar results despite significant differences in topology.

Three-dimensional finite element analysis of a bicrystal using a crystal plasticity constitutive theory was performed to compute the maximum plastic shear strain range Delta gamma(p)(max) in the matrix, at the particle/matrix interface, and at the bicrystal boundary. Using the finite element analysis results, a design of experiments (DOE) technique was employed to understand and quantify the effects of seven parameters on fatigue crack incubation: applied displacement, load ratio, particle modulus, the number of initially active slip systems, the relative crystallographic misorientation at the grain boundary, the particle aspect ratio, and the normalized particle size. The simulations clearly showed that the applied displacement is the most influential parameter. In most cases, particles were found to be more significant than bicrystal boundaries for incubation. The number of initially active slip systems, the particle aspect ratio, and the normalized particle size showed some influences on fatigue incubation. The particle modulus was the least influential parameter.

This paper is based on the comparison of the cold-rolling and subsequent annealing behavior of two hcp metals (cp-Ti and Zr702). A special attention is paid to the consequences of deformation twinning on texture and microstructure evolutions. The Ti sheet develops an important amount of twins in the first stages of deformation, whereas the Zr702 sheet deforms by slip only. Twinning is a very efficient grain fragmentation mechanism. It generates specific texture components at medium strains which smear out after 80\% thickness reduction. Recrystallization mechanisms and kinetics are sensitive to the deformation substructure types and therefore to the occurrence of twinning. However the texture evolves quite few during recrystallization after 80\% cold-rolling in both materials. Twinning orientation relationships are promoted in the misorientation distributions of the deformed microstructures but also slightly show up in the grain boundary populations of recrystallized materials.

Addition of light rare earth elements in small amounts to refractory metal based alloys (e.g., Cr) can increase both ductility and creep resistance of an alloy because the additives absorb residual oxygen in the alloy by forming oxides that can serve as dispersion strengtheners. In this work, three binary systems, Cr-Ce, Cr-La and Cr-Y, were thermodynamically assessed based on limited experimental data available in the literature using the CALPHAD method. Self-consistent and reasonable thermodynamic descriptions for all three systems were obtained. More importantly, two predictions are made: a peritectic reaction in the La-rich side of Cr-La system and a catatectic reaction in the Y-rich side of Cr-Y system. These predictions and the developed databases are subject to future experiments that are needed to clarify several discrepancies in these binaries.

This study reveals the development of texture and microstructure that occurs during friction stir welding of two aluminum alloys. Friction stir welds of single crystal aluminum and 2195 aluminum were investigated using a stop-action technique, where the microstructure surrounding the tool was preserved by immediately quenching the weld end upon completion. Plan view sections of these weld terminations reveal that slight variations in the crystallographic orientation within the base material have different susceptibilities to the shear deformation produced by the rotating tool. Similarly, the misorientations generated during subgrain development can also induce variations in the lattice rotation rate. The divergent orientations that develop can have different susceptibilities to both rotation and grain subdivision. Lattice rotations continue until achieving a readily-sheared orientation, after which no further rotation is observed. The final texture that develops near the tool corresponds to the B and (B) over bar components of the simple shear texture. In the 2195 alloy, the deposited weld also exhibits a simple shear texture, but it varies with a periodicity of the tool advance per revolution between a pure B/(B) over bar component and a mixture of the B/(B) over bar and C components. Thus, the development of textures ahead of the tool can be correlated directly to the increasing temperature and shear deformation of those regions, while the periodic texture variations of the deposited weld indicate a systematically varying component in the friction stir welding process.