The microstructure and texture evolution at different annealing temperatures were analyzed in a hot-rolled commercial purity aluminum alloy from two-dimensional electron backscattered diffraction scans. The newly recrystallized grains were found to cluster together. Recrystallized grains have cube, 001< 100 >, as the dominant texture component at all annealing temperatures. Nucleation and growth behavior of the recrystallized cube grains was observed by measuring the variations in first nearest neighbor boundary pixels of these grains. The texture of nearest neighbor pixels at low fraction recrystallized represents the nucleation environment of newly recrystallized grains. Growth rates of the recrystallized grains were estimated from the variation in grain size with time at different annealing temperatures. Analysis of nucleation and growth behavior of the recrystallized cube grains reveals a significant nucleation advantage at all annealing temperatures: a decreasing growth advantage is observed as the annealing temperature is increased. Further analysis of the nucleation environment of the recrystallizing cube grains also revealed that among the main texture components of deformed grains (S, brass and copper), they grow more rapidly into the S component than into the copper or brass components. This trend persists throughout recrystallization such that the brass component is the slowest to recrystallize. In terms of the oriented nucleation (ON) and oriented growth (OG) theories, ON has a greater impact on the development of recrystallization texture than OG.

Microstructurally small fatigue crack (MSFC) formation includes stages of incubation, nucleation and microstructurally small propagation. In AA 7075-T651, the fracture of Al 7 Cu 2 Fe constituent particles is the major incubation source. In experiments, it has been observed that only a small percentage of these Fe-bearing particles crack in a highly stressed volume. The work presented here addresses the identification of the particles prone to cracking and the prediction of particle cracking frequency, given a distribution of particles and crystallographic texture in such a volume. Three-dimensional elasto-viscoplastic finite element analyses are performed to develop a response surface for the tensile stress in the particle as a function of the strain level surrounding the particle, parent grain orientation and particle aspect ratio. A technique for estimating particle strength from fracture toughness, particle size and intrinsic flaw size is developed. Particle cracking is then determined by comparing particle stress and strength. The frequency of particle cracking is then predicted from sampling measured distributions of grain orientation, particle aspect ratio and size. Good agreement is found between the predicted frequency of particle cracking and two preliminary validation experiments. An estimate of particle cracking frequency is important for simulating the next stages of MSFC formation: inserting all particles into a microstructural model for these stages is computationally intractable and physically unnecessary.

The purpose of this work is to predict elastic and thermodynamic properties of chromium-based alloys based on first-principles calculations and to demonstrate an appropriate computational approach to develop new materials for high-temperature applications in energy systems. In this study, Poisson ratio is used as a screening parameter to identify ductilizing additives to the refractory alloys. The results predict that elements such as Ti, V Zr Nb, Hf and Ta show potential as ductilizers in Cr while Al, Ge, and Ga are predicted to decrease the ductility of Cr. Experimental evidence, where available, validates these predictions.

An efficient full-field formulation based on Fast Fourier Transforms (FFT) for the prediction of the viscoplastic deformation of polycrystals is applied to the study of the subgrain texture and microstructure evolution in polycrystalline copper deformed under tension. Direct input from Orientation Imaging Microscopy (OIM) images is used in the construction of the initial unit cell. Average orientations and misorientations predicted after 11\% tensile strain are directly compared with OIM measurements, showing good agreement. The differences between misorientations of surface grains compared with bulk grains are estimated, and the orientation dependence of intragranular misorientations is studied. Measurements and simulations agree in that grains with initial orientation near <110> tend to develop higher misorientations. This behavior can be explained in terms of attraction towards the two stable orientations and grain interaction. Only models that account explicitly for interaction between individual grains, like the FFT-based formulation, are able to capture these effects

Microstructure sensitive design was used in this study to design a textured soft magnet material to meet a range of magnetic properties. The evolution of microstructure and magnetic properties during mechanical processing was simulated and presented in a spectral representation for microstructure (texture hull) and magnetic property (property hull). The set of properties for a single path (or multiple processing paths) is represented in the property hull with a direct link to the range of desired microstructures. A methodology is proposed to achieve microstructures satisfying the requirement of multiple properties.

The microstructure and texture evolution at different annealing temperatures were analyzed in a hot-rolled commercial purity aluminum alloy from two-dimensional electron backscattered diffraction scans. The newly recrystallized grains were found to cluster together. Recrystallized grains have cube, 001< 100 >, as the dominant texture component at all annealing temperatures. Nucleation and growth behavior of the recrystallized cube grains was observed by measuring the variations in first nearest neighbor boundary pixels of these grains. The texture of nearest neighbor pixels at low fraction recrystallized represents the nucleation environment of newly recrystallized grains. Growth rates of the recrystallized grains were estimated from the variation in grain size with time at different annealing temperatures. Analysis of nucleation and growth behavior of the recrystallized cube grains reveals a significant nucleation advantage at all annealing temperatures: a decreasing growth advantage is observed as the annealing temperature is increased. Further analysis of the nucleation environment of the recrystallizing cube grains also revealed that among the main texture components of deformed grains (S, brass and copper), they grow more rapidly into the S component than into the copper or brass components. This trend persists throughout recrystallization such that the brass component is the slowest to recrystallize. In terms of the oriented nucleation (ON) and oriented growth (OG) theories, ON has a greater impact on the development of recrystallization texture than OG.

The purpose of this work is to predict elastic and thermodynamic properties of chromium-based alloys based on first-principles calculations and to demonstrate an appropriate computational approach to develop new materials for high-temperature applications in energy systems. In this study, Poisson ratio is used as a screening parameter to identify ductilizing additives to the refractory alloys. The results predict that elements such as Ti, V Zr Nb, Hf and Ta show potential as ductilizers in Cr while Al, Ge, and Ga are predicted to decrease the ductility of Cr. Experimental evidence, where available, validates these predictions.

Microstructurally small fatigue crack (MSFC) formation includes stages of incubation, nucleation and microstructurally small propagation. In AA 7075-T651, the fracture of Al 7 Cu 2 Fe constituent particles is the major incubation source. In experiments, it has been observed that only a small percentage of these Fe-bearing particles crack in a highly stressed volume. The work presented here addresses the identification of the particles prone to cracking and the prediction of particle cracking frequency, given a distribution of particles and crystallographic texture in such a volume. Three-dimensional elasto-viscoplastic finite element analyses are performed to develop a response surface for the tensile stress in the particle as a function of the strain level surrounding the particle, parent grain orientation and particle aspect ratio. A technique for estimating particle strength from fracture toughness, particle size and intrinsic flaw size is developed. Particle cracking is then determined by comparing particle stress and strength. The frequency of particle cracking is then predicted from sampling measured distributions of grain orientation, particle aspect ratio and size. Good agreement is found between the predicted frequency of particle cracking and two preliminary validation experiments. An estimate of particle cracking frequency is important for simulating the next stages of MSFC formation: inserting all particles into a microstructural model for these stages is computationally intractable and physically unnecessary.

Microstructure sensitive design was used in this study to design a textured soft magnet material to meet a range of magnetic properties. The evolution of microstructure and magnetic properties during mechanical processing was simulated and presented in a spectral representation for microstructure (texture hull) and magnetic property (property hull). The set of properties for a single path (or multiple processing paths) is represented in the property hull with a direct link to the range of desired microstructures. A methodology is proposed to achieve microstructures satisfying the requirement of multiple properties.