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Christopher A. Schuh - One of the best experts on this subject based on the ideXlab platform.
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Texture mediated grain Boundary Network design in three dimensions
Mechanics of Materials, 2018Co-Authors: Oliver K. Johnson, Christopher A. SchuhAbstract:Abstract Experimental grain Boundary engineering studies have demonstrated the potential for materials properties enhancement via the modification of grain Boundary Network structure. These techniques apply to materials that readily form annealing twins and are amenable to cyclic thermomechanical processing and have resulted in dramatic property enhancement. In this work we present a theoretical framework that enables the design of grain Boundary Networks in polycrystalline materials through an alternative approach: exploitation of a relationship between crystallographic texture and grain Boundary Network structure. Because crystallographic texture is a universal characteristic of polycrystalline materials, this work has the potential to significantly expand the class of materials whose grain Boundary Networks can be controlled. We demonstrate the utility of the approach by application to a concrete design problem involving competing design objectives for yield strength, elastic compliance, and resistance to electromigration. We construct the first materials properties closure to comprise grain Boundary Network sensitive properties and identify an optimal microstructure that is predicted to outperform an undesigned isotropic material.
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Texture mediated grain Boundary Network design in two dimensions
Journal of Materials Research, 2016Co-Authors: Oliver K. Johnson, Christopher A. SchuhAbstract:While materials design in the context of texture dependent properties is well developed, theoretical tools for microstructure design in the context of grain Boundary sensitive properties have not yet been established. In the present work, we present an invertible relationship between texture and grain Boundary Network structure for the case of spatially uncorrelated two-dimensional textures. By exploiting this connection, we develop mathematical tools that permit the rigorous optimization of grain Boundary Network structure. Using a specific multi-objective materials design case study involving elastic, plastic and kinetic properties, we illustrate the utility of this texture mediated approach to grain Boundary Network design. We obtain a microstructure that minimizes grain Boundary Network diffusivity while simultaneously improving yield strength by an amount equal to half of the theoretically possible range. The theoretical tools developed here could complement experimental grain Boundary engineering efforts to help accelerate the discovery of materials with improved performance.
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Texture mediated grain Boundary Network design in two dimensions
Journal of Materials Research, 2016Co-Authors: Oliver K. Johnson, Christopher A. SchuhAbstract:Abstract
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Inferring grain Boundary structure–property relations from effective property measurements
Journal of Materials Science, 2015Co-Authors: Oliver K. Johnson, Michael J. Demkowicz, Christopher A. SchuhAbstract:Grain boundaries strongly affect many materials properties in polycrystalline materials. However, very few structure–property models exist for grain boundaries, due in large part to the complicated and poorly understood way in which the properties of grain boundaries vary with their crystallographic structure. In the present work, we infer grain Boundary structure–property correlations from measurements of the effective properties of a polycrystal. We refer to this approach as grain Boundary properties localization. We apply this technique to a simple model system of grain Boundary diffusivity in a two-dimensional microstructure, and infer the properties of low- and high-angle grain boundaries from the effective diffusivity of the grain Boundary Network. The generalization and use of these methods could greatly reduce the computational and experimental effort required to establish structure–property correlations for grain boundaries. More broadly, the technique of properties localization could be used to infer the properties of many microstructural constituents in complex microstructures.
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Grain Boundary Networks in nanocrystalline alloys from atom probe tomography quantization and autocorrelation mapping
physica status solidi (a), 2015Co-Authors: Ying Chen, Christopher A. SchuhAbstract:A local spatial autocorrelation-based modeling method is developed to reconstruct nanoscale grain structures in nanocrystalline materials from atom probe tomography (APT) data, which provide atomic positions and species, with minimal noise. Using a nanocrystalline alloy with an average grain size of 16 nm as a model material, we reconstruct the three-dimensional grain Boundary Network by carrying out two series of APT data quantization using ellipsoidal binning, the first probing the anisotropy in the apparent local atomic density and the second quantifying the local spatial autocorrelation. This approach enables automatic and efficient quantification and visualization of grain structure in a large volume and at the finest nanoscale grain sizes, and provides a means for correlating local chemistry with grain boundaries or triple junctions in nanocrystalline materials. Nanoscale grain Boundary Networks are reconstructed from atom probe tomography data, which provide atomic positions and species for a fraction of atoms within a nanocrystalline material with an average grain size of 16 nm, using a quantization and local spatial autocorrelation-based approach.
Oliver K. Johnson - One of the best experts on this subject based on the ideXlab platform.
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Texture mediated grain Boundary Network design in three dimensions
Mechanics of Materials, 2018Co-Authors: Oliver K. Johnson, Christopher A. SchuhAbstract:Abstract Experimental grain Boundary engineering studies have demonstrated the potential for materials properties enhancement via the modification of grain Boundary Network structure. These techniques apply to materials that readily form annealing twins and are amenable to cyclic thermomechanical processing and have resulted in dramatic property enhancement. In this work we present a theoretical framework that enables the design of grain Boundary Networks in polycrystalline materials through an alternative approach: exploitation of a relationship between crystallographic texture and grain Boundary Network structure. Because crystallographic texture is a universal characteristic of polycrystalline materials, this work has the potential to significantly expand the class of materials whose grain Boundary Networks can be controlled. We demonstrate the utility of the approach by application to a concrete design problem involving competing design objectives for yield strength, elastic compliance, and resistance to electromigration. We construct the first materials properties closure to comprise grain Boundary Network sensitive properties and identify an optimal microstructure that is predicted to outperform an undesigned isotropic material.
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Texture mediated grain Boundary Network design in two dimensions
Journal of Materials Research, 2016Co-Authors: Oliver K. Johnson, Christopher A. SchuhAbstract:While materials design in the context of texture dependent properties is well developed, theoretical tools for microstructure design in the context of grain Boundary sensitive properties have not yet been established. In the present work, we present an invertible relationship between texture and grain Boundary Network structure for the case of spatially uncorrelated two-dimensional textures. By exploiting this connection, we develop mathematical tools that permit the rigorous optimization of grain Boundary Network structure. Using a specific multi-objective materials design case study involving elastic, plastic and kinetic properties, we illustrate the utility of this texture mediated approach to grain Boundary Network design. We obtain a microstructure that minimizes grain Boundary Network diffusivity while simultaneously improving yield strength by an amount equal to half of the theoretically possible range. The theoretical tools developed here could complement experimental grain Boundary engineering efforts to help accelerate the discovery of materials with improved performance.
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Texture mediated grain Boundary Network design in two dimensions
Journal of Materials Research, 2016Co-Authors: Oliver K. Johnson, Christopher A. SchuhAbstract:Abstract
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Inferring grain Boundary structure–property relations from effective property measurements
Journal of Materials Science, 2015Co-Authors: Oliver K. Johnson, Michael J. Demkowicz, Christopher A. SchuhAbstract:Grain boundaries strongly affect many materials properties in polycrystalline materials. However, very few structure–property models exist for grain boundaries, due in large part to the complicated and poorly understood way in which the properties of grain boundaries vary with their crystallographic structure. In the present work, we infer grain Boundary structure–property correlations from measurements of the effective properties of a polycrystal. We refer to this approach as grain Boundary properties localization. We apply this technique to a simple model system of grain Boundary diffusivity in a two-dimensional microstructure, and infer the properties of low- and high-angle grain boundaries from the effective diffusivity of the grain Boundary Network. The generalization and use of these methods could greatly reduce the computational and experimental effort required to establish structure–property correlations for grain boundaries. More broadly, the technique of properties localization could be used to infer the properties of many microstructural constituents in complex microstructures.
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Grain Boundary Network design
2015Co-Authors: Oliver K. JohnsonAbstract:Grain boundaries in polycrystals form a complex interconnected Network of intercrystalline interfaces. The crystallographic character of individual grain boundaries and the Network structure of the grain Boundary ensemble have been experimentally observed to have a strong influence on many materials properties. This observation suggests that if we could control the types of grain boundaries present in a polycrystal and their spatial arrangement then it would be possible to dramatically improve the properties of polycrystalline materials and tailor them to specific engineering applications. However, there are a number of major obstacles that have, until now, precluded the realization of this opportunity: (1) methods capable of simultaneously quantifying the crystallographic and topological structure of grain Boundary Networks do not exist; (2) theoretical models relating grain Boundary Network structure to physical properties have not yet been developed; and, consequently, (3) there are no techniques to quantitatively identify grain Boundary Network structures that would be beneficial for a given property. In this thesis I address these obstacles by first developing a new statistical description of grain Boundary Network structure called the triple junction distribution function (TJDF), which encodes both crystallographic and topological information. I establish new results regarding the physical symmetries of triple junctions and find a relationship between crystallographic texture and grain Boundary Network structure. I then use the TJDF to develop a model for the effective diffusivity of a grain Boundary Network. Finally, using the relationship between texture and grain Boundary Network structure that I develop, I describe a method for texture-mediated grain Boundary Network design. This process permits the theoretical design of grain Boundary Networks with properties tailored to a given engineering application and is applicable to any polycrystalline material. I demonstrate the potential of this technique by application to a specific design problem involving competing design objectives for mechanical and kinetic materials properties. The result is a designed microstructure that is predicted to outperform an isotropic polycrystal by seven orders of magnitude.
Thomas James Marrow - One of the best experts on this subject based on the ideXlab platform.
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effect of thermomechanical process history on grain Boundary control in an austenitic stainless steel
Scripta Materialia, 2008Co-Authors: Dirk Engelberg, R C Newman, Thomas James MarrowAbstract:The influence of cold roll reduction history on grain Boundary Network development in an austenitic stainless steel has been investigated. A dominant effect of the final thermomechanical process cycles on grain Boundary character development was observed. The application of low-strain processing cycles with 5% cold reduction was found to increase the fraction of Σ3 and Σ3-related variants on solution annealing. Two-step processing treatments with final reductions between 15% and 82% showed no significant differences to their single-step processed equivalents.
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The influence of low‐strain thermo‐mechanical processing on grain Boundary Network characteristics in type 304 austenitic stainless steel
Journal of Microscopy, 2008Co-Authors: Dirk Engelberg, F.j. Humphreys, Thomas James MarrowAbstract:Summary Grain Boundary engineering of austenitic stainless steel, through the introduction of plastic strain and thermal annealing, can be used to develop microstructures with improved resistance to inter-granular degradation. The influence of low-strain thermo-mechanical processing on grain Boundary Network development, with systematic variations of annealing treatments, has been investigated. Three stages of the microstructure development during grain Boundary engineering in low-strain processing conditions are identified, and correlated with changes in grain Boundary character and deviation distributions. Low-energy connected length segments at triple junctions, which have been proposed to be responsible for crack bridging during inter-granular stress corrosion cracking, can be influenced by the choice of the annealing treatment parameters. The development of individual grain Boundary length segments of different character showed consistent trends with increasing grain size. Crack length predictions are consistent with the beneficial effect of designing microstructures with high fractions of twin grain boundaries and smaller grain size.
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The influence of low-strain thermo-mechanical processing on grain Boundary Network characteristics in type 304 austenitic stainless steel.
Journal of microscopy, 2008Co-Authors: Dirk Engelberg, F.j. Humphreys, Thomas James MarrowAbstract:Grain Boundary engineering of austenitic stainless steel, through the introduction of plastic strain and thermal annealing, can be used to develop microstructures with improved resistance to inter-granular degradation. The influence of low-strain thermo-mechanical processing on grain Boundary Network development, with systematic variations of annealing treatments, has been investigated. Three stages of the microstructure development during grain Boundary engineering in low-strain processing conditions are identified, and correlated with changes in grain Boundary character and deviation distributions. Low-energy connected length segments at triple junctions, which have been proposed to be responsible for crack bridging during inter-granular stress corrosion cracking, can be influenced by the choice of the annealing treatment parameters. The development of individual grain Boundary length segments of different character showed consistent trends with increasing grain size. Crack length predictions are consistent with the beneficial effect of designing microstructures with high fractions of twin grain boundaries and smaller grain size.
Ludwig Schultz - One of the best experts on this subject based on the ideXlab platform.
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Influence of the grain Boundary Network on the critical current of YBa 2 Cu 3 O 7 films grown on biaxially textured metallic substrates
Physical Review B, 2003Co-Authors: L. Fernández, B. Holzapfel, F. Schindler, B. De Boer, A. Attenberger, Jens Hänisch, Ludwig SchultzAbstract:YBa 2 Cu 3 O 7 /YSZ/CeO 2 heterostructures have been grown epitaxially on biaxially textured Ni substrates by pulsed laser deposition. The texture of the film was determined by electron backscattering diffraction, providing information on the propagation of the grain Boundary Network from the Ni substrate to the YBa 2 Cu 3 O 7 film via the epitaxial growth. The grain Boundary Network limits the critical current density to 0.3 MA/cm 2 (77 K, 0 T), compared with 1.3 MA/cm 2 (77 K, 0 T) for a film grown on a single crystalline Ni substrate. Transport measurements on the coated conductor sample at different temperatures and magnetic fields show that there is a crossover field between intergrain and intragrain critical current that is shifted to higher magnetic fields as the temperature is reduced.
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Grain Boundary Network transport properties of YBa2Cu3O7 film on biaxially textured metal substrates
Physica C-superconductivity and Its Applications, 2002Co-Authors: L. Fernández, B. Holzapfel, F. Schindler, B. De Boer, Ludwig SchultzAbstract:Abstract YBa 2 Cu 3 O 7 films have been grown epitaxially on biaxially textured Ni substrates and on single crystalline Ni films by laser ablation. The configuration of the samples was YBa 2 Cu 3 O 7 /yttrium-stabilized zirconia/CeO 2 /Ni in both cases. The YBa 2 Cu 3 O 7 coated conductor sample shows due to the grain Boundary Network (GBN) a reduced J c value of 0.3 MA/cm 2 ( T =77 K and B =0 T) compared with the J c corresponding to the sample on the single crystalline Ni film of 1.3 MA/cm 2 ( T =77 K and B =0 T). Texture and electron backscattering diffraction measurements of the samples were performed before and after the growth; this allowed a quantitative evaluation of the average misorientation of the GBN, which determines the critical current density.
Hossein Beladi - One of the best experts on this subject based on the ideXlab platform.
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on the grain Boundary Network characteristics in a martensitic ti 6al 4v alloy
Journal of Materials Science, 2020Co-Authors: Ehsan Farabi, Vahid Tari, Peter Hodgson, Gregory S Rohrer, Hossein BeladiAbstract:The characteristics of the intervariant Boundary Network that resulted from the $$\beta \to \alpha^{\prime}$$ martensitic phase transformation in a Ti–6Al–4V alloy were studied using the crystallographic theories of displacive transformations, five-parameter grain Boundary analysis and triple junction analysis. The microstructure of Ti–6Al–4V martensite consisted of fine laths containing dislocations and fine twins. The misorientation angle distribution revealed four distinct peaks consistent with the intervariant boundaries expected from the Burgers orientation relationship. The phenomenological theory of martensite predicted four-variant clustering to have the lowest transformation strain among different variant clustering combinations. This configuration was consistent with the observed Ti–6Al–4V martensitic microstructure, where four-variant clusters consisted of two pairs of distinct V-shape variants. The $$63.26^\circ /[\overline{10}\, 5\, 5\, \overline{3}]_{{\alpha^{\prime}}}$$ and $$60^\circ /[1\, 1\, \overline{2}\, 0]_{{\alpha^{\prime}}}$$ intervariant boundaries accounted for ~ 38% and 33% of the total population, respectively. The five-parameter Boundary analysis showed that the former had a twist character, being terminated on the $$(\overline{3}\, 2\, 1\, 0)_{{\alpha^{\prime}}}$$ plane, and the latter revealed a symmetric tilt $$(1\, 0\, \overline{1}\, 1)_{{\alpha^{\prime}}}$$ Boundary plane. The $$63.26^\circ /[\overline{10}\, 5\, 5\, \overline{3}]_{{\alpha^{\prime}}}$$ and $$60^\circ /[1\, 1\, \overline{2}\, 0]_{{\alpha^{\prime}}}$$ had the highest connectivity at triple junctions among other intervariant boundaries. Interestingly, the Boundary Network in Ti–6Al–4V martensite was significantly different from the commercially pure Ti martensite, where only $$60^\circ /[1\, 1\, \overline{2}\, 0]_{{\alpha^{\prime}}}$$ intervariant boundaries largely were found at triple junctions due to the formation of three-variant clustering to minimize the transformation strain. This difference is thought to result from a change in the martensitic transformation mechanism (slip vs twinning) caused by the alloy composition.
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On the grain Boundary Network characteristics in a martensitic Ti–6Al–4V alloy
Journal of Materials Science, 2020Co-Authors: Ehsan Farabi, Vahid Tari, Gregory S Rohrer, Peter D. Hodgson, Hossein BeladiAbstract:The characteristics of the intervariant Boundary Network that resulted from the $$\beta \to \alpha^{\prime}$$ β → α ′ martensitic phase transformation in a Ti–6Al–4V alloy were studied using the crystallographic theories of displacive transformations, five-parameter grain Boundary analysis and triple junction analysis. The microstructure of Ti–6Al–4V martensite consisted of fine laths containing dislocations and fine twins. The misorientation angle distribution revealed four distinct peaks consistent with the intervariant boundaries expected from the Burgers orientation relationship. The phenomenological theory of martensite predicted four-variant clustering to have the lowest transformation strain among different variant clustering combinations. This configuration was consistent with the observed Ti–6Al–4V martensitic microstructure, where four-variant clusters consisted of two pairs of distinct V-shape variants. The $$63.26^\circ /[\overline{10}\, 5\, 5\, \overline{3}]_{{\alpha^{\prime}}}$$ 63 . 26 ∘ / [ 10 ¯ 5 5 3 ¯ ] α ′ and $$60^\circ /[1\, 1\, \overline{2}\, 0]_{{\alpha^{\prime}}}$$ 60 ∘ / [ 1 1 2 ¯ 0 ] α ′ intervariant boundaries accounted for ~ 38% and 33% of the total population, respectively. The five-parameter Boundary analysis showed that the former had a twist character, being terminated on the $$(\overline{3}\, 2\, 1\, 0)_{{\alpha^{\prime}}}$$ ( 3 ¯ 2 1 0 ) α ′ plane, and the latter revealed a symmetric tilt $$(1\, 0\, \overline{1}\, 1)_{{\alpha^{\prime}}}$$ ( 1 0 1 ¯ 1 ) α ′ Boundary plane. The $$63.26^\circ /[\overline{10}\, 5\, 5\, \overline{3}]_{{\alpha^{\prime}}}$$ 63 . 26 ∘ / [ 10 ¯ 5 5 3 ¯ ] α ′ and $$60^\circ /[1\, 1\, \overline{2}\, 0]_{{\alpha^{\prime}}}$$ 60 ∘ / [ 1 1 2 ¯ 0 ] α ′ had the highest connectivity at triple junctions among other intervariant boundaries. Interestingly, the Boundary Network in Ti–6Al–4V martensite was significantly different from the commercially pure Ti martensite, where only $$60^\circ /[1\, 1\, \overline{2}\, 0]_{{\alpha^{\prime}}}$$ 60 ∘ / [ 1 1 2 ¯ 0 ] α ′ intervariant boundaries largely were found at triple junctions due to the formation of three-variant clustering to minimize the transformation strain. This difference is thought to result from a change in the martensitic transformation mechanism (slip vs twinning) caused by the alloy composition. Graphic abstract
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The role of phase transformation mechanism on the grain Boundary Network in a commercially pure titanium
Materials Characterization, 2020Co-Authors: Ehsan Farabi, Vahid Tari, Peter Hodgson, Gregory S Rohrer, Hossein BeladiAbstract:Abstract The role of phase transformation mechanism on the development of the grain Boundary Network in a commercially pure Ti was investigated using five-parameter grain Boundary analysis along with an analysis of the triple junctions among intervariant boundaries. High temperature β was subjected to three different cooling regimes (i.e., 175 °C/s, 1 °C/s and 0.02 °C/s) to stimulate shear, diffusion-assisted and pure diffusional β-to-α phase transformation mechanisms, resulting martensite, Widmanstatten, and coarse-grain microstructures, respectively. The phase transformation mechanism appeared to significantly alter the grain Boundary Network in pure Ti. There was a distinct difference in the misorientation angle distribution among microstructures formed through different phase transformation mechanisms, though the peaks were largely consistent with the Burgers orientation relationship. The 60°/ 1 1 2 ¯ 0 intervariant Boundary had the highest population (~60%) in the martensitic/shear transformation, because of a local variant selection mechanism (i.e., three variant clustering) influenced by the transformation strain. However, the local variant selection associated with the transformation strain gradually diminished with a decrease in the cooling rate, leading to a progressive decline in the 60°/ 1 1 2 ¯ 0 population (i.e., the random distribution of intervariant boundaries). The 60°/ 1 1 2 ¯ 0 intervariant Boundary had symmetric tilt 1 ¯ 1 0 1 plane characteristics with a low energy configuration in the martensitic microstructure and an asymmetric tilt character in both diffusion-assisted and diffusional transformations. The three-variant clustering during the martensitic transformation significantly enhanced the connectivity of the 60°/ 1 1 2 ¯ 0 intervariant boundaries at the triple junctions, though it became progressively less connected as the mechanism altered towards diffusion-assisted and diffusional phase transformations.
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the five parameter grain Boundary character and energy distributions of a fully austenitic high manganese steel using three dimensional data
Acta Materialia, 2014Co-Authors: Hossein Beladi, N T Nuhfer, Gregory S RohrerAbstract:Abstract The three-dimensional interfacial grain Boundary Network in a fully austenitic high-manganese steel was studied as a function of all five macroscopic crystallographic parameters (i.e. lattice misorientation and grain Boundary plane normal) using electron backscattering diffraction mapping in conjunction with focused ion beam serial sectioning. The relative grain Boundary area and energy distributions were strongly influenced by both the grain Boundary plane orientation and the lattice misorientation. Grain boundaries terminated by (1 1 1) plane orientations revealed relatively higher populations and lower energies compared with other boundaries. The most frequently observed grain boundaries were {1 1 1} symmetric twist boundaries with the Σ3 misorientation, which also had the lowest energy. On average, the relative areas of different grain Boundary types were inversely correlated to their energies. A comparison between the current result and previously reported observations (e.g. high-purity Ni) revealed that polycrystals with the same atomic structure (e.g. face-centered cubic) have very similar grain Boundary character and energy distributions.