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Microstructural changes in a Fe-15 at.%Cr model alloy neutron irradiated to 1.82 dpa at 290 ℃ were characterized by atom probe tomography. Homogenously distributed α' precipitates as well as fewer clusters containing Si, P,Ni, a...
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Microstructural changes in a Fe-15 at.%Cr model alloy neutron irradiated to 1.82 dpa at 290 ℃ were characterized by atom probe tomography. Homogenously distributed α' precipitates as well as fewer clusters containing Si, P,Ni, and Cr, were observed in the matrix. Grain boundary analyses before and after irradiation revealed segregation of Cr, with W-shape concentration profiles developing in the vicinity of grain boundary carbide and nitride particles. After irradiation, impurities such as C, Si and P were segregated to the grain boundaries. Zones depleted of α' clusters, and Si were found at the interfaces of carbide and nitride precipitates and along grain boundaries in the vicinity of these precipitates.
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Pearlite spheroidization is substantially a spatial-geometric evolution of cementite. In this study, a persistent homology analysis was employed to characterize the topological features of cementite component of pearlite steel, th...
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Pearlite spheroidization is substantially a spatial-geometric evolution of cementite. In this study, a persistent homology analysis was employed to characterize the topological features of cementite component of pearlite steel, through which the lamellar and spherical pearlite microstructures were successfully distinguished. Because the mechanical performance of pearlite steel is highly sensitive to the cementite configuration, an inverse conversion of persistent-homology digital data to an image for some properties of interest was proposed by using Bayesian optimization. The proposed microstructural optimization approach paves a way to interpret persistent-homology information in metallurgy and presents the feasibility of data-driven persistent-homology-based property predictions and microstructural optimization.
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In additively manufactured (AM) metallic materials, the fundamental interrelationships that exist between composition, processing, and microstructure govern these materials' properties and potential improvements or reductions in p...
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In additively manufactured (AM) metallic materials, the fundamental interrelationships that exist between composition, processing, and microstructure govern these materials' properties and potential improvements or reductions in performance. For example, by using AM, it is possible to achieve highly desirable microstructural features (e.g., highly refined precipitates) that could not otherwise be achieved by using conventional approaches. Simultaneously, opportunities exist to manage macro-level microstructural characteristics such as residual stress, porosity, and texture, the last of which might be desirable. To predictably realize optimal microstructures, it is necessary to establish a framework that integrates processing variables, alloy composition, and the resulting microstructure. Although such a framework is largely lacking for AM metallic materials, the basic scientific components of the framework exist in literature. This review considers these key components and presents them in a manner that highlights key interdependencies that would form an integrated framework to engineer microstructures using AM.
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The structure of hexagonal mu sub 7 -MgZnRE phase Mg sub 24.1 Zn sub 64.8 Sm sub 11.1 was determined by single crystal X-ray structural analysis: P6 sub 3 /mmc (No. 194), a=33.565(2) A, c=8.873(2) A, atoms/cell=480, F(000)=14016, ...
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The structure of hexagonal mu sub 7 -MgZnRE phase Mg sub 24.1 Zn sub 64.8 Sm sub 11.1 was determined by single crystal X-ray structural analysis: P6 sub 3 /mmc (No. 194), a=33.565(2) A, c=8.873(2) A, atoms/cell=480, F(000)=14016, mu =30.11 mm exp -1 , D sub calc =5.973 Mg/m exp -3 , R=0.0376 for the observed 1733 reflections with F sub obs >4.0 sigma (F sub obs ). The structure of mu sub 7 -MgZnRE is closely related to that of mu sub 3 -MgZnSm (P6 sub 3 /mmc, a =14.619 A, c= 8.708 A) and the MgZn sub 2 Laves phase (P6 sub 3 /mmc, a =5.223 A, c= 8.566 A). The introduction of Sm increases the distortion of the icosahedral atomic arrangement around Zn and this produces a variety of icosahedral linkages in mu -phases. The structural units of icosahedral columns are introduced for demonstrating the crystalline structures of mu -phases.
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New ternary indides R sub 6 Co sub 26-x Jn sub 14 (R=Er,Tm) have been found in the systems {Er,Tm}-Co-In at 870 K. The crystal structure of Tm sub 6 Co sub 26-x Jn sub 14 (x=7.42) has been refined using single-crystal X-ray data: ...
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New ternary indides R sub 6 Co sub 26-x Jn sub 14 (R=Er,Tm) have been found in the systems {Er,Tm}-Co-In at 870 K. The crystal structure of Tm sub 6 Co sub 26-x Jn sub 14 (x=7.42) has been refined using single-crystal X-ray data: Lu sub 6 Co sub 26-x Jn sub 14 (x=8.41) structure type, Pm3 space group. Z=1, a=8.655(4) A, V=648.4(9) A exp 3 , R=0.0245 for 233 unique reflections hkl (DARTCH-1 diffractometer, Mo K alpha radiation). The lattice parameter for the isostructural compound Er sub 6 Co sub 26-x Jn sub 14 is a=8.663(1) A. The coordination polyhedra of the Tm atoms have 15 vertices. those of the In atoms 12 and 13 vertices and those of the Co atoms eight, ten and 12 vertices. The structure can be described as a stacking of columns double hexagonal antiprisms with two additional atoms opposite the bases, and comprises icosahedra, cubes, trigonal prisms and empty tetrahedra.
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Scales of the Australian lungfish, Neoceratodus forsteri, are secreted within the dermis by a capsule of scleroblasts, and enclosed in a pouch made of collagen fibers, in contact with the epidermis over the posterior third of the ...
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Scales of the Australian lungfish, Neoceratodus forsteri, are secreted within the dermis by a capsule of scleroblasts, and enclosed in a pouch made of collagen fibers, in contact with the epidermis over the posterior third of the scale. Each scale grows from a focus, which represents the first formed part of the scale. On the internal surface of the scale is elasmodin, made of collagen fiber bundles arranged in layers. Elasmodin, unmineralized in N. forsteri, contains cells in the living animal, and the number of layers increases as the scales grow. Squamulin, on the thin external part of the scale, is also laid down in layers, and based on a matrix of fine collagen fibrils, mineralized with a poorly crystalline biogenic calcium hydroxylapatite. Squamulin is divided into separate sections called squamulae, and contains long tubules with cells applied to the wall of the tubule. The anterior and lateral surfaces of the squamulin are ornamented with pediculae, and the posterior surface has longitudinal ridges, from which collagen fibers extend to anchor the scale within the pouch. Elasmodin and squamulin are linked by unmineralized collagen fibrils. The layers, formed at irregular intervals, are connected around the margin of the scale, effectively converting the whole scale into a flat structure resembling a pearl, with the first formed tissues deeply embedded inside the scale, and the youngest on the outer surface. Incremental lines in the hard tissue, and the number of layers in the elasmodin, do not reflect the chronological age of the fish. J. Morphol. 276:1137-1145, 2015. (c) 2015 Wiley Periodicals, Inc.
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The paper presents results of microstructural investigations of Mg-5Al-3Ca-0.7Sr-0.2Mn (ACJM53) magnesium alloys in the as-cast condition and after heat treatment at 450°C for 4.5 hours. Two kinds of transformation were observed ...
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The paper presents results of microstructural investigations of Mg-5Al-3Ca-0.7Sr-0.2Mn (ACJM53) magnesium alloys in the as-cast condition and after heat treatment at 450°C for 4.5 hours. Two kinds of transformation were observed in ACJM53 alloy after heat treatment: (Mg,Al)_2Ca (C36) → Al_2Ca (C15) and Al_3Mg_(13)(Sr,Ca) → Mg_(17)(Sr,Ca)_2 transformations without the change in morphology of output compounds. Morphology of Mg_2Ca (C14) have been changed from fine lamellar to globular and precipitation process of Al_2Ca (C15) phase inside the grains of solid solution was found.
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Lattice parameters for nanocrystalline (nc) materials were found to be alerted with respect to the corresponding coarse-grained polycrystalline counterparts in several systems. In this work, experimental evidences of the lattice s...
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Lattice parameters for nanocrystalline (nc) materials were found to be alerted with respect to the corresponding coarse-grained polycrystalline counterparts in several systems. In this work, experimental evidences of the lattice structure distortion in various nc materials processed by means of different approaches will be summarized and discussed. Strong evidences showed the lattice structure distortion in nc samples which is manifested by an evident change in the lattice parameters, Debye-Waller parameter, and the thermal properties of the nanocrystalline lattice. These results imply that the property changes of nc materials should be attributed not only to the numerous non-equilibrium grain boundaries, but to the distorted nanocrystallites as well. Materials mentioned include Fe, Cu, Ni sub 3 P and Fe sub 2 B.
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This paper is an attempt to describe the current view of the joint effect of microstructure and load on elastic microstructural materials whose stress state is described by approximate microstructural theories rather than by the e...
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This paper is an attempt to describe the current view of the joint effect of microstructure and load on elastic microstructural materials whose stress state is described by approximate microstructural theories rather than by the exact theory of inhomogeneous materials. Two microstructural static effects are detected: microstructural edge effect and microstructural load redistribution.
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The generation of three-dimensional (3D) microstructures with multiple constituents is an important part of multiscale computational simulation and design for a wide range of materials including heterogeneous polycrystalline metal...
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The generation of three-dimensional (3D) microstructures with multiple constituents is an important part of multiscale computational simulation and design for a wide range of materials including heterogeneous polycrystalline metals, ceramics, composites, and energetics. Realistic 3D microstructures for multiphase materials are difficult to obtain experimentally or computationally. Challenges include generation and representation of complex constituent morphologies, topological arrangement and distribution, defect description, and statistical conformity. Here, we present a novel technique for systematically composing complex 3D statistically equivalent microstructure sample sets (SEMSS) with prescribed statistical constituents and morphological attributes. Based on large libraries of varying representations of individual constituents, the technique can be used with experimental micro computerized tomography (CT) scans to establish SEMSS that track the attributes of existing materials as well as to design SEMSS for new materials not yet in existence for computational exploration. Heterogeneous systems involving different combinations of molecular crystallites, metallic particles, oxidizer granules, and a polymeric matrix are designed and generated to track the properties of an existing material. The corresponding SEMSS are used in multiphysics simulations accounting for coupled thermal-mechanical processes or thermal-mechanical-chemically reactive processes. The results are used to quantify microstructure-induced response variations and point out the limitations of two-dimensional (2D) microstructures that are direct sections of the full 3D microstructures. The use of the SEMSS has also enabled uncertainty quantification (UQ) and the development of probabilistic characterizations for variations in macroscopic responses due to intrinsic material microstructural heterogeneities.
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