Grain Boundary Research Papers - Academia.edu (original) (raw)

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- Engineering, Materials Engineering, Mechanical Engineering, Microstructure
- by Mauro Martin and +2
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- Materials Engineering, Condensed Matter Physics, Secondary Ion Mass Spectrometry, Surface Chemistry

The effect of corrosive solutions on stress relaxation behavior of pure Mg and its alloys is studied. Pure magnesium shows a crucial corrosion stress relaxation in 3.5wt.% NaCl even at room temperature in comparison with tests in air. Die-cast Mg alloys AZ91D, AM50 and AS21 at room temperature show a relatively small stress decrease both in air and in different

- by Emmanuel Gutman
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- Stress relaxation, Magnesium, Dislocations, Grain Boundary

The electrical properties of double perovskite Ho2NiTiO6 (HNT) are investigated by impedance spectroscopy in the temperature range 30–420 °C and frequency range 100 Hz to 1 MHz. The X-ray diffraction analysis reveals that the compound crystallizes in monoclinic phase. The imaginary part of impedance (Z″) as a function of frequency shows Debye type relaxation. The frequency dependence of Z″ peak is found to obey an Arrhenius law with an activation energy of 0.129 eV. Impedance data presented in the Nyquist plot (Z″ vs. Z′) are used to identify an equivalent circuit and to know the bulk and interface contributions. The complex impedance analysis of HNT exhibits the appearance of both the grain and grain-boundary contribution. The results of bulk ac conductivity as a function of temperature and frequency are presented. The activation energy (0.129 eV), calculated from the slope of log τ versus 103/T plot, is found to be the nearly same as calculated (0.130 eV) from dc conductivity. The frequency dependent conductivity spectra obey the power law.

- by Alo Dutta
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- Engineering, Materials Science, Impedance Spectroscopy, Power Law
- by DR S R SINGH
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- Materials Engineering, Mechanical Engineering, Civil Engineering, Materials Science
- by Peter Lagerlof
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- Materials Engineering, Mechanical Engineering, Microstructure, Grain Boundaries
- by arun kumar rai
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- Materials Engineering, Materials Science, Kinetics, Nuclear Materials
- by Katayun Barmak
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- Engineering, Image Processing, Statistical Analysis, Applied Physics
- by Lawrence Shadle
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- Mechanical Engineering, Chemical Engineering, Kinetics, Sensitivity Analysis
- by Barbara Shollock
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- Materials Engineering, Mechanical Engineering, Nickel, Grain Boundary
- by Suman Chatterjee
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- Materials Engineering, Grain Boundary
- by Pablo Zavattieri
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- Engineering, Finite Element, Finite Element Analysis, Mathematical Sciences
- by Charles McMahon
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- Materials Engineering, Mechanical Engineering, Embrittlement, Cracking
- by Genrich Krasko
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- Materials Engineering, Condensed Matter Physics, Electronics, Energy
- by Richard Piner and +1
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- Materials Engineering, Condensed Matter Physics, Science, Multidisciplinary

The present work adresses the evaluation of modified 9Cr-1Mo steels magneic hystersis loop and magnetic Barkhsuen emission techniques for the samples subjected to high temperature ageing for different durations. The initially quenched and then tempered material revealed different magnetic behaiour with ageing. The relxation of stresses and reduction of high value of dislocations due to quenching in the initial perriod of ageing was observed with lowering of coercivity and an increase in MBE signal. Further ageing above 150 hours led to fine distribution of carbides in the matrix which led to the subsequent magnetic hardening. The formaiton of the fine carbides was also observed from Scanning electron micrographs. At higher ageing periods beyond 500 hours, the carbides migrated towards the grain boundary leading to loweing in the density of the fine carbides in the matrix and a consequent magnetic softening due to easy domain wall propagation.

- by JN Mohapatra
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- Materials Science, Dislocations, Domain wall, High Temperature
- by Ikumu Watanabe
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- Materials Engineering, Mechanical Engineering, Civil Engineering, Plasticity
- by Andrew Saint
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- Geochemistry, Solar Cell, Grain Boundary, Interdisciplinary Engineering
- by S. Dregia
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- Materials Engineering, Mechanical Engineering, Kinetics, Growth Kinetics
- by P. Šandera
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- Condensed Matter Physics, Quantum Physics, Surface Science, Phosphorus
- by Dong Shin
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- Materials Engineering, Mechanical Engineering, Materials, Strain Rate
- by Kah-Yoong Chan
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- Cultural Studies, Music, Musicology, Folklore

The objective of this review article is to provide a concise discussion of atomistic modeling efforts aimed at understanding the nanoscale behavior and the role of grain boundaries in plasticity of metallic polycrystalline materials. Atomistic simulations of grain boundary behavior during plastic deformation have focused mainly on three distinct configurations: (i) bicrystal models, (ii) columnar nanocrystalline models, and (iii) 3D nanocrystalline models. Bicrystal models facilitate the isolation of specific mechanisms that occur at the grain boundary during plastic deformation, whereas columnar and 3D nanocrystalline models allow for an evaluation of triple junctions and complex stress states characteristic of polycrystalline microstructures. Ultimately, both sets of calculations have merits and are necessary to determine the role of grain boundary structure on material properties. Future directions in grain boundary modeling are discussed, including studies focused on the role of...

- by David McDowell
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- Materials Engineering, Mechanical Engineering, Materials Science, Microstructure
- by roger malina
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- Mechanical Engineering, Surface Roughness, Grain Boundaries, Ultraviolet
- by Anderson Dias
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- Materials Engineering, Kinetics, Magnetic Materials, Scanning Electron Microscopy
- by Anthony deArdo
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- Materials Engineering, Mechanical Engineering, Kinetics, Grain Boundary
- by Mark Horstemeyer
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- Physical sciences, Iron, CHEMICAL SCIENCES, Grain Boundary
- by Adelmo Ortiz-conde
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- Doping, Grain Boundaries, Phosphorus, Spontaneous Emission
- by Dario Narducci
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- Grain Boundary, Polycrystalline Silicon
- by A. Amine Benzerga
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- Engineering, Materials Engineering, Mechanical Engineering, Civil Engineering

The spallation failure of a commercial thermal barrier coating (TBC), consisting of a single-crystal RENE N5 superalloy, a platinum aluminide (Pt-Al) bond coat, and an electron beam-deposited 7 wt pct yttria-stabilized zirconia ceramic layer (7YSZ), was studied following cyclic furnace testing. In the uncycled state and prior to deposition of the ceramic, the Pt-Al bond-coat surface contains a cellular network of ridges corresponding to the underlying bond-coat grain-boundary structure. With thermal cycling, the ridges and associated grain boundaries are the sites of preferential oxidation and cracking, which results in the formation of cavities that are partially filled with oxide. Using a fluorescent penetrant dye in conjunction with a direct-pull test, it is shown that, when specimens are cycled to about 80 pct of life, these grain-boundary regions show extensive debonding. The roles of oxidation and cyclic stress in localized grain boundary region spallation are discussed. The additional factors leading to large-scale TBC spallation are described.

The effect of secondary sintering additives and/or a post-sintering heat treatment on the semicrystalline atomic structure of the intergranular phase in silicon nitride ceramics is investigated. Three different Yb-doped Si3N4 ceramic compositions are examined using a scanning transmission electron microscope, whereby the intergranular atomic structure is directly imaged with Ångstrom resolution. The resulting high-resolution images show that the atomic arrangement of the Yb takes very periodic positions along the interface between the intergranular phase and the matrix grains, and that a postsintering 1250 °C heat treatment, as well as a change of the secondary sintering additives (Al2O3 vs SiO2), does not alter the atomic positions of Yb. This result has implications for the understanding of how the mechanical properties of ceramics are influenced by the presence of the nanoscale intergranular phase, and for associated computational modeling of its precise role and atomic structure.

- by P. Thangadurai and +1
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- Materials Engineering, Physics, Condensed Matter Physics, Heat Treatment
- by Jeffrey Wadsworth
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- Strain Rate, Crystal structure, Ductile Fracture, Grain Boundary
- by Alain Mauger
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- Chemistry, Electronic properties, Grain Boundary
- by Stephen Saddow
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- Engineering, Thin Film, Physical sciences, Leakage Current
- by D. Mangalaraj
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- Materials Engineering, Impedance Spectroscopy, Thin Film, Activation Energy
- by Horacio Espinosa
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- Materials Engineering, Mechanical Engineering, Civil Engineering, Kinetics
- by Luke Nyakiti
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- Engineering, Materials Engineering, Mechanical Engineering, Condensed Matter Physics
- by Z. Skvortsova
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- Materials Engineering, Mechanical Engineering, Magnesium, Grain Boundary
- by Deanne Idar
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- Engineering, Materials Science, Strain Rate, Split Hopkinson Pressure Bar

Microstructure development in Sb2O3-doped ZnO was studied to evaluate the influence of inversion boundaries (IBs) on ZnO grain growth. In general, the addition of Sb2O3 is believed to inhibit the ZnO grain growth via the formation of spinels and IBs, but we have shown that even the conditions of exaggerated grain growth can be created in this system. We designed an experiment for diffusional doping of ZnO under slightly increased partial pressure of Sb2O3. In the high-concentration regime we observed no spinels, and yet the ZnO grains were small and inhibited in growth, while in the low-concentration regime we found huge grains, several times larger than normal ZnO grains, showing an obvious exaggerated growth. By controlling the number of nuclei with IBs we can design coarse-grained microstructures even with Sb2O3 doping, which has far-reaching implications in the production of low-voltage varistor devices.

- by Nina Daneu
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- Materials Engineering, Mechanical Engineering, Microstructure, Manufacturing
- by Pantip Ampornrat
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- Materials Engineering, Nuclear Materials, Activation Energy, Chromium