Relevant bibliographies by topics / Grain coarsening

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  2. Dissertations / Theses
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Academic literature on the topic 'Grain coarsening'

Author: Grafiati
Published: 4 June 2021
Last updated: 11 February 2022

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Journal articles on the topic "Grain coarsening"

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Doherty, Roger D., Elizabeth Hoffman, Christopher Hovanec, and Arnaud Lens. "Abnormal Grain Coarsening and Its Possible Relationship with Particle Limited Normal Grain Coarsening." Materials Science Forum 467-470 (October 2004): 843–52. http://dx.doi.org/10.4028/www.scientific.net/msf.467-470.843.

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The prior literature on abnormal grain coarsening (AGC) at low volume fractions (f) of stable second phase particles in high purity Al alloys is reviewed and reanalyzed in the light of developments in modeling particle inhibition of grain boundary migration. With the usual assumptions (i) of incoherent particles that retain their shape on contact with the grain boundaries and (ii) that all the grain boundaries are equally mobile, it appears impossible to account for process of AGC. Normal grain coarsening (NGC) is shown to be less inhibited by the particles than is AGC. This idea is explored using a new but simple model of particle inhibition by curvature removal. The curvature of the smallest grains is always larger than that of the larger grains. Two possible hypotheses to overcome this difficulty are proposed: First the possible change of shape of particles on slowly moving grain boundaries, of grains with near 14 neighbors should, after a small increment of NGC, promote AGC at low values of the volume fraction f. The second hypothesis involves the observed high density of immobile, low angle grain boundaries (LAGBs) found in recent experiments on high purity Al-Fe-Si alloys cast with very coarse grain sizes. These alloys undergo rapid AGC even at higher values of f (> 0.01). These LAGBs are expected to inhibit the shrinkage of many of the small grains, whose loss is the fundamental mechanism of NGC.
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Kubota, M., and T. Ochi. "Development of Anti-Coarsening Steel for Carburizing." Materials Science Forum 539-543 (March 2007): 4855–60. http://dx.doi.org/10.4028/www.scientific.net/msf.539-543.4855.

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There is a glaring need for omitting intermediate heat treatments in the manufacturing processes of carburized parts and increasing the carburizing temperature aimed at cost reduction. It is necessary to develop techniques to inhibit grain-coarsening since some austenite grains tend to grow abnormally during carburizing and coarse grains have negative effects on the properties of parts. Therefore, we developed new techniques to inhibit grain-coarsening by refining precipitates’ size and increasing their volume fraction based on the abnormal grain growth theory by Gladman. In this study, AlN and Nb(CN) were chosen as the precipitate particles for the pinning of austenite grain growth. And we investigated grain-coarsening behavior in several manufacturing processes of parts. As a result, we developed anti-coarsening steels for various manufacturing processes of carburized parts.
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Jung, Yang-Il, Suk-Joong L. Kang, and Duk Yong Yoon. "Coarsening of polyhedral grains in a liquid matrix." Journal of Materials Research 24, no. 9 (September 2009): 2949–59. http://dx.doi.org/10.1557/jmr.2009.0356.

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The coarsening of polyhedral grains in a liquid matrix was calculated using crystal growth and dissolution equations used in crystal growth theories for faceted crystals. The coarsening behavior was principally governed by the relative value of the maximum driving force for growth (Δgmax), which is determined by the average size and size distribution, to the critical driving force for appreciable growth (Δgc). When Δgmax was much larger than Δgc, pseudonormal grain coarsening occurred. With a reduction of Δgmax relative to Δgc, abnormal grain coarsening (AGC, when Δgmax ≥ Δgc) and stagnant grain coarsening (SGC, when Δgmax < Δgc) were predicted. The observed cyclic AGC and incubation for AGC in real systems with faceted grains were explained in terms of the relative value between Δgmax and Δgc. The effects of various processing and physical parameters, such as the initial grain size and distribution, the liquid volume fraction, step free energy, and temperature, were also evaluated. The calculated results were in good agreement with previous experimental observations.
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Zhang, Chi, and Laszlo S. Toth. "Polycrystal Simulation of Texture-Induced Grain Coarsening during Severe Plastic Deformation." Materials 13, no. 24 (December 21, 2020): 5834. http://dx.doi.org/10.3390/ma13245834.

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During severe plastic deformation (SPD), there is usually extended grain fragmentation, associated with the formation of a crystallographic texture. The effect of texture evolution is, however, coarsening in grain size, as neighbor grains might coalesce into one grain by approaching the same ideal orientation. This work investigates the texture-induced grain coarsening effect in face-centered cubic polycrystals during simple shear, in 3D topology. The 3D polycrystal aggregate was constructed using a cellular automaton model with periodic boundary conditions. The grains constituting the polycrystal were assigned to orientations, which were updated using the Taylor polycrystal plasticity approach. At the end of plastic straining, a grain detection procedure (similar to the one in electron backscatter diffraction, but in 3D) was applied to detect if the orientation difference between neighboring grains decreased below a small critical value (5°). Three types of initial textures were considered in the simulations: shear texture, random texture, and cube-type texture. The most affected case was the further shearing of an initially already shear texture: nearly 40% of the initial volume was concerned by the coalescence effect at a shear strain of 4. The coarsening was less in the initial random texture (~30%) and the smallest in the cube-type texture (~20%). The number of neighboring grains coalescing into one grain went up to 12. It is concluded that the texture-induced coarsening effect in SPD processing cannot be ignored and should be taken into account in the grain fragmentation process.
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Ferry, Michael. "Spatial Uniformity of the Rate of Grain Coarsening in a Submicron Al-Sc Alloy Produced by Severe Plastic Deformation." Materials Science Forum 503-504 (January 2006): 251–58. http://dx.doi.org/10.4028/www.scientific.net/msf.503-504.251.

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The uniformity of grain coarsening throughout the microstructure of a submicron grained particle-containing aluminium alloy has been investigated using high resolution EBSD. The alloy was processed by equal channel angular pressing (ECAP) and low temperature ageing to generate ~0.8 􀁐m diameter grain structure containing a relatively uniform dispersion of nanosized Al3Sc particles. While the initial processing route generated a uniform grain size distribution, the distribution of grain orientations was rather inhomogeneous with certain regions of microstructure containing colonies of grains consisting predominantly of either HAGBs or LAGBs. It was found that, despite the difference in grain boundary character between these regions, the fine particles produced by pre-ageing promote uniform coarsening throughout the microstructure despite the marked differences in boundary character between these regions. An analytical model is outlined which predicts the uniformity of grain coarsening in particle-containing alloys despite the presence of orientation gradients in the microstructure.
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Ferry, Michael. "Uniformity of Grain Coarsening in Submicron Grained Al-Sc Alloy Containing Local Variations in Texture." Materials Science Forum 495-497 (September 2005): 609–14. http://dx.doi.org/10.4028/www.scientific.net/msf.495-497.609.

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The effect of fine particles on the uniformity of grain coarsening in a submicron grained Al-Sc alloy containing significant local variations in texture has been investigated using high resolution EBSD. The alloy was processed by severe plastic deformation and low temperature ageing to generate a fine-grained (0.8 µm diameter) microstructure containing either a dispersion of nanosized Al3Sc particles or a particle-free matrix. The initial processing generated a uniform grain size distribution, but the distribution of grain orientations was inhomogeneous with the microstructure containing colonies of grains consisting predominantly of either HAGBs or LAGBs with the latter possessing orientation gradients of up to 10 o/µm. Despite the marked differences in boundary character between these regions, the alloy undergoes slow and uniform grain coarsening during annealing at temperatures up to 500 oC with no marked change in the grain size distribution, boundary distribution and texture. A model of grain coarsening that takes into account the influence of fine particles on the kinetics of grain growth within an orientation gradient is outlined. The model predicts that a large volume fraction of fine particles (large f/r-value) tends to homogenize the overall rate of grain coarsening despite the presence of orientation gradients in the microstructure.
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Jiang, Ju Fu, Zhi Ming Du, Ying Wang, and Shou Jing Luo. "Microstructural Evolution of 7050 Aluminum Alloy Semisolid Billets Fabricated by RAP Process." Solid State Phenomena 217-218 (September 2014): 29–36. http://dx.doi.org/10.4028/www.scientific.net/ssp.217-218.29.

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In the present study, 7050 supplied in extruded state was heated to different temperatures below solidus or the semisolid state and microstructural evolution and coarsening were investigated. The results showed that complete recrystallisation only occurs after soaking for 5 minutes at 545°C, which is characterised by formation of a lot of fine equiaxed grains. RAP is suitable for fabricating high-quality semisolid billet of 7050 aluminum alloy with an average grain size ranging from 47.4 um to 70.5 um and a roundness ranging from 1.3 to 1.7. Grain growth occurs as the samples were soaked at 610°C and 615°Cfor prolonged soaking time. When the isothermal temperatures were 610°C and 615°C, the coarsening rate constants were 359.5μm3s-1 and 470.5μm3s-1, respectively, indicating an increase of coarsening rate constant (K) with the increasing isothermal temperature. Coarsening tends to occur via Ostwald ripening and coalescence. Ostwald ripening plays an important role during the whole coarsening process, but the grain coalescence only contributes to coarsening after soaking for 12 minutes. 625°C is an optimal temperature to keep cylinder shape of the sample due to collapse of the sample above this temperature, leading to difficult clamping.
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San Martín, David, Francisca García Caballero, Carlos Capdevila, and Carlos García de Andrés. "Discussion on the Rate Controlling Process of Coarsening of Niobium Carbonitrides in a Niobium Microalloyed Steel." Materials Science Forum 500-501 (November 2005): 703–10. http://dx.doi.org/10.4028/www.scientific.net/msf.500-501.703.

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Austenite grain growth in microalloyed steels is governed by the coarsening of fine precipitates present at grain boundaries below the grain coarsening temperature. Zener model is widely used in metals to describe the pinning effect of second phase particles precipitated in the matrix. In this work it has been discussed whether grain boundary or volume diffusion is the rate controlling process for the coarsening of the niobium carbonitrides. Calculations on austenite grain growth kinetics, obtained coupling Zener theory and both rate controlling processes of precipitate coarsening, have been compared against experimental austenite grain size results under nonisothermal heating conditions. In this sense, it has been concluded that the coarsening of niobium carbonitrides is mainly controlled by volume diffusion of Nb in austenite.
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Li, Wei, Yi Peng, Yongjun Zhang, Tim Still, A. G. Yodh, and Yilong Han. "Shear-assisted grain coarsening in colloidal polycrystals." Proceedings of the National Academy of Sciences 117, no. 39 (September 16, 2020): 24055–60. http://dx.doi.org/10.1073/pnas.2013456117.

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Grain growth under shear annealing is crucial for controlling the properties of polycrystalline materials. However, their microscopic kinetics are not well understood because individual atomic trajectories are difficult to track. Here, we study grain growth with single-particle kinetics in colloidal polycrystals using video microscopy. Rich grain-growth phenomena are revealed in three shear regimes, including the normal grain growth (NGG) in weak shear melting–recrystallization process in strong shear. For intermediate shear, early stage NGG is arrested by built-up stress and eventually gives way to dynamic abnormal grain growth (DAGG). We find that DAGG occurs via a melting–recrystallization process, which naturally explains the puzzling stress drop at the onset of DAGG in metals. Moreover, we visualize that grain boundary (GB) migration is coupled with shear via disconnection gliding. The disconnection-gliding dynamics and the collective motions of ambient particles are resolved. We also observed that grain rotation can violate the conventional relation R×θ=constant (R is the grain radius, and θ is the misorientation angle between two grains) by emission and annihilation of dislocations across the grain, resulting in a step-by-step rotation. Besides grain growth, we discover a result in shear-induced melting: The melting volume fraction varies sinusoidally on the angle mismatch between the triangular lattice orientation of the grain and the shear direction. These discoveries hold potential to inform microstructure engineering of polycrystalline materials.
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Doherty, Roger D. "Grain Coarsening – Insights from Curvature Modeling Cyril Stanley Smith Lecture." Materials Science Forum 715-716 (April 2012): 1–12. http://dx.doi.org/10.4028/www.scientific.net/msf.715-716.1.

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Normal and abnormal grain coarsening, NGC and AGC, are briefly reviewed and discussed in the light of grain curvature and kinetic models - notably those of Mullins. The critical importance of the log-normal grain size distribution determined by Hull and the grain shapes measured by Rhines and Craig are reviewed. It is shown that in NGC, as in particle coarsening, the largest grains or particles in their respective distributions grow at the rates, larger by a factor of the ratio of the largest to average size, required to maintain the size distributions during coarsening. The particle curvature removal model for NGC anchorage, giving = 0.2 r/f, developed here, matches surprisingly well the data reviewed by Manohar et al. Finally the need is indicated for further experimental and modeling studies to test the current ideas and to answer the many remaining questions.
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Dissertations / Theses on the topic "Grain coarsening"

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Yu, Wanhua. "Cellular automata modelling of austenite grain coarsening during reheating." Thesis, University of Sheffield, 2002. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.251524.

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Shaw, N. J. "Structure and grain coarsening during the processing of engineering ceramics." Thesis, University of Leeds, 1987. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.378400.

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Payton, Eric John. "Characterization and Modeling of Grain Coarsening in Powder Metallurgical Nickel-Based Superalloys." The Ohio State University, 2009. http://rave.ohiolink.edu/etdc/view?acc_num=osu1250265477.

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Lee, Bongjoon. "Analysis of the Kinetics of Filler Segregation in Granular Block copolymer Microstructure." Research Showcase @ CMU, 2016. http://repository.cmu.edu/dissertations/705.

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Block copolymers have attracted interests for potential application ranging from dynamic photonic sensors to solid-state ion conductors. However, due to nucleation and growth mechanism, block copolymer inherently forms granular microstructure with defects such as grain boundaries. Understanding the microstructure of block copolymer is thus crucial in many applications because the microstructure determines the transport property of functional fillers such as ions in block copolymer template. Previous research has shown that athermal filler segregated to grain boundary of lamellae block copolymer and retards the grain coarsening. However, the kinetics of this grain boundary segregation during thermal annealing has not been revealed. Polystyrene-b-polyisoprene blended with deuterated polystyrene is used for neutron scattering study on studying the kinetics of grain boundary segregation. Deuterated polystyrene will segregate to grain boundaries, therefore, decorate grain boundary. The filler segregation behavior will be studied by comparing neutron scattering of polystyrene-b-polyisoprene/deuterated polystyrene with different annealing times (at T=130 deg C, duration of 0hr, 3hr, 1day, 3day and 7day, respectively). Invariant (Q) analysis along with grain mapping is conducted to quantitatively analyze the kinetics of grain boundary segregation. This kinetic was in good agreement with the McLean’s kinetic model for grain boundary segregation in metals. By applying Langmuir-Mclean’s segregation isotherm equation, we have predicted the equilibrium concentration of filler in grain boundary by calculating the strain energy stored in grain boundary.
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Chang, Chung-Shing. "Fracture processes in simulated HAZ microstructures of stainless steel." Thesis, University of Birmingham, 2000. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.367606.

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Melquíades, Sérgio dos Reis. "O efeito do carbono no aumento do tamanho de grão e nas propriedades magnéticas de aços elétricos semiprocessados após o recozimento final." Universidade de São Paulo, 2006. http://www.teses.usp.br/teses/disponiveis/3/3133/tde-22072007-204504/.

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Recozimentos realizados nos aços elétricos semiprocessados pelos fabricantes de motores sem um controle adequado da descarbonetação pode resultar em regiões das läminas com pequeno tamanho de grão e consequentemente aumento das perdas magnéticas com queda no rendimento dos motores elétricos. A maioria dos fabricantes de motores nacionais utilizam este tipo de aço e fazem internamente o recozimento final em fornos contínuos com atmosfera à base de nitrogênio com cerca de 5 a 10% de H2 e uma pequena fração de vapor dágua suficiente para gerar uma atmosfera que reaja com o carbono do aço, removendo-o. Caso esta descarbonetação não seja realizada com êxito há uma perda significativa no rendimento do motor pela aumento das perdas magnéticas. Amostras comerciais de diferentes aços com variados teores de carbono foram selecionadas para avaliar a influência do teor de carbono, do grau de redução, do tempo e da atmosfera do forno no aumento do tamanho de grão e nas perdas magnéticas. Foram realizados recozimentos a vácuo e em atmosfera descarbonetante. Medições de perdas magnéticas e do tamanho de grão além da avaliação da microestrutura foram efetuados para determinar esta influência. Foi verificado que no recozimento a vácuo, mesmo em variados graus de deformação, amostras com o teor de carbono inicial maior que 300 ppm, tiveram um significativo atraso no aumento do tamanho de grão. Nas situações em que não ocorreu significativo aumento do TG as perdas magnéticas apresentaram valores altos e 9 indesejáveis. Por outro lado amostras isentas de deformação não apresentaram aumento significativo do tamanho de grão mesmo com descarbonetação durante o recozimento. Foi verificado ainda que a formação de grãos colunares ocorre em faixas de deformação específicas, em recozimentos com descarbonetação para aços com mais de 300 ppm de carbono e onde haja um rápido aquecimento da amostra até a temperatura de recozimento.
Annealing applied by the motors plants that are made on the semi processed electrical steels without an exact and precisious control of the decarburization on the lamination can brings undesirable results on the grain size coarsening and as a result an increasing on the core losses with a significant depreciation on the efficiency of the electrical motors. Most of the domestic motors fabrics make use of this kind of electrical steel and they do on their process the final annealing on continuous furnaces with atmospheres based on nitrogenium with around 5 until 10% of hidrogeniun and a little fraction of water vapor enough to generate an atmosphere that reacts to the carbon from the steel, eliminating it. If this decarburization is not been made sucessfully there will be an effective loss on the motor efficiency due the incresing on the core losses. Commercial samples from different steels with several carbon contents were choosen to evaluate the influence of carbon content, strain grade, time and furnace atmosphere on the grain size coarsening and core losses. It was effetived vacumn and decarburizing annealing. Core losses and grain size measurements were made in addition to the evaluation of the microstructure to determine this influence. It was verified that on the vacumn annealing, even on differents strain reductions grades, the samples with initial carbon content bigger than 300 ppm, had a meaninfull late on the grain size increase. On the situation that do not occurred a significative increase on the grain size the core losses presented undesirable high values. On the other hand samples without strain did not presented a significative increase on the grain size even with decarburization during the annealing. It was still verified that the columnar grain formation occur on specific strain grades, on decarburizing annealing and to more than 300 ppm carbon content steels. In addition where there is a fast heating rate until the annealing temperature.
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Danielsson, Olivia. "Effect of carbon activity on microstructure evolution in WC-Ni cemented carbides." Thesis, KTH, Materialvetenskap, 2018. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-226566.

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The aim of this work was to systematically study how the microstructure evolution is affected by the carbon activity in WC-Ni cemented carbides. Seven WC-9.59at%Ni alloys with different carbon activity were sintered at 1500 °C. From investigating these alloys, the carbon window has been experimentally evaluated using light optical microscopy and compared to theoretical carbon window calculated using Thermo-Calc. The overall microstructure of cross sections and raw surfaces have been investigated using scanning electron microscopy. Finally, the WC grain size and distribution have been evaluated using electron backscatter diffraction. It was found that the experimental carbon window was slightly wider than the theoretical carbon window. The WC grain size increased and the grain size distribution got wider with increasing carbon activity. In addition, the largest WC grains showed the largest grain growth by increasing carbon activity. By comparing the present results of grain size and distribution of WC-Ni to previous results of WC-Co, it was found that the WC grain growth was more pronounced and more influenced by the carbon activity.
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Klemm, Robert. "Zyklische Plastizität von mikro- und submikrokristallinem Nickel." Doctoral thesis, Saechsische Landesbibliothek- Staats- und Universitaetsbibliothek Dresden, 2004. http://nbn-resolving.de/urn:nbn:de:swb:14-1085403884093-17423.

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Im Rahmen der vorliegenden Arbeit wurde der Einfluss der Korngröße und der Gefügestabilität auf die zyklische Plastizität von mikro- und submikrokristallinem Nickel, hergestellt durch ECAP und PED, untersucht. Zur Gefügecharakterisierung kamen verschiedene elektronenmikroskopische und röntgenographische Methoden zum Einsatz. Die Untersuchungen zur Gefügestabilität zeigten, dass (i) die Stabilität der Korn- und Substruktur bei der zyklischen Verformung empfindlich vom Gefüge im Ausgangszustand abhängt, (ii) generell die Tendenz zur Umwandlung der vorhandenen Substruktur in eine universelle ermüdungstypische Substruktur besteht, diese Transformation jedoch durch die lokale Gefügebeschaffenheit be- bzw. verhindert sein kann und (iii) zur Erklärung des Entfestigungsverhaltens der ECAP-Materialien sowohl die Transformation der Substruktur als auch die Vergröberung der Kornstruktur berücksichtigt werden müssen. Auf der Basis der Ergebnisse der vorliegenden Arbeit und unter Hinzunahme von Resultaten aus der Literatur lassen sich Schlussfolgerungen zum Einfluss der Korngröße auf die zyklische Plastizität in einem vier Größenordnungen umfassenden Korngrößenbereich ziehen. In grob- und feinkörnigem Nickel bilden sich bei der zyklischen Verformung ermüdungstypische Versetzungsstrukturen, deren Abmessungen kaum von der Korngröße abhängen. Der Versetzungslaufweg in diesen Materialien ist wesentlich kleiner als die Kornabmessungen. Dementsprechend besteht höchstens ein schwacher Einfluss der Korngröße auf das sich bei der Wechselverformung einstellende Spannungsniveau. Bei mikro- und submikrokristallinem Nickel, wo der Versetzungslaufweg in der Größenordung der Kornabmessungen liegt, wird ein deutlicher Umschlag bei der Versetzungsmusterbildung und dem zyklischen Verformungsverhalten beobachtet. In diesem Korngrößenbereich entstehen entweder qualitativ andere (D&lt;DS1=5µm) oder keine Versetzungsstrukturen (D&lt;DS2=1µm) und das Spannungsniveau steigt mit sinkender Korngröße entsprechend einer HALL-PETCH-Beziehung.
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Ekström, Emanuel. "Impact of Milling and Sintering on Growth of WC Grains in Liquid Co - and an evaluation of existing growth theories." Thesis, KTH, Materials Science and Engineering, 2007. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-4591.

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Cemented carbides (WC-Co) are powder metallurgical products produced by liquid phase sintering. WC-Co is widely used for making a large variety of cutting tools, such as drills and inserts turning applications, due to its great mechanical properties, where the hardness of the WC grains is combined with the toughness of the of the Co binder. WC grain size and grain size distribution are the two most important factors to control the mechanical properties of the products.

This study examined the grain growth dependence of different milling and sintering times. The resulting grain size and grain size distribution were measured using image analysis on scanning electron microscopy images (SEM) and by using electron backscatter diffraction (EBSD). In addition, the correlation between hardness and coercivity, the most common indirect measures of grain size, and different methods of calculating average grain radius were investigated. An attempt was also made to study the contribution of defects to grain growth. This work also includes an overview of various grain growth equations and a numerical implementation of these.

Experimental results show that for shorter sintering times, powders milled for short times (15 min and 1 h) have larger average grain radii. There is a crossover after 6 to 8 h of sintering, where the powders milled for a long time (40 h and 200 h), have larger average radii. The measured hardness values correlate well with the average grain radius calculated from the grain surface area and the coercivity correlates with the established equations. EBSD measurements detected boundaries that could not be detected by image analysis, and that were not Sigma 2 boundaries. It is likely that these boundaries are either low energy boundaries or boundaries between grains that are very closely oriented. Comparing heat-treated powder with the untreated resulted in a lower average grain size after sintering for the heat-treated powder. None of the growth equations investigated in this work could fully describe the experimental grain growth.

Through increased understanding of the grain growth, the growth can be controlled and the end product can have the desired tool properties. The occurrence of abnormal grains in cutting tool applications can cause breakage, which is especially important to avoid in applications such as PCB drills. A correlation between hardness and grain size provides further means for cheap and fast indirect measures of the grain size in production.


Hårdmetall är ett pulvermetallurgiskt material som tillverkas genom smältfassintring och som kännetecknas av hårdhet, styvhet och god slitstyrka. Volframkarbidens (WC) kornstorlek och kornstorleksfördelning är två viktiga faktorer för att kontrollera de mekaniska egenskaperna i hårdmetall.

I den här studien har korntillväxtens beroende på malning och sintring undersökts. WC-Co maldes och sintrades fyra olika tider och kornstorleksfördelningen mättes med bildanalys på svepelektronmikroskopbilder samt med ``electron backscatter diffraction'' (EBSD). I arbetet har även korrelationen mellan hårdhet, koercivitet och olika sätt att beräkna medelkornstorleken undersökts. Ett försök har också genomförts för att studera hur defekterna i det malda pulvret påverkar korntillväxten. I arbetet har även ett flertal olika tillväxtekvationer modellerats numeriskt och för och nackdelar med de olika tillväxtekvationerna har vägts mot varandra.

En lång maltid (40 h och 200 h) visade sig ge liten kornstorlek för sintring kortare än 6 h, men för sintringar längre än 8 h gav istället kort malning (15 min och 1 h) den mindre kornstorleken. Det visade sig att uppmätt hårdhet korrelerar bäst med den medelkornstorleksradie som räknats fram från kornytan. I EBSD mätningarna kunde man observera ett flertal korngränser, utöver Sigma 2 korngränser, som inte hade detekterats med bildanalys. Värmebehandlingen av det malda pulvret minskade korntillväxten under efterföljande sintring. Ingen av de undersökta tillväxtekvationerna kunde beskriva de experimentella resultaten fullt ut.

Genom ökad förståelse för korntillväxt kan man kontrollera tillväxten och slutprodukten kan få önskade egenskaper. Förekomsten av abnorm korntillväxt i skärverktyg i hårdmetall är en av de vanligaste kritiska defekterna och det är speciellt viktigt är undvika korntillväxt i tillverkning av små verktyg, som till exempel kretskortsborrar. Hårdhet och koercivitet är de vanligaste indirekta mätmetoderna för att mäta kornstorlek i produktion. En bra korrelation mellan kornstorlek och indirekta mätmetoder ger utökade verktyg för snabba och billiga mätningar.

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Klemm, Robert. "Zyklische Plastizität von mikro- und submikrokristallinem Nickel." Doctoral thesis, Technische Universität Dresden, 2003. https://tud.qucosa.de/id/qucosa%3A23831.

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Im Rahmen der vorliegenden Arbeit wurde der Einfluss der Korngröße und der Gefügestabilität auf die zyklische Plastizität von mikro- und submikrokristallinem Nickel, hergestellt durch ECAP und PED, untersucht. Zur Gefügecharakterisierung kamen verschiedene elektronenmikroskopische und röntgenographische Methoden zum Einsatz. Die Untersuchungen zur Gefügestabilität zeigten, dass (i) die Stabilität der Korn- und Substruktur bei der zyklischen Verformung empfindlich vom Gefüge im Ausgangszustand abhängt, (ii) generell die Tendenz zur Umwandlung der vorhandenen Substruktur in eine universelle ermüdungstypische Substruktur besteht, diese Transformation jedoch durch die lokale Gefügebeschaffenheit be- bzw. verhindert sein kann und (iii) zur Erklärung des Entfestigungsverhaltens der ECAP-Materialien sowohl die Transformation der Substruktur als auch die Vergröberung der Kornstruktur berücksichtigt werden müssen. Auf der Basis der Ergebnisse der vorliegenden Arbeit und unter Hinzunahme von Resultaten aus der Literatur lassen sich Schlussfolgerungen zum Einfluss der Korngröße auf die zyklische Plastizität in einem vier Größenordnungen umfassenden Korngrößenbereich ziehen. In grob- und feinkörnigem Nickel bilden sich bei der zyklischen Verformung ermüdungstypische Versetzungsstrukturen, deren Abmessungen kaum von der Korngröße abhängen. Der Versetzungslaufweg in diesen Materialien ist wesentlich kleiner als die Kornabmessungen. Dementsprechend besteht höchstens ein schwacher Einfluss der Korngröße auf das sich bei der Wechselverformung einstellende Spannungsniveau. Bei mikro- und submikrokristallinem Nickel, wo der Versetzungslaufweg in der Größenordung der Kornabmessungen liegt, wird ein deutlicher Umschlag bei der Versetzungsmusterbildung und dem zyklischen Verformungsverhalten beobachtet. In diesem Korngrößenbereich entstehen entweder qualitativ andere (D&lt;DS1=5µm) oder keine Versetzungsstrukturen (D&lt;DS2=1µm) und das Spannungsniveau steigt mit sinkender Korngröße entsprechend einer HALL-PETCH-Beziehung.
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Books on the topic "Grain coarsening"

1

Mhmed, F. A. Ferrite grain coarsening. Manchester: UMIST, 1997.

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Modeling of coarsening and grain growth: Proceedings of a symposium. Warrendale, Pa: The Society, 1993.

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United States. National Aeronautics and Space Administration., ed. Structure and grain coarsening during the process of engineering ceramics. [Washington, D.C.]: National Aeronautics and Space Administration, 1987.

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Marsh, Steven P. Modeling of Coarsening and Grain Growth: Proceedings of a Symposium Sponsored by the Physical Metallurgy Committee, Held at the Fall Meeting of the. Minerals, Metals, & Materials Society, 1993.

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Book chapters on the topic "Grain coarsening"

1

Streitenberger, P., D. Fan, and V. Tikare. "Coarsening of Fractal Grain Boundaries." In Microstructures, Mechanical Properties and Processes - Computer Simulation and Modelling, 15–21. Weinheim, FRG: Wiley-VCH Verlag GmbH & Co. KGaA, 2005. http://dx.doi.org/10.1002/3527606157.ch3.

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Nestler, Britta. "Motion of Multiple Interfaces: Grain Growth and Coarsening." In Continuum Scale Simulation of Engineering Materials, 327–42. Weinheim, FRG: Wiley-VCH Verlag GmbH & Co. KGaA, 2005. http://dx.doi.org/10.1002/3527603786.ch14.

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Buntebarth, G., and G. Voll. "Quartz Grain Coarsening by Collective Crystallization in Contact Quartzites." In Equilibrium and Kinetics in Contact Metamorphism, 251–65. Berlin, Heidelberg: Springer Berlin Heidelberg, 1991. http://dx.doi.org/10.1007/978-3-642-76145-4_12.

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Nikolić, Z. S. "Computer Simulation of Grain Coarsening during Liquid Phase Sintering." In Materials Science Forum, 387–92. Stafa: Trans Tech Publications Ltd., 2005. http://dx.doi.org/10.4028/0-87849-971-7.387.

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Streitenberger, Peter, and Dana Zöllner. "Self-Similar Coarsening and the Envelope Theorem." In Proceedings of the 6th International Conference on Recrystallization and Grain Growth (ReX&GG 2016), 23–28. Hoboken, NJ, USA: John Wiley & Sons, Inc., 2016. http://dx.doi.org/10.1002/9781119328827.ch4.

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Streitenberger, Peter, and Dana Zöllner. "Self-Similar Coarsening and the Envelope Theorem." In Proceedings of the 6th International Conference on Recrystallization and Grain Growth (ReX&GG 2016), 23–28. Cham: Springer International Publishing, 2016. http://dx.doi.org/10.1007/978-3-319-48770-0_4.

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Wakai, Fumihiro. "Three-Dimensional Simulation of Coarsening and Grain Growth in Sintering." In THERMEC 2006, 2359–64. Stafa: Trans Tech Publications Ltd., 2007. http://dx.doi.org/10.4028/0-87849-428-6.2359.

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Sharma, Hemant, Richard M. Huizenga, Aleksei Bytchkov, Jilt Sietsma, and S. Erik Offerman. "In Situ Observation of Changing Crystal Orientations During Austenite Grain Coarsening." In In-situ Studies with Photons, Neutrons and Electrons Scattering II, 109–29. Cham: Springer International Publishing, 2014. http://dx.doi.org/10.1007/978-3-319-06145-0_7.

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Parr, I. M. D., T. J. Jackson, M. C. Hardy, D. J. Child, C. Argyrakis, K. Severs, V. Saraf, and J. M. Stumpf. "Inhomogeneous Grain Coarsening Behavior in Supersolvus Heat Treated Nickel-Based Superalloy RR1000." In Superalloys 2016, 447–56. Hoboken, NJ, USA: John Wiley & Sons, Inc., 2016. http://dx.doi.org/10.1002/9781119075646.ch48.

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Ferry, M., and N. Burhan. "Statistical Aspects of Grain Coarsening in a Fine Grained Al-Sc Alloy." In Materials Science Forum, 729–34. Stafa: Trans Tech Publications Ltd., 2007. http://dx.doi.org/10.4028/0-87849-443-x.729.

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Conference papers on the topic "Grain coarsening"

1

Mohrbacher, Hardy. "Alloy Design and Processing Strategies for Grain Coarsening-Resistant Carburizing Steels." In International Conference on Advances in Metallurgy of Long and Forged Products. Association for Iron & Steel Technology, 2021. http://dx.doi.org/10.33313/301/002.

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Zhou, T., H. Zurob, and M. Fox. "Austenite Grain Coarsening Behavior in V-Ti Microalloyed Steels during Reheating Process." In MS&T17. MS&T17, 2017. http://dx.doi.org/10.7449/2017/mst_2017_811_818.

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Zhou, T., H. Zurob, and M. Fox. "Austenite Grain Coarsening Behavior in V-Ti Microalloyed Steels during Reheating Process." In MS&T17. MS&T17, 2017. http://dx.doi.org/10.7449/2017mst/2017/mst_2017_811_818.

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Argyrakis, C., D. Child, M. Hardy, T. Jackson, I. Parr, V. Saraf, K. Severs, and J. Stumpf. "Inhomogeneous Grain Coarsening Behavior in Supersolvus Heat Treated Nickel-Based Superalloy RR1000." In Superalloys 2016. The Minerals, Metals & Materials Society, 2016. http://dx.doi.org/10.7449/superalloys/2016/superalloys_2016_447_456.

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Kim, Donghyun, Andrew Mawer, Glenn Y. Masada, and Tess J. Moon. "Modeling and Analysis of Crack Growth in SnPb and SnAgCu Solder Joints in PBGA Packages: Part I — Crack Initiation." In ASME 2003 International Mechanical Engineering Congress and Exposition. ASMEDC, 2003. http://dx.doi.org/10.1115/imece2003-43236.

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Solder joints in electronic packages deform by creep and undergo a microstructural evolution process that includes grain coarsening, voiding, microcracking, and macrocracking. This paper describes an FEM model of the crack initiation process of SnPb and SnAgCu solder joints in 357 plastic ball grid array packages for different aging conditions and simulated under 0–100°C accelerated thermal cycling tests. The simulations show that 1) cracks initiate at the package interface first, and then at the opposite side of the board interface; 2) secondary cracks initiate at the opposite end of the primary crack at the joint interfaces; 3) no secondary cracks occur at the package interface of ages SnPb joints, since compressive stresses oppose void formation; and 4) it takes longer to initiate cracks in SnAgCu joints than SnPb joints. The damage process in the solder joints was simulated from grain coarsening, voiding, to microcracking, with SnAgCu joints not undergoing grain coarsening due to their stable microstructure. The model results were consistent with experimental results in the number and location of cracks in the joints.
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Watwe, A. S., J. M. Hyzak, and D. M. Weaver. "Effect of Processing Parameters on the Kinetics of Grain Coarsening in P/M 718." In Superalloys. TMS, 1997. http://dx.doi.org/10.7449/1997/superalloys_1997_237_246.

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Yoneyama, N., K. Kubushiro, and H. Yoshizawa. "Creep Damage Evaluation of Fine-Grained HAZ in Mod. 9Cr Ferritic Heat-Resistant Steel Weldments." In ASME 2007 Pressure Vessels and Piping Conference. ASMEDC, 2007. http://dx.doi.org/10.1115/creep2007-26726.

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9Cr steel weldments are concerned with evaluation of creep life time and creep rupture mechanism. In fine grain HAZ (FG-HAZ) of weldments, TYPE IV cracking and creep voids occurred at lower stress than rupture stress level of base metal. In the crept specimen, FG-HAZ sometime has large coarsening grains near creep voids. These recovery phenomena are localized in FG-HAZ, and recovered microstructures are dependent on heat input of welding. In this study, creep tests are examined in two types of weldments, and relations between creep life time and coarsened sub-grains or grains have been studied by microstructural changing with EBSP analysis. In crept specimens, boundaries are moved and boundary density is decreasing in the fine-grained HAZ. Maximum grain size and creep life time have linear function, and EBSP can evaluate creep life time of 9Cr weldments. These microstructural changing are considered by morphology of precipitates in the several crept specimens.
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8

Bhalerao, Kishor D., Kurt S. Anderson, and Alain Laederach. "On Adaptivity in Coarse Grain Molecular Dynamics." In ASME 2009 International Design Engineering Technical Conferences and Computers and Information in Engineering Conference. ASMEDC, 2009. http://dx.doi.org/10.1115/detc2009-87827.

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Coarse grain molecular models have gained increasing importance in recent years to understand the macroscopic behavior of large molecular chains such as RNA which are fundamental to many biological processes. In such models, the chemical bonds are considered to be of fixed length and constituent molecules are approximated as rigid or flexible bodies connected via kinematic joints. It has already been demonstrated that the coarse grain models are capable of capturing the global conformational behavior of molecular systems. However, there is no formal way to guide the model coarsening process. One way to enhance the simulation speed and accuracy is to make the system adaptive and allow it to efficiently change the structure and model as the simulation progresses. This paper discusses the challenges in building an adaptive system and proposes certain parameters which could be used to introduce adaptivity in coarse grain molecular dynamics.
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Lee, Jae-Seong, Chan-Hyun Son, Bok-Han Song, and Hyo-Seup Han. "The Microstructure Control and Rolling Contact Fatigue Behavior of a Hot Worked Automotive Application." In ASME 2005 International Mechanical Engineering Congress and Exposition. ASMEDC, 2005. http://dx.doi.org/10.1115/imece2005-80603.

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Once hot forgings for automotive parts such as wheel bearing flange to which cyclic asymmetric bending stress is continuously applied are produced, their microstructure, such as ferrite, should be controlled appropriately for obtaining of superior mechanical properties. However, it is hard to control the microstructure uniformly because mechanical strength is reduced as coarsening of ferrite grains. To investigate the microstructural alteration based on process parameters during hot working, the variation of the ferrite grain size, hereafter FGS, was investigated by utilizing of the computer-controlled servo-hydraulic Gleeble tester which can reproduce hot deformation behavior. In addition, the effect of ferrite grain size of raw material on austenite grain behavior of hot forgings was also examined. The rolling contact fatigue resistance of induction-hardened SAE1055 steel was compared with the result of induction-hardened SAE52100 bearing steel. As a result, it was confirmed that ferrite grain sizes of hot forging depend on heating temperature and cooling-start temperature during hot forging and cooling operations. Induction-hardened SAE1055 steel showed superior rolling contact fatigue resistance to induction-hardened SAE52100 steel. This fact appears that SAE1055 steel is freer from material defects such as segregateion than comparative steel.
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Seo, Eun Jung, John G. Speer, David K. Matlock, and Robert L. Cryderman. "Effect of Mo in Combination with Nb on Austenite Grain Size Control in Vacuum Carburizing Steels." In HT2019. ASM International, 2019. http://dx.doi.org/10.31399/asm.cp.ht2019p0115.

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Abstract Vacuum carburizing with high pressure gas quenching is increasingly employed to reduce near-surface intergranular oxidation (IGO) and reduce quenching distortion. Vacuum carburizing can be conducted at higher operating temperatures, as high as 1100°C, to reduce the processing times and increase furnace productivity. However, processing at elevated temperatures may result in excessive austenite grain coarsening, leading to the degradation of fatigue performance. Microalloying to form small carbonitride precipitates is one effective method to limit austenite grain growth during carburizing. In this study, the effects of microalloying a carburizing steel with molybdenum (Mo) and niobium (Nb) on microstructural grain refinement in the core have been investigated. Additions of Nb alone are found to provide some control of abnormal austenite grain growth. Additions of Mo in combination with Nb provide enhanced resistance to austenite grain growth, especially at high carburizing temperatures up to 1050 °C. The enhanced control is attributed to solute and precipitation effects.
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