Journal articles: 'Grain coarsening'

1

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.

Full text

Abstract:

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.

APA, Harvard, Vancouver, ISO, and other styles

2

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.

Full text

Abstract:

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.

APA, Harvard, Vancouver, ISO, and other styles

3

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.

Full text

Abstract:

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.

APA, Harvard, Vancouver, ISO, and other styles

4

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.

Full text

Abstract:

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.

APA, Harvard, Vancouver, ISO, and other styles

5

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.

Full text

Abstract:

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.

APA, Harvard, Vancouver, ISO, and other styles

6

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.

Full text

Abstract:

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.

APA, Harvard, Vancouver, ISO, and other styles

7

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.

Full text

Abstract:

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.

APA, Harvard, Vancouver, ISO, and other styles

8

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.

Full text

Abstract:

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.

APA, Harvard, Vancouver, ISO, and other styles

9

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.

Full text

Abstract:

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.

APA, Harvard, Vancouver, ISO, and other styles

10

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.

Full text

Abstract:

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.

APA, Harvard, Vancouver, ISO, and other styles

11

Chen, Yu Zeng, A. Herz, Christine Borchers, X. H. Shi, X. Y. Ma, F. Liu, and Reiner Kirchheim. "Inhibition of Grain Coarsening in Nanocrystalline Fe-C Alloys by Interaction between Carbon and Grain Boundaries." Advanced Materials Research 904 (March 2014): 184–88. http://dx.doi.org/10.4028/www.scientific.net/amr.904.184.

Full text

Abstract:

Nanocrystalline Fe-1.77at.%C and Fe-3.27at.%C alloys prepared by ball milling iron powders and graphite powders are annealed below 573K where the precipitation of Fe3C does not occur. Upon annealing, a significant grain coarsening is observed in Fe-1.77at.%C alloy, whereas the grain coarsening is inhibited in Fe-3.27at.%C alloy. Within the framework of thermodynamic theories, the inhibition of grain coarsening in nanocrystalline Fe-C alloys is discussed. It is demonstrated that the inhibition of grain coarsening in the nanocrystalline Fe-C alloys can be ascribed to a vanished driving force for grain growth which is caused by the interaction between carbon and the grain boundaries of nanograins.

APA, Harvard, Vancouver, ISO, and other styles

12

Zhou, Tihe, Ronald O’Malley, Hatem Zurob, Mani Subramanian, Sang-Hyun Cho, and Peng Zhang. "Control of Upstream Austenite Grain Coarsening during the Thin-Slab Cast Direct-Rolling (TSCDR) Process." Metals 9, no. 2 (February 1, 2019): 158. http://dx.doi.org/10.3390/met9020158.

Full text

Abstract:

Thin-slab cast direct-rolling (TSCDR) has become a major process for flat-rolled production. However, the elimination of slab reheating and limited number of thermomechanical deformation passes leave fewer opportunities for austenite grain refinement, resulting in some large grains persisting in the final microstructure. In order to achieve excellent ductile to brittle transition temperature (DBTT) and drop weight tear test (DWTT) properties in thicker gauge high-strength low-alloy products, it is necessary to control austenite grain coarsening prior to the onset of thermomechanical processing. This contribution proposes a suite of methods to refine the austenite grain from both theoretical and practical perspectives, including: increasing cooling rate during casting, liquid core reduction, increasing austenite nucleation sites during the delta-ferrite to austenite phase transformation, controlling holding furnace temperature and time to avoid austenite coarsening, and producing a new alloy with two-phase pinning to arrest grain coarsening. These methodologies can not only refine austenite grain size in the slab center, but also improve the slab homogeneity.

APA, Harvard, Vancouver, ISO, and other styles

13

Fu, Jin Long, Yu Wei Wang, Kai Kun Wang, and Xiao Wei Li. "Microstructure Evolution and Coarsening Mechanism of 7075 Semi-Solid Aluminum Alloy Pre-Deformed by ECAP Method." Solid State Phenomena 256 (September 2016): 294–300. http://dx.doi.org/10.4028/www.scientific.net/ssp.256.294.

Full text

Abstract:

To investigate the influence of refined grains on the microstructure of 7075 aluminum alloy in semi-solid state, a new strain induced melting activation (SIMA) method was put forward containing two main stages: pre-deformation with equal channel angular pressing (ECAP) method and isothermally holding in the semi-solid temperature range. The breaking up and growth mechanisms of the grains and kinetics of equiaxed grains coarsening during the semi-solid holding were investigated. The results showed that the average grain size after ECAP extrusion decreased significantly, e.g., microstructure with average globular diameter less than 5μm was achieved after four-pass ECAP extrusion. Obvious grain coarsening had been found during isothermal holding in the semi-solid state and the roundness of the grains increased with the increasing holding time. The proper microstructure of 66.8μm in diameter and 1.22 in shape factor was obtained under proper soaking condition (at 590°C for 15 min). Two coarsening mechanisms, namely, coalescence in lower liquid fraction and Ostwald ripening in higher liquid fraction contributed to the grain growth process.

APA, Harvard, Vancouver, ISO, and other styles

14

Wakai, Fumihiro. "Three-Dimensional Simulation of Coarsening and Grain Growth in Sintering." Materials Science Forum 539-543 (March 2007): 2359–64. http://dx.doi.org/10.4028/www.scientific.net/msf.539-543.2359.

Full text

Abstract:

The interparticle mass transport causes the larger particles to grow at the expense of the smaller particles in the process of sintering. Coarsening during sintering results from surface motion, while grain growth results from grain boundary motion. The three-dimensional simulation was performed to study coarsening and grain growth during sintering by using the Surface Evolver program. The coarsening and grain growth were affected by the ratio of grain boundary energy to surface energy, the ratio of grain boundary mobility to surface mobility, the size of a particle, and its coordination number.

APA, Harvard, Vancouver, ISO, and other styles

15

Streitenberger, P., D. Förster, and P. Veit. "Thermal Relaxation of Initially Fractal Grain Boundaries." Fractals 05, supp02 (October 1997): 5–21. http://dx.doi.org/10.1142/s0218348x97000887.

Full text

Abstract:

The concept of fractal geometry is used to describe serrated and rugged grain boundaries in the pure materials Zinc and Titanium after deformation and heat treatment. The fractal dimension of the grain boundaries are determined by application of optical and scanning electron microscopy over a wide range of magnifications. Measurements of the coarsening kinetics of the initially fractal-like grain boundaries during isochronous as well as isothermal annealing are presented. The results of the annealing experiments can be explained by an analytic fractal coarsening model yielding the observed dependency of the time law of grain boundary smoothing on the initially fractal dimension of the grain boundaries. The results are supported by a Monte Carlo simulation of the smoothing process of single initially fractal grains.

APA, Harvard, Vancouver, ISO, and other styles

16

Shi, J. L. "Relations Between Coarsening and Densification and Mass Transport Path in Solid-state Sintering of Ceramics: Model Analysis." Journal of Materials Research 14, no. 4 (April 1999): 1378–88. http://dx.doi.org/10.1557/jmr.1999.0188.

Full text

Abstract:

The correlations between coarsening (including grain and pore growth) and densification, and the effects of mass transport on particle coarsening and densification were discussed based on the simple particle array models and for the real particle compacts. Grain boundary motion could cause particle coarsening only under a certain particle size distribution but not densification; mass transport is reasoned to contribute to both grain growth (particle coarsening) and shrinkage for one-dimensional particle arrays. Under a certain limitation for the change of the particle size aspect ratio during sintering, very limited effects of grain grown by itself on the shrinkage of particle a rrays throughreinitiating the sintering could be found. For a real powder compact system, mass transport between the particles, which surround a pore, contributes to the particle coarsening and densification when the pore is thermodynamically unstable and only to particle coarsening when the pore is thermodynamically stable. The mass transport mechanism for both particle coarsening and densification would be the same, which cannot exclude, at least on thermodynamics, the contribution from surface diffusion in the intermediate stage of sintering.

APA, Harvard, Vancouver, ISO, and other styles

17

Yang, Guang Yu, Wan Qi Jie, Qi Tang Hao, and Run Qiang Zhang. "Micro-Structural Evolution of AlCu5MnCdVA Cast Aluminum Alloy by Semi-Solid Isothermal Annealing Process." Advanced Materials Research 26-28 (October 2007): 489–93. http://dx.doi.org/10.4028/www.scientific.net/amr.26-28.489.

Full text

Abstract:

Isothermal grain coarsening of AlCu5MnCdVA aluminum alloy prepared by permanent mould casting during semi-solid treatment process was studied. It was found that the relationship between the average diameter of α (Al) grains and the isothermal holding time fitted the formula r − r = K ⋅ t − − ' 3 0 3 , where the coarsening rate K’ varied with the holding temperature, which equaled to 4.288×10-10m3/s and 5.962×10-10m3/s at the holding temperature. A modified model of liquid film migration has been proposed for explaining of 622°C and 631°C respectively the coarsening rate variation with annealing temperature. The diffusion of the solutes as well as vacancies, and the grain boundary tension are responsible for the microstructure evolution of AlCu5MnCdVA cast alloy.

APA, Harvard, Vancouver, ISO, and other styles

18

Li, X. Y., Z. H. Jin, X. Zhou, and K. Lu. "Constrained minimal-interface structures in polycrystalline copper with extremely fine grains." Science 370, no. 6518 (November 12, 2020): 831–36. http://dx.doi.org/10.1126/science.abe1267.

Full text

Abstract:

Metals usually exist in the form of polycrystalline solids, which are thermodynamically unstable because of the presence of disordered grain boundaries. Grain boundaries tend to be eliminated through coarsening when heated or by transforming into metastable amorphous states when the grains are small enough. Through experiments and molecular dynamics simulations, we discovered a different type of metastable state for extremely fine-grained polycrystalline pure copper. After we reduced grain sizes to a few nanometers with straining, the grain boundaries in the polycrystals evolved into three-dimensional minimal-interface structures constrained by twin boundary networks. This polycrystalline structure that underlies what we call a Schwarz crystal is stable against grain coarsening, even when close to the equilibrium melting point. The polycrystalline samples also exhibit a strength in the vicinity of the theoretical value.

APA, Harvard, Vancouver, ISO, and other styles

19

Kirchheim, Reiner. "Grain coarsening inhibited by solute segregation." Acta Materialia 50, no. 2 (January 2002): 413–19. http://dx.doi.org/10.1016/s1359-6454(01)00338-x.

Full text

APA, Harvard, Vancouver, ISO, and other styles

20

Liu, Silu, and Yonghao Zhao. "Revealing grain coarsening and detwinning in bimodal Cu under tension." REVIEWS ON ADVANCED MATERIALS SCIENCE 60, no. 1 (January 1, 2021): 15–24. http://dx.doi.org/10.1515/rams-2021-0001.

Full text

Abstract:

Abstract Metals with a bimodal grain size distribution have been found to have both high strength and good ductility. However, the coordinated deformation mechanisms underneath the ultrafine-grains (UFGs) and coarse grains (CGs) still remain undiscovered yet. In present work, a bimodal Cu with 80% volume fraction of recrystallized micro-grains was prepared by the annealing of equal-channel angular pressing (ECAP) processed ultrafine grained Cu at 473 K for 40 min. The bimodal Cu has an optimal strength-ductility combination (yield strength of 220 MPa and ductility of 34%), a larger shear fracture angle of 83° and a larger area reduction of 78% compared with the as-ECAPed UFG Cu (yield strength of 410 MPa, ductility of 16%, shear fracture angle of 70°, area reduction of 69%). Grain refinement of recrystallized micro-grains and detwinning of annealing growth twins were observed in the fractured bimodal Cu tensile specimen. The underlying deformation mechanisms for grain refinement and detwinning were analyzed and discussed.

APA, Harvard, Vancouver, ISO, and other styles

21

Nikolic, Zoran, and Kazunari Shinagawa. "Capillary liquid bridge and grain coarsening during liquid phase sintering." Science of Sintering 49, no. 1 (2017): 1–10. http://dx.doi.org/10.2298/sos1701001n.

Full text

Abstract:

The finite element method is employed to simulate the microstructural evolution through grain coarsening within capillary liquid bridge. Liquid and solid phase domains will be represented with curved interfaces defined by the discrete set of points. Numerical method for simulation of grain coarsening will be based on the interfacial concentration as given by the Gibbs-Thomson equation and on modeling of intergrain diffusional interactions. It will be shown that the strong intergrain diffusional interactions can induce large shape distortion of multi grain model. Simulation of the grain coarsening for W-Ni alloy will be demonstrated as a first step.

APA, Harvard, Vancouver, ISO, and other styles

22

Tusima, Katutosi. "Grain Coarsening of Snow Particles Immersed in Water and Solutions." Annals of Glaciology 6 (1985): 126–29. http://dx.doi.org/10.3189/1985aog6-1-126-129.

Full text

Abstract:

In order to clarify the metamorphic process of snow particles immersed in water, distributions of grain size were examined as functions of time (0.1 to 1 000 hrs) and impurity concentrations. When disaggregated snow particles were immersed in water kept at 0°C, each particle became spherical and grain coarsening took place with time. The average diameter increased with cube root of time and the average volume increased in proportion to time. Grain coarsening was not detected in a kerosene environment.In solutions of glucose, NaCl, HC1 and dextran, the growth rate was controlled by the concentration and the diffusivity of the solute. The higher concentration and the lower diffusivity, the grain coarsening was controlled. The grain coarsening is explained by the disappearance of relatively small particles and growth of relatively large ones, caused by differences of the equilibrium temperature of each particle if the total ice mass is conserved.

APA, Harvard, Vancouver, ISO, and other styles

23

Tusima, Katutosi. "Grain Coarsening of Snow Particles Immersed in Water and Solutions." Annals of Glaciology 6 (1985): 126–29. http://dx.doi.org/10.1017/s0260305500010156.

Full text

Abstract:

In order to clarify the metamorphic process of snow particles immersed in water, distributions of grain size were examined as functions of time (0.1 to 1 000 hrs) and impurity concentrations. When disaggregated snow particles were immersed in water kept at 0°C, each particle became spherical and grain coarsening took place with time. The average diameter increased with cube root of time and the average volume increased in proportion to time. Grain coarsening was not detected in a kerosene environment. In solutions of glucose, NaCl, HC1 and dextran, the growth rate was controlled by the concentration and the diffusivity of the solute. The higher concentration and the lower diffusivity, the grain coarsening was controlled. The grain coarsening is explained by the disappearance of relatively small particles and growth of relatively large ones, caused by differences of the equilibrium temperature of each particle if the total ice mass is conserved.

APA, Harvard, Vancouver, ISO, and other styles

24

Liu, Huasong, Yannan Dong, Hongguang Zheng, Xiangchun Liu, Peng Lan, Haiyan Tang, and Jiaquan Zhang. "Precipitation Criterion for Inhibiting Austenite Grain Coarsening during Carburization of Al-Containing 20Cr Gear Steels." Metals 11, no. 3 (March 18, 2021): 504. http://dx.doi.org/10.3390/met11030504.

Full text

Abstract:

AlN precipitates are frequently adopted to pin the austenite grain boundaries for the high-temperature carburization of special gear steels. For these steels, the grain coarsening criterion in the carburizing process is required when encountering the composition optimization for the crack-sensitive steels. In this work, the quantitative influence of the Al and N content on the grain size after carburization is studied through pseudocarburizing experiments based on 20Cr steel. According to the grain structure feature and the kinetic theory, the abnormal grain growth is demonstrated as the mode of austenite grain coarsening in carburization. The AlN precipitate, which provides the dominant pinning force, is ripened in this process and the particle size can be estimated by the Lifshitz−Slyosov−Wagner theory. Both the mass fraction and the pinning strength of AlN precipitate show significant influence on the grain growth behavior with the critical values indicating the grain coarsening. These criteria correspond to the conditions of abnormal grain growth when bearing the Zener pinning, which has been analyzed by the multiple phase-field simulation. Accordingly, the models to predict the austenite grain coarsening in carburization were constructed. The prediction is validated by the additional experiments, resulting in accuracies of 92% and 75% for the two models, respectively. Finally, one of the models is applied to optimize the Al and N contents of commercial steel.

APA, Harvard, Vancouver, ISO, and other styles

25

Randjelovic, B., K. Shinagawa, and Z. S. Nikolic. "A mathematical approach to Ostwald ripening due to diffusion and deformation in liquid bridge." Science of Sintering 45, no. 3 (2013): 261–71. http://dx.doi.org/10.2298/sos1303261r.

Full text

Abstract:

From many experiments with mixtures of small and large grains, it can be concluded that during liquid phase sintering, smaller grains partially dissolve and a solid phase precipitates on the larger grains and grain coarsening occurs. The growth rate can be controlled either by the solid-liquid phase boundary reaction or by diffusion through the liquid phase. The microstructure may change either by larger grains growing during the Ostwald ripening process or by shape accommodation. In this study, two-dimensional mathematical approach for simulation of grain coarsening by grain boundary migration based on a physical and corresponding numerical modeling of liquid phase sintering will be considered. A combined mathematical method of analyzing viscous deformation and solute diffusion in liquid bridge between two grains with different sizes will be proposed. The viscous FE method will be used for calculating meniscus of the liquid bridge, with the interfacial tensions taken into consideration. The FE method for diffusion will be also implemented by using the same mesh as the deformation analysis.

APA, Harvard, Vancouver, ISO, and other styles

26

Zöllner, Dana, and Peter Streitenberger. "Potts Model Simulation of Grain Boundary Junction Limited Grain Growth." Materials Science Forum 715-716 (April 2012): 623–28. http://dx.doi.org/10.4028/www.scientific.net/msf.715-716.623.

Full text

Abstract:

The standard Monte Carlo (MC) Potts model is modified regarding the mobility of grain boundaries and their junctions allowing the simulation of a size effect observed in nanocrystalline grain growth. In large simulation studies different properties are measured. For initially very small grains the early growth regime corresponds to a separate coarsening state, which is characterised by an average growth law and a self-similar grain size distribution that both show strong deviations from the parabolic normal grain growth behaviour. The simulation results can be described by a theoretical model based on a statistical mean-field theory for nanocrystalline grain growth.

APA, Harvard, Vancouver, ISO, and other styles

27

Liu, Ning, Gencang Yang, Feng Liu, Yuzeng Chen, Changlin Yang, Yiping Lu, Da Chen, and Yaohe Zhou. "Grain refinement and grain coarsening of undercooled Fe–Co alloy." Materials Characterization 57, no. 2 (August 2006): 115–20. http://dx.doi.org/10.1016/j.matchar.2005.12.008.

Full text

APA, Harvard, Vancouver, ISO, and other styles

28

Hossein Nedjad, S., Mahmoud Nili-Ahmadabadi, Tadashi Furuhara, and Tadashi Maki. "Evolution of Precipitate Coarsening Reaction in a Nanostructured Fe-Ni-Mn Maraging Alloy." Solid State Phenomena 114 (July 2006): 159–64. http://dx.doi.org/10.4028/www.scientific.net/ssp.114.159.

Full text

Abstract:

Fe-Ni-Mn maraging alloys show discontinuous coarsening of fct θ-NiMn precipitates along prior austenite grain boundaries (PAGBs) during isothermal aging. Heavy cold rolling of a solution annealed Fe-10Ni-7Mn (wt. %) maraging alloy and subsequent aging treatment at 773 K led to the formation of a nanostructured material. Hardness measurement and transmission electron microscopy were used to study the aging behaviour and microstructural evolution of the nanostructured alloy. At the early stage of aging, an ultrafine grained structure was observed with fine matrix precipitates. However, at later stages of aging, severe coarsening of precipitates was found. At that stage, a lamellar microstructure composed of finely precipitated ferrite laths and ultrafine ferrite grains were identified. Coarse fct θ-NiMn precipitates were identified at the ultrafine ferritic grain boundaries. Development of the coarsening reaction was found to increase the ultrafine grained ferritic regions with prolonged aging.

APA, Harvard, Vancouver, ISO, and other styles

29

Sha, Qing Yun, Li Feng Qiao, Rong Jie Xu, Guo Jian Huang, and Zu Qing Sun. "Comparison of Grain Growth between Fine-Grained and Coarse-Grained Austenite in a Nb-V-Ti Microalloyed Steel." Materials Science Forum 638-642 (January 2010): 3496–501. http://dx.doi.org/10.4028/www.scientific.net/msf.638-642.3496.

Full text

Abstract:

Comparison of grain growth of fine-grained and coarse-grained austenite in a Nb-V-Ti microalloyed steel during reheating or equalization at the same temperature was investigated using cold-charging and hot-charging specimens respectively in this study. The results show that the different grain growth behavior appears in fine-grained and coarse-grained austenite. The uniform grain growth and lower growth rate at reheating temperature studied was found in fine-grained austenite, while partial grain growth and higher growth rate was present in coarse-grained austenite. During reheating or equalization, the slow growth rate in fine-grained austenite may be contributed to stronger pinning force of fine precipitates while higher grain growth rate in coarse-grained austenite were believed to the result of lager size difference among part of grains. Grain coarsening occurs in fine-grained austenite as result of precipitate unpinning at extending holding time, but coarse-grained austenite remained wide size distribution at the same condition and this should not be considered as grain coarsening. coarse-grained austenite remained wide size distribution at the

APA, Harvard, Vancouver, ISO, and other styles

30

Kim, Jeong Min, Sok Yun Hong, Ji Hun Jang, and Kyung Jong Lee. "Determination of the Grain Coarsening Temperature in Nb Microalloyed Steels by Multiphase-Field Model." Materials Science Forum 879 (November 2016): 921–25. http://dx.doi.org/10.4028/www.scientific.net/msf.879.921.

Full text

Abstract:

The grain coarsening temperature in Nb microalloyed steels is investigated by multiphase-field model. In this study, the pinning force is treated as time-dependent using mean-field kinetics of precipitates including volume fraction and their size. The grain size is calculated with time under various temperature range. The grain coarsening temperature is determined by the ratio of the largest radius of grain vs. the average grain radius criteria (Rmax / Ravg > 2.94) in two-dimensional growth. Through this model, it is possible to simulate grain growth in microalloyed steels more precisely.

APA, Harvard, Vancouver, ISO, and other styles

31

Fan, Cuncai, Zhongxia Shang, Tongjun Niu, Jin Li, Haiyan Wang, and Xinghang Zhang. "Dual Beam In Situ Radiation Studies of Nanocrystalline Cu." Materials 12, no. 17 (August 25, 2019): 2721. http://dx.doi.org/10.3390/ma12172721.

Full text

Abstract:

Nanocrystalline metals have shown enhanced radiation tolerance as grain boundaries serve as effective defect sinks for removing radiation-induced defects. However, the thermal and radiation stability of nanograins are of concerns since radiation may induce grain boundary migration and grain coarsening in nanocrystalline metals when the grain size falls in the range of several to tens of nanometers. In addition, prior in situ radiation studies on nanocrystalline metals have focused primarily on single heavy ion beam radiations, with little consideration of the helium effect on damage evolution. In this work, we utilized in situ single-beam (1 MeV Kr++) and dual-beam (1 MeV Kr++ and 12 keV He+) irradiations to investigate the influence of helium on the radiation response and grain coarsening in nanocrystalline Cu at 300 °C. The grain size, orientation, and individual grain boundary character were quantitatively examined before and after irradiations. Statistic results suggest that helium bubbles at grain boundaries and grain interiors may retard the grain coarsening. These findings provide new perspective on the radiation response of nanocrystalline metals.

APA, Harvard, Vancouver, ISO, and other styles

32

Tian, Wen Tong, H. Yang, and X. Cao. "Microstructural Evolution of 7A04 Alloy Prepared by FE-ECAE in Semi-Solid State." Key Engineering Materials 426-427 (January 2010): 274–78. http://dx.doi.org/10.4028/www.scientific.net/kem.426-427.274.

Full text

Abstract:

In the paper, forward extrusion-equal channel angular extrusion (FE-ECAE), which is new strain-induced melt activation (SIMA) method, is introduced in making semi-solid billet of 7A04 alloy. The principle of the method is that by using FE-ECAE as strain induced step and semi-solid isothermal treatment as melt activation step. The results show that semi-solid billet with highly spheroidal and homogeneous refined grains can be prepared by FE-ECAE method. The equivalent strain in FE-ECAE before reheating has a great influence on its microstructural evolution. Grain size decreases and its shape also approaches to sphericity with increasing equivalent strain. The main mechanism of the initial semi-solid grains coarsening was coalescence. With the prolongation of isothermal holding time, the grains grew up and spheroidized, in which the mean diameter of grain and liquid volume fraction increased. In the meantime, the higher the reheating temperature, the faster the grain grew and spheroidized. Subsequently, the main mechanism of grains coarsening was Ostwald ripening. The suitable reheating temperature of 7A04 alloy was 610°C.

APA, Harvard, Vancouver, ISO, and other styles

33

Rofman, Oleg V., and Pete S. Bate. "Dynamic Grain and Particle Growth in a Non-Superplastic Al-4Cu Alloy." Materials Science Forum 558-559 (October 2007): 797–802. http://dx.doi.org/10.4028/www.scientific.net/msf.558-559.797.

Full text

Abstract:

The effect of deformation on the microstructure of a Al-4wt.%Cu alloy has been investigated. Evaluation of the microstructural changes was made by comparing results after both static annealing and tensile testing (deformed and non-deformed regions) at 450 °C. Uniaxial perturbed-rate tests showed that the Al-4wt.%Cu has a low value of the strain rate sensitivity index (m ~ 0.22) and cannot be considered as a superplastic material. It was found that in the deformed regions, specimens showed a significant increase in the grain and particle size. These changes were accompanied by an increase in the aspect ratio of the matrix grains. Tensile tests carried out at constant strain rates and stopped at intermediate strains helped to estimate the rate of the grain and particle growth and the contribution of deformation to it. To examine in detail the mechanism of the particle coarsening during deformation, additional tensile tests were made using the Al-4wt.%Cu alloy annealed at temperature conditions leading to abnormal grain size. Results of these tests also showed strain-induced particle coarsening, so that dynamic particle coarsening was not simply caused by boundary migration effects.

APA, Harvard, Vancouver, ISO, and other styles

34

Liu, Fen, and Jun Cai Zhang. "Nb Microalloyed Steel of Grain Coarsening Law." Applied Mechanics and Materials 174-177 (May 2012): 433–36. http://dx.doi.org/10.4028/www.scientific.net/amm.174-177.433.

Full text

Abstract:

With the process parameters and processing conditions in the mill, a systematic experimental research were conducted to Q345 steel containing niobium austenite grain growth law, and analysis the dissolution and precipitation behavior of Nb carbonitride. The results shows that Nb-microalloyed steel heated to 1180 ~ 1230 °C can significantly improve strength and toughness of steel and performance.

APA, Harvard, Vancouver, ISO, and other styles

35

Cao, P., Ma Qian, and D. H. StJohn. "Grain coarsening of magnesium alloys by beryllium." Scripta Materialia 51, no. 7 (October 2004): 647–51. http://dx.doi.org/10.1016/j.scriptamat.2004.06.022.

Full text

APA, Harvard, Vancouver, ISO, and other styles

36

Beke, D. L., C. Cserháti, and I. A. Szabó. "Segregation inhibited grain coarsening in nanocrystalline alloys." Journal of Applied Physics 95, no. 9 (May 2004): 4996–5001. http://dx.doi.org/10.1063/1.1688461.

Full text

APA, Harvard, Vancouver, ISO, and other styles

37

Rutenberg, Andrew D., and Benjamin P. Vollmayr-Lee. "Anisotropic Coarsening: Grain Shapes and Nonuniversal Persistence." Physical Review Letters 83, no. 19 (November 8, 1999): 3772–75. http://dx.doi.org/10.1103/physrevlett.83.3772.

Full text

APA, Harvard, Vancouver, ISO, and other styles

38

Fang, Qihong, Li Li, Xin Wang, Jia Li, and Liang Jiang. "Abnormal grain coarsening mechanism in conical nickel." Journal of Alloys and Compounds 768 (November 2018): 613–17. http://dx.doi.org/10.1016/j.jallcom.2018.07.270.

Full text

APA, Harvard, Vancouver, ISO, and other styles

39

Liu, Zhilin, Dong Qiu, Feng Wang, John A. Taylor, and Mingxing Zhang. "Crystallography of grain refinement in cast zinc–copper alloys." Journal of Applied Crystallography 48, no. 3 (May 31, 2015): 890–900. http://dx.doi.org/10.1107/s1600576715008936.

Full text

Abstract:

Adding the peritectic forming element Cu effectively reduced the average grain size of cast Zn by over 85%. At a specified cast condition, the smallest grain size was obtained at 2 wt% Cu addition. A further increase in Cu content led to grain coarsening in the cast Zn–Cu alloys. Although the solute effect of Cu was predominately responsible for the grain refinement through restriction of the grain growth, it was found that the variation of grain size is also closely related to the formation of the pro-peritectic phase, ∊-CuZn4. Crystallographic calculations using the edge-to-edge matching model showed low interatomic misfit and interplanar mismatch between Zn and the ∊-CuZn4phase. In addition, a reproducible h.c.p.–h.c.p. (h.c.p. denotes hexagonal close-packed) orientation relationship between Zn and the ∊-CuZn4particles (located within the Zn grain centres) was also experimentally determined using the electron backscattered diffraction method. This indicated the high potency of the pro-peritectic ∊-CuZn4particles as effective heterogeneous nucleation sites for η-Zn, which further refined the Zn grains. However, when the Cu content was over 2.0 wt%, formation of large ∊-CuZn4particles resulted in grain coarsening of the cast alloys.

APA, Harvard, Vancouver, ISO, and other styles

40

Solis-Bravo, Gregorio, Matthew Merwin, and C. Isaac Garcia. "Impact of Precipitate Morphology on the Dissolution and Grain-Coarsening Behavior of a Ti-Nb Microalloyed Linepipe Steel." Metals 10, no. 1 (January 4, 2020): 89. http://dx.doi.org/10.3390/met10010089.

Full text

Abstract:

The relationship between precipitate morphology and dissolution on grain coarsening behavior was studied in two Ti-Nb microalloyed Linepipe (LP) Steels. The developed understanding highlights the importance of the complex relationship between precipitate constitutive make-up, dissolution mechanism and grain boundary (GB) pinning force. Equilibrium-based empirical solubility products were used to calculate precipitate volume fractions and compared to experimental measurements. Scanning Electron Microscopy (SEM), Electron Backscatter Diffraction (EBSD) and Electron Probe Micro-Analysis (EPMA) were conducted on bulk samples. Transmission Electron Microscopy (TEM)-based techniques were used on C-replica extractions and thin-foils. A retardation in the grain-coarsening temperature compared to the predicted coarsening temperature based on equilibrium calculations was noticed. In addition, a consistent NbC epitaxial formation over pre-existing TiN was observed. The resulting reduction in total precipitate/matrix interface area and the low energy of the TiN/NbC interface are pointed to as responsible mechanisms for the retardation in the kinetics of precipitates’ dissolution. This dissolution retardation mechanism suggests that a lower Nb content might be effective in controlling the grain coarsening behavior of austenite.

APA, Harvard, Vancouver, ISO, and other styles

41

Adachi, Hiroki, Kozo Osamura, Jun Kusui, and Shigeru Okaniwa. "Effect of Hot-Extrusion Conditions on Mechanical Properties and Microstructure of P/M Al-Zn-Mg-Cu Alloys Containing Zr." Materials Science Forum 519-521 (July 2006): 1479–84. http://dx.doi.org/10.4028/www.scientific.net/msf.519-521.1479.

Full text

Abstract:

The effect of extrusion rate and ratio on the Al3Zr induced dynamic recrystallization (DRX) that occurs during hot extrusion of RS-P/M Al-Zn-Mg-Cu-Zr alloys was investigated. An increase in the logarithm of extrusion rate promoted DRX and lead to a monotonic increase in the number of fine grains. Although DRX was also promoted and the grain size reduced by an increase in extrusion ratio from 10 to 20, the DRX behavior hardly changed, even when the extrusion ratio exceeded 20. However, with increasing extrusion ratio, the width of fibrous grain, i.e., the unrecrystallized region, decreased and the tensile strength increased to 879 MPa. When the extrusion rate and ratio exceeded 54 mm/min and 20, respectively, a marked grain coarsening occurred upon solution treatment, and the tensile strength tended to decrease, because of the high dislocation density induced by hot extrusion. By annealing at 563 K before solution treatment, it was possible to prevent grain coarsening, and thus prevent the strength decrease.

APA, Harvard, Vancouver, ISO, and other styles

42

Yang, T., Y. L. Zhao, W. P. Li, C. Y. Yu, J. H. Luan, D. Y. Lin, L. Fan, et al. "Ultrahigh-strength and ductile superlattice alloys with nanoscale disordered interfaces." Science 369, no. 6502 (July 23, 2020): 427–32. http://dx.doi.org/10.1126/science.abb6830.

Full text

Abstract:

Alloys that have high strengths at high temperatures are crucial for a variety of important industries including aerospace. Alloys with ordered superlattice structures are attractive for this purpose but generally suffer from poor ductility and rapid grain coarsening. We discovered that nanoscale disordered interfaces can effectively overcome these problems. Interfacial disordering is driven by multielement cosegregation that creates a distinctive nanolayer between adjacent micrometer-scale superlattice grains. This nanolayer acts as a sustainable ductilizing source, which prevents brittle intergranular fractures by enhancing dislocation mobilities. Our superlattice materials have ultrahigh strengths of 1.6 gigapascals with tensile ductilities of 25% at ambient temperature. Simultaneously, we achieved negligible grain coarsening with exceptional softening resistance at elevated temperatures. Designing similar nanolayers may open a pathway for further optimization of alloy properties.

APA, Harvard, Vancouver, ISO, and other styles

43

Wu, Dan, Fuming Wang, Jin Cheng, and Changrong Li. "Effect of Nb and V on Austenite Grain Growth Behavior of the Cr-Mo-V Steel for Brake Discs." High Temperature Materials and Processes 37, no. 9-10 (October 25, 2018): 899–907. http://dx.doi.org/10.1515/htmp-2017-0077.

Full text

Abstract:

AbstractIn order to improve the performance of the steel for brake discs, including strength, toughness and thermal fatigue resistance, Nb and V are added to the steel. The effect of Nb and V on austenite grain growth behavior of the Cr-Mo-V steel for brake discs was studied by analyzing the phase equilibria as well as the microstructures. The precipitation behaviors of precipitates were also investigated based on transmission electron microscopy and energy-dispersive spectroscopy. The results showed that V-rich M8C7 and NbC particles existed at the experimental temperatures. The abnormal grain growth in Nb-free steels was affected by the partial dissolution and coarsening of M8C7 particles. With increasing V content, the grains were refined, but the mixed grain phenomenon became more serious. There were many small NbC particles in Nb-bearing steel, so the grains were effectively refined. Furthermore, a prediction model, which calculates the austenite grain size considering precipitate pinning effect, was established, and the model was well consistent with the actual situation in the Nb-bearing steel up to 1,100 °C. The grains of the Nb-free steels were sensitive to the increments of temperature and time due to the rapid dissolution or coarsening of M8C7 particles.

APA, Harvard, Vancouver, ISO, and other styles

44

Li, Zhiqiang, Junsheng Wang, and Houbing Huang. "Grain boundary curvature based 2D cellular automata simulation of grain coarsening." Journal of Alloys and Compounds 791 (June 2019): 411–22. http://dx.doi.org/10.1016/j.jallcom.2019.03.195.

Full text

APA, Harvard, Vancouver, ISO, and other styles

45

Symonova, A. A., O. N. Verezub, A. A. Sycheva, N. V. Verezub, V. L. Havin, and G. Kaptay. "Surface grain coarsening and surface softening during machining of ultra-fine grained titanium." Journal of Mining and Metallurgy, Section B: Metallurgy 48, no. 3 (2012): 449–59. http://dx.doi.org/10.2298/jmmb121109056s.

Full text

Abstract:

Experiments are run to show that different machining conditions applied to ultra-fine grained pure titanium lead to different levels of grain coarsening and softening near the machined surface. Under ?hard? machining conditions the upper 40 microns of the machined surface are altered with a decreased microhardness. The experimental results are reasonably reproduced by model calculations. Expanding the parameter field of the model calculations, the surface coarsening diagram and the surface softening diagram due to machining are presented, showing the region of technological parameters, under which neither grain coarsening nor softening takes place along the machined surface.

APA, Harvard, Vancouver, ISO, and other styles

46

Ito, Kunio. "Simulation of Grains Growing as Influenced by Triple Line Dragging." Materials Science Forum 753 (March 2013): 121–24. http://dx.doi.org/10.4028/www.scientific.net/msf.753.121.

Full text

Abstract:

A grain whose orientation and size were specified was embedded in a matrix grain structure. The matrix contained texture components in certain special orientations and those in general orientations, and the embedded grain had a certain special three-orientations-relation with grains in the former components. The dependence of growing behavior of an embedded grain on its number of faces of a grain has been examined by a modified Potts MC type 3D simulation and found to depend on the triple line dragging, suggesting that three-orientations-relation dependent triple line dragging can change the crystallographic texture through grain coarsening.

APA, Harvard, Vancouver, ISO, and other styles

47

Neishi, Yutaka, Masayoshi Akiyama, and Kouichi Kuroda. "Experimentally Based Study on the Effect of Initial Grain Size for Characterization of the Grain Coarsening Phenomenon During Hot Rolling of a Medium Carbon Steel." Journal of Manufacturing Science and Engineering 122, no. 1 (June 1, 1999): 109–16. http://dx.doi.org/10.1115/1.538912.

Full text

Abstract:

Laboratory experiments using a hot deformation simulator were carried out to clarify the effect of initial grain size on the grain coarsening phenomenon in hot metal working with light reduction. As an example of medium carbon steel, AISI1045 was adopted and specimens of various grain sizes were prepared by changing the thermo-mechanical histories. They were subjected to a hot deformation testing by the simulator. The threshold grain size to cause the grain coarsening phenomenon was then determined and a criterion was presented to ensure a fine grain after hot rolling. The validity of the new criterion was checked through hot rolling of bars by a prototype mill in a laboratory. [S1087-1357(00)00801-7]

APA, Harvard, Vancouver, ISO, and other styles

48

Burhan, N., and Michael Ferry. "Changes in Grain Size Distribution of a Submicron Grained Al-Sc Alloy during High Temperature Annealing." Materials Science Forum 519-521 (July 2006): 1617–22. http://dx.doi.org/10.4028/www.scientific.net/msf.519-521.1617.

Full text

Abstract:

Severe plastic straining is an established method for producing submicron grain (SMG) structures in alloys. However, the development of such a fine grained structure in single-phase alloys is usually futile if they are to be exposed or processed at elevated temperatures. This is a direct consequence of the natural tendency for rapid and substantial grain coarsening which completely removes the benefits obtained by grain refinement. This problem may be avoided by the introduction of nanosized, highly stable particles in the metal matrix. In this work, a SMG structure was generated in an Al-0.3 wt.% Sc alloy by Equal Channel Angular Pressing (ECAP). The alloy was prepared initially to produce a fine grained microstructure exhibiting a large fraction of high angle grain boundaries and a dispersion of nanosized Al3Sc particles. The evolution of microstructure during annealing at temperatures up to 550 °C was examined in detail and grain size distributions generated from the data. It was shown that grain coarsening is rapid at temperatures above 450 °C and the initial log-normal grain size distribution exhibiting low variance and skewness was altered considerably. The statistical information generated from the grain size distributions confirms that discontinuous grain coarsening occurs in this alloy only at temperatures greater than 500 °C.

APA, Harvard, Vancouver, ISO, and other styles

49

Wang, Sheng Yu, Anthony D. Rollett, and Elizabeth A. Holm. "Recrystallized Grain Size in Single Phase Materials." Materials Science Forum 715-716 (April 2012): 361–66. http://dx.doi.org/10.4028/www.scientific.net/msf.715-716.361.

Full text

Abstract:

During large-strain plastic deformation, subgrain structures typically develop within the grains. At large enough equivalent strains above, say 0.5, recrystallization occurs via abnormal coarsening of the subgrain structure or abnormal (sub-) grain growth (AsGG). The fraction of subgrains that develop into new, recrystallized grains has been quantified as a function of texture spread (Grain Reference Orientation Deviation) using Monte Carlo simulation. When this fraction is combined with the known monotonic increase in mean misorientation with strain, the recrystallized grain size can be predicted as a function of von Mises strain. The prediction is in good agreement with experimental results drawn from the literature.

APA, Harvard, Vancouver, ISO, and other styles

50

Sanjari, Mehdi, Amir Rezaei Farkoosh, Abu S. H. Kabir, Jing Su, In Ho Jung, Steve Yue, Babak Shalchi Amirkhiz, and You Liang He. "The Role of the Nd/Zn Ratio on the Stability of Mg-Zn-Nd Clusters and the Evolution of Texture in Two Mg-Zn-Nd Alloys during Annealing." Materials Science Forum 879 (November 2016): 542–47. http://dx.doi.org/10.4028/www.scientific.net/msf.879.542.

Full text

Abstract:

Texture evolution in two magnesium alloys, Mg-4%Zn-1%Nd and Mg-1%Zn-1%Nd (weight percentage), was studied after rolling and the subsequent isothermal annealing. The finish rolling was completed in a single pass with a thickness reduction rate of ~30% at 100 °C and a rolling speed of 1000 m/min. After cooling to room temperature, the rolled samples were annealed at 350 °C for different annealing times. Upon annealing, the maximum intensity of the basal pole texture decreases as recrystallization progresses. In the Mg-1Zn-1Nd alloy (with a high Nd/Zn ratio), texture weakening is maintained even after complete recrystallization and grain coarsening, while in the Mg-4Zn-1Nd alloy, texture strengthening occurs after grain coarsening, and a single peak replaces the double split basal peaks. In the Mg-1Zn-1Nd alloy, grain coarsening is accompanied by a bimodal grain size distribution, whereas in the Mg-4Zn-1Nd alloy, the grain coarsening leads to a uniform grain size distribution. TEM investigations show the formation of the Zn and Nd rich clusters at early stage of annealing in both alloys. During recrystallization, these clusters were dissolved in the Mg-4Zn-1Nd alloy, but they are more stable in the Mg-1Zn-1Nd alloy. In our opinion, the formation of these stable clusters is one of the main factors for texture weakening of the Mg-Zn-RE alloys.

APA, Harvard, Vancouver, ISO, and other styles

Journal articles on the topic 'Grain coarsening'

Create a spot-on reference in APA, MLA, Chicago, Harvard, and other styles