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Journal articles on the topic 'Stability of grain structure'

Author: Grafiati
Published: 4 June 2021
Last updated: 15 February 2022

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1

Humphreys, John F., and Pete S. Bate. "Refinement and Stability of Grain Structure." Materials Science Forum 357-359 (January 2001): 477–88. http://dx.doi.org/10.4028/www.scientific.net/msf.357-359.477.

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2

Minton, Timothy, and Joe Au. "Stability of Friction Stir Welds at Superplastic Forming Temperatures." Key Engineering Materials 410-411 (March 2009): 117–25. http://dx.doi.org/10.4028/www.scientific.net/kem.410-411.117.

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Friction stir welding is a solid state joining process which enables most metals and alloys to be welded without fusion temperatures occurring. The centre of the weld is comprised of dynamically recrystallized material which is beneficial for superplastic deformation. The high temperatures involved with conventional fusion welding techniques disrupt the delicate microstructure of superplastic materials. Superplasticity is heavily reliant on a small grained equiaxed matrix structure pinned by a fine distribution of hard second phase particles to inhibit grain growth during forming of the material. During the superplastic forming operation, the heavily strained structure present in the parent material undergoes a transformation from a banded structure comprising of very long, thin grains to fine equiaxed grains through various static and dynamic recrystallization mechanisms. During forming of friction stir welded materials the stability of the weld region has been investigated. Grain growth is more apparent in the strain hardening of AA5083 due to the relatively small amounts of strengthening precipitates. This material statically recrystallizes during the preheat stage of the superplastic forming process, the grains then begin to grow during a dynamic recovery process becoming far too large to allow superplastic deformation. AA2004 is specially designed superplastic forming (SPF) alloy which contains a large amount of Zr for grain stability. This alloying element is preferentially distributed along the grain boundaries which prevents grain growth during SPF. During the forming process the AA2004 dynamically recrystallizes; disruption to the parent material structure causes discontinuous dynamic recrystallization that results in a heterogeneous structure and makes the material prone to abnormal grain growth. The weld regions of FSWs in AA5083 and AA4004 have been shown to exhibit AGG in weld nugget and shoulder influenced regions. The stability of the superplastic material is reliant on their strengthening precipitates. The Zr in the AA2004 is a much more effective precipitate for maintaining stability.
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3

Poortmans, Stijn, and Bert Verlinden. "Thermal Stability of CP-Aluminium during Annealing after ECAE." Materials Science Forum 467-470 (October 2004): 1319–24. http://dx.doi.org/10.4028/www.scientific.net/msf.467-470.1319.

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Samples of a hot-rolled AA1050 Aluminium alloy have been deformed by ECAE for 4 and 8 passes following route C. The structural stability of the samples after annealing treatments in the range 200°C to 350°C during 1 to 1000 minutes has been investigated. After 4 ECAE passes, the microstructure is not homogeneous. EBSD-scans show that the former grains can still be identified and that these grains show a different stage of subdivision. After 8 passes the structure is more homogeneous. During subsequent annealing the (sub)structure changes following a common pattern, but with different kinetics in all former grains. At first the dislocation density decreases, illustrated by an increase in image quality of the EBSD-scans and a sharpening of the (sub)structure can be observed. The (sub)grain size remains practically constant during this phase. At a given time, different from one (original) grain to another, some (sub)grains start to grow following an ‘abnormal grain growth’ pattern. This happens at all investigated temperatures. The kinetics and mechanisms of this microstructural evolution will be discussed.
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4

Guerra, Arman, and Douglas P. Holmes. "Emergence of structure in columns of grains and elastic loops." Soft Matter 17, no. 33 (2021): 7662–69. http://dx.doi.org/10.1039/d1sm00787d.

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5

Wang, Chao, and Guoquan Liu. "On the stability of grain structure with initial Weibull grain size distribution." Materials Letters 57, no. 28 (October 2003): 4424–28. http://dx.doi.org/10.1016/s0167-577x(03)00335-5.

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6

MAZZONE, A. M. "STABILITY OF GRAINS OF METALLIC OXIDES WITH A RUTILE STRUCTURE: A QUANTUM MECHANICAL STUDY." International Journal of Modern Physics C 12, no. 08 (October 2001): 1147–53. http://dx.doi.org/10.1142/s0129183101002395.

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The focus of this study is on the stability of grains of metallic oxides, i.e., TiO2 and SnO2 , with a rutile lattice. To this purpose, the grain binding and fragmentation energies have been evaluated quantum mechanically at semi-empirical level using the extended Debye–Hueckel approximation. The grain size and shape are variable and the shapes have been chosen to reproduce, with some approximation, realistic structures found in nanocrystalline technologies. The results show noticeable differences with respects to the known behavior of homonuclear structures. In fact, the grain stability generally increases with the cluster size, as in the homonuclear case. However, its primary dependence is on the oxygen content, rather than on the grain size. On the contrary, the density of states has a critical dependence on the cluster size and is almost equal for the two materials.
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7

Dyakonov, Grigory, Sergey Mironov, Tatyana Yakovleva, and Irina Semenova. "Thermal Stability and Recrystallization of Titanium Grade 4 with Ultrafine-Grained Structure." MATEC Web of Conferences 321 (2020): 11060. http://dx.doi.org/10.1051/matecconf/202032111060.

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The paper examined annealing behavior of ultrafine-grained Ti Grade 4. The ultrafine-grained microstructure was produced by equal-channel angular pressing (ECAP) technique by using a Conform scheme and was characterized by a mean grain size of d=0.3 μm and non-equilibrium grain boundaries. The ultrafine-grained structure was found to be stable up to 400°C. The excellent thermal stability was attributed to a strain-ageing, i.e., the enhanced diffusion of interstitial solutes resulting in a formation of solute atmospheres at/near grain boundaries and dislocations. At 450–500°C, a rapid growth of strain-free grains was observed to occur. This process eliminated severely-deformed microstructure and gave rise to abrupt material softening. A further increase of the annealing temperature above 600°С resulted in precipitation of lenticular dispersoids as well as iron-rich globular β-particles. This surprising phenomenon promoted a subtle hardening effect.
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8

Dennis, J., Pete S. Bate, and John F. Humphreys. "Abnormal Grain Growth in Metals." Materials Science Forum 558-559 (October 2007): 717–22. http://dx.doi.org/10.4028/www.scientific.net/msf.558-559.717.

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Grain growth may occur in two forms, normal grain growth, characterized by a constant grain size distribution during growth, and abnormal grain growth, where one or more abnormally large grains may form in the microstructure. The presence of abnormally large grains in an otherwise uniform microstructure may be detrimental to the mechanical properties of a polycrystalline structure. Little is understood of the exact cause of abnormal grain growth. The annealing conditions leading to the onset of abnormal grain growth have been investigated via a series of grain growth experiments carried out on an Al-4wt%Cu alloy. The structure of which consisted of equiaxed grains (<8μ) pinned by a fine dispersion of sub-micron second phase particles, which may dissolve upon annealing. Minority texture components may experience accelerated growth due to a higher energy and mobility compared to the surrounding grain structure. The combination of these two events may result in the abnormal growth of some grains. SEM imaging and EBSD data has then made it possible to characterize the influence of particle dissolution and grain boundary misorientation on the onset of abnormal grain growth. The stability of ‘island grains’ found to exist internally in abnormally large grains has also been investigated in relation to the misorientation relationship and localized second phase volume fraction found there. There was only weak evidence of special misorientation relationships between the island grains and the abnormally large grains in which they exist, and although there was evidence of an enhanced fraction of pinning particles at island grain boundaries, this was also true of boundaries in general. The larger size of island grains is their dominant characteristic, and grains which become island grains may have been incipient abnormal grains.
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9

Tang, Fa Wei, Xiao Yan Song, Hai Bin Wang, Xue Mei Liu, and Chao Hou. "Thermal Stability of Nanograin Structure in Cu-Zn Alloy System." Defect and Diffusion Forum 381 (November 2017): 33–38. http://dx.doi.org/10.4028/www.scientific.net/ddf.381.33.

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To describe the thermal stability of the nanocrystalline solid solution with weak segregation such as Cu-Zn system, we developed a hybrid model combining the first principles calculation and thermodynamic evaluation. The dependence of the solute segregation behavior on the solute concentration, grain size and temperature were demonstrated. We found that the segregation energy does not change with the solute concentration monotonically. At a constant solute concentration and a given temperature, a nanograin structure can remain stable if the initial grain size is kept in a critical range. The model predictions were confirmed by the experimental measurements that a state of steady nanograin growth can be achieved by designing a certain solute concentration and a proper initial grain size.
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10

Tong, W. P., L. M. Wang, G. J. Ma, N. R. Tao, and Liang Zuo. "An Effect of High Magnetic Field on Grain Growth in Nanocrystalline Iron." Materials Science Forum 539-543 (March 2007): 2793–97. http://dx.doi.org/10.4028/www.scientific.net/msf.539-543.2793.

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A nanostructured surface layer on a pure iron sample was prepared by surface mechanical attrition treatment (SMAT). The thermal stability of SMAT sample was investigated at different temperatures with or without a high magnetic field (H =12T). It was found that a high magnetically annealing enhanced grain growth at the early stage of annealing, and produced a uniform nanocrystalline grain structure. After homogeneous grains developed, further grain growth became restrained.
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11

Krill III, Carl E., and Rainer Birringer. "Investigations of Grain-Boundary Structure and Stability in Nanocrystalline Pd." Materials Science Forum 225-227 (July 1996): 263–74. http://dx.doi.org/10.4028/www.scientific.net/msf.225-227.263.

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12

Xing, Z. P., S. B. Kang, and H. W. Kim. "Structure stability of AA3003 alloy with ultra-fine grain size." Journal of Materials Science 39, no. 4 (February 2004): 1259–65. http://dx.doi.org/10.1023/b:jmsc.0000013884.69611.72.

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13

Morikawa, Tatsuya, Daisuke Kinoshita, Yoshihito Kawamura, and Kenji Higashida. "Fine-Grained Structure in Extruded Magnesium Alloy with Long-Period Stacking Order Phase." Materials Science Forum 561-565 (October 2007): 905–8. http://dx.doi.org/10.4028/www.scientific.net/msf.561-565.905.

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Microstructures developed by warm extrusion for Mg97Zn1Y2 alloy including long-period stacking order (LPSO) phase have been investigated using SEM and TEM. The extruded magnesium alloy with LPSO phase exhibits high strength and sufficient ductility. Such superior mechanical properties appear by warm extrusion around the temperature of 623K. The microstructure of the extruded alloy consists of matrix of fine-grained hcp phase and elongated grains with fine-lamellae including LPSO phase. The grain size of hcp matrix was about 1μm, indicating that remarkable grain refinement was occurred by extrusion since the grain size of as-cast alloy was about 500μm. Special attention has been paid on the enrichment of solutes at stacking faults and grain boundaries in the fine-grained matrix, which would contribute not only to the strengthening but also to the stability of fine-grained structure because of its role of an inhibiter against grain coarsening.
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14

Hou, Jianxin, Xiuyan Li, and Ke Lu. "Formation of Nanolaminated Structure with Enhanced Thermal Stability in Copper." Nanomaterials 11, no. 9 (August 31, 2021): 2252. http://dx.doi.org/10.3390/nano11092252.

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Nanolaminated structure with an average boundary spacing of 67 nm has been fabricated in copper by high-rate shear deformation at ambient temperature. The nanolaminated structure with an increased fraction of low angle grain boundaries exhibits a high microhardness of 2.1 GPa. The structure coarsening temperature is 180 K higher than that of its equiaxial nanograined counterpart. Formation of nanolaminated structure provides an alternative way to relax grain boundaries and to stabilize nanostructured metals with medium to low stacking faults energies besides activation of partial dislocations.
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15

Bdikin, Igor K., Galina K. Strukova, G. V. Strukov, V. V. Kedrov, D. V. Matveev, S. A. Zverkov, and Andréi L. Kholkin. "Growth, Crystal Structure and Stability of Ag-Ni/Cu Films." Materials Science Forum 514-516 (May 2006): 1166–70. http://dx.doi.org/10.4028/www.scientific.net/msf.514-516.1166.

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AgxNi1-x (x=0.0-1.0) films were grown on Cu substrates by electrodeposition method. The films were found to be a nanocrystalline mixture of pure silver and nickel. The grain sizes were determined by X-ray diffraction and electron microscopy techniques. The minimal value was 3.3 m for the alloy with 70 wt% concentration of Ni. The stability of the grown films upon heating in ir and in vacuum was examined. An increase in the grain size was found to begin at 150°C.
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16

Jun, Joong Hwan, and Min Ha Lee. "Effect of Bi Addition on Thermal Stability and Tensile Ductility of Mg-3%Zn-0.4%Zr Alloy." Materials Science Forum 654-656 (June 2010): 647–50. http://dx.doi.org/10.4028/www.scientific.net/msf.654-656.647.

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Thermal stability of  grains and tensile ductilities at room and elevated temperatures were investigated and compared for Mg-3%Zn-0.4%Zr and Mg-3%Zn-0.4%Zr-1%Bi alloys in hot-rolled state. The Bi-added alloy showed slightly finer-grained microstructure with enhanced thermal stability, which is closely associated with fine Mg-Bi compounds acting as obstacles for the migration of grain boundaries. The Mg-3%Zn-0.4%Zr-1%Bi alloy exhibited better tensile strength at room temperature and tensile ductilities at elevated temperature. Finer and more homogeneous grain structure with higher thermal stability would be responsible for the enhanced tensile properties in the Bi-added alloy.
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17

Popov, Vladimir V., E. N. Popova, D. D. Kuznetsov, A. V. Stolbovsky, E. V. Shorohov, Gerrit Reglitz, Sergiy V. Divinski, and Gerhard Wilde. "Nanostructuring of Ni by Various Modes of Severe Plastic Deformation." Defect and Diffusion Forum 354 (June 2014): 109–19. http://dx.doi.org/10.4028/www.scientific.net/ddf.354.109.

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Various modes of severe plastic deformation (SPD), such as high-pressure torsion (HPT) at cryogenic temperature, equal channel angular pressing (ECAP) and dynamic channel-angular pressing (DCAP), have been applied for nanostructuring of Ni, and the thermal stability of the structure obtained has been studied. The nanocrystalline structure with average grain sizes of 80 nm and the microhardness of 6200 MPa is produced by HPT in liquid nitrogen. DCAP and ECAP result in the submicrocrystalline structure of a mixed type, with ultra-fine grains separated by high-angle boundaries along with deformation bands and coarse cells with low-angle dislocation boundaries. The thermal stability of the structures obtained by ECAP and DCAP is approximately the same, and it is higher than after the HPT at cryogenic temperature.
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18

Yu, Hong Yao, Jian Xin Dong, and Xi Shan Xie. "650°C Long-Term Structure Stability Study on 18Cr-9Ni-3CuNbN Heat-Resistant Steel." Materials Science Forum 654-656 (June 2010): 118–21. http://dx.doi.org/10.4028/www.scientific.net/msf.654-656.118.

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The Cu-containing austenitic heat-resistant steel 18Cr-9Ni-3CuNbN has been widely used as superheater and reheater tube material for modern ultra-super-critical (USC) power plants in the world. High temperature structure stability is considered to be an important factor for long-term service. Long-term aging at 650°C for this steel was conducted from 100 to 10,000hours. Effect of aging time on microstructure was studied by means of SEM, TEM and 3DAP (three dimensional atom probe). Micro-hardness tests were carried out after aging at 650°C for different times to be considered as a representative of strength. Experimental results show that Cu-rich phase, MX and M23C6 are major strengthening precipitates in this steel. With on increasing of aging time, fine nano-size Cu-rich phase particles precipitate in the grains and its size is in the range of several nanometers to 35nm till 10,000h at 650°C. The fraction of MX also increases with aging time and its average size is about 100nm till 10,000h. Carbide M23C6 mainly precipitates at grain boundaries and coarsens quickly. Investigation results show that the most important strengthening effect for 18Cr-9Ni-3CuNbN steel is contributed by Cu-rich phase and MX in the grains and M23C6 carbide at the grain boundaries.
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19

Ercolani, Nicholas M., Nikola Kamburov, and Joceline Lega. "The phase structure of grain boundaries." Philosophical Transactions of the Royal Society A: Mathematical, Physical and Engineering Sciences 376, no. 2117 (March 5, 2018): 20170193. http://dx.doi.org/10.1098/rsta.2017.0193.

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This article discusses numerical and analytical results on grain boundaries, which are line defects that separate roll patterns oriented in different directions. The work is set in the context of a canonical pattern-forming system, the Swift–Hohenberg (SH) equation, and of its phase diffusion equation, the regularized Cross–Newell equation. It is well known that, as the angle made by the rolls on each side of a grain boundary is decreased, dislocations appear at the core of the defect. Our goal is to shed some light on this transition, which provides an example of defect formation in a system that is variational. Numerical results of the SH equation that aim to analyse the phase structure of far-from-threshold grain boundaries are presented. These observations are then connected to properties of the associated phase diffusion equation. Outcomes of this work regarding the role played by phase derivatives in the creation of defects in pattern-forming systems, about the role of harmonic analysis in understanding the phase structure in such systems, and future research directions are also discussed. This article is part of the theme issue ‘Stability of nonlinear waves and patterns and related topics’.
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20

McKernan, Stuart, M. Grant Norton, and C. Barry Carter. "The 45° grain boundaries in YBa2Cu3O7−δ." Journal of Materials Research 7, no. 5 (May 1992): 1052–59. http://dx.doi.org/10.1557/jmr.1992.1052.

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High-angle grain boundaries in YBa2Cu3O7−δ thin films are of technological interest because of the weak coupling observed between the grains; however, not all high-angle grain boundaries show this weak-link behavior. The microstructure of both these boundaries is not understood, nor is the reason for the differing electrical transport properties. High-angle grain boundaries in YBa2Cu3O7−δ thin films on MgO, where the angular misorientation between the grains is ∼45°, have been examined using high-resolution electron microscopy. The results show that the boundary structure can appear quite different even when the angular misorientation between the two grains is the same. The stability of the grain boundaries under the electron irradiation in the electron microscope was found to be a function of the accelerating voltage—400 kV leads to rapid disordering of the boundary region.
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21

Morton, Allan J., Brigitte Décamps, Mark A. Gibson, and Alan Wolfenden. "Microstructural stability in rapidly solidified ternary iron aluminides." Proceedings, annual meeting, Electron Microscopy Society of America 48, no. 4 (August 1990): 988–89. http://dx.doi.org/10.1017/s0424820100178070.

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Iron aluminides containing ternary additions of Cr, Si and other alloying elements offer good oxidation and sulphidation resistance at a relatively low cost but these alloys have only moderate strength at elevated temperatures and are of limited ductility. The generation of a distribution of fine dispersoids throughout the matrix of these alloys can provide increased strength and also improve ductility by reducing grain size.We report a study of the microstructural stability of rapidly solidified strip of iron aluminides containing chromium and minor additions of both titanium and boron. As cast strip thickness was in the range 80-120μm.Figure 1 shows the grain structure near the centre of the as cast strip of a 66.5Fe-28.5Al-5.0Cr (at.%) alloy. The grain size in this view of the strip is quite small (2-5μm) although optical metallography of the longitudinal and transverse cross sections show that the grain structure is columnar through much of the strip thickness.
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22

Siegl, R., V. Vitek, D. E. Luzzi, and M. Yan. "Phase stability and grain boundary structure in the Cu-Bi system." Journal of Phase Equilibria 18, no. 6 (December 1997): 562–66. http://dx.doi.org/10.1007/bf02665812.

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23

Shvindlerman, L. S., and G. Gottstein. "Cornerstones of grain structure evolution and stability: Vacancies, boundaries, triple junctions." Journal of Materials Science 40, no. 4 (February 2005): 819–39. http://dx.doi.org/10.1007/s10853-005-6498-z.

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24

Peltonen-Sainio, P., K. Moore, and E. Pehu. "Phenotypic stability of oats measured with different stability analyses." Journal of Agricultural Science 121, no. 1 (August 1993): 13–19. http://dx.doi.org/10.1017/s0021859600076747.

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SUMMARYThe phenotypic stability of seven Finnish and Nordic oat cultivars and 12 breeding lines developed at the Hankkija Plant Breeding Institute, Finland, was studied using the Finlay–Wilkinson regression method, Eberhart–Russell stability analysis, principal component analysis (PCA) with biplot presentation, canonical variate analysis (CVA) and Procrustes analysis. Comparison of stability analyses was based on four dissimilar growing seasons. In addition to the measurement of phenotypic stability of grain yield, the performance of 12 morpho-physiological traits was evaluated, including maturity class and structure of canopy and plant stand.The different stability analyses examined produced uniform results and ranked the cultivars and breeding lines without major disagreements. Lines with exceptionally stable yield performance over the different growing seasons were identified. In general, there was an association of high yielding ability with poor stability. However, some cultivars deviated from this tendency and showed high grain yield production and average stability of yield performance.
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25

Ning, Jiang Li, Da Ming Jiang, Bing Yu Qian, Xi Gang Fan, Bao You Zhang, Jie Yu, and Xin Mei Zhang. "Microstructure and Thermal Stability of Al-Mg-Mn Alloys by Equal Channel Angular Pressing at Elevated Temperature." Materials Science Forum 546-549 (May 2007): 929–32. http://dx.doi.org/10.4028/www.scientific.net/msf.546-549.929.

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Two Al-Mg-Mn alloys having similar compositions but with and without Zr addition were subjected to equal channel angular pressing (ECAP) at 350°C using route BC and a 90° die, followed by water quenching or air cooling. A series of annealing experiments were conducted at various temperatures from 400°C to 460°C on the water-quenched alloys. Fine structures with grain size of approximately 1~2μm were obtained in these alloys after 6 passes. The water-quenched alloy containing Zr exhibited finer structure compared with the Zr-free alloy in the same cooling condition, which was due to the existence of Al3Zr dispersoids. And in the air cooling condition, it was found that in the Zr-free alloy static recovery occurred, and in partial regions some small grains without dislocation inside appeared suggesting the occurrence of static recrystallization. This demonstrated a fairly restored structure. However, the microstructure of the alloy containing Zr kept stable during the air cooling process. In addition, in the annealing experiments, secondary recrystallization took place in the Zr-free alloy annealed at 410°C for 1h, while the alloy containing Zr kept stable up to 460°C. TEM observation showed that the Al3Zr dispersoids pinned the motion of the grain boundaries, thereby the secondary recrystallization and grain growth were inhibited.
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26

Feng, Gang, Chao Ge Zhang, Xian Rui Zhao, and Li Ma. "Study on Structure Stability of Ti-Al Multilaminate Material at High Temperature." Applied Mechanics and Materials 217-219 (November 2012): 307–13. http://dx.doi.org/10.4028/www.scientific.net/amm.217-219.307.

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Ti-Al multilaminate composite was prepared by high-power EB-PVD technology, and under vacuum condition, the samples were annealed at different temperatures. The changed microstructure of the samples after annealing was characterized by XRD, SEM and EDS. The experimental results show that, with the increment of temperature, the ordered phases reduce due to the diffusion of Al into Ti, and the breakdown of layered architecture was induced mainly by pore formation, grain growth and the grain boundary grooving.
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27

Prangnell, Philip B., Jacob R. Bowen, M. Berta, P. J. Apps, and Pete S. Bate. "Stability of Ultra-Fine ‘Grain Structures’ Produced by Severe Deformation." Materials Science Forum 467-470 (October 2004): 1261–70. http://dx.doi.org/10.4028/www.scientific.net/msf.467-470.1261.

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Severe deformation techniques allow metallic alloys to be deformed to ultra-high plastic strains, without any geometrical change to the work piece. They thus offer potential for the cheap production of submicron grained materials, in a bulk form. After processing severely deformed materials do not have conventional, idealized, grain structures, contain significant fractions of low angle boundaries, and are often heterogeneous. Due to their high stored energy, they are unstable on annealing and in most cases can be thought of as continuously recrystallizing. However, locally discontinuous behaviors are often observed, due to the retained less mobile low angle boundaries, as well as abnormal grain growth at elevated temperatures. Monte-Carlo-Potts models have been used to show the sensitivity of the annealing behavior to the initial starting structure present after deformation. The effect of coarse (~1µm) particles and fine dispersoid particles are also discussed.
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28

Mohd Tahir, Suraya, Nosrati Shohreh, Mohamed Ariff Azmah Hanim, and Mansor Hashim. "Thermal Stability of CK60 Steel Nano-Crystallized By Drilling Method." Applied Mechanics and Materials 564 (June 2014): 461–66. http://dx.doi.org/10.4028/www.scientific.net/amm.564.461.

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In present study drilling as a new Surface Sever Plastic Deformation technique (SSPD) has been applied to commercial CK60 steel plate to create a nanoCrystalline (NC) structured layer.The CK60 steel plate with tempered martensitic crystalline structure has been drilledusing hard titanium coated drilling bit under 20 m/min cutting speed. The formed surface nanocrystalline (NC) layers characterized by using field emission scanning electron microscope (FESEM) and microhardness tests. The results showed that the hardness of formed NC layer with almost 50nm grain sizes was more than twice of the martensitic base metal hardness. The thermal stability of NC layer has been studied in the range of 673 to 923K and the results showed that created fine grain structurehad higher thermal stabilitycompared to CK60 steel samples with coarse granular crystalline structure. The microhardness of NC layers reduced from 9.8 to 9.1 GPa after 1 hour tempering at923K.
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29

Meleshkina, E. P., O. I. Bundina, and A. S. Khuhrin. "Sustainable grain complex development of Russia: formation of grain clusters." E3S Web of Conferences 254 (2021): 10012. http://dx.doi.org/10.1051/e3sconf/202125410012.

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Human civilization is developing in the regime with aggravation and maximum aggravation in 2025 — 2030. The development instability, the probability of not only unlikely - but also incredible events - global disasters, “Black Swans”, has drastically increased. There are tectonic changes happening in nature and society. In these conditions, more than ever, the importance of the Concept of Sustainable Development has increased not only as a theoretical and intellectual message to the development of humanity in total turbulence, but above all, to practical implementation of this Concept. Firstly, the changes taking place affected agriculture of the countries of the world and Russia, and especially its grain complex. From the perspective of system-synergistic, bioeconomic, cluster and global approaches, the definition to the “sustainable development of the grain complex” concept was developed, the structure of its potential development, a set of measures to increase the grain complex development stability in the format of agroforestry clusters system creation was proposed. The cluster system formation will be a radical tool to increase the stability, efficiency, and competitiveness of Russia's grain economy, weaken global climate change and prevent disasters.
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30

Senkov, O. N., N. Srisukhumbowornchai, M. L. Öveçoglu, and F. H. Froes. "High-temperature stability of nanocrystalline structure in a TiAl alloy prepared by mechanical alloying and hot isostatic pressing." Journal of Materials Research 13, no. 12 (December 1998): 3399–410. http://dx.doi.org/10.1557/jmr.1998.0463.

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A fully dense nanocrystalline compact of the Ti–47Al–3Cr (at. %) alloy was produced by mechanical alloying and hot isostatic pressing at 725 °C. Microstructure characteristics and grain growth behavior of this compact were studied after annealing for up to 800 h in the temperature range of 725 to 1200 °C, using analytical transmission electron microscopy techniques. The temperature and time dependencies of the grain sizes and the grain size distributions were determined. The grain growth occurred, with a timeand temperature-invariant single-peak grain size distribution (when normalized by the mean grain size), which was consistent with normal grain growth. The experimentally measured grain growth exponent decreased from 10 to 4.6 when the temperature was increased. The grain growth kinetics was described by a single thermally activated rate process limited by a permanent pinning force on the grain boundaries. The microhardness decreased on annealing and followed the Hall–Petch relationship with the parameters Hυo = 5.8 GPa and KH = 1.6 MPa m0.5.
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31

Kimmel, Giora, and Jacob Zabicky. "Stability, Instability, Metastability and Grain Size in Nanocrystalline Ceramic Oxide Systems." Solid State Phenomena 140 (October 2008): 29–36. http://dx.doi.org/10.4028/www.scientific.net/ssp.140.29.

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The following nanocrystalline binary oxide systems were studied: Mg-Ti, Ni-Ti, Zr-Al, as well as some pure and doped unary oxides. The xerogels were heated at a constant T (200 to 1600°C) for 3 to 6 hours. There was a threshold tempearture for oxide formation and in many cases the products were metastable nanocrystalline phases, depending on the grain size and composition, including doping. The oxide phases of Ni-Ti, Mg-Ti, and Zr-Al, formed at 900 °C are different from those formed at higher temperature. New ranges of solid solutions and the formations of higher temperature structures were found. A transition phase can be defined as a structure formed at relative low tempearture, irreversibly transforming at higher temperature into an equilibrium phase of the same elemental composition. Some low temperature transition phases have a structure similar to that of a high temperature equilibrium phase, e.g., (the equilibrium phase is given in parentheses) tetragonal ZrO2 (monoclinic) and low-T qandilite-like solid solutions (qandilite + geikielite). Others are unique with no representation in the equilibrium phase diagram, e.g., gamma-like alumina (corundum) and anatase (rutile), which are formed as nanocrystalline oxides due to a low growth rate caused either by a low temperature of calcination or due to additives. To asses the importance of crystal size in the stabilization of transition phases, the following studies were undertaken: (a) XRPD analysis of all unary, doped and binary compositions; (b) the evolution of transition phases in HT XRPD of the Mg titanates; (c) the phase evolution was studied with time at temperatures were mixtures of transition and equilibrium phases were found; (d) the retention of pure tetragonal ZrO2 on quenching Al-Zr oxides after calcinations at high tempetature; (e) additional evidence from HRTEM, SEM and DTA experiments was also collected. A model, correlating the size effect with the unusual phases and structures is proposed.
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32

Yu, Hong Yao, Cheng Yu Chi, Jian Xin Dong, and Xi Shan Xie. "650°C Long-Term Structure Stability Study on 18Cr10NiNb Heat-Resistant Steel." Advanced Materials Research 399-401 (November 2011): 180–84. http://dx.doi.org/10.4028/www.scientific.net/amr.399-401.180.

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The Nb-contained austenitic heat-resistant steel 18Cr10NiNb(TP347H) has been widely used as super-heater and re-heater tube material for modern ultra-super-critical (USC) power plants in the world. High temperature structure stability is considered to be one of the most important factors for long-term service. Long-term aging at 650 °C for this steel was conducted till 10,000 hours. Effect of aging time on microstructure was studied by means of SEM and TEM. Tensile tests were carried out after aging at 650 °C for different times. Experimental results show that MX phase and M23C6 carbides are major strengthening precipitates in this steel. With increasing of aging time, fine nano-size MX particles precipitate in grains and its size keeps about 50 nm till 10,000 h at 650 °C. Carbide M23C6 mainly precipitates at grain boundaries but coarsens quickly. Investigation results show that MX phase plays the most important strengthening effect in grains. The amount of MX phase increases with increasing of Nb and C contents. The effects of Nb and C contents on mole fractions of MX phase in 18Cr10NiNb steel have been calculated by using Thermo-Calc software.
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33

Oda, Eiji, Takao Ohtaki, Akio Kuroda, Hiroshi Fujiwara, Kei Ameyama, and Kayo Yoshida. "Thermal Stability of Nano Grain Structure Tungsten Prepared by SPD-PM Process." Advanced Materials Research 15-17 (February 2006): 564–69. http://dx.doi.org/10.4028/www.scientific.net/amr.15-17.564.

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34

Klemm, R., E. Thiele, C. Holste, J. Eckert, and N. Schell. "Thermal stability of grain structure and defects in submicrocrystalline and nanocrystalline nickel." Scripta Materialia 46, no. 9 (May 2002): 685–90. http://dx.doi.org/10.1016/s1359-6462(02)00054-4.

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35

Man, Jiří, Antti Järvenpää, Matias Jaskari, Ivo Kuběna, Stanislava Fintová, Alice Chlupová, L. Pentti Karjalainen, and Jaroslav Polák. "Cyclic deformation behaviour and stability of grain-refined 301LN austenitic stainless structure." MATEC Web of Conferences 165 (2018): 06005. http://dx.doi.org/10.1051/matecconf/201816506005.

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Low cycle fatigue (LCF) behaviour of metastable austenitic 301LN stainless steel with different grain sizes – coarse-grained (13 μm), fine-grained (1.4 μm) and ultrafine-grained (0.6 μm) – produced by reversion annealing after prior cold rolling was investigated. Fully symmetrical LCF tests with constant total strain amplitudes of 0.5% and 0.6% were performed at room temperature with a low constant strain rate of 2×10-3 s-1. Microstructural changes in different positions within the gauge part of the specimens were examined by optical microscopy (polarized light) and electron backscatter diffraction (EBSD) technique; for quantitative assessment of the volume fraction of deformation induced martensite (DIM) a Feritscope FMP 30 was adopted. The cyclic stress-strain response and specific changes of hysteresis loop shapes in the very early stage of cycling are confronted with the character of DIM formation and its distribution in the whole volume of the material. A possible effect of strain rate (frequency of cycling) on the destabilization of austenitic structure during cyclic straining of materials with different grain sizes is highlighted.
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36

Wang, J., N. Li, and A. Misra. "Structure and stability of Σ3 grain boundaries in face centered cubic metals." Philosophical Magazine 93, no. 4 (February 2013): 315–27. http://dx.doi.org/10.1080/14786435.2012.716908.

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37

Schuh, Christopher A., and Ke Lu. "Stability of nanocrystalline metals: The role of grain-boundary chemistry and structure." MRS Bulletin 46, no. 3 (March 2021): 225–35. http://dx.doi.org/10.1557/s43577-021-00055-x.

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38

Arkhangelskiy, S. I., and D. M. Levin. "Statistical analysis of the parameters and grain size distribution functions of single-phase polycrystalline materials." Industrial laboratory. Diagnostics of materials 86, no. 4 (April 23, 2020): 39–45. http://dx.doi.org/10.26896/1028-6861-2020-86-4-39-45.

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A statistical analysis of the grain size distribution is important both for developing theories of the grain growth and microstructure formation, and for describing the size dependences of various characteristics of the physical and mechanical properties of polycrystalline materials. The grain size distribution is also an important characteristic of the structure uniformity and, therefore, stability of the properties of the products during operation. Statistical Monte Carlo modeling of single-phase and equiaxed polycrystalline microstructures was carried out to determine the type of statistically valid distribution function and reliable estimates of the average grain size. Statistical parameters (mean values, variances, variation coefficient) and distribution functions of the characteristics of the grain microstructure were obtained. It is shown that the distribution function of the effective grain sizes for the studied polycrystal model is most adequately described by γ-distribution, which is recommended to be used in analysis of the experimental distribution functions of grain sizes of single-phase polycrystalline materials with equiaxed grains. The general average (mathematical expectation) of the effective grain size (projection diameter) with γ-distribution function (parameters of the distribution function are to be previously determined in analysis of the grain structure of polycrystalline materials) should be taken as a statistically valid and reliable estimate of the average grain size. The results of statistical modeling are proved by the experimental data of metallographic study of the microstructures of single-phase model and industrial materials with different degree of the grain structure heterogeneity.
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39

Chen, Tao, Zhiyong Zhou, Ruihong Liang, and Xianlin Dong. "Grain size effect on piezoelectric properties of Sr2Nb2O7 ceramics." Journal of Advanced Dielectrics 08, no. 04 (August 2018): 1820003. http://dx.doi.org/10.1142/s2010135x18200035.

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Grain size effect on piezoelectric properties and thermal stability of perovskite layer structured (PLS) Sr2Nb2O7 ceramics are investigated. The Sr2Nb2O7 ceramics with different average grain sizes from 1.2[Formula: see text][Formula: see text]m to 3.6[Formula: see text][Formula: see text]m were prepared in different sintering temperatures by solid state reaction method. The average grain size increases, accompanied by a higher relative density of up to 96%. Pure Sr2Nb2O7 ceramics with larger grain size show a remarkable [Formula: see text] of ([Formula: see text])pC/N while still with a very high [Formula: see text] of ([Formula: see text]C. The thermal depolarization temperature of samples with large grain sizes reach over 1200∘C and the thermal stability increased with increasing of grain size. The ferroelectric domains structure was observed by PFM and larger grain is easy to form ferroelectric domain then enhance piezoelectric properties. This study demonstrates enhanced piezoelectric properties can be achieved in pure Sr2Nb2O7 by solid state reaction method and bring great revitalization to the Sr2Nb2O7-based ceramics as a promising high-temperature piezoelectric material.
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40

Zhang, Yue, Artur V. Ganeev, X. Gao, Alfred V. Sharafutdinov, Jing Tao Wang, and Igor V. Alexandrov. "Influence of HPT Deformation Temperature on Microstructures and Thermal Stability of Ultrafine-Grained Tungsten." Materials Science Forum 584-586 (June 2008): 1000–1005. http://dx.doi.org/10.4028/www.scientific.net/msf.584-586.1000.

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In the present work high pressure torsion (HPT) was imposed on commercial purity (CP) tungsten at different temperatures of 450 °С and 490 °С to achieve different microstructures and grain boundary misorientation spectra (GBMS). After HPT at 450°С, ultrafine grained microstructure with an average grain size of ~150 nm was developed in the metal. HPT at 490 °С results in an elongated structures with average width of ~500nm. EBSD investigations showed that over 92% are HAGB type in microstructure HPT-processed at 450°С, and in contrast, over 50% of grain boundaries are LAGB in sample processed at 490°С. Annealing at 900°С for 1h, of the sample with homogeneous UFG structure resulted from HPT at 450°C, leads to only limited decrease (~20%) in microhardness.
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41

Van Der Kolff, E. J., M. Berkahn, Richard Wuhrer, and Wing Yiu Yeung. "On Structural Stability of Nanostructured Aluminium." Materials Science Forum 475-479 (January 2005): 3501–4. http://dx.doi.org/10.4028/www.scientific.net/msf.475-479.3501.

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Nano- and submicron-structured aluminium was produced by equal channel angular extrusion with a total strain of ~17. Large residual stress and strain energy were built up in the extruded metal and subsequent heat treatments were applied to investigate the stability of the nanostructures. X-ray diffractometry and transmission electron microscopy were performed to evaluate the microstructural changes in the nanograin metal. It was found that the nanostructures remained stable at temperatures up to 250oC. Above 250oC, changes in the major x-ray peak reflections became evident, suggesting substantial grain growth had occurred. Electron microscopy confirmed that at low annealing temperatures, the fine grain structures were stable and indeed became more equiaxed and well defined.
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42

Zhao, Jun, Han Zhang, Zhi Wang, Hong Yan Zhai, Quan Xing Wen, Min Wang, and Yu Wei Gao. "On Preparation of In Situ Composite Steel with Ultra-High Strength and its Thermal Stability." Advanced Materials Research 152-153 (October 2010): 436–40. http://dx.doi.org/10.4028/www.scientific.net/amr.152-153.436.

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A new type of in-situ composite nano-multilayer plate with ultra-high strength (b 2112 MPa), Q235 steel plate with nano-layered structure of lath martensite produced by severe cold-rolling, was developed. After cold-rolling, subsequent annealing has great effect on the deformed lath morphology and grain refinement. Microstructure recrystallizing course have taken place after long time annealing at 350 °C. The recrystallization activation energy is 151 kJmol-1. Microstructure characteristics along rolling direction arrangement was decreased after annealing at 400 °C. In addition to the ultrafine ferrite grains, nano-carbides precipitated uniformly in the specimen annealed at 500 °C. Annealing at and above 600 °C resulted in coarse ferrite grains with spheroidized coarse carbides, causing grain growth. The average crystal size is about 4.7 m after annealing for 60 min at 600 °C.
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43

Anil Kumar, V., M. K. Karthikeyan, Rohit Kumar Gupta, P. Ramkumar, and P. P. Sinha. "Equal Channel Angular Pressing of Al Alloy AA2219." Advanced Materials Research 67 (April 2009): 53–58. http://dx.doi.org/10.4028/www.scientific.net/amr.67.53.

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Severe plastic deformation processes (SPD) are gaining importance as advanced materials processing techniques and hold immense potential in obtaining ultra fine-grained high strength materials. Among the SPD techniques, Equal channel angular pressing (ECAP) has its own merits to produce materials with ultra fine grains in bulk with better mechanical properties. The material deforms with high level of plastic strain inside the channel resulting in grain refinement of the output material with improvement in mechanical properties. A very viable die configuration was conceptualized and die was made with 1200 channel angle. Processing of 25 mm dia. of Al alloy AA2219 at room temperature was successfully carried out and grain refinement was observed. The mechanism of grain refinement has been studied using optical and transmission electron microscopy (TEM). It was observed that low energy dislocation structure (LEDS) forms concurrently with sub-grain structure due to dislocation rearrangements, which provide stability to the evolving sub-grain structure. Dislocation mobility is hindered by the presence of precipitates and / or intermetallic dispersoids present in the matrix and results in presence of dislocations in grain interiors. The pile up of dislocations at intermetallic dispersoids was confirmed from the dark field TEM micrographs. Present paper describes the experimental procedure and followed to attain severe plastic deformation through ECAP. Increase in hardness as well as refinement in the grain size after 5-passes have been discussed in light of extensive optical and TEM. The mechanisms of grain refinement to achieve nano-grained structure and strengthening accrued from the grain refinement through ECAP has been discussed.
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44

ZUO, B., N. SARASWATI, T. SRITHARAN, and H. H. HNG. "PRODUCTION AND GRAIN STABILITY OF NANOCRYSTALLINE Fe-Si POWDERS AND THE EFFECTS OF ALUMINIUM ADDITION." International Journal of Nanoscience 04, no. 04 (August 2005): 667–76. http://dx.doi.org/10.1142/s0219581x05003413.

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The present work studied the production of nanocrystalline Fe 90 Si 10, Fe 75 Si 25 and Fe 75 Si 15 Al 10 alloys via a high-energy ball milling technique and their grain growth responses to high-temperature annealing treatments. The grain sizes of the resulting powders were determined by X-ray diffraction peak broadening and were also confirmed by transmission electron microscopy. A minimum crystallite size of 13-17 nm could be achieved in Fe 90 Si 10, Fe 75 Si 25 and Fe 75 Si 15 Al 10 alloys. The lattice parameters of as-milled Fe 90 Si 10, Fe 75 Si 25 and Fe 75 Si 15 Al 10 attained minimum values of about 0.2860, 0.2842 and 0.2862 nm respectively after 60 h, and thereafter remained constant for prolonged milling times. The grain size of Fe 90 Si 10 increased from approximately 17 nm to about 35 nm after annealing at 873 K. Fe 75 Si 25 exhibited some stability against grain growth at low temperatures but not above 673 K. Fe 75 Si 15 Al 10 grains showed better stability with no significant grain growth until 873 K. For Fe 75 Si 25 and Fe 75 Si 15 Al 10 alloys annealing at 773 K, 873 K and 973 K resulted in the formation of ordered DO 3 structure.
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45

Kundu, Amrita, Claire L. Davis, and Martin Strangwood. "Pinning of Austenite Grain Boundaries by Mixed AlN and Nb(C,N) Precipitates." Solid State Phenomena 172-174 (June 2011): 458–63. http://dx.doi.org/10.4028/www.scientific.net/ssp.172-174.458.

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The use of Nb(C,N) to pin prior austenite grains during thermomechanical processing can give rise to bimodal structures linked to Nb segregation and subsequent variation in precipitate distribution and stability on reheating and deformation. The segregation tendency of Al is much less compared with Nb so that AlN may provide grain boundary pinning in regions of reduced Nb(C,N) volume fraction and stability. Quantification of precipitate and prior austenite grain size distributions after reheating has confirmed the governing mechanisms of precipitate dissolution / coarsening whilst identifying grain boundary pinning by AlN at temperature below 1125 °C, but controlled by Nb(C,N) at higher temperatures.
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46

Górny, M., G. Sikora, and M. Kawalec. "Effect of Titanium and Boron on the Stability of Grain Refinement of Al-Cu Alloy." Archives of Foundry Engineering 16, no. 3 (September 1, 2016): 35–38. http://dx.doi.org/10.1515/afe-2016-0045.

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Abstract The present research was conducted on thin-walled castings with 5 mm wall thicknesses. This study addresses the effect of the influence of different master alloys, namely: (1) Al-5%Ti-1%B, (2) Al-5%Ti and (3) Al-3%B, respectively on the structure and the degree of undercooling (ΔTα = Tα−Tmin, where Tα - the equilibrium solidification temperature, Tmin - the minimum temperature at the beginning of α(Al) solidification) of an Al-Cu alloy. The process of fading has been investigated at different times spent on the refinement treatment ie. from 3, 20, 45 and 90 minutes respectively, from the dissolution of master alloys. A thermal analysis was performed (using a type-S thermocouple) to determine cooling curves. The degree of undercooling and recalescence were determined from cooling and solidification curves, whereas macrostructure characteristics were conducted based on a metallographic examination. The fading effect of the refinement of the primary structure is accompanied by a significant change in the number (dimension) of primary grains, which is strongly correlated to solidification parameters, determined by thermal analysis. In addition to that, the analysis of grain refinement stability has been shown with relation to different grain refinements and initial titanium concentration in Al-Cu base alloy. Finally, it has been shown that the refinement process of the primary structure is unstable and requires strict metallurgical control.
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47

Avlokulov, Anvar. "Return on Assets and Financial Soundness Analysis: Case Study of Grain Industry Companies in Uzbekistan." INTERNATIONAL JOURNAL OF MANAGEMENT SCIENCE AND BUSINESS ADMINISTRATION 4, no. 6 (2018): 52–56. http://dx.doi.org/10.18775/ijmsba.1849-5664-5419.2014.46.1006.

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Ensuring financial stability and soundness of companies operating in a particular industry depends on the several internal and external factors, which can be classified as firm and macro levels. According to classical business finance theories, return on assets (ROA) are thought to be the most effective instrument of measuring monitoring the financial status of companies. In most literature, revenues from sales, total operating cost and asset structure of a company plays an important role in shaping an acceptable ROA indicator. In this paper, impact level of these factors on ROA was examined in case of three grain processing companies in Uzbekistan. Conducted OLS test showed that total operating cost and asset structure had negative influence on ROA, while revenues from sale supported the financial stability of the companies.
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48

Lai, Yu-Chang, Po-Ching Wu, and Tung-Han Chuang. "Thermal stability of grain structure for Ag nanotwinned films sputtered with substrate bias." Materialia 20 (December 2021): 101215. http://dx.doi.org/10.1016/j.mtla.2021.101215.

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49

Detor, A. J., and C. A. Schuh. "Microstructural evolution during the heat treatment of nanocrystalline alloys." Journal of Materials Research 22, no. 11 (November 2007): 3233–48. http://dx.doi.org/10.1557/jmr.2007.0403.

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Nanocrystalline alloys often show exceptional thermal stability as a consequence of kinetic and thermodynamic impediments to grain growth. However, evaluating the various contributions to stability requires detailed investigation of the solute distribution, which is challenging within the fine structural-length-scales of nanocrystalline materials. In the present work, we use a variety of techniques to assess changes in the grain size, chemical ordering, grain-boundary segregation, and grain-boundary structure during the heat treatment of Ni–W specimens synthesized over a wide range of grain sizes from 3 to 70 nm. A schematic microstructural evolution map is also developed based on analytical models of the various processes activated during annealing, highlighting the effects of alloying in nanocrystalline materials.
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50

Shi, Bi, Hong Wei Song, Jun Bao Zhang, Han-Qing Cao, and Xiu Fang Wang. "Low Carbon Low Alloy Submicro-Steel with Nano-Precipitation." Materials Science Forum 503-504 (January 2006): 511–14. http://dx.doi.org/10.4028/www.scientific.net/msf.503-504.511.

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In the present work, low carbon low alloy submicro-steel sheet has been developed successfully by severe warm-rolling (SWR) at 500 °C through a single pass. The result shows submicro-structure can be fabricated by severe rolling. The formation of the submicro-structure is attributed to the grain refinement mechanism induced by the severe plastic deformation (SPD). The refinement involves the cutting and subdividing of the original micro-crystals into ultrafine grains by dense dislocation arrays. To a certain extent, dynamic recrystallization in ferrite during SWR also seems to contribute to the formation of the submicro-structure. The thermal stability of the submicro-steel was investigated by annealing the steel at different temperatures. The investigation indicated that the submicro-steel can be subjected to annealing at 550°C without apparent grain growth. The unusually high thermal stability can be attributed to the pining effect of numerous uniformly distributed nano-precipitates in the steel. The sizes of the nano-precipitates belong to two different orders. The average diameter of the large precipitates is about 30 nm and the smaller one less than 10 nm.
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