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Littérature scientifique sur le sujet « Γ' precipitation »

Auteur : Grafiati

Publié le 8 mars 2025

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Articles de revues sur le sujet "Γ' precipitation"

Xu, H. P., A. H. W. Ngan, B. J. Duggan et Q. Z. Chen. « Toughening of γ′-Ni3A1 by γ precipitation ». Materials Letters 31, n^o 3-6 (juin 1997) : 233–37. http://dx.doi.org/10.1016/s0167-577x(96)00280-7.

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Li, Zhiru. « Influence of Different Precipitation Periods on Dendrolimus superans Occurrence : A Biostatistical Analysis ». International Journal of Agriculture and Biology 25, n^o 01 (1 janvier 2021) : 61–67. http://dx.doi.org/10.17957/ijab/15.1638.

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Precipitation is one of the most important abiotic factors that affect Dendrolimus superans occurrence. In this study, agrey slope-correlation model was used, and a simplified grey slope-correlation model was constructed to uncover the most crucial periods of precipitation that pest occurrence. Results revealed that thetwo models were similar; however, the simplified grey slope-correlation model required less calculative steps and was easier to operate. The calculation results revealed that the most crucial period occurred during thefirst 10 days of July (γ13 = 0.67, γ`13 = 0.69). The other precipitation periods associated with pest occurrence included thefirst 10 days of August (γ16 = 0.62, γ`16 = 0.61), the third 10 days of May (γ09 = 0.59, γ`09 = 0.62), the sec10 days of May (γ08 = 0.58, γ`08 = 0.60), and the third 10 days of August (γ18 = 0.58, γ`18 = 0.60). The less associated precipitation periods included the first 10 days of March (γ01 = 0.54, γ`01 = 0.47), the sec10 days of March (γ02 = 0.50, γ`02 = 0.49), the third 10 days of April (γ06 = 0.47, γ`06 = 0.48), the sec10 days of June (γ11 = 0.51, γ`11 = 0.48), and the third 10 days of June (γ12 = 0.51, γ`12 = 0.51). Precipitation in May (γ07 + γ08 + γ09 = 1.74, γ`07 + γ`08 + γ`09 = 1.79) and July (γ13 + γ14 + γ15 = 1.74, γ`13 + γ`14 + γ`15 = 1.79) was mostly associated with D.superansoccurrence. The findings of this study provided a simple operative model for determining the most crucial precipitation periods of pest occurrence, and these analytical methods can serve as a theoretical reference for pest forecasting and early warning, which contributes to ecological protection.© 2021Friends Science Publishers

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Watanabe, Chihiro, et Ryoichi Monzen. « Precipitation Process in a Cu-Ni-Be Alloy ». Solid State Phenomena 172-174 (juin 2011) : 432–36. http://dx.doi.org/10.4028/www.scientific.net/ssp.172-174.432.

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The precipitation process in an aged Cu-1.9wt%Ni-0.3wt%Be alloy has been examined by high-resolution transmission electron microscopy. The precipitation sequence found is: Guinier- Preston (G.P.) zones → γ'' → γ' → stable γ. The disk-shaped G.P. zones and the disk-shaped γ'', γ' and γ precipitated phases are composed of monolayers of Be atoms on {100}αof the Cu matrix and alternative Be and Ni matrix layers parallel to {100}α. The γ'' phases consisting of two to eight Be-layers has a body-centered tetragonal (bct) lattice witha=b=0.24 nm andc=0.28 nm. The γ' or γ phase is bct witha=b=0.24 nm andc=0.26 nm ora=b=0.26 nm andc=0.27 nm. The γ'', γ' or γ phase aligns with the matrix according to the Bain orientation relationship. The growth kinetics of disk-shaped γ precipitates on aging at 500°C has been also investigated. The {001}αhabit planes of the γ precipitates migrate by a ledge mechanism. The average thickness of the γ disks increases with aging timetast1/2. An analysis of experimental data using a kinetic model yields the diffusivity of solute in the Cu matrix, which is in agreement with the reported diffusivity of Ni in Cu.

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Lück, Janik Marius, et Joachim Rösler. « Reducing the γ′-Particle Size in CMSX-4 for Membrane Development ». Materials 15, n^o 4 (10 février 2022) : 1320. http://dx.doi.org/10.3390/ma15041320.

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Colloidal emulsions for lipophilic drugs can be fabricated using premix membrane emulsification. The state of the art is the application of membranes made from, for example, polycarbonate or polyester, which, however, are prone to fouling and cause waste, due to the low number of cycles. With the use of metallic membranes made from the nickel based single crystalline superalloy CMSX-4, these key disadvantages are eliminated. However, instead, the pore size and the resulting droplet size distribution need to be adjusted and improved. This can be realized by tailoring the size of the γ′-particles, which is controllable by the time and temperature used during precipitation heat treatment and the quenching method after homogenization heat treatment. Therefore, we utilized different heat treatment protocols, varying the cooling rate (water quenching and air cooling) after homogenization heat treatment and the holding time and temperature during precipitation heat treatment. Then, we investigated the γ/γ′-microstructure, including the γ′-morphology and γ′-particle size. We show that water quenching has a significant impact on the γ/γ′-microstructure and often leads to irregular-shaped and poorly aligned γ′-particles after precipitation heat treatment. In comparison, air cooling, followed by a subsequent precipitation heat treatment, results in well-aligned and cubic shaped γ′-particles and is, therefore, favorable for membrane fabrication. A reduction in precipitation temperature leads to morphology changes to the γ′-particles. A reduction of the holding time during precipitation heat treatment diminishes the γ′-particle growth, resulting in smaller γ′-particles. Additionally, a suitable heat treatment protocol for membrane fabrication was identified with a γ′-edge length of 224 ± 52 nm and well-aligned, cubic shaped γ′-particles.

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Zelinskiy, A. S., G. A. Yakovlev et D. E. Fil’trov. « Связь мощности дозы гамма-излучения с интенсивностью ливневых осадков ». Вестник КРАУНЦ. Физико-математические науки, n^o 3 (22 novembre 2021) : 189–99. http://dx.doi.org/10.26117/2079-6641-2021-36-3-189-199.

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Experimental and theoretical studies of the influence of the intensity, amount and duration of liquid atmospheric precipitation on the formation of γ-background in the surface layer of the atmosphere are presented. It was observed that precipitation causes an increase in the γ-radiation dose rate in the form of bursts. In this case, the total amount of precipitation in an event determines the magnitude of the burst of the dose rate, and the intensity of precipitation determines the rate of increase in the dose rate of γ-radiation. A mathematical model, which establishes a quantitative relationship between the dose rate of γ-radiation and the intensity (amount) of liquid atmospheric precipitation has been developed and verified (R2 = 0.93). Представлены экспериментальные и теоретические исследования влияния интенсивности, количества и продолжительности жидких атмосферных осадков на формирование γ-фона в приземном слое атмосферы. Было замечено, что осадки вызывают увеличение мощности дозы γ-излучения в виде всплесков. В этом случае общее количество осадков в событии определяет величину всплеска мощности дозы, а интенсивность осадков определяет скорость увеличения мощности дозы γ-излучения. Разработана и проверена математическая модель, устанавливающая количественную связь между мощностью дозы γ-излучения и интенсивностью (количеством) жидких атмосферных осадков (R2 = 0,93).

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Sun, W. R., Z. Q. Hu, J. H. Lee, S. M. Ceo et S. J. Choe. « Influence of solidification rate on precipitation and microstructure of directional solidification IN792 + Hf superalloy ». Journal of Materials Research 14, n^o 10 (octobre 1999) : 3873–81. http://dx.doi.org/10.1557/jmr.1999.0524.

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The effect of solidification rate on the precipitation and microstructure of directional solidification IN792 + Hf alloy was studied. The solidification sequence and the initial precipitation temperature of different phases were determined by the observation of the quenched microstructure combined with the differential thermal analysis measurement. The script carbide was turned into faceted carbide with the drop of solidification rate. It was concluded by microstructure analysis that the faceted carbide was pushed by the γ solid front before it was captured. The incorporation of γ phase into the faceted carbide was due to the dendrite growth of the carbide toward one point and the mergence of the dendrites. Some long carbide bars were formed along the grain boundaries by continual reaction of eutectic (γ + MC carbide) at a solidification rate of 0.5 μm/s. Two zones, the γ′ forming elements enriched zone and depleted zone, were found in the residual liquid area. Eutectic γ/γ′ nucleated in the γ′ forming elements enriched zone. The η-phase precipitation was controlled by the ratio of (Ti + Hf + Ta + W)/Al in the residual liquid. The growth of eutectic γ/γ′ increased the ratio and induced the η-phase precipitation. A lower solidification rate decreased the ratio by sufficient diffusion and hence efficiently suppressed the η-phase precipitation.

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Chen, S., P. A. Beaven et R. Wagner. « Carbide precipitation in γ-TiAl alloys ». Scripta Metallurgica et Materialia 26, n^o 8 (avril 1992) : 1205–10. http://dx.doi.org/10.1016/0956-716x(92)90564-u.

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Campbell, S. J., et G. L. Whittle. « γ-Fe precipitation in melt-spunCuFe ». Hyperfine Interactions 41, n^o 1 (décembre 1988) : 567–70. http://dx.doi.org/10.1007/bf02400454.

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Turi, Maria-Lynn, George Weatherly et Gary Purdy. « Grain boundary precipitation of γ in γ′ Ni3(Al,Ti) ». Materials Science and Engineering : A 192-193 (février 1995) : 945–49. http://dx.doi.org/10.1016/0921-5093(94)03325-0.

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Zeng, Xubin, Mike Barlage, Chris Castro et Kelly Fling. « Comparison of Land–Precipitation Coupling Strength Using Observations and Models ». Journal of Hydrometeorology 11, n^o 4 (1 août 2010) : 979–94. http://dx.doi.org/10.1175/2010jhm1226.1.

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Abstract Numerous studies have attempted to address the land–precipitation coupling, but scientists’ understanding remains limited and discrepancies still exist from different studies. A new parameter Γ is proposed here to estimate the land–precipitation coupling strength based on the ratio of the covariance between monthly or seasonal precipitation and evaporation anomalies (from their climatological means) over the variance of precipitation anomalies. The Γ value is easy to compute and insensitive to the horizontal scales used; however, it does not provide causality. A relatively high Γ is a necessary—but not sufficient—condition for a relatively strong land–precipitation coupling. A computation of Γ values using two global reanalyses (ECMWF and NCEP), one regional reanalysis [North American Regional Reanalysis (NARR)], and observed precipitation along with Variable Infiltration Capacity (VIC)-derived evaporation data indicates that the land–precipitation coupling is stronger in summer and weaker in winter. The strongest coupling (i.e., hot spots) occurs over the western and central parts of North America, part of the Eurasia midlatitude, and Sahel in boreal summer and over most of Australia, Argentina, and South Africa in austral summer. The Community Climate System Model, version 3 (CCSM3) shows much higher Γ values, consistent with the strong coupling shown by its atmosphere–land coupled components in previous studies. Its overall spatial pattern of Γ values is not affected much over most regions by the doubling of CO2 in CCSM3. The Γ values from the Regional Atmospheric Modeling System (RAMS) are more realistic than those from CCSM3; however, they are still higher than those from observations over North America.

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Thèses sur le sujet "Γ' precipitation"

Orlacchio, Federico. « Évolution de la microstructure du superalliage à base nickel γ-γ' René 65 au cours de sa mise en forme pour la fabrication de disques de turbine ». Electronic Thesis or Diss., Université Paris sciences et lettres, 2024. http://www.theses.fr/2024UPSLM034.

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Les superalliages à base nickel sont des matériaux métalliques de haute performance offrant d'excellents propriétés mécaniques à hautes températures. Pour cette raison, ils sont largement utilisés dans l'industrie aérospatiale pour les parties les plus chaudes et les plus sollicitées des turboréacteurs. Afin d'augmenter la température de fonctionnement et, en même temps, de réduire la consommation de carburant et les émissions de gaz à effet de serre, le superalliage polycristallin à base nickel γ-γ' René 65 a été choisi pour la fabrication de certains disques de turbine des turboréacteurs de nouvelle génération. Cette famille de superalliages présente, en service comme lors de la mise en forme à chaud, deux phases distinctes, nommées γ, solution solide riche en Ni, et γ', composé intermétallique avec composition stœchiométrique Ni3(Al,Ti). Lors de la mise en forme, les deux phases peuvent évoluer simultanément, avec des cinétiques comparables et différents mécanismes d'interactions possibles tels que l'ancrage de Smith-Zener et la recristallisation en hétéroépitaxie, rendant l'étude des évolutions de microstructures sous-jacentes complexe et ambitieuse. L'objectif principal de ce travail est l'étude des évolutions microstructurales à l'œuvre lors des différentes opérations de forgeage à chaud pour les deux phases, γ et γ', avec une approche principalement expérimentale. Pour y parvenir, un chemin themomécanique avec un traitement thermique subsolvus, suivi d'une compression à chaud et se finalisant par un traitement de mise en solution, a été reproduit en laboratoire. Au cours de ce travail, la cinétique expérimentale de dissolution des précipités γ' ainsi que la cinétique de recristallisation statique de la matrice γ au cours d'un traitement subsolvus ont été déterminées. L'effet sur la recristallisation dynamique des paramètres thermomécaniques, tels que le niveau, la vitesse et la température de déformation, a été étudié en détail dans le domaine subsolvus de l'alliage. L'évolution de la microstructure pendant la mise en solution, i.e en régime de croissance de grains, a été analysée à partir de différentes microstructures initiales. En outre, un modèle de croissance de grain en champ moyen en présence de précipités γ', a été calibré et validé pour l'alliage René 65. Ce travail permet de mieux comprendre le comportement en mise en forme des superalliages à base de nickel γ-γ', dans le domaine subsolvus, c'est-à-dire dans un contexte de forte interaction et de couplage entre la matrice γ et les précipités γ'. En conclusion, les résultats obtenus s'avèrent également industriellement important pour, à l'avenir, optimiser le procédé de forgeage à chaud de cet alliage
Nickel-based superalloys are high-performance metallic materials offering excellent mechanical properties at high temperatures. For this reason, they are widely used in the aerospace industry for the hottest, most highly stressed parts of jet engines. To increase operating temperature and, at the same time, reduce fuel consumption and greenhouse gas emissions, the nickel-based polycrystalline superalloy γ-γ' René 65 has been chosen for the manufacture of certain turbine disks in new-generation turbojet engines. In service and during hot forming, this family of superalloys features two distinct phases: γ, a Ni-rich solid solution, and γ', an intermetallic compound with a stoichiometric Ni3(Al,Ti) composition. During forging, both phases can evolve simultaneously, with comparable kinetics and different possible interaction mechanisms such as Smith-Zener pinning and heteroepitaxial recrystallization, making the study of underlying microstructural evolutions complex and ambitious. The main objective of this work is to study the microstructural evolutions at work during the various hot forging operations for the two phases, γ and γ', using a mainly experimental approach. To achieve this, a themomechanical path with subsolvus heat treatment, followed by hot compression and finalized by solution treatment, was reproduced in the laboratory. In the course of this work, the experimental dissolution kinetics of γ' precipitates and the static recrystallization kinetics of the γ matrix during subsolvus treatment were determined. The effect of thermomechanical parameters such as deformation level, strain rate and temperature on dynamic recrystallization has been studied in detail in the subsolvus domain of the alloy. The evolution of the microstructure during solution treatment, i.e. in the grain growth regime, was analyzed from different initial microstructures. In addition, a mean-field grain growth model in the presence of γ' precipitates was calibrated and validated for the René 65 alloy. This work provides a better understanding of the forging behavior of nickel-based γ-γ' superalloys in the subsolvus domain, i.e. in a context of strong interaction and coupling between the γ matrix and γ' precipitates. In conclusion, the results obtained are also industrially important for future optimization of the hot-forging process for this alloy

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Ahmad, Afandi. « Development of Fe-based Superalloys Strengthened by the γ'Phase ». Kyoto University, 2020. http://hdl.handle.net/2433/259045.

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Ko, Chien-Shen, et 柯建盛. « Kinetics of the CO oxidation of Au/γ-Al2O3 catalysts Prepared by Deposition-precipitation ». Thesis, 2004. http://ndltd.ncl.edu.tw/handle/58dssw.

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碩士
元智大學
化學工程學系
92
Alumina-supported gold catalysts were prepared by deposition-precipitation method. The preparation parameters investigated include pH, pretreatment , sequence of raw material addition. The Au/γ-Al2O3 prepared at pH >9.5 became very active for CO oxidation above at 213K after a calcination at 573K for 2h. This activity is similar to the 1.5% Au/TiO2 reference catalyst. With a feed of 1% CO+10% O2 in He, almost 90% of the CO was converted at 298K at CO a space velocity of 21,415 μ mole/g-cat/h. Lower CO oxidation activity was observed, when the calcination temperature reduced to 473K or when a calcination time of 1h was used. Kinetic studies were performed with both 1% Au/γ-Al2O3 and 1.5% Au/TiO2. Both catalysts showed a near -1 order rate dependence on CO and a near 0.2 order rate dependence on O2 between 213K and 253K. This conforms to a single-site Langmuir-Hinshelwood rate model. However, it is not sure whether the O2 was dissociative or nondissociative adsorbed.

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Chapitres de livres sur le sujet "Γ' precipitation"

Zhang, Fan, Weisheng Cao, Chuan Zhang, Shuanglin Chen, Jun Zhu et Duchao Lv. « Simulation of Co-precipitation Kinetics of γ′ and γ″ in Superalloy 718 ». Dans Proceedings of the 9th International Symposium on Superalloy 718 & ; Derivatives : Energy, Aerospace, and Industrial Applications, 147–61. Cham : Springer International Publishing, 2018. http://dx.doi.org/10.1007/978-3-319-89480-5_8.

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Kim, Il Ho, et S. I. Kwun. « Precipitation Behavior of γ" in Severely Plastic Deformed Ni-Base Alloys ». Dans Progress in Powder Metallurgy, 213–16. Stafa : Trans Tech Publications Ltd., 2007. http://dx.doi.org/10.4028/0-87849-419-7.213.

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Mukhopadhyay, Semanti, Fei Xue, Hariharan Sriram, Robert W. Hayes, Emmanuelle A. Marquis, Yunzhi Wang et Michael J. Mills. « Preferential γ′ Precipitation on Coherent Annealing Twin Boundaries in Alloy 718 ». Dans The Minerals, Metals & ; Materials Series, 135–46. Cham : Springer Nature Switzerland, 2023. http://dx.doi.org/10.1007/978-3-031-27447-3_9.

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Zajac, Stanislaw. « Precipitation of Microalloy Carbo-Nitrides Prior, during and after γ/α Transformation ». Dans Materials Science Forum, 75–86. Stafa : Trans Tech Publications Ltd., 2005. http://dx.doi.org/10.4028/0-87849-981-4.75.

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Imata, Hideo, et Keiko Takahashi. « Specific Binding and Precipitation of γ-Cyclodextrin with Monosaccharide in an Aqueous Solution ». Dans Proceedings of the Ninth International Symposium on Cyclodextrins, 15–18. Dordrecht : Springer Netherlands, 1999. http://dx.doi.org/10.1007/978-94-011-4681-4_4.

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Koyama, Toshiyuki, et Hidehiro Onodera. « Phase-Field Simulation of γ"(D0₂₂) Precipitation in Ni Base Superalloys ». Dans Materials Science Forum, 2287–92. Stafa : Trans Tech Publications Ltd., 2007. http://dx.doi.org/10.4028/0-87849-462-6.2287.

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Park, June Soo, Dong Hyun Kim et Young Kook Lee. « NbC Precipitation Kinetics during and after γ/α Transformation of a Nb Microalloyed Steel ». Dans THERMEC 2006, 4191–95. Stafa : Trans Tech Publications Ltd., 2007. http://dx.doi.org/10.4028/0-87849-428-6.4191.

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Wu, Kaisheng, Youhai Wen et Jeffrey A. Hawk. « Phase Field Simulations on the Precipitation Kinetics of γ′ in Ni-Base Superalloy Haynes 282 ». Dans TMS2013 Supplemental Proceedings, 711–18. Hoboken, NJ, USA : John Wiley & Sons, Inc., 2013. http://dx.doi.org/10.1002/9781118663547.ch88.

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Kim, Il Ho, et S. I. Kwun. « Influence of Plastic Deformation during ECAP on Precipitation Temperature of γ″ in IN 718 Alloy ». Dans Solid State Phenomena, 431–36. Stafa : Trans Tech Publications Ltd., 2006. http://dx.doi.org/10.4028/3-908451-25-6.431.

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Qin, Hailong, Hai Chi, Ying Tao, Mingzhao Xie, Songyi Shi, Hongyao Yu, Jinli Xie, Qing Tan et Zhongnan Bi. « Characterization of γ′ Precipitation Behavior in Additively Manufactured IN738LC Superalloy via In-Situ Small-Angle Neutron Scattering ». Dans The Minerals, Metals & ; Materials Series, 211–23. Cham : Springer Nature Switzerland, 2023. http://dx.doi.org/10.1007/978-3-031-27447-3_14.

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Actes de conférences sur le sujet "Γ' precipitation"

Semba, H., H. Okada et M. Igarashi. « Creep Properties and Strengthening Mechanisms In 23Cr-45Ni-7W (HR6W) Alloy and Ni-Base Superalloys For 700°C A-USC Boilers ». Dans AM-EPRI 2007, sous la direction de R. Viswanathan, D. Gandy et K. Coleman, 168–84. ASM International, 2007. https://doi.org/10.31399/asm.cp.am-epri-2007p0168.

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Abstract The development of materials technologies for piping and tubing in advanced ultrasupercritical (A-USC) power plants operating at steam temperatures above 700°C represents a critical engineering challenge. The 23Cr-45Ni-7W alloy (HR6W), originally developed in Japan as a high-strength tubing material for 650°C ultra-supercritical (USC) boilers, was systematically investigated to evaluate its potential for A-USC plant applications. Comparative research with γ-strengthened Alloy 617 revealed that the tungsten content is intimately correlated with Laves phase precipitation and plays a crucial role in controlling creep strength. Extensive creep rupture tests conducted at temperatures between 650-800°C for up to 60,000 hours demonstrated the alloy's long-term stability, with 105-hour extrapolated creep rupture strengths estimated at 88 MPa at 700°C and 64 MPa at 750°C. Microstructural observations after creep tests and aging confirmed the material's microstructural stability, which is closely linked to long-term creep strength and toughness. While Alloy 617 exhibited higher creep rupture strength at 700 and 750°C, the materials showed comparable performance at 800°C. Thermodynamic calculations and microstructural analysis revealed that the Laves phase in HR6W gradually decreases with increasing temperature, whereas the γ' phase in Alloy 617 rapidly diminishes and almost completely dissolves at 800°C, potentially causing an abrupt drop in creep strength above 750°C. After comprehensive evaluation of creep properties, microstructural stability, and other reported mechanical characteristics, including creep-fatigue resistance, HR6W emerges as a promising candidate for piping and tubing in A-USC power plants.

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Shen, Hongwei, Weili Wang, Zhizheng Wang, Lihong Zhang, Xishan Xie et Shuhong Fu. « The Application of Ni-Base Alloy Nimonic 80A for Buckets of USC Steam Turbine in China ». Dans AM-EPRI 2007, sous la direction de R. Viswanathan, D. Gandy et K. Coleman, 402–12. ASM International, 2007. https://doi.org/10.31399/asm.cp.am-epri-2007p0402.

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Abstract Nimonic 80A, a Ni-base superalloy mainly strengthened by Al and Ti to form γ'-Ni3 (Al, Ti) precipitation in Ni-Cr solid solution strengthened austenite matrix, has been used in different industries for more than half century (especially for aero-engine application). In consideration of high strengths and corrosion resistance both Shanghai Turbine Company (STC) has adopted Nimonic 80A as bucket material for ultra-super-critical (USC) turbines with the steam parameters of 600°C, 25MPa. First series of two 1000MW USC steam turbines made by Shanghai Turbine Co. were already put in service on the end of 2006. Large amount of Nimonic 80A with different sizes are produced in Special Steel Branch of BAOSTEEL, Shanghai. Vacuum induction melting and Ar protected atmosphere electro-slag remelting (VIM+PESR) process has been selected for premium quality high strength Nimonic 80A. For higher mechanical properties the alloying element adjustment, optimization of hot deformation and heat treatment followed by detail structure characterization have been done in this paper. The Chinese premium quality high strength Nimonic 80A can fully fulfill the USC turbine bucket requirements.

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Yuan, Zhetao, Satoru Kobayashi et Masao Takeyama. « Microstructure Control Using the Formation of Laves Phase through Interphase Precipitation in Ferritic Heat Resistant Steels ». Dans AM-EPRI 2019, sous la direction de J. Shingledecker et M. Takeyama. ASM International, 2019. http://dx.doi.org/10.31399/asm.cp.am-epri-2019p0090.

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Abstract The formation of periodically arrayed rows of very fine Fe2Hf Laves phase particles was recently found in 9 wt. % chromium ferritic matrix through interphase precipitation along a reaction path of δ-ferrite → γ-austenite + Fe2Hf with a subsequent phase transformation of the γ phase into the α-ferrite phase. One of the problems on the formation of the fine Laves phase dispersion is a poor heat treatability; the interphase precipitation (δ-Fe→γ-Fe+Fe2Hf) is competitive with the precipitation of Laves phase from the δ phase in the eutectoid-type reaction pathway (δ→δ+Fe2Hf). In the present work, the effect of supersaturation on the precipitation of Laves phase from δ phase (δ→δ+Fe2Hf) and the δ→γ transformation in the reaction pathway was investigated by changing the Hf and Cr contents. The results obtained suggest that it is effective to have a high supersaturation for the precipitation of Laves phase and an adequately high supersaturation for the δ→γ transformation at the same time in order to widen the window of the interphase precipitation

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Kobayashi, Satoru, Tomoki Otsuka, Masao Takeyama, Chuya Aoki et Tomonori Ueno. « Grain Boundary Design Using Precipitation of Delta-Ni3Nb Phase for Ni-Based Wrought Alloys ». Dans AM-EPRI 2019, sous la direction de J. Shingledecker et M. Takeyama. ASM International, 2019. http://dx.doi.org/10.31399/asm.cp.am-epri-2019p0391.

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Abstract Effects of alloying additions of Ti or Mo to a simplified chemical composition of the γ′′-Ni3Nb strengthened type Ni-based alloy 718 on the precipitation mode of δ-Ni3Nb phase were investigated to aim at designing grain boundaries using the δ phase for raising temperature capability of the γ′′ strengthened Ni-based wrought alloys. In the base alloy of Ni-22Cr-16Fe-3.5Nb, the δ phase precipitated at the grain boundaries of the matrix phase in a platelet form by continuous precipitation mode at temperatures above 1273K (1000°C) but in a lamellar morphology by discontinuous precipitation mode below that temperature. The boundary temperature where the continuous/discontinuous precipitation mode changes was raised by addition of 1 % Ti and lowered by addition of 5% Mo. The increase in the boundary temperature by Ti addition can be considered to have occurred by an increase in the solvus temperature of γ′′ phase. The decrease in the boundary temperature by Mo addition can be interpreted by the reduction of the strain energy caused by the coherent γ′′ precipitates and/or the volume change by the formation of δ phase from the γ/γ′′ phases, which may promote the continuous precipitation with respect to the discontinuous precipitation.

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Otake, Takuji, Takashi Nishimoto et Takuma Okajima. « Influence of Initial Precipitated γ′′ Phase Microstructure on δ-Phase Precipitation Behavior in Alloy 718 ». Dans AM-EPRI 2019, sous la direction de J. Shingledecker et M. Takeyama. ASM International, 2019. http://dx.doi.org/10.31399/asm.cp.am-epri-2019p0738.

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Abstract Alloy 718 is one of the most useful heat-resistant alloys for important device components that require high-temperature properties. In order to obtain excellent mechanical properties, it is necessary to form fine grains, for which the pinning effect of the δ phase can be used in some cases. To precipitate a sufficient amount for the pinning effect, time-consuming isothermal heat treatments are required. Thus, a metallurgical method with a shortened holding time would improve production efficiency considerably. Our goal is to optimize the forging process to control grain size by utilizing the δ phase, and the purpose of this study was to investigate the influence of the initial microstructure of the precipitated γ″ phase on δ-phase precipitation behavior in Alloy 718. As a solute treatment, Alloy 718 was heated at 1050 °C for 4 h, followed by heating of some samples at 870 °C for 10 h to precipitate the γ″ phase. The specimen with precipitated γ″ phase showed more precipitated δ phase than that under the solute condition by comparing results of heating at 915 °C. This suggested that utilizing the γ″ phase promoted δ-phase precipitation, and it is thus expected to shorten the heat treatment time for δ-phase precipitation.

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Kikuchi, Kenta, Hirotoyo Nakashima et Masao Takeyama. « Experimental and Computational Study on Grain Boundary and Grain Interior Precipitation of Fe2Nb Laves Phase in Fe-Cr-Ni-Nb Austenitic Heat Resistant Steels ». Dans AM-EPRI 2019, sous la direction de J. Shingledecker et M. Takeyama. ASM International, 2019. http://dx.doi.org/10.31399/asm.cp.am-epri-2019p1408.

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Abstract The precipitation behavior of various phases in austenitic heat-resistant model steels, including the Fe2Nb Laves phase (C14 structure) on grain boundaries (GB) and grain interiors (GI), and the Ni3Nb metastable γ“ phase and stable δ phase on GI, was investigated through experimental study at different temperatures and thermokinetic calculation. The steel samples were prepared by arc melting followed by 65% cold rolling. Subsequently, the samples were solution treated within the γ single-phase region to control the grain size to approximately 150 μm. Aging of the solution-treated samples was carried out at temperatures ranging from 973 K to 1473 K for up to 3600 hours. Microstructural observations were conducted using FE-SEM, and the chemical compositions of the γ matrix and precipitates of Laves and δ phases were analyzed using EPMA. The precipitation modeling was performed using MatCalc software, utilizing a thermodynamic database constructed by our research group to calculate the chemical potential of each phase. Classical nucleation theory was applied for nucleation, while the SFFK model was employed for the growth and coarsening stages. Distinct phases were defined for grain boundary and grain interior Laves phase, with all precipitates assumed to have spherical morphology in the calculations. The precipitation start time was defined as the time when the precipitate fraction reached 1%. Experimental results indicated that above 973 K, Laves phase nucleation primarily occurred on grain boundaries before extending into the grain interior, with the nose temperature located around 1273 K. To replicate the experimentally determined Time-Temperature-Precipitation (TTP) diagram, interaction parameters among elements were adjusted. Additionally, by introducing lower interfacial energy between the γ matrix and Laves phase, the TTP diagram was successfully reproduced via calculation, suggesting relative stability at the interface.

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Khoiroh, Lilik, Lisana Rodliya, Nur Aini et Rachmawati Ningsih. « Synthesis of Maghemite Pigment (γ-Fe2O3) from Lathe Waste Using Precipitation-Calcination Route ». Dans Proceedings of the 2nd International Conference on Quran and Hadith Studies Information Technology and Media in Conjunction with the 1st International Conference on Islam, Science and Technology, ICONQUHAS & ICONIST, Bandung, October 2-4, 2018, Indonesia. EAI, 2020. http://dx.doi.org/10.4108/eai.2-10-2018.2295571.

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Kumagai, Yoshiki, Yoshinori Sumi et Hiroyuki Takabayashi. « Influence of γ′ Morphology on Hot Workability of Alloy U520 below the γ′-Solvus Temperature ». Dans AM-EPRI 2019, sous la direction de J. Shingledecker et M. Takeyama. ASM International, 2019. http://dx.doi.org/10.31399/asm.cp.am-epri-2019p0506.

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Abstract The relationship between the hot workability and the precipitation morphology of γ′ phase in the Alloy U520 was examined with a focus on the presence of γ′-nodule. To change the morphology of γ’ phase, forged bars of the Alloy U520 were solution treated followed by cooling process with the cooling rates of 5~100 K/h. After the heat treatment, both γ’ phases of intragranular particle and nodule along grain boundaries were observed, and the both sizes increased by slowing down the cooling rate. That is, the area fraction of γ’-nodule increased from about 0.1 % in the sample cooled at 100 K/h to about 70 % at 5 K/h. In Gleeble tension test, the slow-cooled samples basically exhibited higher ductility than water-quenched samples below the γ′-solvus temperature. However, the ductility was maximized in the sample cooled at 20 K/h, and excessive decrease of cooling rate resulted in a drop in ductility. EBSD analysis revealed that dynamic recrystallization (DRX) was often occurred in grain interior but suppressed at γ′-nodule area, indicating that presence of γ′-nodule had a negative influence on hot workability at subsolvus temperature.

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Giroud, Tiphaine, Philippe Egea, Peter Vikner, Solange Vivès et Charlotte Mayer. « Development Of An Invar Strengthened By Ni3Nb-Gamma'' Phase Precipitation Suitable For Additive Manufacturing ». Dans Euro Powder Metallurgy 2023 Congress & Exhibition. EPMA, 2023. http://dx.doi.org/10.59499/ep235749781.

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Stellar® InvHard is a Nb-enriched Invar designed for additive manufacturing (Laser Powder Bed Fusion). It will be launched on the market in 2023. Compared to Invar 36, Stellar® InvHard exhibits increased mechanical strength while maintaining a low coefficient of thermal expansion. The hardening of this alloy is inspired by superalloys 706 and 718 strengthened by Ni3Nb-γ'' phase that precipitates in the austenitic matrix; also containing carbides and Nb-rich δ phase. The precipitation of the γ'' phase can be controlled through annealing and aging treatment’s optimization, leading to a hardness in a range: 300-420 HV and the effect on coefficient of thermal expansion increase is limited thanks to the small size of such precipitates. Insights on microstructure and processability will also be presented along to coefficient of thermal expansion.

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Hasebe, Y., M. Yoshida, E. Maeda et S. Ohsaki. « Effects of Phosphorus Addition on the Creep Behavior and Microstructure of Wrought γ′-Strengthened Ni-Based Superalloys ». Dans AM-EPRI 2019, sous la direction de J. Shingledecker et M. Takeyama. ASM International, 2019. http://dx.doi.org/10.31399/asm.cp.am-epri-2019p0479.

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Abstract In this work, the effects of phosphorus addition on the creep properties and microstructural changes of wrought γ’-strengthened Ni-based superalloys (Haynes 282) were investigated, focusing on the effects of carbides precipitation. In an alloy with a phosphorus content of 8 ppm, precipitation of M23C6 carbides was observed in both grain boundaries and the grain interior prior to the creep tests. Grain boundary coverage by carbide increased with phosphorus content up to approximately 30 ppm. On the other hand, the amount of M23C6 in the grain interior decreased with phosphorus content. The results of the creep tests revealed the relationship between the time to rupture and the grain boundary coverage by carbides. The microstructure of the crept specimens showed the existence of misorientation at the vicinity of grain boundaries without carbides, as demonstrated via electron backscattered diffraction (EBSD) analysis. These results suggest that the observed improvement in the time to rupture is due to a grain-boundary precipitation strengthening mechanism caused by grain boundary carbides and that phosphorus content affects the precipitation behavior of M23C6 carbides in the grain interior and grain boundaries. These behaviors were different between alloys with the single addition of phosphorus and alloys with the multiple addition of phosphorus and niobium.

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