Articles de revues : « Γ' precipitation »

1

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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7

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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8

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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9

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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10

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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11

Xue, Y. P., Jia Rong Li, Jin Qian Zhao et J. C. Xiong. « The Precipitation Behavior of γ′ Phase in Single Crystal Ni-Based DD6 Superalloy for Turbine Blade ». Materials Science Forum 898 (juin 2017) : 534–44. http://dx.doi.org/10.4028/www.scientific.net/msf.898.534.

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The precipitation behavior of γ′ precipitates in typical section dimensions of DD6 single crystal superalloy turbine blade was investigated experimentally during directional solidification process. The phase transformation temperatures in the single crystal Ni-based DD6 superalloy from DSC analysis and JmatPro simulation were basically in consistent with the isothermal solidification experiments. The solidification route of DD6 single crystal superalloy could be described as follows: L1 → γ + L2; L2 → (γ + γ′)eutectic + MC; γ → γ′/γ. With increasing continuous cooling rates, the primary γ′ precipitates tended to be refined, and the size distributions of the primary γ′ precipitates at every temperature measuring position followed the normal distribution. In comparison to the interdendritic regions, nearly a 60% reduction in the average sizes of the primary γ′ precipitates was measured in the dendritic core regions. The result of the primary γ′ size difference was strongly affected by the multi-component segregations between the interdendritic and dendritic regions, where the γ′ forming elements of Al and Ta segregated towards the interdendritic regions. Furthermore, the secondary γ′ precipitation was found to occur within a relatively wide corridor of γ matrix for low cooling rates (12.6, 23.3 and 29.7 °C/min) during the directional solidification process. The occurrence of the secondary γ′ precipitation resulted from the complex interaction of multiple thermodynamic and kinetic factors in the γ′ nucleation and the diffusion rate of γ′ forming elements.

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12

Zhao, Yu Hong, Hua Hou et Yu Hui Zhao. « Atomic-Scale Computer Simulation for early Precipitation Process of Ni₇₅Al_XV_25-X Alloy with Middle Al Composition ». Materials Science Forum 704-705 (décembre 2011) : 1328–37. http://dx.doi.org/10.4028/www.scientific.net/msf.704-705.1328.

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The microscopic phase field approach was applied for modeling the early precipitation process of Ni75AlxV25-xalloy. Without any a prior assumption, this model can be used to simulate the temporal evolution of arbitrary morphologies and microstructures on atomic scale. Through the simulated atomic pictures, calculated order parameters and volume fraction of the θ (Ni3V) and γ′ (Ni3Al) ordered phases, Ni75AlxV25-xalloys with Al composition of 0.05, 0.053 and 0.055 (atom fraction) were studied. Results show: For these alloys, θ and γ′ precipitated at the same time. With the increase of Al content, the amount of γ′ phase is increasing and that of θ phase is decreasing; the precipitation characteristic of γ′ phase transforms from Non-Classical Nucleation and Growth (NCNG) to Congruent Ordering + Spinodal Decomposition (CO+SD) gradually, otherwise, the precipitation characteristic of θ phase transforms from Congruent Ordering + Spinodal Decomposition (CO+SD) to Non-Classical Nucleation and Growth (NCNG) mechanism gradually. Both θ and γ′ has undergone the transition process of mixture precipitation mechanism with the characteristic of both NCNG and CO+SD mechanism. No incontinuous transition of precipitation mechanism has been found.

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13

Larcher, N. V., et I. G. Solorzano. « High-resolution observations of metastable γ’ precipitation in Al-15at.%Ag ». Proceedings, annual meeting, Electron Microscopy Society of America 54 (11 août 1996) : 1004–5. http://dx.doi.org/10.1017/s0424820100167482.

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It is currently well established that, for an Al-Ag alloy quenched from the α phase and aged within the metastable solvus, the aging sequence is: supersaturated α → GP zones → γ’ → γ (Ag2Al). While GP zones and plate-shaped γ’ are metastable phases, continuously distributed in the matrix, formation of the equilibrium phase γ takes place at grain boundaries by discontinuous precipitation (DP). The crystal structure of both γ’ and γ is hep with the following orientation relationship with respect to the fee α matrix: {0001}γ′,γ // {111}α, <1120>γ′,γ, // <110>α.The mechanisms and kinetics of continuous matrix precipitation (CMP) in dilute Al-Ag alloys have been studied in considerable detail. The quantitative description of DP kinetics, however, has received less attention. The present contribution reports the microstructural evolution resulting from aging an Al-Ag alloy with Ag content higher than those previously reported in the literature, focusing the observations of γ' plate-shaped metastable precipitates.

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14

Yakovleva, Valentina, Grigorii Yakovlev, Roman Parovik, Aleksey Zelinskiy et Aleksey Kobzev. « Rainfall Intensity and Quantity Estimation Method Based on Gamma-Dose Rate Monitoring ». Sensors 21, n^o 19 (25 septembre 2021) : 6411. http://dx.doi.org/10.3390/s21196411.

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The features of the atmospheric γ-background reaction to liquid atmospheric precipitation in the form of bursts is investigated, and various forms of them are analyzed. A method is described for interpreting forms of the measured γ-background response with the determination of the beginning and ending time of precipitation, the distinctive features of changes in the intensity of precipitation and the number of single (separate) events that form one burst. It is revealed that a change in the intensity of precipitation in one event leads to a change in the γ-radiation dose rate increase speed (time derivative). A method of estimating the average value of the intensity and amount of precipitation for one event, reconstructing the intensity spectrum from experimental data on the dynamics of the measured dose rate of γ-radiation, is developed. The method takes into account the radioactive decay of radon daughter products in the atmosphere and on the soil surface during precipitation, as well as the purification of the atmosphere from radionuclides. Recommendations are given for using the developed method to correct for changes (daily variations) in radon flux density from the ground surface, which lead to variations in radon in the atmosphere. Experimental verification of the method shows good agreement between the values of the intensity of liquid atmospheric precipitation, calculated and measured with the help of shuttle and optical rain precipitation gauges.

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Wusatowska-Sarnek, Agnieszka M., Martin J. Blackburn et Mark Aindow. « γ' Precipitation Kinetics in P/M IN100 ». Materials Science Forum 426-432 (août 2003) : 767–72. http://dx.doi.org/10.4028/www.scientific.net/msf.426-432.767.

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Kagawa, Masahiro, Heishiro Ohta, Hiroshi Komatsu et Yasuhiko Syono. « Precipitation of γ-Fe2O3from Ultrahigh Temperature Plasma ». Japanese Journal of Applied Physics 24, Part 1, No. 4 (20 avril 1985) : 477–81. http://dx.doi.org/10.1143/jjap.24.477.

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Sharma, G., R. V. Ramanujan et G. P. Tiwari. « Interphase precipitation in a γ-TiAl alloy ». Materials Science and Engineering : A 269, n^o 1-2 (août 1999) : 21–25. http://dx.doi.org/10.1016/s0921-5093(99)00081-7.

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Klein, J., S. J. Campbell, F. Aubertin, U. Gonser et O. Schneeweiss. « γ-Fe Precipitation in Cu97Fe3 and Cu75Au24Fe1 ». physica status solidi (b) 166, n^o 1 (1 juillet 1991) : 87–96. http://dx.doi.org/10.1002/pssb.2221660109.

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Cai, Junjian, Chengkai Qian, Xin Huo, Qu Liu, Kejian Li, Wen Ji, Zheng Li et al. « Characterizing Short-Time Aging Precipitation Behavior of a Novel Nickel–Iron-Based Alloy via Electrical Performance ». Materials 17, n^o 16 (21 août 2024) : 4143. http://dx.doi.org/10.3390/ma17164143.

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In this paper, the precipitation behavior and its effect on resistivity in a new type of nickel–iron-based alloy during short-term aging were investigated. During the aging process, the γ′ phase increases in average size and decreases in number, with its area fraction fluctuating over time. This fluctuation is caused by the mismatch in the redissolution and growth rates of the γ′ phase. As the area fraction of the γ′ phase increases, the content of solute atoms in the matrix that scatter electrons decreases, lowering the resistivity of the alloy. Additionally, the continuous precipitation of M23C6 at grain boundaries during aging causes the resistivity to gradually increase. This paper explains the fluctuation in the total amount of γ′ phase during short-term aging and proposes a new method for characterizing the precipitation behavior of the γ′ phase in the novel alloy using the relative trend of resistivity changes.

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20

Semiatin, S. L., N. C. Levkulich et J. S. Tiley. « An Investigation of Tertiary γ′ Precipitation in a Powder-Metallurgy, γ-γ′ Nickel-Base Superalloy ». Metallurgical and Materials Transactions A 50, n^o 11 (19 août 2019) : 5281–96. http://dx.doi.org/10.1007/s11661-019-05422-7.

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Liu, J., J. X. Dong, M. Z. Chen et X. S. Xie. « Nanoanalysis of precipitation in a modified Inconel 718 alloy ». Proceedings, annual meeting, Electron Microscopy Society of America 52 (1994) : 702–3. http://dx.doi.org/10.1017/s0424820100171249.

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The nickel-base superalloy Inconel 718 (IN718) is strengthened primarily by precipitation of two types of intermetallic phases in the austenite (γ) matrix: metastable γ' (cubic Ll2 structure) and γ" (tetragonal D022 structure) precipitates. Minor changes of the chemistry of the IN718 alloy can significantly affect its mechanical properties at high temperatures. It has been found that the microstructural stability of the precipitates and the high temperature performance of IN718 depend critically on the (Ti+Al)/Nb and Al/Ti ratios. The small sizes of these intermetallic phases and the fact that γ' precipitates are frequently associated with γ" precipitates in modified IN718 make it difficult to determine their composition. In this study, nanometer resolution analytical electron microscopy techniques have been used to characterize the structure, the morphology and the composition of the precipitated phases.The fabrication and the heat treatment of the modified IN718 alloy and its high temperature mechanical properties have been reported elsewhere.

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Peddada, S. R., I. M. Robertson et H. K. Birnbaum. « Hydride precipitation in vapor deposited Ti thin films ». Journal of Materials Research 8, n^o 2 (février 1993) : 291–96. http://dx.doi.org/10.1557/jmr.1993.0291.

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Titanium hydrides having two different crystal structures were observed in α–Ti thin films grown epitaxially on sapphire substrates by e-beam physical vapor deposition. One of the hydrides (γ-hydride) had a face-centered tetragonal structure (c/a > 1) with an ordered arrangement of hydrogen atoms. The second hydride formed was the fcc δ-hydride. The γ-hydride grew as platelets in the α–Ti lattice with {10$\overline 1$0}Ti habit planes, whereas the γ-hydrides formed directly on the sapphire substrate parallel to the (0001)Ti. These hydrides are one of the principal causes of film decohesion.

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Weatherly, G. C. « Interfaces and precipitation ». Proceedings, annual meeting, Electron Microscopy Society of America 50, n^o 1 (août 1992) : 224–25. http://dx.doi.org/10.1017/s0424820100121521.

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An important class of alloy transformation involves the precipitation of a body-centred cubic phase in a close packed cubic or hexagonal matrix (or vice-versa). In the past ten years, numerous investigations have demonstrated that the precipitate grows as a lath or needle-shaped particle, with the growth direction of the axis of the particle parallel to an invariant line of the phase transformation. Although there are an infinite number of potential invariant lines in such a transformation, commonly one observes that the growth direction is close to the common close-packed directions e.g. <110>f and <111>b, with a rational or near-rational orientation relationship between the two phases. These observations can be rationalized by invoking the geometric principles embodied in Bollmann's O-lattice theory or by appealing to the minimization of strain energy principle associated with the set(s) of misfit dislocations lying parallel to the invariant line. Figure 1 shows an example of this characteristic morphology of a lath of γ (face—centred) precipitated in a matrix of α (body-centred) in a two-phase stainless steel. The lath is bounded by well-developed facet planes_(see Fig. 1) with a growth direction about 5° from the common close packed [111]α, [101]γ directions. Sets of misfit dislocations and steps are visible at the (416)α and (275)α facet planes.

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Grosdidier, T., A. Hazotte et A. Simon. « Precipitation and dissolution processes in γ / γ ′ single crystal nickel-based superalloys ». Materials Science and Engineering : A 256, n^o 1-2 (novembre 1998) : 183–96. http://dx.doi.org/10.1016/s0921-5093(98)00795-3.

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Tian, W. H., T. Sano et M. Nemoto. « Hardening of ordered γ′-Ni3(Al, Ti) by precipitation of disordered γ ». Scripta Metallurgica 20, n^o 6 (juin 1986) : 933–36. http://dx.doi.org/10.1016/0036-9748(86)90469-2.

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Zhao, Yu Hong, Dong Ying Ju et Hua Hou. « Atomic-Scale Computer Simulation of Mixture Precipitation Mechanism for Ni₇₅Al_xV_25-x Alloy ». Materials Science Forum 475-479 (janvier 2005) : 3115–18. http://dx.doi.org/10.4028/www.scientific.net/msf.475-479.3115.

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With the microscopic phase-field model, the early precipitation mechanisms of the ternary Ni75AlxV25-x alloys with middle Al composition were explored by computer simulation in this paper. Through the simulated atomic pictures and composition order parameters of precipitates, we can explain the complex precipitation mechanisms of θ (Ni3V) and γ′ (Ni3Al) ordered phases. Simulated results also show that the precipitation characteristic of γ′ phase transforms from non-classical nucleation and growth to congruent ordering + Spinodal decomposition gradually, otherwise, the precipitation characteristic of θ phase transforms from congruent ordering + Spinodal decomposition to non-classical nucleation and growth mechanism gradually.

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Alviany, Riza, Arifuddin Wahyudi, Ignatius Gunardi, Achmad Roesyadi, Firman Kurniawansyah et Danawati Hari Prajitno. « Diethyl Ether Production as a Substitute for Gasoline ». MATEC Web of Conferences 156 (2018) : 06003. http://dx.doi.org/10.1051/matecconf/201815606003.

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Diethyl ether is one of alternative fuel that could be used as a significant component of a blend or as a complete replacement for transportation fuel. The aim of this research is to produce diethyl ether through dehydration reaction of ethanol with fixed bed reactor using nanocrystalline γ-Al2O3 catalyst. Nanocrystalline γ-Al2O3 catalyst was synthesized by precipitation method using Al(NO3)3.9H2O as precursors and NH4OH as the precipitating agent. Dehydration reaction was performed at temperature range of 125 to 225°C. The result shows that synthesized γ-Al2O3 catalyst gave higher ethanol conversion and diethyl ether yield than that of commercial Al2O3 catalyst. The use of synthesized γ-Al2O3 catalyst could reach ethanol conversion as high as 94.71% and diethyl ether yield as high as 11,29%.

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Yang, Shu Yu, Min Jiang et Lei Wang. « Thermodynamic Description of the γ' Phase in the Co-Al-W Based Superalloys ». Materials Science Forum 747-748 (février 2013) : 654–58. http://dx.doi.org/10.4028/www.scientific.net/msf.747-748.654.

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The phase equilibrium and the precipitation behavior of the γ' phase in the Co-Al-W-Ni-Cr superalloys were studied by thermodynamic method. The phase equilibrium of the Co-Al-W-15Ni-5Cr alloy at 900 was calculated, and it was found that there were a γ' single-phase region and a γ+γ' two-phase region. The effects of Al/W ratio on the precipitation of the γ' phase were studied, and it was clear that higher mole fraction of the γ' phase can be obtained with the Al/W ratio of 2.5. The stability of the γ' phase can be improved by adding of Ni, as well as the servicing temperature of the Co-Al-W based superalloys. The results obtained in this work can be used for the developing of the new-type Co-based superalloys.

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Cheng, Jun, Kejian Li, Zhengang Yang, Xin Huo, Manjie Fan, Songlin Li, Shengzhi Li, Qu Liu, Qingxian Ma et Zhipeng Cai. « Investigation of Precipitation Behavior of a Novel Ni-Fe-Based Superalloy during High-Temperature Aging Treatment ». Materials 17, n^o 19 (4 octobre 2024) : 4875. http://dx.doi.org/10.3390/ma17194875.

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The precipitation behavior of a novel Ni-Fe-based superalloy developed for advanced ultra-supercritical (A-USC) coal-fired power plant applications during high-temperature aging treatment was investigated. The results showed that the major precipitates in the novel alloy were randomly distributed MC carbides, M23C6 carbides at grain boundaries, and the γ′-Ni3 (Al, Ti) phase in grain interiors after aging. MC remained relatively stable during both short-term and long-term aging. M23C6 quickly precipitated and exhibited a discrete distribution at grain boundaries during short-term aging, and partly developed into continuous films during long-term aging. After uniform precipitation, the shape of γ′ remained spherical, and the size kept increasing with aging time according to the Lifshitz–Slyozov–Wagner (LSW) model. The hardness of the novel alloy was mainly associated with the precipitation behavior of γ′; as γ′ gradually precipitated, the hardness steadily increased; after complete precipitation, as the size of γ′ increased, the hardness first increased and then decreased, reaching the peak hardness when the average radius of γ′ achieved the critical size. In addition, the novel alloy exhibited abnormal coarsening behavior at grain boundaries during both short-term and long-term aging. The coarsened grain boundaries were actually precipitate-free zones (PFZs) and the coarsened and elongated rod-like particles inside were identified as γ′ precipitates. The mechanism of strain-induced grain boundary migration and the discontinuous coarsening reaction is proposed for the formation of PFZs. Furthermore, PFZs were considered to be potential crack sources during the creep rupture test, leading to earlier failure of the material.

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Ismail, Hamisah, Zalita Zainuddin, Hasmaliza Mohamad et Muhammad Azmi Abdul Hamid. « Compatibility of Concentrated NaOH as a Precipitation Agent in the Synthesis of Maghemite (γ-Fe2O3) Nanoparticles via Co-precipitation Method ». Journal of Physical Science 33, n^o 2 (25 août 2022) : 61–75. http://dx.doi.org/10.21315/jps2022.33.2.4.

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Maghemite (γ-Fe2O3) nanoparticles were synthesised using the coprecipitation method, with different concentrations (5 M, 10 M, 11 M, 12 M and 13.4 M) of sodium hydroxide (NaOH) as the precipitation agent. The resulting powder was characterised using x-ray diffraction (XRD), vibrating sample magnetometer (VSM), and transmission electron microscope (TEM). All characterisations were performed at room temperature. The XRD results showed that the γ-Fe2O3 powder was in a single phase for samples synthesised using 11 M, 12 M and 13.4 M NaOH and the crystallite size ranged between 5.74 nm–6.42 nm. TEM observations and analysis showed that the particles were in a cubo-spheroidal shape and the mean physical size of the nanoparticles was between 8.52 nm and 8.59 nm. Hysteresis loop indicated that γ-Fe2O3 nanoparticles have superparamagnetic properties with an acceptable range of saturation magnetisation of 31.08 emu/g–48.88 emu/g and negligible coercivity value. MTT assay demonstrated that the γ-Fe2O3 nanoparticles exhibited biocompatibility with V79-4 cells at different dosages (1000 μg/mL–50 μg/mL) for 48 h. The results suggested that maghemite can be a valuable low-cost biomagnetic material in biomedical applications.

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Zhang, Hongjun, Chong Li, Qianying Guo, Huijun Li et Yongchang Liu. « Deformation Mechanism of L1 2 ‐ γ ′ Phase in Bimodal γ ″‐ γ ′ Precipitation Hardened Inconel 718 Superalloy ». Advanced Engineering Materials 20, n^o 11 (12 septembre 2018) : 1800652. http://dx.doi.org/10.1002/adem.201800652.

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Cahyaning, Angelin, Brina Miftahurrohmah, Grandys Frieska Prassida et Tikno Tikno. « FILLING THE PRECIPITATION GAPS : ACCURATE IMPUTATION WITH SUPPORT VECTOR REGRESSION IN NORTH SULAWESI ». VARIANCE : Journal of Statistics and Its Applications 6, n^o 2 (31 octobre 2024) : 183–94. http://dx.doi.org/10.30598/variancevol6iss2page183-194.

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Incomplete precipitation data poses major challenges in accurate precipitation predictions, hindering the effectiveness of water resource management and disaster risk mitigation efforts in North Sulawesi, Indonesia. This research aims to develop a precipitation prediction model using Support Vector Regression (SVR) to handle missing data. The precipitation data used comes from BMKG and ERA5 stations. The results show that using the RBF kernel with parameters ∁ = 1000, ɛ = 0.1, γ = 100 produces the best predictions, except Dtatiun Meteorologi Naha with γ = 1000. The best model is shown in the model evaluation RMSE of 0.099, MAE of 0.099, and R² of 0.999. The ability of SVR to capture precipitation trends is shown in the model evaluation results. The best model obtained is used for the missing data imputation process.

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Wu, Yu Sheng, Jiao Ma et Fang Hu. « Thermal Stabilization of γ-Al₂O₃ with Modification of Polyethylene Glycol by Reverse Precipitation Method ». Advanced Materials Research 560-561 (août 2012) : 169–73. http://dx.doi.org/10.4028/www.scientific.net/amr.560-561.169.

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A series of γ-Al2O3 modified with different content of polyethylene glycol (PEG) was prepared by a reverse precipitation method. The phase transformation, thermal stabilization and the morphology of PEG-modified γ-Al2O3 was studied by XRD, BET and TEM, respectively. The results showed that the γ-Al2O3 with 1mol% PEG-modified has the excellent thermal stabilization after calcined at 1100°C for 3h. With the content of PEG increasing, the surface area of γ-Al2O3 was reduced gradually. Simultaneity, the γ-Al2O3 phase was transferred to θ-Al2O3 with the surface area 92 m2g-1 and a pore volume of 0.77 cm3g-1. The high surface area maintained at such high treatment temperature shows the 1mol% PEG-modified γ-Al2O3 prepared by reverse precipitation method can be applied in the automotive three-way catalyst support.

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Kim, Il Ho, et S. I. Kwun. « Precipitation Behavior of γ" in Severely Plastic Deformed Ni-Base Alloys ». Materials Science Forum 534-536 (janvier 2007) : 213–16. http://dx.doi.org/10.4028/www.scientific.net/msf.534-536.213.

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The precipitation behaviors of γ″(Ni3Nb) in four Ni-base alloys were investigated. The four alloys were forged Ni20Cr20Fe5Nb alloy, mechanically alloyed Ni20Cr20Fe5Nb alloy, IN 718 alloy and ECAPed(equal channel angular pressing) IN 718 alloy. Aging treatment was employed at either 600°C or 720°C for 20 hrs. The TEM observation and hardness test were performed to identify the formation of γ″. The precipitation of γ″ was noticed after aging at 600°C for 20 hrs in the mechanically alloyed Ni20Cr20Fe5Nb alloy and ECAPed IN 718 alloy, while it was observed after aging at 720°C for 20 hrs in the forged Ni20Cr20Fe5Nb alloy and IN 718 alloy before ECAP. It seemed that the lower aging temperature for γ″ precipitation in the mechanically alloyed Ni20Cr20Fe5Nb alloy and ECAPed IN 718 alloy than in the forged Ni20Cr20Fe5Nb alloy and IN 718 alloy before ECAP appeared to be due to the severe plastic deformation which occurred during mechanical alloying or ECAP.

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Sadiq, S., et D. R. F. West. « γ′ precipitation in some model nickel based superalloys ». Materials Science and Technology 5, n^o 9 (septembre 1989) : 952–56. http://dx.doi.org/10.1179/mst.1989.5.9.952.

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Khan, Shabana, Jung B. Singh et A. Verma. « Precipitation behaviour of γ′ phase in Alloy 693 ». Materials Characterization 119 (septembre 2016) : 24–33. http://dx.doi.org/10.1016/j.matchar.2016.07.007.

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Wang, Shaoyan, Xiaoan Li, Shaofeng Wang, Yang Li et Yuchun Zhai. « Synthesis of γ-alumina via precipitation in ethanol ». Materials Letters 62, n^o 20 (juillet 2008) : 3552–54. http://dx.doi.org/10.1016/j.matlet.2008.03.048.

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Larson, D. J., et M. K. Miller. « Precipitation and segregation in α2+γ titanium aluminides ». Materials Science and Engineering : A 250, n^o 1 (juillet 1998) : 65–71. http://dx.doi.org/10.1016/s0921-5093(98)00537-1.

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Woo, O. T., G. C. Weatherly, C. E. Coleman et R. W. Gilbert. « The precipitation of γ-deuterides (hydrides) in titanium ». Acta Metallurgica 33, n^o 10 (octobre 1985) : 1897–906. http://dx.doi.org/10.1016/0001-6160(85)90011-2.

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Nembach, Eckhard, et Günter Neite. « Precipitation hardening of superalloys by ordered γ′-particles ». Progress in Materials Science 29, n^o 3 (janvier 1985) : 177–319. http://dx.doi.org/10.1016/0079-6425(85)90001-5.

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Burke, M. G., et R. Bajaj. « Irradiation-induced precipitation in direct-aged alloy 625 ». Proceedings, annual meeting, Electron Microscopy Society of America 54 (11 août 1996) : 994–95. http://dx.doi.org/10.1017/s0424820100167433.

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Direct-aged alloy 625 (DA-A625) is a precipitation-hardened nickel-base superalloy with good mechanical properties and excellent corrosion resistance. Its superior stress corrosion cracking (SCC) performance makes it a candidate material for applications in light water reactors where resistance to irradiation-assisted SCC (IASCC) is important. This alloy derives its strength from the intragranular precipitation of fine DO22 – ordered γ” precipitates. These precipitates have a disc-like morphology and are crystallo-grahically related to the γ matrix such that the [001] axis of the precipitates are oriented parallel to <100> directions in the matrix. This alloy is generally solution-annealed then aged within the temperature range ~600 to 750°C. In direct-aging, the alloy is immediately aged at ~ 660°C for 80 h following hot-working. In addition to the γ° precipitates, intergranular M23C6, M7C3, M6C, or MC carbides can form in this material.

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Semiatin, S. L., F. Zhang, J. S. Tiley et D. U. Furrer. « A comparison of the precipitation behavior in PM γ-γ′ nickel-base superalloys ». Materials at High Temperatures 33, n^o 4-5 (avril 2016) : 301–9. http://dx.doi.org/10.1080/09603409.2016.1165449.

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Kindrachuk, V., N. Wanderka et J. Banhart. « γ′/γ″ Co-precipitation in Inconel 706 alloy : A 3D finite element study ». Materials Science and Engineering : A 417, n^o 1-2 (février 2006) : 82–89. http://dx.doi.org/10.1016/j.msea.2005.10.062.

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Huang, Jiapeng, Cheng Ai, Yi Ru, Yong Shang, Yanling Pei, Shusuo Li, Shengkai Gong et Heng Zhang. « The Effect of Cooling Rate from Solution Treatment on γ′ Reprecipitates and Creep Behaviors of a Ni-Based Superalloy Single-Crystal Casting ». Crystals 12, n^o 9 (1 septembre 2022) : 1235. http://dx.doi.org/10.3390/cryst12091235.

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Slowing down the coarsening of the γ′ phase and suppressing the precipitation of the topologically close-packed (TCP) phase is crucial for optimizing the creep properties of Ni-based single crystal superalloys, which are affected by the solution treatment history. In the present study, the effect of cooling rate on the morphology, size and lattice misfit of γ′ reprecipitates after solution treatment, as well as the microstructural evolution (e.g., the coarsening of γ′ reprecipitate and precipitation of the TCP phase) and creep properties of samples under different cooling rates at 1100 °C were investigated. The findings suggested that as the cooling rate increasing, the size of γ′ reprecipitates decreased, while the morphology transformed from polygonal to cubic. Additionally, faster cooling rate, on the one hand, the lower the degree of lattice misfit of γ/γ′ phases, which is beneficial to slow down the coarsening of the γ′ phase; on the other hand, the supersaturation of the γ-phase was reduced, i.e., the Mo and Re contents in the γ matrix were lower compared to the slow-cooling sample, which led to a lower TCP phase area fraction during thermal exposure at 1100 °C. It is crucial that the creep life of the alloy significantly improved by increasing the cooling rate after solution treatment; this is facilitated by the formation of rafts from finer cubic γ′ phase and reduction in the TCP phase as a source of microcracks. In conclusion, the findings of this study provide new insights into suppressing the precipitation of the TCP phase and optimizing alloy heat treatment processes to improve creep properties.

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Liu, Chenglu, Lei Gao, Hao Wu, Kesong Miao, He Wu, Rengeng Li et Xuewen Li. « Role of Stabilization Heat Treatment Inducing γ′-γ″ Co-Precipitates and η Phase on Tensile Behaviors of Inconel 706 ». Metals 14, n^o 7 (18 juillet 2024) : 826. http://dx.doi.org/10.3390/met14070826.

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Inconel 706 (IN706) alloy is commonly used in aircraft engines and power plant components that must meet very high performance requirements. The stabilization treatment has a significant effect on the precipitation and evolution of the reinforcing phases of the alloy, favoring the creep properties and adversely affecting the room-temperature tensile properties. However, the mechanism of the effect of the stabilization treatment on the mechanical properties of the alloys remains unclear. In this study, the effect of stabilization treatment time on the microstructure and tensile properties of IN706 alloy was investigated. The results showed that as the stabilization time gradually increased, the tensile strength remained basically unchanged (about 1250 MPa), the yield strength decreased from 1031 MPa to 985 MPa, and the plasticity decreased from 28.2% to 20.2%. The stabilization treatment induces the precipitation of granular, rod-shaped, and needle-like η phases at grain boundaries, accompanied by the appearance of a precipitate free zone (PFZ). Since the η phase is enriched with Ti and Nb, its precipitation along the grain boundary results in the depletion of Ti and Nb in the surrounding regions, thereby constraining the precipitation of the γ′ and γ″ phases, resulting in the appearance of PFZ. With increasing stabilization time, the size increase and volume fraction decrease in γ′-γ″ co-precipitates due to the precipitation of η-phase precipitates, leading to a decrease in their yield strength. Combined with in situ tensile tests, it was found that the decrease in the elongation of the stabilization treatment samples was due to the presence of η phase at the grain boundaries, which induced stress concentration and cracking at the grain boundaries. The results show that the mechanical properties of the material were gradually enhanced as the stabilization time decreased. This means it can help to choose the suitable process for IN706 alloy in different service conditions.

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Zhu, Zhiyuan, Yuanfei Cai, Kexing Song, Yanjun Zhou et Jiasheng Zou. « Precipitation Characteristics of the Metastable γ″ Phase in a Cu-Ni-Be Alloy ». Materials 11, n^o 8 (9 août 2018) : 1394. http://dx.doi.org/10.3390/ma11081394.

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The precipitation sequence of a Cu-Ni-Be alloy is: α-Cu supersaturated solid solution → Guinier-Preston (G.P.) zones → metastable γ″ → γ′ → stable γ (NiBe) phase. The micro-hardness and electrical conductivity during the aging process were measured. The precipitation characteristics and the distribution of the γ″ phase, under peak aging conditions, were analyzed by X-ray diffraction (XRD), transmission electron microscopy (TEM), selected area diffraction pattern (SADP), and high-resolution transmission electron microscopy (HRTEM). The results show that the orientation relationship of the γ′′ phase/α-Cu matrix is: (001)p//(001)α; [100]p//[110]α (p: Precipitates, α: α-Cu supersaturated solid solution), which is in accordance with the Bain relationship in a FCC/BCC (face centered cubic/body centered cubic) structure, with the unique habit plane being {001}α. While the zone axis is parallel to [001]α, three forms of γ″ phases are distributed on the projection surface at the same time. The (001) reciprocal-lattice positions of γ′′ phase in SADP are diffusely scattered, which is consistent with the variation of the d(001) value of the γ′′ phase. The intra-range variation is related to the distortion of the (001) plane of the γ″ phase, due to interfacial dislocations and distortion strain fields. The lattice of the γ″ phase in the HRTEM images was measured as a = b = 0.259 ± 0.002 nm and c = 0.27–0.32 nm. With the increase of thermal exposure time, the stable γ phase has a NiBe phase structure (Standard Card Number: PDF#03-1098, a = b = c = 0.261 nm), and the long diffuse scattering spots will transform into single bright spots. The edge dislocation, generated by interfacial mismatch, promotes the formation of an optimal structure of the precipitated phase, which is the priority of growth in the direction of [110]p.

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Shi, Zhao Xia, Xiao Feng Yan et Chun Hua Duan. « Microstructure and Room Temperature Mechanical Properties of a New Corrosion-Resistant Alloy GH945 for Oil and Gas Applications ». Materials Science Forum 849 (mars 2016) : 609–17. http://dx.doi.org/10.4028/www.scientific.net/msf.849.609.

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The microstructure and mechanical properties of a new corrosion-resistant alloy GH945 with high strength for oil and gas production were studied in this paper. The results showed that the main precipitations of GH945 alloy after solution heat treatment and two-stage age hardening treatment were γ′ and γ′′ phase, MC-type carbide, σ phase and M23C6-type carbide. The increase of primary aging temperature not only promoted the precipitation of σ phase and film of continuous M23C6 carbide on the grain boundary, but also led to the coarsening of γ′ and γ′′ phase, which resulted in the decrease of yield strength and impact toughness. Alloy with high Nb content had high strength but low impact toughness. The following heat treatment was preferably used to obtain the combination of high strength and excellent ductility and toughness for GH945 alloy: 1010 °C/70 min, WQ+ 735 °C/9 h + FC to 615 °C/18 h, AC.

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Jung, Ji Chul, Hee Soo Kim, Ahn Seop Choi, Young Min Chung, Tae Jin Kim, Seong Jun Lee, Seung Hoon Oh et In Kyu Song. « Preparation and Characterization of Bismuth Molybdate Catalyst for Oxidative Dehydrogenation of n-Butene into 1,3-Butadiene ». Solid State Phenomena 119 (janvier 2007) : 251–54. http://dx.doi.org/10.4028/www.scientific.net/ssp.119.251.

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α-Bi2Mo3O12 and γ-Bi2MoO6 catalysts were prepared by co-precipitation method, and they were applied to the oxidative dehydrogenation of n-butene into 1,3-butadiene in a continuous flow fixed-bed reactor. Formation of α-Bi2Mo3O12 and γ-Bi2MoO6 catalysts was well confirmed by XRD, Raman spectroscopy, and ICP-AES analyses. The γ-Bi2MoO6 catalyst exhibited a better catalytic performance than the α-Bi2Mo3O12 catalyst. Catalytic performance of γ-Bi2MoO6 strongly depended on the pH value used in the co-precipitation step. It was also revealed that a mixed catalyst comprising γ-Bi2MoO6 (90 wt%) and small amount of α-Bi2Mo3O12 (10 wt%) showed the best catalytic performance due to the synergy effect of two components. It is believed that the high catalytic performance of the mixed catalyst resulted from high diffusion coefficient of lattice oxygen in the γ-Bi2MoO6 and from abundant chemisorption sites for n-butene in the α-Bi2Mo3O12.

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Slama, C., C. Servant et G. Cizeron. « Aging of the Inconel 718 alloy between 500 and 750 °C ». Journal of Materials Research 12, n^o 9 (septembre 1997) : 2298–316. http://dx.doi.org/10.1557/jmr.1997.0306.

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The aging of the NC 19 Fe Nb alloy (Inconel 718), previously quenched from 990 °C, is characterized by a hardness peak at 650 °C, then a maximum in hardness at about 750 °C. Over this temperature, the hardness progressively decreases. In the 550–650 °C temperature range, TEM observations have revealed that β (Ni3Nb) precipitates are formed as long platelets parallel between them within the same grain, as well as extremely fine γ′[Ni3(Ti, Al)] particles responsible for the observed improvement in hardness. For a tempering temperature higher than 650 °C, a first hardening occurs after a 4 h treatment, which has been associated with the γ′ phase precipitation, with a more or less spherical shape. Beyond this time, a second hardening takes place linked to the γ″ phase precipitation (Ni3Nb, bct D022 structure), as thin platelet shaped, perfectly coherent with the matrix. The misfit between the γ and γ″ phases is about 3% in the 〈001〉γ″ direction and lower than 1% in the 〈100〉γ″ and 〈010〉γ″ directions. During a longer aging at 750 °C, the γ″ platelets progressively dissolve while β precipitates grow.

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Liu, Hengsan, Lin Zhang, Xinbo He, Xuanhui Qu et Guoqing Zhang. « The Precipitation Behavior of Secondary γ′ Phase in Superalloy FGH96 During Aging Treatment ». High Temperature Materials and Processes 33, n^o 5 (29 septembre 2014) : 485–88. http://dx.doi.org/10.1515/htmp-2013-0013.

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AbstractMicrostructural evolution of secondary γ′ precipitates in superalloy FGH96 under various aging treatments after 1200 °C solution treatment was investigated. The results indicate that particle size of secondary γ′ precipitates increases from about 73 μm to about 587 μm with the increasing of aging temperature in the range of 850–1120 °C, and the shape of secondary γ′ precipitates changes from spherical to cuboidal, and to butterfly-like with the increase of aging temperature. In case of the aging temperature of 1120 °C, the γ′ precipitates change into butterfly-like and the size is the largest. When the aging temperature reached 1140 °C, the γ′ precipitates are refined.

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