scholarly journals On the Dependence of γ′ Precipitate Size in a Nickel-Based Superalloy on the Cooling Rate from Super-Solvus Temperature Heat Treatment

Materials ◽  
2018 ◽  
Vol 11 (9) ◽  
pp. 1528 ◽  
Author(s):  
Chrysanthi Papadaki ◽  
Wei Li ◽  
Alexander Korsunsky
Keyword(s):  
Cooling Rate ◽  
Numerical Models ◽  
Measurement Data ◽  
Solution Treatment ◽  
Precipitate Size ◽  
Solution Treatment Temperature ◽  
Distribution Analysis ◽  
Polycrystalline Nickel ◽  
Precipitate Growth ◽  
The Mean

The ability to predict the sizes of secondary and tertiary γ′ precipitate is of particular importance for the development and use of polycrystalline nickel-based superalloys in demanding applications, since the size of the precipitate exerts a strong effect on the mechanical properties. Many studies have been devoted to the development and application of sophisticated numerical models that incorporate the influence of chemical composition, concentration gradients, and interfacial properties on precipitate size and morphology. In the present study, we choose a different approach, concentrating on identifying a correlation between the mean secondary and tertiary γ′ size and the cooling rate from solution treatment temperature. The data are collected using the precipitate size distribution analysis from high-resolution scanning electron microscopy. This correlation is expressed in the form of a power law, established using experimental measurement data and rationalized using a re-derivation of McLean’s theory for precipitate growth, based on well-established thermodynamic principles. Specifically, McLean’s model is recast to consider the effect of cooling rate. The derived model captures the correlation correctly despite its simplicity, and is able to predict the mean secondary and tertiary γ′ precipitate size in a nickel superalloy, without complex modeling.

Voids in Quenched Nickel

1968 ◽  
Vol 26 ◽  
pp. 266-267
Author(s):  
J. J. Laidler
Keyword(s):  
Electron Beam ◽  
Ambient Temperature ◽  
Cooling Rate ◽  
Three Dimensional ◽  
Cooling Curve ◽  
Polycrystalline Nickel ◽  
Quenching Temperature ◽  
Long Tail ◽  
Diffusion Pump

The presence of three-dimensional voids in quenched metals has long been suspected, and voids have indeed been observed directly in a number of metals. These include aluminum, platinum, and copper, silver and gold. Attempts at the production of observable quenched-in defects in nickel have been generally unsuccessful, so the present work was initiated in order to establish the conditions under which such defects may be formed.Electron beam zone-melted polycrystalline nickel foils, 99.997% pure, were quenched from 1420°C in an evacuated chamber into a bath containing a silicone diffusion pump fluid . The pressure in the chamber at the quenching temperature was less than 10-5 Torr . With an oil quench such as this, the cooling rate is approximately 5,000°C/second above 400°C; below 400°C, the cooling curve has a long tail. Therefore, the quenched specimens are aged in place for several seconds at a temperature which continuously approaches the ambient temperature of the system.

Spatial Variability of Physical Parameters and Processes in Two Field Soils

1991 ◽  
Vol 22 (5) ◽  
pp. 327-340 ◽  
Author(s):  
K. Høgh Jensen ◽  
J. C. Refsgaard
Keyword(s):  
Transport Model ◽  
Flow Direction ◽  
Measurement Data ◽  
Flow Simulation ◽  
Solute Concentration ◽  
Conclusive Evidence ◽  
Physical Parameters ◽  
Effective Parameters ◽  
The Mean ◽  
Tracer Experiments

A numerical analysis of solute transport in two spatially heterogeneous fields is carried out assuming that the fields are composed of ensembles of one-dimensional non-interacting soil columns, each column representing a possible soil profile in statistical terms. The basis for the analysis is the flow simulation described in Part II (Jensen and Refsgaard, this issue), which serves as input to a transport model based on the convection-dispersion equation. The simulations of the average and variation in solute concentration in planes perpendicular to the flow direction are compared to measurements obtained from tracer experiments carried out at the two fields. Due to the limited amount of measurement data, it is difficult to draw conclusive evidence of the simulations, but reliable simulations are obtained of the mean behaviour within the two fields. The concept of equivalent soil properties is also tested for the transport problem in heterogeneous soils. Based on effective parameters for the retention and hydraulic conductivity functions it is possible to predict the mean transport in the two experimental fields.

Non-isothermal crystallization behavior of spinel crystals in FeO-SiO2-TiO2-V2O3-Cr2O3 slag

2018 ◽  
Vol 116 (1) ◽  
pp. 110
Author(s):  
Lixiong Shao ◽  
Jiang Diao ◽  
Wang Zhou ◽  
Tao Zhang ◽  
Bing Xie
Keyword(s):  
Cooling Rate ◽  
Crystallization Behavior ◽  
Crystal Size ◽  
Growth Mechanisms ◽  
Vanadium Slag ◽  
Growth Behaviour ◽  
Temperature Range ◽  
Chromium Spinel ◽  
Mean Diameter ◽  
The Mean

The growth behaviour of spinel crystals in vanadium slag with high Cr2O3 content was investigated and clarified by statistical analyses based on the Crystal Size Distribution (CSD) theory. The results indicate that low cooling rate and Cr2O3 content benefit the growth of spinel crystals. The chromium spinel crystals firstly precipitated and then acted as the heterogeneous nuclei of vanadium and titanium spinel crystals. The growth mechanisms of the spinel crystals at the cooling rate of 5 K/min consist two regimes: firstly, nucleation control in the temperature range of 1873 to 1773 K, in which the shapes of CSD curves are asymptotic; secondly, surface and supply control within the temperature range of 1773 to 1473 K, in which the shapes of CSD curves are lognormal. The mean diameter of spinel crystals increases from 3.97 to 52.21 µm with the decrease of temperature from 1873 to 1473 K.

Changes in Microstructure of Biomedical Co-Cr-Mo-C Alloys with Solution Treating and Aging

2010 ◽  
Vol 89-91 ◽  
pp. 377-382 ◽  
Author(s):  
S. Mineta ◽  
Shigenobu Namba ◽  
Takashi Yoneda ◽  
Kyosuke Ueda ◽  
Takayuki Narushima
Keyword(s):  
Solution Treatment ◽  
Heating Time ◽  
Treatment Temperature ◽  
Vacuum Furnace ◽  
Solution Treatment Temperature ◽  
Precipitate Dissolution ◽  
Heat Treated ◽  
M23c6 Type ◽  
Type Carbide ◽  
Time Required

Microstructural changes occurring in biomedical Co-Cr-Mo alloys with three carbon levels due to solution treatment and aging were investigated. Ingots of Co-Cr-Mo alloys with three different carbon levels were prepared by vacuum furnace melting; their chemical composition was Co-28Cr-6Mo-xC (x = 0.12, 0.25 and 0.35 mass%). Precipitates were electrolytically extracted from as-cast and heat-treated alloys. An M23C6 type carbide and a phase were detected as precipitates in as-cast Co-28Cr-6Mo-0.12C alloy, and an M23C6 type carbide and an  phase (M6C-M12C type carbide) were detected in as-cast Co-28Cr-6Mo-0.25C and Co-28Cr-6Mo-0.35C alloys. Only the M23C6 type carbide was detected during solution treatment. Complete precipitate dissolution occurred in all the three alloys after solution treatment. The holding time required for complete precipitate dissolution increased with increasing carbon content and decreasing solution treatment temperature. Complete precipitate dissolution occurred in the Co-Cr-Mo-C alloys solution treated at 1523 K for 43.2 ks; they were then subjected to aging from 873 to 1473 K for a heating time up to 44.1 ks after complete precipitate dissolution in solution treatment at 1523 K for 43.2 ks. The M23C6 type carbide with a grain size of 0.1–3 m was observed after aging. A time-temperature-precipitation diagram of the M23C6 type carbide formed in the Co-28Cr-6Mo-0.25C alloy was plotted.

Detection and Analysis of Rats’ Bioelectromagnetic Signal

2014 ◽  
Vol 536-537 ◽  
pp. 13-17
Author(s):  
Hong Long Cao ◽  
Fen Ju Qin ◽  
Xue Guan Liu ◽  
He Ming Zhao
Keyword(s):  
Standard Deviation ◽  
Automatic System ◽  
Measurement Method ◽  
Measurement Accuracy ◽  
Biological Activities ◽  
Measurement Data ◽  
Measured Data ◽  
The Mean ◽  
Frequency Window ◽  
Window Effects

In this paper, we designed an automatic system and automatic test software, and they can carry out Kunming rats bioelectromagnetic measurement in standard status and anesthesia automatically in anechoic chamber where the electromagnetic field outside is shielded, the reflection wave is absorbed, and the measurement accuracy will be improved. We get a great number of measurement data with frequency-sweep measurement method. The mean and standard deviation of amplitudes vs. frequencies is calculated and analyzed. The results show the measurement method is feasible. We have plotted the means of measured data as multiple sets of Y values in a series of bars with standard deviations bars included and distributed in the frequency axis of X. It is found that the fluctuation of the mean and standard deviation in some frequencies is not evident which may explain frequency window effects, while in other frequencies, such a fluctuation can be obviously observed, which may suggest that bioelectromagnetic signal is influenced by biological activities (standard and anaesthesia status) in these frequency points.

Intercomparison of Mesoscale Model Simulations of the Daytime Valley Wind System

2011 ◽  
Vol 139 (5) ◽  
pp. 1389-1409 ◽  
Author(s):  
Juerg Schmidli ◽  
Brian Billings ◽  
Fotini K. Chow ◽  
Stephan F. J. de Wekker ◽  
James Doyle ◽  
...  
Keyword(s):  
Land Surface ◽  
Mesoscale Model ◽  
Numerical Models ◽  
Surface Wind ◽  
Sensible Heat Flux ◽  
Surface Wind Speed ◽  
Time Shift ◽  
Wind System ◽  
Valley Wind ◽  
The Mean

Three-dimensional simulations of the daytime thermally induced valley wind system for an idealized valley–plain configuration, obtained from nine nonhydrostatic mesoscale models, are compared with special emphasis on the evolution of the along-valley wind. The models use the same initial and lateral boundary conditions, and standard parameterizations for turbulence, radiation, and land surface processes. The evolution of the mean along-valley wind (averaged over the valley cross section) is similar for all models, except for a time shift between individual models of up to 2 h and slight differences in the speed of the evolution. The analysis suggests that these differences are primarily due to differences in the simulated surface energy balance such as the dependence of the sensible heat flux on surface wind speed. Additional sensitivity experiments indicate that the evolution of the mean along-valley flow is largely independent of the choice of the dynamical core and of the turbulence parameterization scheme. The latter does, however, have a significant influence on the vertical structure of the boundary layer and of the along-valley wind. Thus, this ideal case may be useful for testing and evaluation of mesoscale numerical models with respect to land surface–atmosphere interactions and turbulence parameterizations.

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