The Effect of Migration Energies on Reducing Overprediction in Radiation-Induced Segregation Models

1994 ◽  
Vol 373 ◽  
Author(s):  
T. R. Allen ◽  
G. S. Was
Keyword(s):  
Grain Boundary ◽  
Boundary Segregation ◽  
Grain Boundary Segregation ◽  
Experimental Uncertainty ◽  
Migration Energy ◽  
Model Calculations ◽  
Ni Alloys ◽  
Vacancy Migration ◽  
Radiation Induced ◽  
Vacancy Migration Energy

AbstractModels for calculating radiation-induced segregation (RIS) in concentrated alloys based solely on differences in the magnitude of the vacancy driven flux typically overpredict the amount of grain boundary segregation. A simple sensitivity analysis is used to show that the overprediction may be linked to the choice of input parameters. By varying the Cr-vacancy migration energy from 1.300eV to 1.320 eV and the Fe-vacancy migration energy from1.300eV to 1.305 eV, well within their experimental uncertainty, RIS model calculations are brought into better agreement with AES and STEM-EDS measurements of grain boundary segregation in Fe-Cr-Ni alloys irradiated with protons at 7x 10−6 dpa/s at various temperatures and doses.

scholarly journals Modeling the Effect of Irradiation and Post-Irradiation Annealing on Grain Boundary Composition in Austenitic Fe-Cr-Ni Alloys

1998 ◽  
Vol 527 ◽  
Author(s):  
T.R. Allen ◽  
J.T. Busby ◽  
E. A. Kenik ◽  
G.S. Was
Keyword(s):  
Grain Boundary ◽  
Bulk Alloy ◽  
Model Calculations ◽  
Post Irradiation ◽  
Ni Alloys ◽  
Boundary Composition ◽  
Wide Range ◽  
Input Parameters ◽  
Radiation Induced ◽  
Single Set

ABSTRACTMany irradiation effects in Fe-Cr-Ni alloys such as radiation-induced segregation, radiation-enhanced diffusion, and void swelling are known to vary with bulk alloy composition. The development of microstructural and microchemical changes during irradiation and during post-irradiation annealing is determined by the rate of diffusion of point defects and alloying elements. To accurately predict the changes in grain boundary chemistry due to radiation-induced segregation and post-irradiation annealing, the composition dependence of diffusion parameters, such as the migration energy, must be known. A model has been developed which calculates migration energies using pair interaction energies, thereby accounting for the effect of composition on diffusivity. The advantages of this calculational method are that a single set of input parameters can be used for a wide range of bulk alloy compositions, and the effects of local order can easily be incorporated into the calculations. A description of the model is presented, and model calculations are compared to segregation measurements from seven different iron-chromium-nickel alloys, irradiated with protons to doses from 0.1 to 3.0 dpa at temperatures between 200°C and 600°C. Results show that segregation trends can be modeled using a single set of input parameters with the difference between model calculation and measurement being less than 5 at%, but usually less than 2 at%. Additionally, model predictions are compared to grain boundary composition measurements of neutron irradiated 304 stainless steel following annealing. For the limited annealing data available, model calculations correctly predict the magnitude and time scale for recovery of the grain boundary composition.

Irradiation Assisted Grain Boundary Segregation in Steels

2006 ◽  
Vol 981 ◽  
Author(s):  
Zheng Lu ◽  
Roy G Faulkner
Keyword(s):  
Grain Boundary ◽  
Boundary Segregation ◽  
Analytical Techniques ◽  
Solute Drag ◽  
Grain Boundary Segregation ◽  
Rate Theory ◽  
Comprehensive Information ◽  
Fusion Applications ◽  
Radiation Induced ◽  
Reactor Pressure

AbstractThe understanding of radiation-induced grain boundary segregation (RIS) has considerably improved over the past decade. New models have been introduced and much effort has been devoted to obtaining comprehensive information on segregation from the literature. Analytical techniques have also improved so that chemical analysis of layers 1 nm thick is almost routine. This invited paper will review the major methods used currently for RIS prediction: namely, Rate Theory, Inverse Kirkendall, and Solute Drag approaches. A summary is made of the available data on phosphorus RIS in reactor pressure vessel (RPV) steels. This will be discussed in the light of the predictions of the various models in an effort to show which models are the most reliable and easy to use for forecasting P segregation behaviour in steels. A consequence of RIS in RPV steels is a radiation induced shift in the ductile to brittle transition temperature (DBTT). It will be shown how it is possible to relate radiation-induced P segregation levels to DBTT shift. Examples of this exercise will be given for RPV steels and for ferritic steels being considered for first wall fusion applications. Cr RIS in high alloy stainless steels and associated irradiation-assisted stress corrosion cracking (IASCC) will be briefly discussed.

Effect of Ni and Cr concentration on grain boundary segregation in FeCrNi alloys

1996 ◽  
Vol 239 ◽  
pp. 205-209 ◽  
Author(s):  
H. Kinoshita ◽  
S. Watanabe ◽  
S. Mochizuki ◽  
N. Sakaguchi ◽  
H. Takahashi
Keyword(s):  
Grain Boundary ◽  
Boundary Segregation ◽  
Grain Boundary Segregation ◽  
Ni Alloys ◽  
Cr Concentration

Radiation-Induced Grain Boundary Segregation

1998 ◽  
Vol 294-296 ◽  
pp. 67-74 ◽  
Author(s):  
R.G. Faulkner ◽  
S. Song ◽  
D. Meade ◽  
C.C. Goodwin
Keyword(s):  
Grain Boundary ◽  
Boundary Segregation ◽  
Grain Boundary Segregation ◽  
Radiation Induced
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