Modeling of Segregation and Microstructural Evolution near Grain Boundary in FE-CR-NI Alloy Under Irradiation

1998 ◽  
Vol 538 ◽  
Author(s):  
N. Sakaguchi ◽  
S. Watanabe ◽  
H. Takahashi
Keyword(s):  
Activation Energy ◽  
Grain Boundary ◽  
Point Defects ◽  
Solute Segregation ◽  
Extended Defects ◽  
Diffusional Process ◽  
Free Zone ◽  
Ni Alloy ◽  
Radiation Induced ◽  
Simultaneous Evolution

AbstractWe have investigated the solute segregation and simultaneous evolution of extended defects in an Fe-Cr-Ni alloy during irradiation by computer simulation. It sheds a light on the accomplishment of performing “the combined total calculation” or “the muliscale modeling” which deals with both radiation-induced segregation and various kinds of internal sink evolution. The formation of dislocation-free zone (DLFZ) was predicted in the vicinity of a grain boundary. It indicated that DLFZ formation is controlled by solute diffusional process via point defects diffusion near the grain boundary and the activation energy obtained by the width of DLFZ corresponds to the half of the value of the radiation-enhanced solute diffusivity.

Cr-Vacancy Elastic and Chemical Interactions in Irradiated Stainless Steels

1998 ◽  
Vol 540 ◽  
Author(s):  
E. P. Simonen ◽  
S. M. Bruemmer
Keyword(s):  
Grain Boundary ◽  
Point Defects ◽  
Stainless Steels ◽  
Austenitic Stainless Steels ◽  
Solution Annealing ◽  
Chemical Interactions ◽  
Radiation Induced ◽  
Solute Interactions ◽  
Present Evaluation ◽  
Nonequilibrium Segregation

AbstractInteractions between point defects and major solute strongly influence grain boundary concentrations during heat treatment, irradiation and annealing of austenitic stainless steels. Previous approaches to nonequilibrium segregation emphasize only elastic defect-solute interactions. The present evaluation of nonequilibrium concentrations at grain boundaries indicates chemical interactions unique to solution annealing and cooling during thermal nonequilibrium segregation (TNES). Subsequent to TNES, radiation-induced segregation and post-irradiation annealing are modeled and compared with measured changes in grain boundary composition. The latter two mechanisms are controlled by exchanges between vacancies and major solute such as Cr.

scholarly journals Моделирование радиационно-индуцированной сегрегации в сплавах Fe-Cr-Ni

2019 ◽  
Vol 61 (12) ◽  
pp. 2281
Author(s):  
Р.В. Скороход ◽  
А.В. Коропов
Keyword(s):  
Steady State ◽  
Point Defects ◽  
Kirkendall Effect ◽  
Concentration Profiles ◽  
Migration Energy ◽  
Dose Rates ◽  
Dislocation Densities ◽  
Ni Alloy ◽  
Different Temperatures ◽  
Radiation Induced

In the model of radiation-induced segregation, based on the first and second Fick’s laws and with inverse Kirkendall effect considered, the concentration profiles of the components of the concentrated Fe-Cr-Ni alloy and radiation point defects are obtained at different temperatures, dislocation densities, dose rates. The concentration profiles were calculated from the start of irradiation to the steady state. The sensitivity of concentrations of alloy components near the surface is analyzed as function of input parameters (vacancies migration energy for Cr, Ni, Fe, interstitial migration energy, etc.).

Microstructural Evolution in Reduced TiO2

1981 ◽  
Vol 39 ◽  
pp. 74-75
Author(s):  
W. T. Donlon ◽  
S. Shinozaki ◽  
E. M. Logothetis ◽  
W. Kaizer
Keyword(s):  
Microstructural Evolution ◽  
Point Defects ◽  
Extended Defects ◽  
Small Deviations ◽  
Controlled Atmospheres ◽  
Limited Solubility ◽  
Thin Foils ◽  
Heat Treated ◽  
Porous Polycrystalline ◽  
Crystallographic Shear

Since point defects have a limited solubility in the rutile (TiO2) lattice, small deviations from stoichiometry are known to produce crystallographic shear (CS) planes which accomodate local variations in composition. The material used in this study was porous polycrystalline TiO2 (60% dense), in the form of 3mm. diameter disks, 1mm thick. Samples were mechanically polished, ion-milled by conventional techniques, and initially examined with the use of a Siemens EM102. The electron transparent thin foils were then heat-treated under controlled atmospheres of CO/CO2 and H2 and reexamined in the same manner.The “as-received” material contained mostly TiO2 grains (∼5μm diameter) which had no extended defects. Several grains however, aid exhibit a structure similar to micro-twinned grains observed in reduced rutile. Lattice fringe images (Fig. 1) of these grains reveal that the adjoining layers are not simply twin related variants of a single TinO2n-1 compound. Rather these layers (100 - 250 Å wide) are alternately comprised of stoichiometric TiO2 (rutile) and reduced TiO2 in the form of Ti8O15, with the Ti8O15 layers on either side of the TiO2 being twin related.

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