Download or read book Development of Computational Tools for Predicting Thermal and Radiation Induced Solute Segregation at Grain Boundaries in Fe based Alloys written by and published by . This book was released on 2016 with total page 43 pages. Available in PDF, EPUB and Kindle. Book excerpt: Radiation induced segregation (RIS) has been frequently reported in structural materials such as austenitic, ferritic, and ferritic-martensitic stainless steels (SS) that have been widely used in light water reactors (LWRs). RIS has been linked to secondary degradation effects in SS including irradiation induced stress corrosion cracking (IASCC). Earlier studies on thermal segregation in Fe based alloys found that metalloids elements such as P, S, Si, Ge, Sn etc. embrittle the materials when enrichment was observed at grain boundaries (GBs). RIS of Fe-Cr- Ni based austenitic steels has been modeled in the U.S. 2015 fiscal year (FY2015), which identified the pre-enrichment due to thermal segregation can have an important role on the subsequent RIS. The goal of this work is to develop thermal segregation models for alloying elements in steels for future integration with RIS modeling.
Download or read book Characteristics of Radiation Induced Solute Segregation in Candidate and Model Ferritic Alloys written by T. Muroga and published by . This book was released on 1990 with total page 15 pages. Available in PDF, EPUB and Kindle. Book excerpt: Compositional changes have been measured at grain boundaries, dislocation loops, and precipitates in Japanese ferritic/martensitic steel (JFMS, fusion candidate ferritic/ martensitic steel) and high purity Fe-10Cr, Fe-10Cr-1Ni and Fe-10Cr-5Ni model alloys irradiated with 1 or 1.25 MeV electrons in a high voltage electron microscope (HVEM). The depletion of chromium at grain boundaries and nearby matrices is derived in all alloys above 300°C. The enrichment of silicon as well as the depletion of chromium is observed at grain boundaries and precipitate (MC, M6C and M23C6)-matrix interfaces in JFMS. These decompositions obey the conventional solute size dependence. On the other hand, the segregation of nickel seems to depend on the bias of the sinks. The void swelling and the precipitate stability in ferritic steels are discussed based on the present information on defect-solute interactions, loop bias, and solute-precipitate interactions.
Download or read book Modeling of Radiation induced Segregation in Austenitic Fe Cr Ni Alloys written by Todd Randall Allen and published by . This book was released on 1997 with total page 926 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Grain Boundary Segregation in Metals written by Pavel Lejcek and published by Springer Science & Business Media. This book was released on 2010-07-20 with total page 249 pages. Available in PDF, EPUB and Kindle. Book excerpt: Grain boundaries are important structural components of polycrystalline materials used in the vast majority of technical applications. Because grain boundaries form a continuous network throughout such materials, their properties may limit their practical use. One of the serious phenomena which evoke these limitations is the grain boundary segregation of impurities. It results in the loss of grain boundary cohesion and consequently, in brittle fracture of the materials. The current book deals with fundamentals of grain boundary segregation in metallic materials and its relationship to the grain boundary structure, classification and other materials properties.
Download or read book The Spectral Model of Grain Boundary Solute Segregation written by Malik Mamoon Abdelhalim Wagih and published by . This book was released on 2021 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: And, we proceed to apply the developed criteria to screen over 200 alloy combinations. Among its benefits, this spectral approach enables strict enforcement of the third law of thermodynamics, where an average segregation energy does not. Fifth, we take the first step to extend the developed framework to handle solute segregation beyond the dilute limit, by outlining a thermodynamic segregation isotherm that accounts for both the spectrality of grain boundary sites, and solute-solute interactions; we also develop a computational framework to extract, and delineate both effects. Finally, we hope that the developed spectral thermodynamic framework, machine learning models, and solute segregation database in this thesis would help unlock the full potential of GB segregation as an alloy design tool, and enable the design of microstructures that maximize the useful impacts of segregation.
Download or read book Grain Boundary Sensitive Design in Fe and Ni Based Alloys for Materials Response in Irradiation Environments written by Christopher Michael Barr and published by . This book was released on 2016 with total page 386 pages. Available in PDF, EPUB and Kindle. Book excerpt: Ni and Fe based fcc alloys are frequently used as critical structural materials in nuclear energy applications. However, despite extensive studies, fundamental questions remain regarding point defect migration and solute segregation to grain boundaries after high temperature irradiation and corrosion. Specifically, a systematic study on the role of grain size and grain boundary character must be completed to develop insights into new material or processing routes that have enhanced radiation tolerance, improved corrosion resistance, and thermal stability. In this dissertation, an experimental approach is used to examine the response of grain boundary character and grain size in a both model and engineering alloys under extreme environments. After severe plastic deformation and thermomechanical processing to induce a range of grain boundary types and grain sizes, heavy ion irradiation was carried out at a range of temperatures. Post-irradiation analysis of specific grain boundaries using TEM/STEM and atom probe tomography is used to examine the interaction of irradiation induced defects, defect denuded zones, and deleterious Cr solute segregation as function of grain boundary character and grain size. The results indicate variations observed in the Cr depletion and defect evolution as a function of the grain boundary plane and coherency. The ultrafine grain size indicated a grain size dependent response with reduced defect size. Overall, the work highlights the critical role for considering both the grain boundary character distribution and ultrafine grain sizes for the development of new advanced alloys for extreme environments.
Download or read book Modeling the Effect of Irradiation and Post irradiation Annealing on Grain Boundary Composition in Austenitic Fe Cr Ni Alloys written by and published by . This book was released on 1998 with total page 6 pages. Available in PDF, EPUB and Kindle. Book excerpt: Many 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 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.
Download or read book The Influence of Solute Segregation on the Dislocation Structure of Grain Boundaries in Iron alloys written by Chun-Hung Lin and published by . This book was released on 1990 with total page 412 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book A Model of Vacancy Flux Induced Segregation to Grain Boundaries During Cooling written by S. J. Bercovici and published by . This book was released on 1969 with total page 6 pages. Available in PDF, EPUB and Kindle. Book excerpt: A recently developed method of analysis provided a direct measure of grain-boundary solute enrichment in slowly cooled Zn-Cd alloys as a function of holding temperature. These experimental data are here compared with the change of boundary solute enrichment computed from a model based on the vacancy flux generated uphill diffusion of solute to boundaries. The agreement between experiment and theory is satisfactory. This agreement is considered to be a direct proof that previously reported grain-boundary hardening of slowly cooled dilute alloys is a consequence of non-equilibrium solute adsorption. (Author).
Download or read book The Effect of Composition and Phase on Segregation of Fe Cr Based Alloys written by H. Takahashi and published by . This book was released on 1990 with total page 10 pages. Available in PDF, EPUB and Kindle. Book excerpt: The segregation behavior of Fe-Cr-Mn alloys during electron-irradiation was studied using a high-voltage electron microscope at a temperature range between 723 and 823 K. The ferritic Fe-7Cr-3Mn, Fe-5Cr-5Mn, and Fe-3Cr-7Mn alloys and the austenitic Fe-10Cr-15Mn and Fe-10Cr-15Mn-3Al alloys were used. Irradiation-induced segregation was observed for all of the Fe-Cr-Mn alloys. That is, manganese tended to enrich and chromium deplete near grain boundaries. However, both manganese and chromium were enriched to high concentrations not only at grain boundaries but also in the grain so that new phases were formed. Furthermore, the amount of segregation depended on the initial manganese and chromium solute concentration along with the aluminum addition. From these results it is suggested that compositional changes due to enrichment or depletion or both can result in a phase transformation during irradiation, even local phenomena.
Download or read book Modeling Radiation Induced Segregation in Iron Chromium Alloys written by and published by . This book was released on 2015 with total page 11 pages. Available in PDF, EPUB and Kindle. Book excerpt: Radiation induced segregation in ferritic Fe-Cr alloys is studied by Atomistic Kinetic Monte Carlo simulations that include di usion of chemical species by vacancy and interstitial migration, recombination, and elimination at sinks. The parameters of the di usion model are tted to DFT calculations. Transport coe cients that control the coupling between di usion of defects and chemical species are measured in dilute and concentrated alloys. Radiation induced segregation near grain boundaries is directly simulated with this model. We nd that the di usion of vacancies toward sinks leads to a Cr depletion. Meanwhile, the di usion of self-interstitials causes an enrichment of Cr in the vicinity of sinks. For concentrations lower than 15%Cr, we predict that sinks will be enriched with Cr for temperatures lower than a threshold. When the temperature is above this threshold value, the sinks will be depleted in Cr. These results are compared to previous experimental studies and models. Cases of radiation induced precipitation and radiation accelerated precipitation are considered.
Download or read book Modelling of Radiation Induced Segregation in Austenitic Fe Alloys at the Atomistic Level written by Jean-Baptiste Piochaud and published by . This book was released on 2013 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: In pressurized water reactors, under irradiation internal structures are subject of irradiation assisted stress corrosion cracking which is influenced by radiation induced segregation (RIS). In this work RIS of 316 stainless steels is modelled considering a model ternary Fe-10Ni-20Cr alloy. For this purpose we have built an Fe-Ni-Cr pair interaction model to simulate RIS at the atomistic level using an atomistic kinetic Monte Carlo approach. The pair interactions have been deduced from density functional theory (DFT) data available in the pure fcc systems but also from DFT calculations we have performed in the Fe-10Ni-20Cr target alloy. Point defect formation energies were calculated and found to depend strongly on the local environment of the defect. As a consequence, a rather good estimation of these energies can be obtained from the knowledge of the number and respective positions of the Ni and Cr atoms in the vicinity of the defect. This work shows that a model based only on interaction parameters between elements positioned in perfect lattice sites (solute atoms and vacancy) cannot capture alone both the thermodynamic and the kinetic aspect of RIS. A more accurate of estimating the barriers encountered by the diffusing species is required than the one used in our model, which has to depend on the saddle point environment. This study therefore shows thus the need to estimate point defect migration energies using the DFT approach to calibrate a model that can be used in the framework of atomic kinetic Monte Carlo simulations. We also found that the reproduction by our pair interaction model of DFT data for the self-interstitial atoms was found to be incompatible with the modelling of RIS under electron irradiation.
Download or read book Radiation induced Grain Boundary Segregation in Dilute Alloys written by Shenhua Song and published by . This book was released on 1995 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book The influence of solute segregation on the grain boundary strength of iron based alloys written by Doo Young Lee and published by . This book was released on 1983 with total page 356 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book On Radiation induced Segregation and the Compositional Dependence of Swelling in Fe Ni Cr Alloys written by W. G. Wolfer and published by . This book was released on 1982 with total page 19 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book An Analyses of Radiation induced Segregation in Fe Cr Ni Alloys written by V. A. Pečenkin and published by . This book was released on 1995 with total page 26 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Evaluation of Radiation Induced Segregation in Fe Ni Cr Alloys written by Carlos Daniel Flores and published by . This book was released on 1994 with total page 316 pages. Available in PDF, EPUB and Kindle. Book excerpt:
