Download or read book The Effect of Ordering on Radiation Induced Segregation in Austenitic Iron and Nickel Base Alloys written by TR. Allen and published by . This book was released on 1999 with total page 15 pages. Available in PDF, EPUB and Kindle. Book excerpt: Comparison of radiation-induced segregation (RIS) measurements from austenitic iron- and nickel-base alloys with calculations using the Perks vacancy-driven RIS model have shown that chromium segregates slower and iron segregates faster than expected from high temperature diffusion measurements. The effect is more pronounced in nickel-base alloys. The segregation process is affected by short range ordering forces and the ordering is strongest in nickel-base alloys. Since nickel enriches and chromium depletes in all iron-chromium-nickel alloys under irradiation, a tendency to form nickel- chromium pairs reduces the chromium segregation, especially in nickel-base alloys. In this work, Perks' model is altered to include ordering energies, and the calculated RIS is compared to segregation measurements from iron-chromium-nickel alloys irradiated with 3.2MeV protons. A single set of ordering energies, an attractive potential between nickel and chromium and a repulsive potential between nickel and iron are used for each alloy. Calculations that do not include ordering overpredict the chromium depletion by up to 4 at% in iron-base alloys and 8 at% in nickel-base alloys. Calculations that include the ordering reduce the difference between model predicted and measured chromium concentrations to less than 2 at% for most iron- and nickel-base alloys.
Download or read book Effects of Radiation on Materials written by R. K. Nanstad and published by ASTM International. This book was released on 1999 with total page 1135 pages. Available in PDF, EPUB and Kindle. Book excerpt:
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 The Correlation Between Swelling and Radiation Induced Segregation in Iron Chromium Nickel Alloys written by GS. Was and published by . This book was released on 2000 with total page 17 pages. Available in PDF, EPUB and Kindle. Book excerpt: The magnitudes of both void swelling and radiation-induced segregation (RIS) in austenitic iron-chromium-nickel alloys are dependent on bulk alloy composition. In this work, the resistance to swelling from major element segregation is estimated and alloys with greater nickel enrichment and fast-developing segregation profiles are shown to be less prone to swelling. In austenitic iron-chromium-nickel alloys, the total swelling depends on the duration of the transient swelling period that precedes steady-state swelling. A longer transient swelling period leads to less overall swelling for the same irradiation dose. The duration of this transient period depends on the void nucleation rate which is determined directly by the average vacancy diffusivity and indirectly by the magnitude of the segregation to the void surface. Alloys with faster vacancy diffusion have a slower void nucleation rate, a longer transient swelling period, and less swelling. Radiation-induced segregation affects swelling by decreasing the vacancy flux to the void. Because the diffusivity of nickel via the vacancy flux is slow relative to chromium, nickel enriches and chromium depletes at void surfaces during irradiation in all austenitic iron-chromium-nickel alloys. This local composition change reduces the subsequent vacancy flux to the voids, increasing the bulk point defect recombination rate, reducing the bulk vacancy concentration, which further reduces the nucleation rate and swelling. Alloys that display the greatest amount of nickel enrichment and chromium depletion are found to be most resistant to void swelling, as predicted from both void nucleation and void growth considerations.
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 Energy Research Abstracts written by and published by . This book was released on 1990 with total page 852 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Effect of Radiation Induced Segregation on Precipitate Stability and Swelling in Irradiated Alloys written by VA. Pechenkin and published by . This book was released on 1999 with total page 16 pages. Available in PDF, EPUB and Kindle. Book excerpt: The radiation-induced segregation of alloy components near point defect sinks with a particular attention to Fe-Cr-Ni based alloys is analyzed. The influence of point defect generation rate on temperature ranges of stability for radiation-retarded M23C6 and radiation-induced Ni3Si precipitates in austenitic stainless steels is considered. A method of calculation of steady-state segregation-induced bias in irradiated binary alloys, taking into account Kirkendall forces and drift forces caused by point defect migration and formation energy gradients near sinks, is proposed. Contributions of various forces to the bias in Fe-Cr-Ni and V-Fe alloys are evaluated. The effect of void-precipitate association on swelling is analyzed. The radiation-induced segregation of components and segregation-induced bias for motionless and moving grain boundaries in a Fe-Cr-Ni alloy are calculated by solving the set of coupled diffusion equations for component and point defect concentrations.
Download or read book The Influence of Pre irradiation Heat Treatments on Thermal Non equilibrium and Radiation induced Segregation Behavior in Model Austenitic Stainless Steel Alloys written by and published by . This book was released on 2002 with total page 5 pages. Available in PDF, EPUB and Kindle. Book excerpt: The effect of pre-irradiation heat treatments on thermal non-equilibrium grain boundary segregation (TNES) and subsequent radiation-induced grain boundary segregation (RIS) is studied in a series of model austenitic stainless steels. The alloys used for this study are based on AISI 316 stainless steel and have the following nominal compositions: Fe-16Cr-13Ni-1.25Mn (base 316), Fe-16Cr-13Ni-1.25Mn-2.0Mo (316 + Mo) and Fe-16Cr-13Ni-1.25Mn-2.0Mo-0.07P (316 + Mo + P). Samples were heat treated at temperatures ranging from 1100 to 1300 C and cooled at 4 different rates (salt brine quench, water quench, air cool and furnace cool) to evaluate the effect of annealing temperature and quench rate on TNES. The alloys were than processed with the treatment (temperature and cooling rate) that resulted in the maximum Cr enrichment. Alloys with and without the heat treatment to enrich the grain boundaries with Cr were characterized following irradiation to 1 dpa at 400 C with high-energy protons in order to understand the influence of alloying additions and pre-irradiation grain boundary chemistry on irradiation-induced elemental enrichment and depletion profiles. Various mechanistic models will be examined to explain the observed behavior.
Download or read book Chemical Abstracts written by and published by . This book was released on 2002 with total page 2726 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Radiation induced Segregation and the Relationship to Physical Properties in Irradiated Austenitic Alloys written by and published by . This book was released on 2002 with total page 12 pages. Available in PDF, EPUB and Kindle. Book excerpt: Radiation-induced changes in composition are studied because these changes can degrade failure of materials irradiated in nuclear reactors. In this work, the effect of alloy composition on radiation-induced segregation, hardening, and void swelling is presented. Five alloys, Fe-18Cr-8Ni, Fe-16Cr-13Ni, Fe-18Cr-40Ni, Fe-16Cr-13Ni+Mo, and Fe-16Cr-13Ni+Mo+P (all compositions in wt. %), were irradiated with 3.2 MeV protons at 400 C to a dose of 0.5 displacements per atom. The change in grain boundary composition was measured using field emission gun scanning transmission electron microscopy and the hardening was measured using Vickers indentation. Void swelling is calculated from the void size distribution measured using transmission electron microscopy. After irradiation, Cr depletes and Ni enriches at grain boundaries. Increasing bulk Ni concentration causes greater Cr depletion and Ni enrichment at grain boundaries. For alloys with 16 Cr, the addition of P reduces the Cr depletion and Ni enrichment. Hardening does not directly correlate with composition, but a framework for isolating the effect of hardening and segregation on cracking is suggested. The amount of void swelling in the irradiated material is shown to correspond inversely with segregation. Those alloys with greater segregation tend to swell less.
Download or read book The Correlation Between Swelling and Radiation induced Segregation in Iron chromium nickel Alloys written by and published by . This book was released on 1998 with total page 20 pages. Available in PDF, EPUB and Kindle. Book excerpt: The magnitudes of both void swelling and radiation-induced segregation (RIS) in iron-chromium-nickel alloys are dependent on bulk alloy composition. Because the diffusivity of nickel via the vacancy flux is slow relative to chromium, nickel enriches and chromium depletes at void surfaces during irradiation. This local composition change reduces the subsequent vacancy flux to the void, thereby reducing void swelling. In this work, the resistance to swelling from major element segregation is estimated using diffusivities derived from grain boundary segregation measurements in irradiated iron-chromium-nickel alloys. The resistance to void swelling in iron- and nickel-base alloys correlates with the segregation and both are functions of bulk alloy composition. Alloys that display the greatest amount of nickel enrichment and chromium depletion are found to be most resistant to void swelling, as predicted. Additionally, swelling is shown to be greater in alloys in which the RIS profiles are slow to develop.
Download or read book Microstructure Evolution During Irradiation Volume 439 written by Ian M. Robertson and published by . This book was released on 1997-06-25 with total page 770 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book from MRS discusses the evolution of a material's microstructure as a result of its interaction with energetic particles such as ions, neutrons or electrons. The book is inter-disciplinary and emphasizes all classes of materials including metals, intermetallic compounds, ceramics, polymers, superconductors, semiconductors and insulators. A strong focus is placed on experimental techniques for measuring and quantifying damage and microstructure changes, and on computer simulation techniques for predicting and understanding this phenomena. Topics include: ion-implantation damage in semiconductors; radiation damage in metals; radiation damage in ceramics; radiation effects in polymers and beam-induced effects.
Download or read book Fusion Energy Update written by and published by . This book was released on 1986 with total page 614 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book The Effect of Bulk Composition on Swelling and Radiation induced Segregation in Austenitic Alloys written by and published by . This book was released on 2000 with total page 5 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Radiation induced segregation in Fe Cr Ni alloys written by A. D. Marwick and published by . This book was released on 1983 with total page 14 pages. Available in PDF, EPUB and Kindle. Book excerpt:
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 Proceedings of the International Symposium on Environmental Degradation of Materials in Nuclear Power Systems Water Reactors written by and published by . This book was released on 1986 with total page 680 pages. Available in PDF, EPUB and Kindle. Book excerpt:
