Download or read book Thermodynamic and Kinetic Modeling of Evolution of Mn Ni Si rich Precipitates in Low Cu Reactor Pressure Vessel Steels written by Huibin Ke and published by . This book was released on 2017 with total page 108 pages. Available in PDF, EPUB and Kindle. Book excerpt: Formation of large volume fractions of Mn-Ni-Si precipitates (MNSPs) causes excess irradiation embrittlement of reactor pressure vessel (RPV) steels at high, extended-life fluences. Thus, a new and unique, semi-empirical cluster dynamics model was developed to study the evolution of MNSPs in low-Cu RPV steels. The model has been developed based on experimental data under irradiation conditions and validated against data on post-irradiation annealing conditions. The model is based on CALPHAD thermodynamics and radiation enhanced diffusion kinetics. The thermodynamics dictates the compositional and temperature dependence of the free energy reductions that drive precipitation. The model treats both homogeneous and heterogeneous nucleation, where the latter occurs on cascade damage, like dislocation loops. The model has only four adjustable parameters that were fit to an atom probe tomography (APT) database. The model predictions are in semi-quantitative agreement with systematic Mn, Ni and Si composition variations in the alloys characterized by APT, including a sensitivity to local tip-to-tip variations even in the same steel. The model predicts that heterogeneous nucleation plays a critical role in MNSP formation in lower alloy Ni contents. Single variable assessments of compositional effects show that Ni plays a dominant role, while even small variations in irradiation temperature can have a large effect on the MNSP evolution. Within typical RPV steel ranges, Mn and Si have smaller effects. The delayed but then rapid growth of MNSPs to large volume fractions at high fluence is well predicted by the model. For purposes of illustration, rather than prediction, the effect of MNSPs on transition temperature shifts are presented based on well-established microstructure-property and property-property models. Solubility of Fe in MNSPs is also investigated with ab initio method and is found that the solubility of Fe is less than 1.0% in G-phase formed in typical RPV steels.
Download or read book Modeling of Late Blooming Phases and Precipitation Kinetics in Aging Reactor Pressure Vessel RPV Steels written by and published by . This book was released on 2013 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: The principle work at the atomic scale is to develop a predictive quantitative model for the microstructure evolution of RPV steels under thermal aging and neutron radiation. We have developed an AKMC method for the precipitation kinetics in bcc-Fe, with Cu, Ni, Mn and Si being the alloying elements. In addition, we used MD simulations to provide input parameters (if not available in literature). MMC simulations were also carried out to explore the possible segregation/precipitation morphologies at the lattice defects. First we briefly describe each of the simulation algorithms, then will present our results.
Download or read book The Character Stability and Consequences of Mn Ni Si Precipitates in Irradiated Reactor Pressure Vessel Steels written by Peter Benjamin Wells and published by . This book was released on 2016 with total page 221 pages. Available in PDF, EPUB and Kindle. Book excerpt: Finally, the large fv of MNSPs that are shown to form in all steels, including those low in Cu, at high fluence, even those without added Cu, result in large amounts of hardening and embrittlement. A preliminary embrittlement prediction model, which incorporates MNSPs at high fluence, is presented, along with results from a recent test reactor irradiation to fluences representative of extended lifetimes. This model shows very good agreement with the data.
Download or read book Metals Abstracts written by and published by . This book was released on 1999 with total page 1014 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Effects of Neutron Irradiation on Precipitation in Reactor Pressure Vessel Steels written by RG. Faulkner and published by . This book was released on 2005 with total page 15 pages. Available in PDF, EPUB and Kindle. Book excerpt: Several MnMoNi pressure vessel steels with varying Ni, Cu, and Mo contents have been investigated in the irradiated and unirradiated condition. Examination using analytical transmission electron microscopy was performed in order to understand more fully the nature of both the inter- and intra-granular precipitation in these alloys. In particular, attention has been paid to the carbide population, which exists in the material in addition to the copper precipitates, which have received detailed study elsewhere. The most dramatic revelations concern the discovery that fine, intra-granular (10 nm diameter) Fe3C particles are present in these steels, in addition to the normally expected copper-rich precipitates of a similar size. Neutron irradiation increases the volume fractions of inter- and intra-granular precipitation of all phases (Fe3C, Cu-rich, and Mo2C). Neutron irradiation has the least effect in increasing volume fraction in high Ni; high Cu alloys (WV). The effects of neutron irradiation on precipitation rates are greatest in low Ni; high Cu alloys (SG (SH)). Inter-granular precipitation is most prevalent in the high Ni; low Cu material (WF). It is significant that this material contains the least intra-granular fine-scale precipitation. This is probably because the Cu precipitation is minimal. Mo and C have an important influence on the amount of Mo2C phase formed, with large amounts being observed in high Mo-C, irradiated material (SH) (0.48 % Mo). These results are discussed in terms of various models for inter-and intra-granular precipitate nucleation and growth.
Download or read book Effects of Nickel on Irradiation Embrittlement of Light Water Reactor Pressure Vessel Steels written by International Atomic Energy Agency and published by IAEA. This book was released on 2005 with total page 70 pages. Available in PDF, EPUB and Kindle. Book excerpt: This publication sets out the findings of a co-ordinated research project to determine the influence of the mechanism of the deterioration effect in radiation embrittlement of reactor pressure vessel steels with a high nickel content in nuclear power plants, including procurement of materials, determination of mechanical properties, irradiation and testing of specimens, and microstructural characterisation.
Download or read book Structural Characterization of Nanoscale Intermetallic Precipitates in Highly Neutron Irradiated Reactor Pressure Vessel Steels written by and published by . This book was released on 2015 with total page 5 pages. Available in PDF, EPUB and Kindle. Book excerpt: Here, massive, thick-walled pressure vessels are permanent nuclear reactor structures that are exposed to a damaging flux of neutrons from the adjacent core. The neutrons cause embrittlement of the vessel steel that increases with dose (fluence or service time), as manifested by an increasing temperature transition from ductile-to-brittle fracture. Moreover, extending reactor life requires demonstrating that large safety margins against brittle fracture are maintained at the higher neutron fluence associated with 60 to 80 years of service. Here synchrotron-based x-ray diffraction and small angle x-ray scattering measurements are used to characterize a new class of highly embrittling nm-scale Mn-Ni-Si precipitates that develop in the irradiated steels at high fluence. Furthermore, these precipitates can lead to severe embrittlement that is not accounted for in current regulatory models. Application of the complementarity techniques has, for the very first time, successfully characterized the crystal structures of the nanoprecipitates, while also yielding self-consistent compositions, volume fractions and size distributions.
Download or read book Small Angle Neutron Scattering Modeling of Copper rich Precipitates in Steel written by and published by . This book was released on 1997 with total page 8 pages. Available in PDF, EPUB and Kindle. Book excerpt: The magnetic to nuclear scattering intensity ratio observed in the scattering from copper rich precipitates in irradiated pressure vessel steels is much smaller than the value of 11.4 expected for a pure copper precipitate in iron. A model for precipitates in pressure vessel steels which matches the observed scattering typically incorporates manganese, nickel, silicon and other elements and it is assumed that the precipitate is non-magnetic. In the present work consideration is given to the effect of composition gradients and ferromagnetic penetration into the precipitate on the small angle scattering cross section for copper rich clusters as distinguished from conventional precipitates. The calculation is an extension of a scattering model for micelles which consist of shells of varying scattering density. A discrepancy between recent SANS scattering experiments on pressure vessel steels was found to be related to applied magnetic field strength. The assumption of cluster structure and its relation to atom probe FIM findings as well as the effects of insufficient field for magnetic saturation is discussed.
Download or read book Contributions to the Data on Theoretical Metallurgy written by Alla D. Mah and published by . This book was released on 1976 with total page 136 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Long term Irradiation Effects on Reactor pressure Vessel Steels written by Arne Wagner and published by . This book was released on 2017* with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Small-Angle Neutron Scattering (SANS); Atom-Probe Tomography (APT); Long-Term Irradiation Effects; Low-Cu Reactor-Pressure Vessel Steel (RPV); Neutrons; Flux Effects; Late-Blooming Effect; Mn-Ni-Enriched Clusters
Download or read book Irradiation Embrittlement of Reactor Pressure Vessel Steels written by GE. Lucas and published by . This book was released on 1986 with total page 36 pages. Available in PDF, EPUB and Kindle. Book excerpt: A model of irradiation embrittlement is described for predicting the 41-J Charpy V-notch temperature shifts (?T) as a function of metallurgical variables and neutron exposure conditions. This forecasting procedure combines semi-empirical physical models with statistical analyses of test and power reactor data, and calibration against data from fundamental experiments in which both mechanical property and microstructural changes are evaluated. The models are based on the evolution of a damage microstructure, which includes both copper precipitates and a radiation damage component enhanced by nickel. The precipitate volume is also increased by nickel and impurity phosphorus. Predicted hardening and shifts associated with these extended defects are based on empirically validated models. The model is able to self-consistently rationalize a wide array of microstructural and mechanical property data for commercial pressure vessel steels as well as model alloys.
Download or read book A Study of the Evolution of Precipitates in Pressure Vessel Steels Using Small Angle Neutron Scattering written by Jeffry Alan Fint and published by . This book was released on 1990 with total page 278 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Morphological Evolution and Kinetics of Precipitation of gamma Ni3Al Precipitates at Low Volume Fractions in Dilute Ni Al Alloys written by Abhay Maheshwari and published by . This book was released on 1993 with total page 164 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book First Principles based Thermokinetic Modeling of Steels and Ni Alloys for Nuclear Applications written by and published by . This book was released on 2013 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: The objective of this dissertation was to develop multiscale modeling frameworks for describing modes of thermal and radiation-induced degradation in steels and Ni alloys for nuclear applications. The development of these models was performed according to the following general method: first, electronic structure calculations were performed to obtain key atomistic energies and insights. These calculations then formed a foundation for atomistic simulations and continuum level models used to describe microstructural processes of interest. The results of these models were compared to experimental measurements, and used to identify the fundamental mechanisms underlying the observed material phenomena. This approach was applied to three distinct topics. The first is the theory and prediction of radiation induced segregation in the Ni-Cr and Fe-Cr systems. In this subproject, the modeling effort yielded an important new understanding of the role of interstitial diffusion in radiation induced segregation. The effects of defect annihilation kinetics at grain boundaries were also examined. The second topic was the kinetics of the disorder-order phase transformation in Ni-Cr alloys. This project resulted in a physics-based model for describing the phase transformation that shows good agreement with both atomistic simulations and experimental measurements. The predictions of this model indicate that this phase transformation may be of serious concern in Ni-Cr alloys near the Ni2Cr stoichiometry during very long service lifetimes. Finally, the third topic was the evolution of oxide nanoprecipitates in nanostructured ferritic alloys. The key results of this effort were a better understanding of nanoprecipitate coarsening mechanisms and the effects of alloy composition on nanoprecipitate size distribution. The predictions of this model also indicate that the nanoprecipitates in nanostructured ferritic alloys should be thermally stable for as long as 80 years at proposed operating temperatures. In all three projects the first principles-based foundation provided by the electronic structure calculations allowed the resulting models to go beyond empirical fitting, and to provide understanding of the mechanisms underlying the microstructural processes of interest.
Download or read book Improved Embrittlement Correlations for Reactor Pressure Vessel Steels written by E. D. Eason and published by . This book was released on 1998-11-01 with total page 127 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Integrity of Reactor Pressure Vessels in Nuclear Power Plants written by and published by . This book was released on 2009 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: This publication is intended to assist nuclear utilities in optimizing the service life of nuclear power plants. It reviews the latest research on the effects of neutron irradiation on the steels and welds of reactor pressure vessels within light water cooled and moderated reactors.
Download or read book Manufacturing and Application of Stainless Steels written by Andrea Di Schino and published by MDPI. This book was released on 2020-04-15 with total page 260 pages. Available in PDF, EPUB and Kindle. Book excerpt: Stainless steels represent a quite interesting material family, both from a scientific and commercial point of view, following to their excellent combination in terms of strength and ductility together with corrosion resistance. Thanks to such properties, stainless steels have been indispensable for the technological progress during the last century and their annual consumption increased faster than other materials. They find application in all these fields requiring good corrosion resistance together with ability to be worked into complex geometries. Despite to their diffusion as a consolidated materials, many research fields are active regarding the possibility to increase stainless steels mechanical properties and corrosion resistance by grain refinement or by alloying by interstitial elements. At the same time innovations are coming from the manufacturing process of such a family of materials, also including the possibility to manufacture them starting from metals powder for 3D printing. The Special Issue scope embraces interdisciplinary work covering physical metallurgy and processes, reporting about experimental and theoretical progress concerning microstructural evolution during processing, microstructure-properties relations, applications including automotive, energy and structural.
