Download or read book MICROSTRUCTURAL EVOLUTION OF MARTENSITIC STEELS DURING FAST NEUTRON IRASIATION written by P.J. MAZIASZ. and published by . This book was released on 1989 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Microstructural Evolution of Martensitic Steels During Fast Neutron Iradiation written by and published by . This book was released on 1989 with total page 6 pages. Available in PDF, EPUB and Kindle. Book excerpt: Irradiation of martensitic/ferritic steels with fast neutrons (E> 0.1 MeV) to displacement damage levels of 30--50 dpa at temperatures of 300--500°C produces significant changes in the as-tempered microstructure. Dislocation loops and networks can be produced, irradiation-induced precipitates can form, the lath/subgrain boundary structure and the thermal precipitates produced during tempering can become unstable, and if helium is present, bubbles and voids can form. These microstructural changes caused by irradiation can have important effects on the properties of this class of steels for both fast breeder reactor (FBR) and magnetic fusion reactor (MFR) applications. The purpose of this paper is to compare reactor-irradiated and long-term thermally aged 9Cr--1MoVNb specimens, in order to distinguish effects due to displacement damage from those caused by elevated-temperature exposure alone. 7 refs., 1 fig.

Download or read book Small Angle Neutron Scattering Study of Irradiated Martensitic Steels written by M-H Mathon and published by . This book was released on 2005 with total page 15 pages. Available in PDF, EPUB and Kindle. Book excerpt: Martensitic/ferritic steels (containing 7-13 % Cr) are candidate materials for internal structures in pressurized water, fast breeder, and fusion reactors. Approval for use requires verification of structural stability under neutron irradiation in relation to the evolution of mechanical properties. In this context, several conventional and Reduced Activation (RA) martensitic materials were neutron irradiated at 325°C up to 6 dpa. They were investigated by Small Angle Neutron Scattering (SANS) under a magnetic field after various doses.

Download or read book Microstructural Evolution of Reduced Activation and Conventional Martensitic Steels After Thermal Aging and Neutron Irradiation written by M-H Mathon and published by . This book was released on 2001 with total page 20 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Response of Ferritic Martensitic Steels to Neutrons at Irradiation Temperatures from 20 to 823 K written by Hideki Matsui and published by . This book was released on 1990 with total page 18 pages. Available in PDF, EPUB and Kindle. Book excerpt: The objectives of this work are to evaluate mechanical property changes by means of small specimen testing techniques, to evaluate the influence of the cascade damage produced by 14-MeV neutrons from RTNS-II on microstructural evolution, and to understand mechanical property changes in term of microstructural evolution at irradiation temperatures of from 20 to 823 K.

Download or read book Microstructural Evolution in a Ferritic martensitic Stainless Steel and Its Relation to High temperature Deformation and Rupture Models written by and published by . This book was released on 1991 with total page 19 pages. Available in PDF, EPUB and Kindle. Book excerpt: The ferritic-martensitic stainless steel HT-9 exhibits an anomalously high creep strength in comparison to its high-temperature flow strength from tensile tests performed at moderate rates. A constitutive relation describing its high-temperature tensile behavior over a wide range of conditions has been developed. When applied to creep conditions the model predicts deformation rates orders of magnitude higher than observed. To account for the observed creep strength, a fine distribution of precipitates is postulated to evolve over time during creep. The precipitate density is calculated at each temperature and stress to give the observed creep rate. The apparent precipitation kinetics thereby extracted from this analysis is used in a model for the rupture-time kinetics that compares favorably with observation. Properly austenitized and tempered material was aged over times comparable to creep conditions, and in a way consistent with the precipitation kinetics from the model. Microstructural observations support the postulates and results of the model system. 16 refs., 10 figs.

Download or read book Influence of Minor Alloying Elements and Stress on Microstructural Evolution and Void Swelling of Austenitic Steels Under Neutron Irradiation written by R. Hübner and published by . This book was released on 2000 with total page 14 pages. Available in PDF, EPUB and Kindle. Book excerpt: A pressurized tube experiment was carried out in the British Prototype Fast Reactor (PFR) at Dounreay, U.K. in order to determine swelling and stress-induced swelling of four heats of the commercial German austenitic steel DIN 1.4970, with different contents of the minor alloying elements Si, Ti and Ti/C ratio. The maximum doses achieved are 106 dpaNRT at 420°C, 81 dpaNRT at 500°C and 61 dpaNRT at 600°C. The hoop stresses of the pressurized tubes were 0, 60 and 120 MPa at all irradiation temperatures. TEM-examinations have been carried out to determine the influence of the minor alloying elements and the stress on the void swelling and the microstructural evolution. All alloys exhibited the highest swelling values at 420°C and no swelling at 600°C. The measurements show the large effect of the minor alloying elements upon swelling and in-pile creep. The maximum swelling suppression is achieved by a high Si-content and an understoichiometric Ti/C ratio (understabilization). The analysis of the microstructural evolution shows that the swelling resistance is correlated to the formation and stability of very fine ?'-precipitates. For the alloy with the highest swelling resistance these precipitates can be found up to 106 dpaNRT at 420°C, whereas they dissolve in the course of irradiation for the alloys with lower swelling resistance.

Download or read book Evolution of Microstructure during Long term Creep of a Tempered Martensite Ferritic Steel written by Ali Aghajani Bazazi and published by Cuvillier Verlag. This book was released on 2009-12-08 with total page 118 pages. Available in PDF, EPUB and Kindle. Book excerpt: Tempered martensite ferritic steels are used for critical components in fossil fired power plants that operate in the creep range. The materials contain a high density of dislocations and precipitates form on all types of internal interfaces, the majority of which represent subgrain boundaries. Most previous studies suffer from either only relating to short term creep experiments or from being incomplete in not considering all relevant elements of the microstructure. No systematic effort was made to investigate the evolution of microstructures under conditions of long term creep. In the present study the evolution of the microstructure of a 12% Cr tempered martensite ferritic steel was investigated under conditions of long term aging and creep. Transmission electron microscopy (TEM) and electron back scattered diffraction (EBSD) techniques were used to characterize materials from interrupted creep tests (0.5%, 1%, 1.6% and rupture at 11.9%; creep conditions: 550°C, 120 MPa, rupture time: 139 971 h). It is shown that subgrains coarsen, that the close correlation between carbides and subgrain boundaries loosens during long term creep, and that the frequency of small angle boundaries increases. In addition, the evolution of dislocation densities during long term aging and creep was studied using high angle annular dark field (HAADF) scanning transmission electron microscopy (STEM). During aging the dislocation density remains constant, while during long term creep the dislocation density continuously decreases. All these elementary deformation processes have already been discussed in short term creep studies. The present study shows that they also govern long term creep, however, during long term creep, precipitation and coarsening reactions occur which are not observed during short term creep. Cr rich M23C6, VX carbides and Laves phase were identified as the major precipitates in the microstructure of the 12% Chromium tempered martensite ferritic steel. Their chemical compositions, sizes, volume fractions and number densities were evaluated in all interrupted specimens. M23C6 particles coarsen and establish their equilibrium concentration after 51072 hours. VX particles are stable. The Laves phase particles do not reach thermodynamic equilibrium as they form and grow during long term creep. This is due to Silicon which is found in the Laves phase particles and which diffuses slowly in the steel matrix.

Download or read book Microstructural Effects of Neutron Irradiation on Ferritic martensitic Stainless Steels written by Terence Stuart Morgan and published by . This book was released on 1992 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Microstructural Evolution During the Dynamic Deformation of High Strength Navy Steels written by and published by . This book was released on 2008 with total page 36 pages. Available in PDF, EPUB and Kindle. Book excerpt: We have characterized the propensity for adiabatic shear band formation (an associated microstructural evolution) under dynamic deformation conditions in an ultra-high strength (160 Ksi/I 1.1GPa) Fe-10 Ni-0.lC-Cr, Mo, V steel and demonstrated that this steel is highly prone to shear localization and failure. In the as-received condition, the steel has a lath martensite microstructure. During dynamic deformation, shear localization occurs and manifests by an optically visible shear band; the original microstructure is discemible within the band. With progression in severity of localization, there is evidence for a central region within the shear band composed of approx. 300 nm size equiaxed grains constituting austenite, with a low dislocation content, and heavily twinned ferrite. In the extreme situation, a crack "chases" the shear band, and examination of the resulting fracture surfaces provides evidence for the presence of a thin liquid film layer. We have also observed that lowering the Ni content in the alloy significantly and adding Cu to the alloy, enables improvements in resistance to shear localization, both in terms of initiation and propagation of the shear band.

Download or read book Official Communiqu of the 4821st closed Meeting of the Security Council Held in Private at Headquarters New York on Tuesday 9 September 2003 written by and published by . This book was released on 2003 with total page 1 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Microstructural Evolution of NF709 20Cr 25Ni 1 5MoNbTiN Under Neutron Irradiation written by and published by . This book was released on 2015 with total page 7 pages. Available in PDF, EPUB and Kindle. Book excerpt: In this study, because of its superior creep and corrosion resistance as compared with general austenitic stainless steels, NF709 has emerged as a candidate structural material for advanced nuclear reactors. To obtain fundamental information about the radiation resistance of this material, this study examined the microstructural evolution of NF709 subjected to neutron irradiation to 3 displacements per atom at 500 °C. Transmission electron microscopy, scanning electron microscopy, and high-energy x-ray diffraction were employed to characterize radiation-induced segregation, Frank loops, voids, as well as the formation and reduction of precipitates. Radiation hardening of ~76% was estimated by nanoindentation, approximately consistent with the calculation according to the dispersed barrier-hardening model, suggesting Frank loops as the primary hardening source.

Download or read book Void Swelling and Microstructural Change in Neutron Irradiated Type 316 Stainless Steel written by M. Itoh and published by . This book was released on 1987 with total page 13 pages. Available in PDF, EPUB and Kindle. Book excerpt: Microstructural observations were made on cold-worked Type 316 stainless steel following fast neutron irradiation to a peak neutron fluence of 1.3 x 1027 n/m2 (E > 0.1 MeV) at temperatures from 400 to 620°C. The results show that nickel depletion in the matrix after neutron irradiation is related to the formation of phosphides and void swelling. Phosphorus in solution retards not only the recovery of dislocations but also the development of nickel- and silicon-rich phases, and this results in suppressing nickel depletion in the matrix and an extension of the transient regime in void swelling. Phosphides are formed during the transient regime at temperatures from 490 to 570°C. After phosphides are formed, retardation effects on both dislocation recovery and the formation of nickel- and silicon-rich phases are lost, and this leads to the onset of void swelling.