Download or read book Comparison of Observed and Predicted Data on Radiation Induced Grain Boundary Phosphorus Segregation in VVER Type Steels written by AV. Nikolaeva and published by . This book was released on 2000 with total page 13 pages. Available in PDF, EPUB and Kindle. Book excerpt: The influence of impurity grain boundary segregation on mechanical properties of low-alloy Cr-Ni-Mo steels is discussed. Mechanisms of impurity and alloying effects on grain boundary embrittlement of low-alloy steels are considered. An approach for estimation of radiation enhanced grain boundary segregation kinetics is proposed. The approach takes into account the reduction of dislocation density (from 1x1014 to 1x1013 m-2) due to irradiation that was observed for low-alloy Cr-Ni-Mo steels. The influence of collision cascades on the radiation damage is also considered. Auger spectroscopy is used for grain boundary segregation detection. The contribution of grain boundary embrittlement to mechanical property degradation due to neutron irradiation is assessed.

Download or read book Radiation Induced Grain Boundary Segregation of Phosphorus in ASME SA533B Ferritic Pressure Vessel Steel written by D. Meade and published by . This book was released on 2000 with total page 16 pages. Available in PDF, EPUB and Kindle. Book excerpt: The segregation of phosphorus to grain boundaries is well known to cause embrittlement in a range of ferritic pressure vessel steels. Modelling of segregation is therefore useful in predicting the service life of pressure vessels, particularly in those pressure vessels used in nuclear reactor power generating plant where significant cost savings can be made. In this paper, predictions of the radiation induced grain boundary segregation of phosphorus in ASME SA533B pressure vessel steels are made using an analytical model for impurity segregation in dilute ternary alloys. The model takes into account equilibrium-type segregation, together with a newly adopted approach incorporating the site competition effects that exist between phosphorus and carbon. The site competition effect causes the predicted phosphorus segregation to fall to levels significantly lower than the predictions obtained from models of dilute binary alloys. The predictions are compared to FEGSTEM results of samples irradiated at between 255°C and 315°C, doses between 1.5 and 38mdpa and dose rates ranging from 6x10-9 to 8.9x10-11 dpa/s. The predictions obtained from the model are in close agreement to the experimentally observed segregated phosphorus results.

Download or read book Effects of Radiation on Materials written by Margaret L. Hamilton and published by ASTM International. This book was released on 2000 with total page 1266 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Effects of Radiation on Materials written by Todd R. Allen and published by ASTM International. This book was released on 2006 with total page 411 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Effects of Radiation on Materials written by and published by . This book was released on 2000 with total page 1296 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Radiation and Thermally Induced Phosphorus Inter Granular Segregation in Pressure Vessel Steels written by Z. Lu and published by . This book was released on 2005 with total page 15 pages. Available in PDF, EPUB and Kindle. Book excerpt: A survey of neutron- and thermally-induced phosphorus inter-granular segregation behavior in C-Mn welds, LWR plates, LWR HAZ materials, and VVER steels is described in this paper. The materials were irradiated up to doses of 0.13 dpa (fast neutron energy > 1 MeV), with dose rates ranging from 1.75 × 10−8 dpa/s to 10−12 dpa/s, at temperatures between 190°C and 400°C. Irradiation-induced P inter-granular segregation has been found in LWR and VVER materials at high doses (generally 10-130 mdpa) but is absent in all Magnox C-Mn submerged-arc welds at lower doses (1.5-13 mdpa). The dose sensitivity of the irradiation-induced P monolayer coverage depends on the material examined, being highest for VVER plates and weld, lower for the LWR materials, and zero for the C-Mn welds. There are high initial P segregations (arising from pre-heat-treatment) in C-Mn weld and LWR HAZ materials and low initial P segregation in LWR and VVER steels. Comparisons of the experimental data with model predictions are made. The amount of phosphorus segregation is shown via site competition models to be related to free carbon concentration. The model results show a good agreement with experimental measurements.

Download or read book The Effect of Molybdenum on the Grain Boundary Segregation of Chromium Exhibited by Austenitic Stainless Steels After Neutron Irradiation in a BWR written by JC. Walmsley and published by . This book was released on 2000 with total page 15 pages. Available in PDF, EPUB and Kindle. Book excerpt: Analytical investigations employing field-emission gun scanning transmission electron microscopy (FEGSTEM) have indicated that the degree of chromium depletion at grain boundaries is less pronounced in AISI type-316 when compared to type-304 stainless steel after neutron irradiation in Boiling Water Reactor (BWR) conditions to a fluence of 1026 n.m-2 (E > 1 MeV). An explanation of this observation is proposed, which is based on the non-equilibrium segregation (NES) theory of grain boundary segregation. NES model predictions for the radiation-induced segregation of chromium and molybdenum in an austenitic matrix are presented together for the first time. The predicted segregation profiles are compared with the FEGSTEM data, whilst the predicted trends as a function of neutron dose are discussed in terms of possible microstructural evolution in a BWR environment. In particular it will be demonstrated how, according to NES theory, the binding of molybdenum to self-interstitial atoms (SIAs) will take precedence over chromium. In turn, the subsequent migration of molybdenum-SIA "complexes" retard the migration of chromium away from the grain boundary, thus moderating the magnitude of radiation-induced chromium depletion.

Download or read book The Modeling of Radiation Induced Phosphorus Segregation at Point Defect Sinks in Dilute Fe P Alloys written by IA. Stepanov and published by . This book was released on 2004 with total page 11 pages. Available in PDF, EPUB and Kindle. Book excerpt: Both the intergranular and intragranular segregation of phosphorus may significantly contribute to irradiation embrittlement of reactor pressure vessel steels. The modeling of phosphorus radiation-induced segregation at cylindrical (dislocations), spherical (precipitates and voids) and flat (sample surfaces, grain boundaries) point defect sinks has been carried out in order to compare the kinetics and extent of segregation at various point defect sinks. Dilute Fe-P alloys relevant to model and VVER-440 pressure vessel steels were considered.

Download or read book Solute Segregation and Void Formation on Grain Boundaries in Electron Irradiated Type 316 Stainless Steel written by S. Ohnuki and published by . This book was released on 1985 with total page 11 pages. Available in PDF, EPUB and Kindle. Book excerpt: Radiation-induced segregation and void formation on grain boundaries in titanium-modified Type 316 stainless steel were investigated by electron irradiation and X-ray microanalysis (EDX). Strong enrichment and depletion of solutes were observed on grain boundaries during irradiation. Moreover, preferential void formation on grain boundaries occurred and grain boundary migration was induced by the irradiation. These facts indicate that grain boundaries act as preferential sinks for radiation-induced point defects, and the sink behavior may be changed by the development of the segregation under irradiation.

Download or read book Chemical Abstracts written by and published by . This book was released on 2002 with total page 2540 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Radiation induced Grain Boundary Segregation in Austenitic Stainless Steels written by and published by . This book was released on 1994 with total page 12 pages. Available in PDF, EPUB and Kindle. Book excerpt: Radiation-induced segregation (RIS) to grain boundaries in Fe-Ni-Cr-Si stainless alloys has been measured as a function of irradiation temperature and dose. Heavy-ion irradiation was used to produce damage levels from 1 to 20 displacements per atom (dpa) at temperatures from 175 to 550°C. Measured Fe, Ni, and Cr segregation increased sharply with irradiation dose (from G to 5 dpa) and temperature (from 175 to about 350°C). However, grain boundary concentrations did not change significantly as dose or temperatures were further increased. Although interfacial compositions were similar, the width of radiation-induced enrichment or depletion profiles increased consistently with increasing dose or temperature. Impurity segregation (Si and P) was also measured, but only Si enrichment appeared to be radiation-induced. Grain boundary Si peaked at levels approaching 10 at% after irradiation doses to 10 dpa at an intermediate temperature of 325°C. No evidence of grain boundary silicide precipitation was detected after irradiation at any temperature. Equilibrium segregation of P was measured in the high-P alloys, but interfacial concentration did not increase with irradiation exposure. Comparisons to reported RIS in neutron-irradiated stainless steels revealed similar grain boundary compositional changes for both major alloying and impurity elements.

Download or read book Grain Boundary Phosphorus Segregation Under Irradiation and Thermal Aging and Its Effect on the Ductile to Brittle Transition written by S. Song and published by . This book was released on 2001 with total page 15 pages. Available in PDF, EPUB and Kindle. Book excerpt: Embrittlement of low-alloy steel components used in the nuclear power industry is classified into hardening embrittlement and non-hardening embrittlement. Hardening embrittlement stems from precipitation of carbides or copper-rich compounds. Non-hardening embrittlement results mainly from grain boundary segregation of phosphorus. To examine the non-hardening embrittlement in 2.25Cr 1Mo steel, phosphorus intergranular segregation in samples subjected to neutron irradiation and thermal aging at 270°C and 400°C is determined by modelling and transmission electron microscopy. The ductile-to-brittle transition temperature for the steel is determined by means of small punch testing with 3 mm diameter disc specimens. It is indicated that there is a reasonable agreement between the behavior of intergranular phosphorus segregation and shifts in the ductile-to-brittle transition temperature. Measured and predicted phosphorus intergranular segregation in a range of pressure vessel steels is also discussed.

Download or read book Measurement and Modeling of Radiation induced Grain Boundary Grain Boundary Segregation in Stainless Steels written by and published by . This book was released on 1995 with total page 20 pages. Available in PDF, EPUB and Kindle. Book excerpt: Grain boundary radiation-induced segregation (RIS) in Fe-Ni-Cr stainless alloys has been measured and modelled as a function of irradiation temperature and dose. Heavy-ion irradiation was used to produce damage levels from 1 to 20 displacements per atom (dpa) at temperatures from 175 to 550°C. Measured Fe, Ni, and Cr segregation increased sharply with irradiation dose (from 0 to 5 dpa) and temperature (from 175 to about 350°C). However, grain boundary concentrations did not change significantly as dose or temperatures were further increased. Impurity segregation (Si and P) was also measured, but only Si enrichment appeared to be radiation-induced. Grain boundary Si levels peaked at an intermediate temperature of (approximately)325°C reaching levels of (approximately)8 at. %. Equilibrium segregation of P was measured in the high-P alloys, but interfacial concentration did not increase with irradiation exposure. Examination of reported RIS in neutron-irradiated stainless steels revealed similar effects of irradiation dose on grain boundary compositional changes for both major alloying and impurity element's. The Inverse Kirkendall model accurately predicted major alloying element RIS in ion- and neutron-irradiated alloys over the wide range of temperature and dose conditions. In addition, preliminary calculations indicate that the Johnson-Lam model can reasonably estimate grain boundary Si enrichment if back diffusion is enhanced.

Download or read book The Effect of Heat Treatment on Phosphorus Segregation in a Submerged Arc Weld Metal written by WB. Beere and published by . This book was released on 1999 with total page 14 pages. Available in PDF, EPUB and Kindle. Book excerpt: Intergranular fracture (IGF) has been observed in carbon-manganese steels after irradiation or high temperature exposure for prolonged periods. The effect is associated with an increase in the ductile-brittle transition temperature and has been related to phosphorus diffusion to grain boundaries. Phosphorus also diffuses thermally at the temperatures used for post-weld heat treatments such that in principle, the slightly different heat treatments given to different parts of a large vessel could lead to differing grain boundary phosphorus coverage and hence susceptibility to IGF. The effect of typical heat treatments on phosphorus coverage has been investigated using a finite difference model based on a theory that has been fitted to a wide range of constant temperature data. Regardless of previous history, the grain boundary coverage of phosphorus was predicted to depend on the final anneal and cooling rate. These differed insufficiently in the typical heat treatments to produce significant differences in segregation. It was concluded that the ductile-brittle transition temperature in submerged-arc welds would be unaffected in vessels that had seen typical post-weld heat treatments.

Download or read book Measurement and Modeling of Radiation induced Grain Boundary Segregation in Stainless Steels written by 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 Temper Embrittlement Irradiation Induced Phosphorus Segregation and Implications for Post Irradiation Annealing of Reactor Pressure Vessels written by CA. English and published by . This book was released on 1999 with total page 21 pages. Available in PDF, EPUB and Kindle. Book excerpt: Three steels designated JPB, JPC and JPG from the IAEA Phase 3 Programme containing two copper and phosphorus levels were pre- and post-irradiation Charpy and hardness tested in the as-received (AR), 1200°C/0.5h heat treated (HT) and heat treated and 450°C/2000h aged (HTA) conditions. The HT condition, was designed to simulate coarse grained heat-affected zones (HAZ's) and showed a marked sensitivity to thermal ageing in all three alloys. Embrittlement after thermal ageing was greater in the higher phosphorus alloys JPB and JPG. Charpy shifts due to thermal ageing of between 118 and 209°C were observed and accompanied by pronounced intergranular fracture, due to phosphorus segregation. The irradiation embrittlement response was complex. The low copper alloys, JPC and JPB, in the HT and HTA condition exhibited significant irradiation induced Charpy shift but very low or even negative hardness changes indicating non-hardening embrittlement. The higher copper alloy, JPG, also exhibited irradiation hardening in line with its copper content. Fractographic and microchemical studies indicated irradiation induced phosphorus segregation and a transition from cleavage to intergranular failure at grain boundary phosphorus concentrations above a critical level. The enhanced grain boundary phosphorus level increased with dose in agreement with a kinetic segregation model developed at Harwell.

Download or read book Grain Boundary Phosphorus Segregation Under Neutron Irradiation and Aging in 2 25Cr1Mo Steel written by M. Victoria and published by . This book was released on 2000 with total page 11 pages. Available in PDF, EPUB and Kindle. Book excerpt: Impurity segregation to grain boundaries under irradiation is one of the important radiation effects on materials. For this reason, phosphorus segregation to prior austenite grain boundaries in a P-doped 2.25Cr1Mo steel subjected to neutron irradiation and aging is examined using field emission gun scanning transmission electron microscopy (FEGSTEM) with energy dispersive X-ray microanalysis (EDX). The steel samples are irradiated and aged around 270 °C and 400 °C, respectively. The irradiation dose rate and dose are $∼1.05×10-8 dpa/s and $∼0.042 dpa respectively for 270 °C irradiation, and $∼1.75×10-8 dpa/s and $∼0.13 dpa respectively for 400 °C irradiation. The FEGSTEM results indicate that there is no apparent phosphorus segregation during 270 °C irradiation but there is some during 400 °C irradiation.