Influence of Neutron Irradiation on Dislocation Structure and Phase Composition of Zr-Base Alloys PDF Download
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Author: VN. Shishov
Publisher:
ISBN:
Category : Composition
Languages : en
Pages : 20
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Book Description
Studied were evolution of dislocation structure, phase, and element composition of binary alloys Zr-1Nb and Zr-2.5Nb and multicomponent alloys Zr-1Nb-1.2Sn-0.4Fe and Zr-1.2Sn-0.4Fe under neutron irradiation. The investigations were carried out using cladding and pressure tubes before and after irradiation to a fluence of ~1026 n/m2 (E >= 0.1 MeV) in experimental and commercial reactors at 300 to 350°C using TEM, EDX, and XRD. In most cases, irradiation-induced defects are in the form of dislocation loops with Burgers vector 1/3 ?1120?. The density of dislocations with a ?c? component is less than 2 x 1014 m-2. A higher fluence or the presence of strain results in the ordering of the dislocation structure of ?c? component and ?a?-type dislocation loops. Before irradiation, the multicomponent alloys contain fine precipitates of Zr-Nb-Fe composition, and the matrix is depleted in Fe. Under irradiation, recrystallization proceeds intensively (as distinct from Zr-Nb alloys), changes take place in size, distribution, and composition of precipitates (with a relative decrease of Fe content compared to Nb), and the Fecontent of ?-Zr matrix is increased. None of the materials studied showed any significant evidence of secondary phase particle amorphization. The density of dislocations with ?a? and ?c? components and irradiation-induced defects, their mean size, the extent of ordering, and the planes of their occurrence were determined. A comparison was made between irradiation-induced evolutions of microstructures of the different alloys.
Author: VN. Shishov
Publisher:
ISBN:
Category : Composition
Languages : en
Pages : 20
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Book Description
Studied were evolution of dislocation structure, phase, and element composition of binary alloys Zr-1Nb and Zr-2.5Nb and multicomponent alloys Zr-1Nb-1.2Sn-0.4Fe and Zr-1.2Sn-0.4Fe under neutron irradiation. The investigations were carried out using cladding and pressure tubes before and after irradiation to a fluence of ~1026 n/m2 (E >= 0.1 MeV) in experimental and commercial reactors at 300 to 350°C using TEM, EDX, and XRD. In most cases, irradiation-induced defects are in the form of dislocation loops with Burgers vector 1/3 ?1120?. The density of dislocations with a ?c? component is less than 2 x 1014 m-2. A higher fluence or the presence of strain results in the ordering of the dislocation structure of ?c? component and ?a?-type dislocation loops. Before irradiation, the multicomponent alloys contain fine precipitates of Zr-Nb-Fe composition, and the matrix is depleted in Fe. Under irradiation, recrystallization proceeds intensively (as distinct from Zr-Nb alloys), changes take place in size, distribution, and composition of precipitates (with a relative decrease of Fe content compared to Nb), and the Fecontent of ?-Zr matrix is increased. None of the materials studied showed any significant evidence of secondary phase particle amorphization. The density of dislocations with ?a? and ?c? components and irradiation-induced defects, their mean size, the extent of ordering, and the planes of their occurrence were determined. A comparison was made between irradiation-induced evolutions of microstructures of the different alloys.
Author: VN. Shishov
Publisher:
ISBN:
Category : Dislocation
Languages : en
Pages : 20
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Book Description
On account of the search for the optimal composition and structure-phase state of Zr alloys much attention is paid to upgrade the E110 (Zr-1 %Nb) and E635 (Zr-1 %Nb-0.35 %Fe-1.2 %Sn) alloys that have proved well in terms of irradiation-induced creep and growth, high strength characteristics, and corrosion. The difference between the alloy properties is determined by their states related to their compositions. The structure-phase state of the Zr-Nb and Zr-Nb-Fe-Sn systems has been studied after heat treatment in the ?-- and ? + ?- regions and its influence on the irradiation-induced growth (IIG) during BOR-60 irradiation at T =315-350 %C was investigated. A substantial difference has been shown in the deformation effected by IIG of those alloys; it is less for Zr-Nb-Fe-Sn alloys in dissimilar structure-phase states. The incubation period of the accelerated growth stage is determined by the ?-matrix composition, the phase state and the initial dislocation structure. Neutron irradiation leads to a redistribution of alloying elements between the matrix and the precipitates, and to changes in the ?-solid solution composition. These changes affect accumulation and mobility of irradiation defects, anisotropy and formation of vacancy c-component dislocation loops. The appearance of c-loops usually correlates with an axial direction acceleration of the IIG of tubes conforming to their texture. The basic regularities of the phase transformation have been established: a) ?-Nb precipitates in Zr-Nb alloys are altered in composition to reduce the Nb content from 85-90 % to ~ 50 %, fine precipitates likely enriched in Nb are formed; b) ?-Zr precipitates are subject to irradiation-stimulated decomposition; c) Laves phase precipitates change composition (the content of Fe decreases) and crystal structure, HCP to BCC (?-Nb); d) (Zr,Nb)2Fe precipitates having the FCC lattice retain their composition and crystal structure; e) no amorphization of any secondary phase precipitates is observable under the given conditions of irradiation (T = 315-350 °C). Based on the dpa, the results were compared pertaining to Zr-alloy IIG deformation vs. fluence in various reactors at different energies of fast neutrons. The presented graphs enable comparison between the results of numerous experiments and enable predictions of Zr-material behavior in long-term operation and at high burn-up in commercial reactors.
Author: LP. Sinelnikov
Publisher:
ISBN:
Category : Dislocation
Languages : en
Pages : 17
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Book Description
Tubes from zirconium-base alloys are used widely in the pressure tube reactor core. The lifetime of the zirconium component in the reactor core will be determined by structure changes and alloy properties under long-term neutron irradiation. The studies were carried out using Zr-1Sn-1Nb-0.4Fe (E635) and Zr-2.5Nb (E125) alloy samples cut out of a pressure tube (PT) in the initial condition and after 7 and 15.5 years operated (42 000 and 95 000 effective hours) under irradiation to the neutron fluxes of 3 x 1017 and 2 x 1017 n/m2 s (E > 1 MeV) at 304°C in RBMK-1000 and 314°C in RBMK-1500, respectively. The E125 alloy PTs were in two conditions, as cold worked and annealed (A) and as thermomechanically treated (TMT-1) (B). The E635 alloy PTs were cold worked and annealed (A) (Tablel). The examinations were implemented using analytical transmission electron microscopy (TEM), energy dispersive X-ray (EDX), and X-ray diffraction (XRD) analyses. New data showing the microstructure changes are presented. Both the alloys have a partially recrystallized grain structure with a high density of intragranular dislocations in the initial state. The main part of dislocations belong to ?a? type. Density of secondary phase precipitates is high. They are ?-Nb (bec) in Zr-2.5Nb. In Zr-1.3Sn-1Nb-0.4Fe, precipitates consist of Zr, Nb, and Fe, and the constituent ratio is close to 1:1:1 Zr(Nb,Fe)2 (hcp). Linear dislocations (Type a) are annealed under irradiation, while the density of ?c?-component dislocations is not practically changed. Grain structure of the Zr-2.5Nb alloy is retained, and it is practically completely recrystallized in Zr-1.3Sn-1Nb-0.4Fe. The phase structure and microchemical composition are modified by irradiation. Nb concentration changes in ?-Nb are observed in Zr-2.5Nb. A substantial decrease of Fe concentration and irradiation defect accumulation are observed in the intermetallic precipitates Zr(Nb,Fe)2 in the E635 alloy. This leads to crystal lattice disordering and new precipitates Nb-enriched are formed. Dislocation loops are formed under irradiation. Loop dimensions vary widely in Zr-2.5Nb. They show a tendency to ordering under high-fluence irradiation. Uniform structure of loops with a high tendency to ordering is formed in the alloy Zr-l.3Sn-lNb-0.4Fe; 70% of them are interstitial loops of the ?a? type. Irradiation-induced Fe depletion of intermetallic particles and a Fe content increase in saturated ?-Zr matrix may be a cause of the microstructure and performance changes in E635 alloy pressure tubes. The correlation between irradiation-induced dislocation structure and hardening of the E125 alloy is discussed.
Author: George P. Sabol
Publisher: ASTM International
ISBN: 0803124066
Category : Nuclear fuel claddings
Languages : en
Pages : 907
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Author: Frederic R. Shober
Publisher:
ISBN:
Category : Metals
Languages : en
Pages : 120
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Book Description
The effect of fast-neutron (>1 Mev) irradiation on the mechanical properties of structural metals and alloys was studied. Although the yield strengths and ultimate tensile strengths are increased su stantially for most materials, the ductility suffers severe decreases. This report presents these changes in properties of several structural metals for a number of neutron exposures within the 1.0 x 10 to the 18th power to 5.0 x 10 to the 21st power n/sq cm range. Data summarizing these effects on several classes of materials such as carbon steels, low-alloy steels, stainless steels, Zr-base alloys, ni-base alloys, Al-base alloys, and Ta are given. Additional data which show the influence f irradiation temperatures and of post-irradiation annealing on the radiation-induced property changes are also given and discussed. Increases as great as 175% in yield strength, 100% in ultimate strength, and decreases of 80% in total elongation are reported for fast-neutron exposures as great as 5 10 to the 21st power n/sq cm. (Author).
Author: AV. Tselischev
Publisher:
ISBN:
Category : Composition
Languages : en
Pages : 22
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Book Description
The studies of the dislocation structure, phase, and microchemical compositions of alloy Zr-1Nb-1.2Sn-0.35Fe (E635) and its modifications containing Fe from 0.15 to 0.65% were carried out before and after research reactor irradiation at ~350°C to maximal fluence of ~1027 m-2 (E > 0.1 MeV) and at ~60°C. The size and concentration of the a-type loops depend on the alloy composition and fluence and saturate even at low doses (1 dpa). The evolution of the c-component dislocation structure in recrystallized alloys of E365 type is determined by the chemical and phase compositions of alloys specifically, by the Fe/Nb ratio and the threshold dose, and is consistent with the irradiation growth strain acceleration. In E635 alloy containing 0.15%Fe the accelerated growth is observed after the dose of 15 dpa and is attended with the evolution of the c dislocation structure which is similar to Zr-1Nb (E110) alloy behavior. The irradiation induced growth of E635 type alloy containing 0.65% Fe is similar to that of E635 having the normal composition; no
Author: J. Koutský
Publisher: Elsevier
ISBN: 1483291626
Category : Technology & Engineering
Languages : en
Pages : 362
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Book Description
Maintaining the integrity of nuclear power plants is critical in the prevention or control of severe accidents. This monograph deals with both basic groups of structural materials used in the design of light-water nuclear reactors, making the primary safety barriers of NPPs. Emphasis is placed on materials used in VVER-type nuclear reactors: Cr-Mo-V and Cr-Ni-Mo-V steel for RPV and Zr-Nb alloys for fuel element cladding. The book is divided into 7 main chapters, with the exception of the opening one and the chapter providing a phenomenological background for the subject of radiation damage. Chapters 3-6 are devoted to RPV steels and chapters 7-9 to zirconium alloys, analysing their radiation damage structure, changes of mechanical properties due to neutron irradiation as well as factors influencing the degree of their performance degradation. The recovery of damaged materials is also discussed. Considerable attention is paid to a comparison of VVER-type and western-type light-water materials. This monograph will be of great value to postgraduate students in nuclear engineering and materials science, and for designers and research workers in nuclear energy.
Author: David B. Williams
Publisher: Springer Science & Business Media
ISBN: 1475725191
Category : Science
Languages : en
Pages : 708
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Book Description
Electron microscopy has revolutionized our understanding the extraordinary intellectual demands required of the mi of materials by completing the processing-structure-prop croscopist in order to do the job properly: crystallography, erties links down to atomistic levels. It now is even possible diffraction, image contrast, inelastic scattering events, and to tailor the microstructure (and meso structure ) of materials spectroscopy. Remember, these used to be fields in them to achieve specific sets of properties; the extraordinary abili selves. Today, one has to understand the fundamentals ties of modem transmission electron microscopy-TEM of all of these areas before one can hope to tackle signifi instruments to provide almost all of the structural, phase, cant problems in materials science. TEM is a technique of and crystallographic data allow us to accomplish this feat. characterizing materials down to the atomic limits. It must Therefore, it is obvious that any curriculum in modem mate be used with care and attention, in many cases involving rials education must include suitable courses in electron mi teams of experts from different venues. The fundamentals croscopy. It is also essential that suitable texts be available are, of course, based in physics, so aspiring materials sci for the preparation of the students and researchers who must entists would be well advised to have prior exposure to, for carry out electron microscopy properly and quantitatively.
Author: GP. Kobylyansky
Publisher:
ISBN:
Category : Dislocation
Languages : en
Pages : 17
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Book Description
Zirconium alloy components subjected to long-term operation and high doses in thermal reactors need to be highly irradiation resistant to provide integrity of components, primarily, their geometrical sizes. Transmission and scanning electron microscopy, energy dispersive X-ray microanalysis used to investigate thin foils and extraction replicas of irradiated zirconium, Zr-1Nb (E110) and Zr-1.2Sn-1Nb-0.4Fe (E635) alloys allowed us to analyze the evolution of their microstructure under neutron irradiation. The experimental irradiations that were conducted at 350°C to 1027 n/m2 (E >= 0.1 MeV) show that the most irradiation resistant alloy proved to be a multicomponent E635 alloy. It is not essentially subject to growth. Dislocation structure and phase composition were studied as interrelated to different stages of irradiation induced growth. The accelerated growth correlates with a high density of basal -- plane c-component dislocations.
Author: D. W. White
Publisher:
ISBN:
Category : Irradiation-induced growth
Languages : en
Pages : 19
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Book Description
This paper is devoted to the study of the effect of the texture, phase composition, and microstructure on the irradiation-induced growth strain (GS) of zirconium-based alloys. GS measurements and TEM microstructural examinations were performed on Zry-2, NSF, and E635 samples in the recrystallized, beta quenched and cold-worked (CW) conditions. The samples were irradiated in the BOR-60 reactor in the temperature range of 315-325°C up to a neutron fluence level of 1.1 x 1026 n/m2 (E>1MeV), i.e., up to a damage dose of 23 dpa. Growth strains of NSF and E635 alloys in all states and in the longitudinal and transverse directions are lower as compared to those of Zry-2, and do not exceed 0.2 % even at the maximum fluence level. As for recrystallized Zry-2, the GS kinetics are characterized by the appearance of the accelerated growth stage. A combination of a certain amount of Nb, Fe, and Sn in the matrix content plays a key role in GS kinetics. The higher the degree of CW, the higher the irradiation growth but its rate of increase with increasing fluence is different for alloys of different compositions. The maximum GS, reaching 0.72 %, is observed in the 20 % CW Zry-2 samples. Texture, along with the alloy composition, is one of the main GS-determining factors. Irradiation growth of the transversal samples is lower as compared to the longitudinal ones because of texture. As for quenched alloys, the texture is practically isotropic and GS values are low, independent of the alloy composition. In CW materials, the density of ‹c›- dislocations greatly affects the irradiation growth strain. Particles of Zr(Fe,Cr)2 and Zr2(Fe,Ni) phases in Zry-2 as well as Zr(Nb,Fe)2 in NSF and E635 are depleted in iron under irradiation. The Fe goes into the matrix and modifies its properties. The HCP lattice structure in the Laves phases in NSF and E635 changes into BCC (?-Nb-type). FCC (Zr,Nb)2Fe precipitates preserve on the whole their composition and structure; no amorphization of the Nb-containing precipitates is observed. The Zr2(Fe,Ni) precipitates with a BCT lattice remain crystalline, and HCP Zr(Cr,Fe)2 precipitates undergo amorphization. The average particle size in the irradiated alloys is larger and the concentration is a little lower as compared to the unirradiated ones. Irradiation-induced fine dispersed precipitates about 3 nm in size, probably enriched in niobium, appear in NSF and E635. The observed changes of microhardness are discussed from the viewpoint of generation of radiation defects (clusters, dislocation loops), evolution of the initial dislocation structure, and matrix composition (enrichment in Fe, Cr, and, probably, Nb).
