Download or read book Effects of Neutron Irradiation and Thermal Annealing on Model Alloys Using Positron Annihilation Techniques written by AT. Motta and published by . This book was released on 2001 with total page 15 pages. Available in PDF, EPUB and Kindle. Book excerpt: We present the results of a systematic investigation of neutron-irradiated and thermally annealed Fe-Cu-Ni-P model alloys using positron annihilation spectroscopy (PAS), including lifetime and Doppler broadening techniques, and Rockwell hardness. These alloys were examined in the as-fabricated state, after irradiation at 270° C to 1 x 1019 n.cm-2, and to 8 x 1019 n.cm-2, and after successive post-irradiation isochronal anneals at temperatures from 200 to 600° C. The results can be qualitatively explained by invoking an irradiation-induced microstructure consisting of a combination of small dislocation-type defects or defect clusters (matrix damage) and dense precipitation of fine scale irradiation-induced precipitates. The matrix damage anneals between 350° C and 450° C. The irradiation-induced precipitates also evolve with annealing, but at higher temperatures. The combined effect of high Cu and high Ni concentrations leads to more extensive irradiation-induced precipitation than in cases where either element is missing, whereas the effect of P is less pronounced. We analyze and compare the results with similar measurements performed on irradiated pressure-vessel steels and with other positron measurements on model alloys, reported in the literature.

Download or read book Annihilation of Positrons in Neutron Irradiated Metals and Alloys written by Ivaylo Mincov and published by LAP Lambert Academic Publishing. This book was released on 2010-09 with total page 80 pages. Available in PDF, EPUB and Kindle. Book excerpt: In the recent years there is an increasing interest towards the positron annihilation spectroscopy as an examination technique in many fields of knowledge. Its basic applications are for scientific investigation in physics and materials science, because the method is non-destructive and very sensitive to different kinds of defects and phase transitions, but it found its place also in some practically aimed activities like medicine. In the present book are represented investigations of metals and alloys irradiated with 14 MeV generator neutrons. The investigated metals are of the most often used ones for the purposes of the nuclear reactor industry. The discussion goes mainly around the clusters formation in them as a result of neutron irradiation and their growing and disappearance in high temperature annealing. The methods of the positron spectroscopy, experimental setup used in the measurements and mathematical methods for data analysis are also mentioned. The obtained results may be very useful not only for scientists, but for all specialists in the field of nuclear energetics - projectors, constructors and nuclear engineers as well as for mechanical engineers and constructors.

Download or read book Report on the Effects of Neutron Radiation on Structural Materials written by M. Kangilaski and published by . This book was released on 1967 with total page 264 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Neutron Irradiation of Pure Metals and Aluminum zinc Alloys written by James Albert Horak and published by . This book was released on 1966 with total page 88 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book The Effect of Nuclear Radiation on Structural Metals written by Frederic R. Shober and published by . This book was released on 1961 with total page 120 pages. Available in PDF, EPUB and Kindle. Book excerpt: 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).

Download or read book Properties of Reactor Structural Alloys After Neutron Or Particle Irradiation written by C. J. Baroch and published by ASTM International. This book was released on 1975 with total page 640 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Positron Annihilation written by and published by . This book was released on 1979 with total page 1008 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Study of Radiation Damage in Metals by Positron Annihilation Neutron Irradiation written by and published by . This book was released on 1977 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Positron annihilation is a sensitive technique for probing defects in metals and it has recently been shown to be a valuable tool for the study of radiation damage. After an introduction to the three basic experimental methods (angular correlation, Doppler broadening, and lifetime measurements), the interaction of positrons with lattice defects is reviewed. Results for the annealing of damage after low temperature irradiation are used to show that positron annihilation has provided new information on annealing kinetics. The role of positron techniques in characterizing complex defect structures resulting from high-temperature neutron irradiation is reviewed and the possible utility of positron annihilation as a nondestructive monitor of property changes is pointed out.

Download or read book Proceedings of the Fifth International Conference on Positron Annihilation April 8 11 L979 Lake Yamanaka Japan written by Ryukiti R. Hasiguti and published by . This book was released on 1979 with total page 1020 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Effects of Neutron Irradiation in Non fissionable Metals and Alloys written by International Atomic Energy Agency and published by . This book was released on 1962 with total page 180 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Positron Annihilation Spectroscopy and Small Angle Neutron Scattering Characterization of the Effect of Mn on the Nanostructural Features Formed in Irradiated Fe Cu Mn Alloys written by R. H. Howell and published by . This book was released on 2003 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: The size, number density and composition of the nanometer defects responsible for the hardening and embrittlement in irradiated Fe-0.9wt.% Cu and Fe-0.9wt.% Cu-1.0wt% Mn model reactor pressure vessel alloys were measured using small angle neutron scattering and positron annihilation spectroscopy. These alloys were irradiated at 290 C to relatively low neutron fluences (E> 1 MeV, 6.0 x 10{sup 20} to 4.0 x 10{sup 21} n/m{sup 2}) in order to study the effect of manganese on the nucleation and growth of copper rich precipitates and secondary defect features. Copper rich precipitates were present in both alloys following irradiation. The Fe-Cu-Mn alloy had smaller precipitates and a larger number density of precipitates, suggesting Mn segregation at the iron matrix-precipitate interface which reduces the interfacial energy and in turn the driving force for coarsening. Mn also retards the precipitation kinetics and inhibits large vacancy cluster formation, suggesting a strong Mn-vacancy interaction which reduces radiation enhanced diffusion.

Download or read book Positron Annihilation Spectroscopy and Small Angle Neutron Scattering Characterization of Nanostructural Features in Irradiated Fe Cu Mn Alloys written by and published by . This book was released on 2001 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Radiation embrittlement of nuclear reactor pressure vessel steels results from a high number density of nanometer sized Cu-Mn-Ni rich precipitates (CRPs) and sub-nanometer matrix features, thought to be vacancy-solute cluster complexes (VSC). However, questions exist regarding both the composition of the precipitates and the defect character and composition of the matrix features. We present results of positron annihilation spectroscopy (PAS) and small angle neutron scattering (SANS) characterization of irradiated and thermally aged Fe-Cu and Fe-Cu-Mn alloys. These complementary techniques provide insight into the composition and character of both types of nanoscale features. The SANS measurements indicate populations of CRPs and VSCs in both alloys. The CRPs are coarser in the Fe-Cu alloy and the number densities of CRP and VSC increase with the addition of Mn. The PAS involved measuring both the positron lifetimes and the Doppler broadened annihilation spectra in the high momentum region to provide elemental sensitivity at the annihilation site. The spectra in Fe-Cu-Mn specimens thermally aged to peak hardness at 450 C and irradiated at 288 C are nearly identical to elemental Cu. Positron lifetime and spectrum measurements in Fe-Cu specimens irradiated at 288 C clearly show the existence of long lifetime ((almost equal to)500 ps) open volume defects, which also contain Cu. Thus the SANS and PAS provide a self-consistent picture of nanostructures composed of CRPs and VSCs and tend to discount high Fe concentrations in the CRPs.

Download or read book Neutron Irradiation Effects on Iron Containing Aluminum and Nitrogen written by RR. Hasiguti and published by . This book was released on 1970 with total page 12 pages. Available in PDF, EPUB and Kindle. Book excerpt: Several authors have emphasized that aluminum nitride in iron and iron alloys not only lowers the transition temperature but also suppresses the rise of the transition temperature due to irradiation. To clarify the mechanism of the effect of aluminum nitride, structural changes after irradiation and annealing are observed by means of internal friction and electron microscopy. Materials investigated are iron, containing 0.05 wt% Al and 0.01 wt% N with 1 ppm C and a few ppm 0, and iron, containing 0.02 wt% Al and 0.005 wt% N with 10 ppm C and 20 ppm 0. The materials are annealed at 750 C before irradiation and irradiated in the JRR-2 at temperatures of 60 C and up to 1.2x1019 n/cm2, E 1 MeV. Two new peaks in internal friction are found at ~125 C and ~155 C after irradiation. Besides these changes a new type of precipitate is observed by electron microscopy. These precipitates are thin, doughnut shaped disks with a diameter of 0.3 ?m and are considered to be complex defects of irradiation induced point defects, nitrogen, and aluminum atoms. The 125 C peak of internal friction disappears after annealing at 250 C for 30 min; the 150 C peak disappears after annealing at 150 C for 30 min or aging at room temperature for about half a year. Resolution of free nitrogen is observed, but precipitates do not disappear even after annealing at 350 C for 30 min. The precipitates suppress the formation of irradiation induced complex nitrogen defects and irradiation hardening because of the strong effect of aluminum on nitrogen atoms.

Download or read book Effects of Neutron Irradiation on the Elevated Temperature Mechanical Properties of Nickel Base and Refractory Metal Alloys written by T. T. Claudson and published by . This book was released on 1967 with total page 28 pages. Available in PDF, EPUB and Kindle. Book excerpt: Nuclear research and power reactors are now being designed which must operate at temperatures and coolant environments dictating the use of nickel-base and refractory metal alloys for structural components, fuel cladding, and power equipment. Investigation of the effects of irradiation and environment upon the mechanical properties of several nickel-base and refractory metal alloys has been initiated at the Pacific Northwest Laboratory. Tension specimens of Inconel 600, Inconel 625, Inconel 702, Inconel 718, Incoloy 800, Hastelloy C, Hastelloy N, Hastelloy X-280, and Hastelloy R-235 have been irradiated to exposures exceeding 1 x 1021 nvt (E > 1 Mev) in 50 C water, 280 C water, and 740 C gaseous environments. These specimens have been tested in the pre- and postirradiated conditions at room temperature, 300 C, and 650 C. Several metallurgical conditions of the materials have also been examined and the changes in mechanical properties due to the irradiation have been noted. The Cb-1 Zr, Cb-752, TZM Mo, and W-25 Re refractory metals have been irradiated at ambient temperatures, and the effects of irradiation upon the mechanical properties have been evaluated at room temperature and 1090 C. The data obtained for both the nickel-base and refractory metal alloys tested indicate that there is a marked effect upon the mechanical properties due to the thermal environment. In addition to this effect, effects due to the irradiation were also found. Comparison of the elevated temperature data to the room temperature data shows a marked decrease in both strength and ductility. Metallographic examination of these materials is continuing in an attempt to find the cause of these damages.

Download or read book Characterization of Radiation Effects and Ab Initio Modeling of Defects in a High Entropy Alloy for Nuclear Power Application written by Congyi Li and published by . This book was released on 2018 with total page 127 pages. Available in PDF, EPUB and Kindle. Book excerpt: A novel Co-free NiFeMnCr HEA was synthesized for both ion and neutron irradiation studies. 3 and 5.8MeV heavy ion irradiations were conducted at room temperature and 400 - 700 °C from 0.03 to 10dpa. Post-irradiation examination included x-ray diffraction, nanoindentation hardness and transmission electron microscopy. The HEA exhibited quantitatively superior radiation resistance than conventional alloys, including suppressed void swelling and solute segregation. Neutron irradiation was conducted at 60 °C from 0.1 to 1dpa. Microhardness, electrical resistivity and positron annihilation spectroscopy measurements were performed at room temperature before and after isochronal annealing up to 700°C on the neutron-irradiated samples. The HEA retains fundamental stability after neutron irradiation. Compared with metals and conventional alloys, the HEA showed similar annealing trend of hardness and vacancy-type of defects. On the other hand, this HEA showed unique annealing trend of electrical resistivity. The large radiation induced resistivity increase (>10 [mu][Omega]·cm) did not recover up to 700 °C, suggesting short range ordering phenomena may be critical in radiation effects of HEA. In parallel, ab initio modeling was conducted to establish a solid foundation for multiscale modeling of HEA as well as to reveal unique defect physics of HEA. Magnetic structure was computed based on coherent potential. Vacancy energetics were computed by Vienna Ab initio Simulation Package (VASP). Modeling results shows that it is reasonable to neglect magnetic interactions. The statistical distribution of vacancy formation energy is weakly dependent upon either the chemical species of the atom site associated with the vacancy, or local chemical environment. The calculated migration energy values show a large spread, varying between 0.55 to 1.68eV, although the mean value is comparable to that of conventional austenitic alloys. Finally, positron lifetime of bulk HEA, mono-vacancy and small vacancy clusters were computed by a finite element based ab initio package to facilitate the interpretation of experimental results from positron annihilation spectroscopy.

Download or read book Characterization of Radiation Induced Lattice Defects by Means of Positron Annihilation Spectroscopy written by Riley Craig Ferguson and published by . This book was released on 2023 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: Positrons provide a non-destructive technique for probing the nature and size of defects in materials with atomic-scale sensitivity. This work will focus on the powerful capabilities of positron annihilation spectroscopy (PAS) to study the evolution of defects and defect structures. This invaluable tool can aid in developing and characterizing advanced materials, with diverse applications such as nuclear reactors, optoelectronics, nanotechnology, polymers, medical sciences, and more. The work presented in this thesis aims to gain a fundamental understanding of the formation and evolution of defect structures of various metals and alloys under irradiation by applying the techniques and concepts of PAS. Various other characterization techniques are also utilized simultaneously to interpret the positron data better and further enhance our understanding of these materials. Depth-resolved PAS was used to identify vacancy clusters and measure their density as a function of depth in three samples (HfMoTiVZr, HfNbTiZr, and HfNbTaTiZr bulk alloys), performed at the Helmholtz-Zentrum Dresden-Rossendorf (HZDR) in Dresden, Germany. The samples were studied before and after irradiation from 10 MeV Si ions. The behavior of these alloys under irradiation is discussed and quantified in this work. A single branch of samples from the multi-principal element alloy (MPEA) HfNbTaTiZr (Nb, HfNb, HfNbZr, HfNbTiZr, HfNbTaTiZr) was synthesized into thin films on MgO substrate at the Center of Integrated Nanotechnologies (CINT) at the Los Alamos National Laboratory (LANL), to study the role of chemical complexity in an alloy's response to irradiation. There are four sets of these MPEA-based thin film samples, where one will be kept as a reference, and one will be studied with in situ PAS (iPAS), and two sets will be studied with ex situ PAS. The synthesis of these MPEA-based thin films and the design of the PAS experiment for each set is described in this work, along with other characterization techniques used together with this work. This work was made possible through the support of the National Science Foundation (NSF) under grant number DMR-2005064 and by the Fundamental Understanding of Transport Under Reactor Extremes (FUTURE), an Energy Frontier Research Center funded by the DOE, Office of Science, Basic Energy Sciences.

Download or read book Effects of Neutron Irradiation on Thermal Conductivity of SiC based Composites and Monolithic Ceramics written by and published by . This book was released on 1997 with total page 26 pages. Available in PDF, EPUB and Kindle. Book excerpt: A variety of SiC-based composites and monolithic ceramics were characterized by measuring their thermal diffusivity in the unirradiated, thermal annealed, and irradiated conditions over the temperature range 400 to 1,000 C. The irradiation was conducted in the EBR-II to doses of 33 and 43 dpa-SiC (185 EFPD) at a nominal temperature of 1,000 C. The annealed specimens were held at 1,010 C for 165 days to approximately duplicate the thermal exposure of the irradiated specimens. Thermal diffusivity was measured using the laser flash method, and was converted to thermal conductivity using density data and calculated specific heat values. Exposure to the 165 day anneal did not appreciably degrade the conductivity of the monolithic or particulate-reinforced composites, but the conductivity of the fiber-reinforced composites was slightly degraded. The crystalline SiC-based materials tested in this study exhibited thermal conductivity degradation after irradiation, presumably caused by the presence of irradiation-induced defects. Irradiation-induced conductivity degradation was greater at lower temperatures, and was typically more pronounced for materials with higher unirradiated conductivity. Annealing the irradiated specimens for one hour at 150 C above the irradiation temperature produced an increase in thermal conductivity, which is likely the result of interstitial-vacancy pair recombination. Multiple post-irradiation anneals on CVD [beta]-SiC indicated that a portion of the irradiation-induced damage was permanent. A possible explanation for this phenomenon was the formation of stable dislocation loops at the high irradiation temperature and/or high dose that prevented subsequent interstitial/vacancy recombination.