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Body-centered cubic ion correlation experiment

Description: The results of an interlaboratory correlation experiment involving eight laboratory sites studying the ion irradiation of molybdenum are presented. The program was comprised of three parts. The first part compared the radiation damage produced in a reference specimen of molybdenum by ions of different masses and different energies. The second part of the program compared measurements on a common micrograph supplied to all participants in the program. The results from all the sites agreed very well. The value of standard deviation in the measurement of void volume fraction corresponded to 10 percent of the average measured value and the spread between highest and lowest reported value was 35 percent. The third part of the program compared the microstructural characteristics of a transmission electron microscope (TEM) specimen that was passed from site to site (''round robin''). The results of this part of the experiment showed greater variations from the different participants than the results from the common micrograph. One of the principal sources of discrepancy was the measurement of the foil thickness which was necessary for computation of void number density. The standard deviation in the measurements of void volume fraction (swelling) corresponded to 20 percent of the measured average value. The spread between the highest and lowest value was 70 percent. This latter value gives an idea of the conceivable differences in results due to experimental techniques between two experiments.
Date: April 1, 1977
Creator: Brimhall, J.L. (comp.)
Partner: UNT Libraries Government Documents Department

Radiation damage studies in CTR materials using dual-beam irradiation

Description: A dual beam, ion irradiation facility for studying radiation damage problems applicable to fusion first walls has been described. Experiments on molybdenum have shown that co-implanted helium can alter the internal void microstructure during heavy ion irradiation but does not appreciably change the total swelling. Heavy ion irradiation of a Nb-1 Zr alloy have shown that irradiation can induce precipitate formation and that existing precipitates can influence the damage microstructure.
Date: January 1, 1980
Creator: Brimhall, J.L.
Partner: UNT Libraries Government Documents Department

Effect of helium on void swelling in vanadium

Description: Little difference in void microstructural swelling of vanadium is observed when helium is injected simultaneously with a 46- or 5-MeV nickel beam as compared to no helium injection, at least at high dose rates. At lower dose rates, a strong helium effect is seen when the helium is injected prior to heavy ion bombardment. The effect of the helium is shown to be a strong function of the overall displacement damage rate. (DLC)
Date: January 1, 1975
Creator: Brimhall, J.L. & Simonen, E.P.
Partner: UNT Libraries Government Documents Department

Mechanical strength and stability of lithium aluminate

Description: Pacific Northwest Laboratory (PNL) investigated the strength and resistance to thermal shock of lithium aluminate annular pellets. The room temperature, axial compressive fracture strength of pellets made at Westinghouse Advanced Energy Systems (WAES) varied from 80 to 133 ksi. The strength at 430{degrees}C (806{degrees}F) was to 30 to 40% lower. The strength at 900{degrees}C (1652{degrees}F) showed a wide variation with one measurement near 90 ksi. These strength values are consistent with other data and predictions made in the literature when the grain size and porosity of the microstructure are taken into account. In diametral compression tests, the fracture strengths were much lower due to the existence of tensile stresses in some pellet regions from this type of loading. However, the fracture stresses were still generally higher than those reported in the literature; this fracture resistance probably reflects the better quality of the pellets tested in this study. Measurements on pellets made at PNL indicated lower strengths compared to the WAES material. This strength difference could be accounted for by different processing technologies: material made at PNL was cold-pressed and sintered with high porosity whereas the WAES material was isostatically hot-pressed with high density. Thermal shocking of the material by ramping to 900{degrees}C in two minutes did not have an observable effect on the microstructure or the strength of any of the pellets.
Date: June 1, 1992
Creator: Brimhall, J.L.
Partner: UNT Libraries Government Documents Department

Mechanical strength and stability of lithium aluminate

Description: Pacific Northwest Laboratory (PNL) investigated the strength and resistance to thermal shock of lithium aluminate annular pellets. The room temperature, axial compressive fracture strength of pellets made at Westinghouse Advanced Energy Systems (WAES) varied from 80 to 133 ksi. The strength at 430{degrees}C (806{degrees}F) was to 30 to 40% lower. The strength at 900{degrees}C (1652{degrees}F) showed a wide variation with one measurement near 90 ksi. These strength values are consistent with other data and predictions made in the literature when the grain size and porosity of the microstructure are taken into account. In diametral compression tests, the fracture strengths were much lower due to the existence of tensile stresses in some pellet regions from this type of loading. However, the fracture stresses were still generally higher than those reported in the literature; this fracture resistance probably reflects the better quality of the pellets tested in this study. Measurements on pellets made at PNL indicated lower strengths compared to the WAES material. This strength difference could be accounted for by different processing technologies: material made at PNL was cold-pressed and sintered with high porosity whereas the WAES material was isostatically hot-pressed with high density. Thermal shocking of the material by ramping to 900{degrees}C in two minutes did not have an observable effect on the microstructure or the strength of any of the pellets.
Date: June 1, 1992
Creator: Brimhall, J. L.
Partner: UNT Libraries Government Documents Department

Radiation-induced segregation in candidate fusion-reactor alloys

Description: The effect of radiation on surface segregation of minor and impurity elements has been studied in four candidate fusion reactor alloys. Radiation induced surface segregation of phosphorus was found in both 316 type stainless steel and in Nimonic PE-16. Segregation and depletion of the other alloying elements in 316 stainless steel agreed with that reported by other investigators. Segregation of nitrogen in ferritic HT-9 was enhanced by radiation but no phosphorus segregation was detected. No significant radiation enhanced or induced segregation was observed in a Ti-6Al-4V alloy. The results indicate that radiaton enhanced grain boundary segregation could contribute to the embrittlement of 316 SS and PE-16.
Date: July 1, 1981
Creator: Brimhall, J.L.; Baer, D.R. & Jones, R.H.
Partner: UNT Libraries Government Documents Department

Effect of pulsed irradiation on void swelling in nickel

Description: This study has compared the void microstructure in nickel induced by a pulsed ion bombardment to that induced by a steady-state irradiation. Pulse cycles of 10 seconds on and 10 seconds off produced no measurable difference in the void growth and swelling in the temperature range 775 to 975/sup 0/K compared to continuous irradiation at the same instantaneous dose rate. Void annealing during the pulse annealing period was minimal due to the large void sizes which were obtained in these irradiations. Hence no measurable effect of pulsing on void growth was observed.
Date: July 1, 1981
Creator: Brimhall, J.L.; Charlot, L.A. & Simonen, E.P.
Partner: UNT Libraries Government Documents Department

Develop techniques for ion implantation of PLZT (lead-lanthanum-zirconate-titanate) for adaptive optics

Description: Research was conducted at Pacific Northwest Laboratory to develop high photosensitivity adaptive optical elements utilizing ion implanted lanthanum-doped lead-zirconate-titanate (PLZT). One centimeter square samples were prepared by implanting ferroelectric and anti-ferroelectric PLZT with a variety of species or combinations of species. These included Ne, O, Ni, Ne/Cr, Ne/Al, Ne/Ni, Ne/O, and Ni/O, at a variety of energies and fluences. An indium-tin oxide (ITO) electrode coating was designed to give a balance of high conductivity and optical transmission at near uv to near ir wavelengths. Samples were characterized for photosensitivity; implanted layer thickness, index of refraction, and density; electrode (ITO) conductivity; and in some cases, residual stress curvature. Thin film anti-ferroelectric PLZT was deposited in a preliminary experiment. The structure was amorphous with x-ray diffraction showing the beginnings of a structure at substrate temperatures of approximately 550/sup 0/C. This report summarizes the research and provides a sampling of the data taken during the report period.
Date: July 1, 1987
Creator: Batishko, C.R.; Brimhall, J.L.; Pawlewicz, W.T.; Stahl, K.A. & Toburen, L.H.
Partner: UNT Libraries Government Documents Department

Evaluation of wear rates and mechanisms of titanium diboride-graphite composite materials proposed for use as cathodes in Hall-Heroult cells

Description: Purpose of this study was to measure the initial wear rates of TiB/sub 2/ carbon-containing cathode materials (TiB/sub 2/-G) under electrolytic conditions. Parameters evaluated included bath ratio, current density, and aluminum pad thickness. In order to measure initial wear rates, the tests were limited to 8 h.
Date: January 1, 1987
Creator: Pool, K.H.; Brimhall, J.L.; Raney, P.J. & Hart, P.E.
Partner: UNT Libraries Government Documents Department

Structure and properties of composites synthesized in situ using solid state displacement reactions

Description: Solid state displacement reactions can produce in situ intermetallic and ceramic matrix composites in a process where an intermetallic or ceramic phase(s) and a potential reinforcing phase(s) are grown together during a solid state reaction. Interpenetrating and dispersed microstructures, important for desirable composite properties, have been produced by means of displacement reaction processing techniques. Two such composites have been synthesized which exhibit two distinct microstructures: MoSi{sub 2} reinforced with SiC particles, which exhibits a dispersed-phase structure, and NiAl/Ni{sub 3}Al reinforced with Al{sub 2}O{sub 3}, which exhibits an interpenetrating-phase structure. Strength in bending and chevron-notch fracture toughness have been determined as a function of temperature, and measured properties compare favorably with composites produced by other means. The measured properties are discussed with regard to the observed microstructures. The potential for displacement reaction processing is assessed, and it appears to be a cost-effective synthesis method compared to others.
Date: October 1, 1993
Creator: Henager, C. H. Jr. & Brimhall, J. L.
Partner: UNT Libraries Government Documents Department

Temperature and strain-rate effects on deformation mechanisms in irradiated stainless steel

Description: Analysis of the deformation microstructures in ion-irradiated stainless steel shows twinning to be the predominant deformation mode at room temperature. Dislocation channelling also occurs under slow strain rate conditions. Stresses required for twinning were calculated by the model of Venables and are compatible with observed yield stresses in neutron-irradiated material if loops are the principal twin source. Computation of the expected radiation hardening from the defect structure, based on a simple model, is consistent with yield strengths measured on neutron-irradiated steels. Lower yield stresses and greater thermal energy at 288 C lessen the probability of twinning and dislocation channeling becomes the primary deformation mode at the higher temperature. However, preliminary early results show that some twinning does occur in the irradiated stainless steel even at the higher temperature when higher strain rates are used.
Date: November 1, 1994
Creator: Brimhall, J. L.; Cole, J. I.; Vetrano, J. S. & Bruemmer, S. M.
Partner: UNT Libraries Government Documents Department

Metastable phase formation in Be-Nb intermetallic compounds

Description: Amorphous structures or metastable crystalline phases are produced in sputter-deposited Beryllium-Niobium (Be-Nb) alloys (5-15 at. % Nb) depending on the substrate temperature. The metastable phases transform to the stable Be{sub 12}Nb, Be{sub 17}Nb{sub 2}Nb phases on annealing at temperatures >800{degree}C. No Be{sub 5}Nb phase was found and the Be{sub 17}Nb{sub 2} phase is stable to low temperature. The Be{sub 12}Nb phase appeared to have a stoichiometric range of about 5.5 to 7.7 at. % Nb. The formation of the metastable phases is consistent with current models and theories. 17 refs., 1 fig., 2 tabs.
Date: November 1, 1990
Creator: Brimhall, J.L.; Charlot, L.A. & Bruemmer, S.M.
Partner: UNT Libraries Government Documents Department

Radiation hardening effects on localized deformation and stress corrosion cracking of stainless steels

Description: Radiation hardening in austenitic stainless steels modifies deformation characteristics and correlate well with increased susceptibility to intergranular stress corrosion cracking (IGSCC). Available data on neutron-irradiated materials have been analyzed and correlations developed between fluence, yield strength, and cracking susceptibility in high-temperature water environments. Large heat-to-heat differences in critical fluence (0.2 to 2.5 {times} 10{sup 21} n/cm{sup 2}) for IGSCC are documented. In many cases, this variability is consistent with yield strength differences among irradiated materials. IGSCC correlates better to yield strength than to fluence for most heats suggesting a possible role of radiation-induced hardening (and microstructure) on cracking. Microstructural evolution during proton and heavy-ion irradiation has been characterized in low-carbon 302SSs. Hardening results from dislocation loops. SEM and TEM are used to examine dose, strain, and temperature effects on deformation. This hardened microstructure produces inhomogeneous planar deformation within the matrix. Regularly spaced steps are created at the surface during deformation which increase in number with increasing macroscopic strain. Twinning is the dominant deformation mechanism at low temperature, while dislocation channeling is observed at 288C. Deformation characteristics are discussed in terms of potential impact on IGSCC.
Date: August 1, 1993
Creator: Bruemmer, S. M.; Cole, J. I.; Brimhall, J. L.; Carter, R. D. & Was, G. S.
Partner: UNT Libraries Government Documents Department