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Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

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At least 253 records · Page 14
All sourcesNASA NTRSDOE OSTI
NASA NTRS1980

Hot corrosion of Co-Cr, Co-Cr-Al, and Ni-Cr alloys in the temperature range of 700-750 deg C

The effect of SO3 pressure in the gas phase on the Na2SO4 induced hot corrosion of Co-Cr, Ni-Cr, and Co-Cr-Al alloys was studied in the temperature range 700 to 750 C. The degradation of the Co-Cr and Ni-Cr alloys was found to be associated with the formation of liquid mixed sulfates (CoSO4-Na2SO4 or NiSO4-Na2SO4) which provided a selective dissolution of the Co or Ni and a subsequent sulfidation oxidation mode of attack which prevented the maintenance of a protective Cr2O3 film. A clear mechanism was not developed for the degradation of Co-Cr-Al alloys. A pitting corrosion morphology was induced by a number of different mechanisms.

Chiang, K. T.↗
NASA NTRS1979

Empirical relationships between interplanetary conditions, magnetospheric flux transfer, and the AL index

Holzer and Slavin (1978) have found that the transfer of magnetic flux to and from the dayside magnetosphere as inferred from observed displacements of the magnetopause surface is correlated with both the magnitude of the auroral zone magnetic index AL and the incident flux of southward IMF. Empirical expressions specifying the rate at which magnetic flux is eroded in terms of interplanetary parameters and the rate of magnetic flux return as a function of AL have been developed. These relations are then used to predict magnetotail magnetic field enhancements from interplanetary and ground based data during an interval of substorm activity. The total magnetic flux in the tail is increased during intervals when the amount of flux transferred into its volume by dayside erosion exceeds the flux lost to the dayside by magnetospheric convection. Using Ogo-5 tail observations it is found for the sample events considered that these magnetic field enhancements can be described by empirical expressions for the magnetic flux transfer rates.

Slavin, J. A.↗
NASA NTRS1979

Skylab observations of the Al I autoionization lines gamma 1932 and gamma 1936 during a solar flare

Observations are presented of the Al I autoionization lines gamma 1932 and gamma 1936 during the H alpha class SN subflare of 1973 August 9, obtained from the NRL slit spectrograph aboard Skylab. These profiles are compared with observations from an active-region plage and with the quiet-sun observations of McAllister. Line profiles through model flare and quiet-sun atmospheres are computed assuming local thermodynamic equilibrium. The Al I autoionization lines are sensitive to the conditions just below the temperature-minimum region of the model atmosphere, and the observations support evidence that increased heating of this region occurs during flares. It shown, using observations from three additional flares, that excess flare heating down to the T sub min region probably occurs only near loop footpoints. The behavior of Fe and Fe II lines in the 1920 A range is also discussed.

Cook, J. W.↗
NASA NTRS1980

Isotopic yields of Mg, Al from the carbon and neon zones in the explosion of a massive star

A model is developed for the nucleosynthetic yields from the supernova explosion of a massive star of the sort which has been proposed as the initiating event in the formation of the solar system by Cameron and Truran (1977). Calculations start with the Hugoniot curves, estimating the preshock conditions from a 25 solar masses model at the start of core collapse. It is shown that the products of static carbon burning dominate abundance patterns in the ejecta. Both explosive carbon burning and explosive neon burning contribute significantly to Al-26. The production of Al-26 in this model is consistent with the trigger hypothesis.

Morgan, J. A.↗
NASA NTRS1982

Quiet sun observations of the Al I autoionization lines lambda 1932 and lambda 1936

Quet sun observations obtained during a rocket flight of the Al I autoionization lines 1932 A and 1936 A at solar pointings ranging from mu = 0.73 out to the visible limb. Absolute intensities are estimated to be accurate to about + or - 20%. These lines weaken progressively with decreasing mu but never go into emission before finally disappearing with the continuum just beyond the visible solar limb. The observations are then compared with LTE line profiles computed through the quiet sun atmosphere of Vernazza et al. (1976). Several areas of disagreement between the synthetic and observed profiles are discussed.

Cook, J. W.↗
NASA NTRS1982

Nucleosynthesis in novae - A source of Ne-E and Al-26

It is shown upon computation of the nucleosynthesis products of explosive hydrogen burning, in the framework of recent nova models, that nova condensates will probably contain isotopic anomalies in Ne-22, from Na-22 decay, and Mg-26, from Al-26 decay. It is found, for all the models considered, that while too much Ne-20 and -21 is produced relative to Ne-22 to explain the presumably almost pure Ne-22 meteoritic Ne-E component, the Na-22 abundance is high enough to explain Ne-E as its decay product if nova condensates are preserved in Ne samples. It is also determined that while Al-26 is coproduced with Na-22, its total amount strongly depends on the uncertain, Si-27(p, gamma)P-28 reaction rate. The abundances of all nuclides, up to Ar, are computed and found to be clearly nonsolar in many cases.

Hillebrandt, W.↗
NASA NTRS1982

The stress-corrosion behavior of Al-Li-Cu alloys: A comparison of test methods

Two powder metallurgy processed (Al-Li-Cu) alloys with and without Mg addition were studied in aqueous 3.5% NaCl solution during the alternate immersion testing of tuning fork specimens, slow crack growth tests using fracture mechanics specimens, and the slow strain rate testing of straining electrode specimens. Scanning electron microscopy and optical metallography were used to demonstrate the character of the interaction between the Al-Li-Cu alloys and the selected environment. Both alloys are susceptible to SC in an aqueous 3.5% NaCl solution under the right electrochemical and microstructural conditions. Each test method yields important information on the character of the SC behavior. Under all conditions investigated, second phase particles strung out in rows along the extrusion direction in the alloys were rapidly attacked, and played principal role in the SC process. With time, larger pits developed from these rows of smaller pits and under certain electrochemical conditions surface cracks initiated from the larger pits and contributed directly to the fracture process. Evidence to support slow crack growth was observed in both the slow strain rate tests and the sustained immersion tests of precracked fracture mechanics specimens. The possible role of H2 in the stress corrosion cracking process is suggested.

Rizzo, P. P.↗
NASA NTRS1982

Diffuse galactic gamma-ray line emission from nucleosynthetic Fe-60, Al-26, and Na-22 - Preliminary limits from HEAO 3

Data obtained during a two-week period in the fall of 1979 with the HEAO 3 gamma-ray spectroscopy experiment have been searched for diffuse galactic plane gamma-ray line emission expected t4 result from the decay of nucleosynthetic Fe-60, Al-26, and Na-22. With the possible exception of the 1809 keV line from Al-26 decay, for which a 2.6-omicron cosmic excess of (6.0 + or - 2.3) x 0.0001 photons/sq cm per sec per rad was measured, no positive detection was made. However, new limits ranging from 1.8 to 11 times 0.0001 photons/sq cm per sec per rad, at the 3-omicron level of confidence, have been placed on diffuse emission in these lines from the vicinity of the galactic center (between -30 and 30 deg). These limits are lower than some theories predict and thus place new constraints on the yields of these radionuclides in explosive nucleosynthesis and on the present rate of galactic nucleosynthesis.

Mahoney, W. A.↗
NASA NTRS1982

Crystallization sequences of Ca-Al-rich inclusions from Allende - An experimental study

The results of equilibrium crystallization experiments at one atmosphere on a sample of the Type B Ca-Al-rich inclusions (CAI) of the Allende meteorite are reported. All the experiments were performed on a synthetic sample approximating the Allende CAI characteristics. The crystallization sequence observed comprised spinel at 1550 C, then melilite at 1400 C, anorthite at 1260 C, and then Ti-Al-rich clinopyroxene, formed at 1230 C. The observation that pyroxenes similar to the titaniferous fassaites found in Type B inclusions can be formed by equilibrium crystallizations of melts with Type B composition indicate that some Type B CAIs were at least partially molten. If the temperatures were not too far above the solidus, the molten condensate compositions would be similar to that occurring in gas-to-solid condensation.

Stolper, E.↗
NASA NTRS1983

Influence of thermomechanical processing on elevated temperature slow plastic flow properties of B2 aluminide Fe-39.8at.% Al

A study of the elevated temperature slow plastic flow properties of the B2 aluminide Fe-39.8at.% Al was undertaken. Polycrystalline materials possessing several different microstructures were produced by the hot extrusion of prealloyed powder and, in some cases, postextrusion heat treatments. Compression tests were conducted in air at 1200, 1300 and 1400 K. Such testing revealed that the extrusion temperature affected the active deformation mechanisms where material extruded at 1505 K had a stress exponent about twice that of the intermetallic extruded at 1200 K. Grain size refinement to about 10 microns was found to strengthen the Fe-39.8at.% Al material; unfortunately, the effectiveness of such strengthening is limited to a homologous temperature of about 0.75 for strain rates of commercial interest (less than 10 to the -7th/sec).

Whittenberger, J. D.↗
NASA NTRS1983

Al-Sm-Eu-Sr systematics of eucrites and moon rocks Implications for planetary bulk compositions

Constraints are placed on the bulk compositions of the eucrite parent body (EPB) and the moon through analysis of the Eu and Sr 'anomalies' of eucrites and lunar rooks. It is noted that the elements Al, REE, and Sr are incompatible with the major minerals of these small, low-f(O2) bodies,except for plagioclase. Predictions can be derived about the concentrations of Al, REE, and Sr in samples affected by plagioclase fractionation, based on the hypothesis that these elements in the EPB and moon are all in proportions close to those in the bulk solar system. It is determined that the predictions are almost idealy fulfilled by eucrites and lunar samples. For the EPB, the ratios REE/Al, Sr/Al, and Sr/REE are found to be constrained probably within 10 percent of the chondritic ratios. For the moon, the constraints are found to be less precise: REE/Al is very probably within 25 percent of chondritic; Sr/Al and Sr/REE are probably within 35 percent of chondritic; Sr/Al and Sr/REE are probably within 35 percent of chondritic. It is concluded that there is a very strong similarity between the bulk compositions of the planets and the compositions of chondritic meteorites.

Warren, P. H.↗
NASA NTRS1983

A surface analytical examination of Stringer particles in Al-Li-Cu alloys

A surface analytical examination of powder metallurgy processed Al-Li-Cu alloys was conducted. The oxide stringer particles often found in these alloys was characterized. Particle characterization is important to more fully understand their impact on the stress corrosion and fracture properties of the alloy. The techniques used were SIMS (Secondary Ion Mass Spectroscopy) and SAM (Scanning Auger Microscopy). The results indicate that the oxide stringer particles contain both Al and Li with relatively high Li content and the Li compounds may be associated with the stringer particles, thereby locally depleting the adjacent matrix of Li solute.

Larson, L. A.↗
NASA NTRS1984

A simple application of the Bailey-Orowan creep model to Fe-39.8 at. pct Al and gamma/gamma prime - alpha

The results of a study to determine the recovery rates and work-hardening coefficients for creep from constant cross-head speed compressive tests are presented. Stressing and straining rates are computed from measured time-load curves obtained from compression testing between 1200 and 1400 K of several B2 crystal structure Fe-39.8 Al intermetallic materials and the directionally solidified eutectic alloy gamma/gamma prime alpha. These quantities are then fitted to the universal form of the Bailey-Orowan equation for creep. The recovery rates were found to be functions of nominal strain rate, stress, and temperature, while the hardening coefficients were dependent only on temperature. While the work-hardening coefficient for gamma/gamma prime - alpha was about 0.05 of the elastic modulus, the work-hardening coefficients for Fe-39.8 at. pct Al were less than 0.002 of the modulus.

Whittenberger, J. D.↗
NASA NTRS1984

The microstructure of minerals in coarse-grained Ca-Al-rich inclusions from the Allende meteorite

Transmission electron microscopy (TEM) is used to investigate the microstructure and microchemistry of minerals in Ca-Al-rich, coarse-grained inclusions (CAI) from the meteorite. The spinels contain only low to moderate dislocation densities and are characterized by a ubiquitous, fine black spotty texture that is thought to originate from a slightly nonstoichiometric composition. Whereas the Ti-Al-pyroxenes are relatively devoid of features, they contain veins of secondary phases apparently deposited in unhealed cracks. Chromite is identified in the veins, indicating transport of oxidized iron during alteration. The melilites show the greatest variety of microstructures and are the most heavily altered phase in CAI. High dislocation densities are common and the crystals exhibit considerable internal strain, suggesting that they have not been annealed.

Barber, D. J.↗
NASA NTRS1984

Application of SIR-B data for groundwater exploration in the Arabian shield and sand-drift monitoring in the AN Nafud and Al Jafurah fringe areas, Kingdom of Saudi Arabia

The primary objectives of the investigation are to determine fully the utility of Shuttle Imaging Radar-B (SIR-B) images for providing valuable surface indicators for ground-water prospecting in the Arabian shield and to identify and assess defining characteristics of sand sheets, sand streaks, and sand dunes in the fringe areas of An Nafud and Al Jafurah. Specific objectives include the determination of the incremental contribution of incidence angle to the total information that can be extracted from SIR-B standard and digitally-enhanced images in the AL Jafurah fringe area; the determination of the incremental contribution of digitally-registered multisensor images; and the development of a groundwater exploration plan for the Ha'il test area in the Arabian Shield.

Berlin, G. L.↗
NASA NTRS1985

A study of interdiffusion in beta + gamma/gamma + gamma prime Ni-Cr-Al

Ternary diffusion in the NiCrAl system at 1200 C was studied with beta + gamma/gamma + gamma prime infinite diffusion couples. Interdiffusion resulted in the formation of complex, multiphase diffusion zones. Concentration/distance profiles for Cr and Al in the phases present in the diffusion zone were measured after 200 hr. The Ni-rich portion of the NiCrAl phase diagram (1200 C) was also determined. From these data, bulk Cr and Al profiles were calculated and translated to diffusion paths on the ternary isotherm. Growth layer kinetics of the layers present in the diffusion zone were also measured.

Carol, L. A.↗
NASA NTRS1985

Study of the effects of implantation on the high Fe-Ni-Cr and Ni-Cr-Al alloys

A theoretical study of the effects of implantation on the corrosion resistance of Fe-Ni-Cr and Ni-Cr-Al alloys was undertaken. The purpose was to elucidate the process by which corrosion scales form on alloy surfaces. The experiments dealt with Ni implanted with Al, exposed to S at high temperatures, and then analyzed using scanning electron microscopy, scanning Auger spectroscopy and X-ray fluorescence spectroscopy. Pair bonding and tight-binding models were developed to study the compositions of the alloys and as a result, a new surface ordering effect was found which may exist in certain real alloys. With these models, the behavior of alloy constituents in the presence of surface concentrations of O or S was also studied. Improvements of the models to take into account the important effects of long- and short-range ordering were considered. The diffusion kinetics of implant profiles at various temperatures were investigated, and it was found that significant non-equilibrium changes in the profiles can take place which may affect the implants' performance in the presence of surface contaminants.

Ribarsky, M. W.↗
NASA NTRS1985

Measurement of interaction cross section of cosmic ray Fe nuclei (E4 GeV/N) with Al target

Although the study of relatvistic heavy ion interaction encumbered by the low intensities of the incident heavy nuclei in cosmic ray experiments, however, one can use a suitable structure of detector to attain a result with a reasonable accuracy. A cross section value of Fe(E 4 GeV/N) with Al is presented. CR-39 was used as detector and Al as target. The cross section value is estimated using maximum likelihood method.

Ren, G. X.↗