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At least 73 records · Page 4
All sourcesNASA NTRSDOE OSTI
NASA NTRS1976

The abundances of zirconium and hafnium in the solar system

The concentrations of zirconium and hafnium have been determined in the Orgueil, Murchison, Allende, Bruderheim, and Alais meteorites by radiochemical neutron activation analysis. The mean Zr/Hf weight ratio in the first four of these meteorites is 31.3 (plus or minus 2.2), indicating no major fractionation of Zr from Hf. Alais contains anomalously high amounts of many refractory lithophile elements, including Zr and Hf. Orgueil contains 3.1 ppm Zr and 0.11 ppm Hf, corresponding to 9.0 and 0.16 atoms, respectively, relative to 1 million Si atoms.

Ganapathy, R.↗
NASA NTRS1977

Graphical method for predicting life of a rocket thrust chamber with half-hard zirconium-copper liner and electroformed nickel closeout

A method for estimating the life of a regeneratively cooled rocket thrust chamber was developed and is based on the hot-gas wall temperature and the temperature difference between the hot-gas wall and the outside surface of the closeout. This method permits a quick estimate of the life of a thrust chamber when design changes or test-cycle variations are considered. Strain range and life are presented graphically as functions of these temperature parameters for a typical high-performance rocket thrust chamber with a half-hard zirconium-copper liner and an electroformed nickel closeout.

Kasper, H. J.↗
NASA NTRS1977

Zirconium modified nickel-copper alloy

An improved material for use in a catalytic reactor which reduces nitrogen oxide from internal combustion engines is in the form of a zirconium-modified, precipitation-strengthened nickel-copper alloy. This material has a nominal composition of Ni-30 Cu-0.2 Zr and is characterized by improved high temperature mechanical properties.

Whittenberger, J. D.↗
NASA NTRS1984

Oxidation characteristics of molybdenum-zirconium oxide cermets

The oxidation of molybdenum is affected by the factors of temperature, the oxygen pressure in the oxidizing atmosphere, and the time of exposure. Studies of the oxidation characteristics of Mo show that the oxidation rate increases strongly when the temperature exceeds 600 C. Investigations of the behavior of cermets with various percentages of zirconium oxide are discussed, taking into account oxidation conditions at temperatures under and above the melting point of molybdenum trioxide.

Heitzinger, B.↗
NASA NTRS1984

Effects of cobalt, boron, and zirconium on the microstructure of Udimet 738

A structural study was carried out on Co modified Udimet 738 alloys containing 0.04, 0.10, and 0.20 wt % Zr at 0.01 and 0.03 wt % B levels. Samples in the as-cast and solution-treated conditions were exposed at 843 C to study structural stability. The structures produced by the interactions of Co, Zr, and B were studied by SEM, X-ray diffraction, and dispersive analysis techniques. The additions of large amounts of Zr and B were found to increase the solidification range of the U-738. Structural changes involved eutectic gamma prime islands, formation of low melting point compounds, and precipitation of borides and Zr rich phases. Boron and zirconium additions did not show substantial changes in mechanical properties. Removal of Co from the alloys resulted in reduction of the matrix solubility for carbon and increase in the gamma prime solvus. Structural instabilities found were continuous grain boundary M23C6 films, MC breakdown, and plate-like phases. Removal of cobalt resulted in a slight decrease in tensile and stress rupture properties. Detailed structural results presented.

Nakanishi, T. G.↗
NASA NTRS1985

Explosive Welding of Aluminum, Titanium and Zirconium to Copper Sheet Metal

The main material properties affecting the explosive weldability of a certain metal combination are the yield strength, the ductility, the density and the sonic velocity of the two metals. Successful welding of the metal combination depends mainly on the correct choice of the explosive welding parameters; i.e., the stand off distance, the weight of the explosive charge relative to the weight of the flyer plate and the detonation velocity of the explosive. Based on the measured and the handbook values of the properties of interest, the explosive welding parameters were calculated and the arrangements for the explosive welding of the Al alloy 6061-T6, titanium and zirconium to OFHC copper were determined. The relatively small sheet metal thickness (1/8") and the fact that the thickness of the explosive layer must exceed a certain minimum value were considered during the determination of the explosive welding conditions. The results of the metallographic investigations and the measurements of the shear strength at the interface demonstrate the usefulness of these calculations to minimize the number of experimental trials.

Hegazy, A. A.↗
NASA NTRS1985

Effect of chloride incorporation on the crystallization of zirconium-barium-lanthanum-aluminum fluoride glass

One aspect of the influence of preparation procedure on the crystallization behavior of a zirconium-barium-lanthanum-aluminum fluoride glass was studied. The crystallization pattern of this glass may be affected by the chlorine concentration within it. In particular, when such glasses are heated at low temperatures, the alpha-Ba-Zr-F6 crystalline phase forms only in those glasses which contain chloride.

Neilson, G. F.↗
NASA NTRS1988

Creep behavior of tungsten/niobium and tungsten/niobium-1 percent zirconium composites

The creep behavior and microstructural stability of tungsten fiber reinforced niobium and niobium 1 percent zirconium was determined at 1400 and 1500 K in order to assess the potential of this material for use in advanced space power systems. The creep behavior of the composite materials could be described by a power law creep equation. A linear relationship was found to exist between the minimum creep rate of the composite and the inverse of the composite creep rupture life. The composite materials had an order of magnitude increase in stress to achieve 1 percent creep strain and in rupture strength at test temperatures of 1400 and 1500 K compared to unreinforced material. The composite materials were also stronger than the unreinforced materials by an order of magnitude when density was taken into consideration. Results obtained on the creep behavior and microstructural stability of the composites show significant potential improvement in high temperature properties and mass reduction for space power system components.

Petrasek, Donald W.↗
NASA NTRS1986

Characterization of precipitates in a niobium-zirconium-carbon alloy

A niobium alloy with 1 percent zirconium and 0.063 percent carbon by weight was investigated in the as-rolled and annealed conditions, and after high-temperature (1350 and 1400 K) exposure with and without an applied stress. In the as-rolled and annealed conditions, large metastable carbides were observed in addition to a regular distribution of small particles. During the high-temperature exposure, the majority of the large carbides were dissolved and a more stable carbide phase formed. This finely dispersed phase had a composition determined to be approximately 70 percent ZrC and approximately 30 percent NbC and showed some evidence of an orientation relationship with the matrix. The precipitates appeared to coarsen slightly after approximately 5000 hr exposure in the presence of an applied stress resulted in a decrease in the size and in the interparticle spacing of the stable precipitates. However, the composition of the precipitate phase and its ability to pin dislocations were not affected by the temperature or stress conditions.

Grobstein, T. L.↗
NASA NTRS1988

Creep behavior of tungsten/niobium and tungsten/niobium-1 percent zirconium composites

A study was conducted to determine the feasibility of using tungsten fiber reinforced niobium or niobium-1 percent zirconium matrix composites to meet the anticipated increased temperature and creep resistance requirements imposed by advanced space power systems. The results obtained on the short time tensile properties indicated that W/Nb composites showed significant improvements in high temperature strength and offer significant mass reductions for high temperature space power systems. The prime material requirement for space power systems applications is long time creep resistance. A study was conducted to determine the effect of high temperature exposure on the properties of these composites, with emphasis upon their creep behavior at elevated temperatures.

Petrasek, D. W.↗
NASA NTRS1989

Observations on the brittle to ductile transition temperatures of B2 nickel aluminides with and without zirconium

The effect of a zirconium addition (0.05 at. pct) to a stoichiometric NiAl alloy on the brittle-to-ductile transition temperature (BDTT) of this alloy was investigated. Constant velocity tensile tests were conducted to fracture between 300 and 1100 K under initial strain rate 0.00014/sec, and the true stress and true strain values were determined from plots of load vs time after subtracting the elastic strain. The inelastic strain was measured under a traveling microscope. Microstructural characterization of as-extruded and fractured specimens was carried out by SEM and TEM. It was found that, while the addition of 0.05 at. pct Zr strengthened the NiAl alloy, it increased its BDTT; this shift in the BDTT could not be attributed either to variations in grain size or to impurity contents. Little or no room-temperature ductility was observed for either alloy.

Raj, S. V.↗
NASA NTRS1991

The effect of copper, chromium, and zirconium on the microstructure and mechanical properties of Al-Zn-Mg-Cu alloys

The present study evaluates the effect of the systematic variation of copper, chromium, and zirconium contents on the microstructure and mechanical properties of a 7000-type aluminum alloy. Fracture toughness and tensile properties are evaluated for each alloy in both the peak aging, T8, and the overaging, T73, conditions. Results show that dimpled rupture essentially characterize the fracture process in these alloys. In the T8 condition, a significant loss of toughness is observed for alloys containing 2.5 pct Cu due to the increase in the quantity of Al-Cu-Mg-rich S-phase particles. An examination of T8 alloys at constant Cu levels shows that Zr-bearing alloys exhibit higher strength and toughness than the Cr-bearing alloys. In the T73 condition, Cr-bearing alloys are inherently tougher than Zr-bearing alloys. A void nucleation and growth mechanism accounts for the loss of toughness in these alloys with increasing copper content.

Wagner, John A.↗
NASA NTRS1953

Preliminary investigation of zirconium boride ceramals for gas-turbine blade applications

Zirconium boride ZrB2 ceramals were investigated for possible gas-turbine-blade application. Included in the study were thermal shock evaluations of disks, preliminary turbine-blade operation, and observations of oxidation resistance. Thermal shock disks of the following three compositions were studied: (a) 97.5 percent ZrB2 plus 2.5 percent B by weight; (b) 92.5 percent ZrB2 plus 7.5 percent B by weight; and (c) 100 percent ZrB2. Thermal shock disks were quenched from temperatures of 1800 degrees, 2000 degrees, 2200 degrees, and 2400 degrees F. The life of turbine blades containing 93 percent ZrB2 plus 7 percent B by weight was determined in gas-turbine tests. The blades were run at approximately 1600 degrees F and 15,000 to 26,000 rpm. The thermal shock resistance of the 97.5 percent ZrB2 plus 2.5 percent boron ceramals compares favorably with that of TiC plus Co and TiC plus Ni ceramals. Oxidation of the disks during the thermal shock evaluation was slight for the comparatively short time (8.3 hr) up through 2000 degrees F. Oxidation of a specimen was severe, however, after 100 hours at 2000 degrees F. The turbine blade performance evaluation of the 93 percent ZrB2 plus 7 percent B composition was preliminary in scope ; no conclusions can be drawn.

Hoffman, Charles A↗
NASA NTRS1958

Boron and Zirconium from Crucible Refractories in a Complex Heat-Resistant Alloy

In a laboratory study of the factors involved in the influence of induction vacuum melting on 55ni-20cr-15co-4mo-3ti-3al heat resistant alloy, it was found that the major factor was the type of ceramic used as the crucible. The study concluded that trace amounts of boron or zirconium derived from reaction of the melt with the crucible refactories improved creep-rupture properties at 1,600 degrees F. Boron was most effective and, in addition, markedly improved hot-workability.

Decker, R F↗
NASA NTRS1996

Nucleation Pathways For Freezing Of Two Grades Of Zirconium

Report discusses classical nucleation theory of freezing and describes experimental study of nucleation mechanisms that predominate during freezing of spherical specimens of initially molten zirconium levitated electrostatically in vacuum.

Rhim, Won-Kyu↗
NASA NTRS1995

Constant-Pressure Specific Heat to Hemispherical Total Emissivity Ratio for Undercooled Liquid Nickel, Zirconium, and Silicon

Radiative cooling curves of nickel, zirconium, and silicon melts that were obtained using the high-temperature, high-vacuum electrostatic levitator (HTHVESL) have been analyzed to determine the ratio between the constant-pressure specific heat and the hemispherical total emissivity, c(sub p)(T)epsilon(sub T)(T). This ratio determined over a wide liquid temperature range for each material allows us to determine c(sub p)(T) if epsilon(sub T)(T) is known or vice versa. Following the recipe, the hemi-spherical total emissivities for each sample at its melting temperature, epsilon(sub T)(T(sub M)), have been determined using c(sub p)(T(sub m)) values available in the literature. They are 0.15, 0.29, and 0.17, for Ni, Zr, and Si, respectively.

Rulison, Aaron J.↗
NASA NTRS1995

Mechanical Properties of Continuous Fiber Reinforced Zirconium Diboride Matrix Composites

Continuous fiber reinforced zirconium diboride matrix composites, SCS-9a-(RBSiCZrB2)matrix, are being developed for leading edge, rocket nozzle and turbine engine applications. Recently, the composite materials have been characterized for tensile properties to 1250 C, the highest temperature tested. The tensile properties are fiber dominated as the matrix is microcracked on fabrication, but favorable failure characteristic are observed. Compression and shear mechanical testing results will be reported if completed. The effects of fiber volume fraction and matrix density on mechanical properties will be discussed. The target applications of the materials will be discussed. Specific testing being performed towards qualification for these applications will be included.

Stuffle, Kevin↗
NASA NTRS2006

Fabrication and Evaluation of Titanium and Zirconium based Wires for use during Extended, Deep Space, Missions

Novel materials and designs are necessary for transport vessels and propulsion systems to fulfill NASA's vision of easier access to space and the expansion of human exploration beyond low-earth orbit. Spacecraft components must necessarily be lighter and stronger than their predecessors and will likely be required to serve new purposes. Furthermore, they must be resilient to the thermal, vacuum, and radiation environment of space for extended periods of time and may need to perform in the near proximity of a nuclear fuel source. To this end research has been initiated to fabricate novel, composite, wires based on titanium and zirconium pearlitic alloys. It is expected that the fabricated wire will well endure in the space environment with application as tethers, sail components, fasteners, and a myriad of other (including earth-based) uses. A background on pearlitic wire, novel alloy development, microstructural characterization, and initial mechanical testing results will be presented and discussed.

Grugel, Richard N.↗