SCIENTIFIC AND TECHNICAL AEROSPACE REPORTS

A Biweekly Publication of the National Aeronautics and Space Administration
VOLUME 44, ISSUE 7 - April 07, 2006

26 METALS AND METALLIC MATERIALS
Includes physical, chemical, and mechanical properties of metals and metallic materials; and metallurgy.

20060009000 NASA Glenn Research Center, Cleveland, OH, USA

Nickel Base Superalloy Turbine Disk

Gabb, Timothy P., Inventor; Gauda, John, Inventor; Telesman, Ignacy, Inventor; Kantzos, Pete T., Inventor; December 13, 2005; 17 pp.; In English Patent Info.: Filed 29 Oct. 2002; US-Patent-6,974,508; US-Patent-Appl-SN-283220; NASA-Case-LEW-17318-1; No Copyright; Avail.: CASI: A03, Hardcopy

A low solvus, high refractory alloy having unusually versatile processing mechanical property capabilities for advanced disks and rotors in gas turbine engines. The nickel base superalloy has a composition consisting essentially of, in weight percent, 3.0-4.0 N, 0.02-0.04 B, 0.02-0.05 C, 12.0-14.0 Cr, 19.0-22.0 Co, 2.0-3.5 Mo, greater than 1.0 to 2.1 Nb, 1.3 to 2.1 Ta,3.04.OTi,4.1 to 5.0 W, 0.03-0.06 Zr, and balance essentially Ni and incidental impurities. The superalloy combines ease of processing with high temperature capabilities to be suitable for use in various turbine engine disk, impeller, and shaft applications. The Co and Cr levels of the superalloy can provide low solvus temperature for high processing versatility. The W, Mo, Ta, and Nb refractory element levels of the superalloy can provide sustained strength, creep, and dwell crack growth resistance at high temperatures. Official Gazette of the U.S. Patent and Trademark Office

Heat Resistant Alloys; Refractory Metal Alloys; Nickel Alloys; Rotors; Gas Turbine Engines; Mechanical Properties

20060009152 NASA Langley Research Center, Hampton, VA, USA

Electron Beam Freeform Fabrication (EBF3) for Cost Effective Near-Net Shape Manufacturing

Taminger, Karen M.; Hafley, Robert A.; March 2006; 14 pp.; In English; Original contains color and black and white illustrations Patent Info.: Filed 581.02.08.07 Report No.(s): NASA/TM-2006-214284; L-19241; No Copyright; Avail.: CASI: A03, Hardcopy

Manufacturing of structural metal parts directly from computer aided design (CAD) data has been investigated by numerous researchers over the past decade. Researchers at NASA Langley Research Center are developing a new solid freeform fabrication process, electron beam freeform fabrication (EBF3), as a rapid metal deposition process that works efficiently with a variety of weldable alloys. EBF3 deposits of 2219 aluminium and Ti-6Al-4V have exhibited a range of grain morphologies depending upon the deposition parameters. These materials have exhibited excellent tensile properties comparable to typical handbook data for wrought plate product after post-processing heat treatments. The EBF3 process is capable of bulk metal deposition at deposition rates in excess of 2500 cubic centimeters per hour (150 in3/hr) or finer detail at lower deposition rates, depending upon the desired application. This process offers the potential for rapidly adding structural details to simpler cast or forged structures rather than the conventional approach of machining large volumes of chips to produce a monolithic metallic structure. Selective addition of metal onto simpler blanks of material can have a significant effect on lead time reduction and lower material and machining costs. Author

Electron Beams; Fabrication; Cost Effectiveness; Manufacturing

20060009160 Worcester Polytechnic Inst., MA, USA

Low Cost and Energy Efficient Methods for the Manufacture of Semi-Solid (SSM) Feedstock. (Report for January 15, 2002-June 30, 2005)

Apelian, D.; Pan, Q.; Jha, M.; January 2005; 48 pp.; In English Report No.(s): DE2005-859300; No Copyright; Avail.: National Technical Information Service (NTIS)

The SSM Consortium (now ACRC) at WPI has been carrying out fundamental, pre-competitive research in SSM for several years. Current and past research (at WPI) has generated many results of fundamental and applied nature, which are available to the SSM community. These include materials characterization, yield stress effects, alloy development, rheological properties, process modeling/simulation, semi-solid slurry formation, etc. Alternative method to produce SSM slurries at lower processing costs and with reduced energy consumption is a critical need. The production of low cost SSM feedstock will certainly lead to a dramatic increase in the tonnage of castings produced by SSM, and will provide end users such as the transportation industry, with lighter, cheaper and high performance materials. In this program, the research team has addressed three critical issues in semi-solid processing. They are: (1) Development of low cost, reliable slurry-on-demand approaches for semi-solid processing; (2) Application of the novel permanent grain refining technology-SiBloy for the manufacture of high-quality SSM feedstock, and (3) Development of computational and modeling tools for semi-solid processing to enhance SSM process control. Salient results from these studies are summarized and detailed in our final technical report. NTIS

Costs; Energy Conservation; Low Cost; Manufacturing; Metals

20060009296 NASA Glenn Research Center, Cleveland, OH, USA

Observations of a Cast Cu-Cr-Zr Alloy

Ellis, David L.; February 2006; 16 pp.; In English Contract(s)/Grant(s): WBS 22-617-44-20 Report No.(s): NASA/TM-2006-213968; E-15286; No Copyright; Avail.: CASI: A03, Hardcopy

Prior work has demonstrated that Cu-Cr-Nb alloys have considerable advantages over the copper alloys currently used in regeneratively cooled rocket engine liners.

Observations indicated that Zr and Nb have similar chemical properties and form very similar compounds.

Glazov and Zakharov et al. reported the presence of Cr2Zr in Cu-Cr-Zr alloys with up to 3.5 wt% Cr and Zr though Zeng et al. calculated that Cr2Zr could not exist in a ternary Cu-Cr-Zr alloy. A cast Cu-6.15 wt% Cr-5.25 wt% Zr alloy was examined to determine if the microstructure developed would be similar to GRCop-84 (Cu-6.65 wt% Cr-5.85 wt% Nb).

It was observed that the Cu-Cr-Zr system did not form any Cr2Zr even after a thermal exposure at 875 C for 176.5 h. Instead the alloy consisted of three phases: Cu, Cu5Zr, and Cr. Author

Copper Alloys; Microstructure; Regenerative Cooling; Rocket Engines; Chemical Properties

20060009953 West Virginia Univ., Morgantown, WV USA

Understanding and Improving High-Temperature Structural Properties of Metal-Silicide Intermetallics

Kang, B. S.; Oct. 2005; 148 pp.; In English Report No.(s): DE2005-859223; No Copyright; Avail.: National Technical Information Service (NTIS)

The objective of this project was to understand and improve high-temperature structural properties of metal-silicide intermetallic alloys. Through research collaboration between the research team at West Virginia University (WVU) and Dr. J.H. Schneibel at Oak Ridge National Laboratory (ORNL), molybdenum silicide alloys were developed at ORNL and evaluated at WVU through atomistic modeling analyses, thermo-mechanical tests, and metallurgical studies.

In this study, molybdenum-based alloys were ductilized by dispersing MgAl(sub 2)O(sub 4) or MgO spinel particles. The addition of spinel particles is hypothesized to getter impurities such as oxygen and nitrogen from the alloy matrix with the result of ductility improvement. The introduction of fine dispersions has also been postulated to improve ductility by acting as a dislocation source or reducing dislocation pile-ups at grain boundaries. The spinel particles, on the other hand, can also act as local notches or crack initiation sites, which is detrimental to the alloy mechanical properties.

Optimization of material processing condition is important to develop the desirable molybdenum alloys with sufficient room-temperature ductility. Atomistic analyses were conducted to further understand the mechanism of ductility improvement of the molybdenum alloys and the results showed that trace amount of residual oxygen may be responsible for the brittle behavior of the as-cast Mo alloys. For the alloys studied, uniaxial tensile tests were conducted at different loading rates, and at room and elevated temperatures. Thermal cycling effect on the mechanical properties was also studied. Tensile tests for specimens subjected to either ten or twenty thermal cycles were conducted.

For each test, a follow-up detailed fractography and microstructural analysis were carried out. The test results were correlated to the size, density, distribution of the spinel particles and processing time. Thermal expansion tests were carried out using thermo-mechanical analyzer (TMA). Results showed that the coefficient of thermal expansion (CTE) value decreases with the addition of spinel and silicide particles. Thermo-cycling tests showed that molybdenum alloy with 6% wt of spinel (MgAl(sub 2)O(sub 4)) developed microcracks which were caused by thermal expansion mismatch between the spinel particles and molybdenum matrix, as well as the processing conditions. Detailed post-mortem studies of microstructures and segregation of impurities to the oxide dispersion/Mo interfaces were conducted using x-ray diffraction (XRD), scanning electron microscopy (SEM), and energy dispersive spectroscopy (EDS). NTIS

High Temperature; Intermetallics; Silicides

20060009960 Department of Energy, Washington, DC, USA, Tennessee Univ., Knoxville, TN, USA, Oak Ridge National Lab., TN USA

Development of Combinatorial Methods for Alloy Design and Optimization

Pharr, G. M.; Pharr, E. P.; Santella, M. L.; Jul. 2005; 98 pp.; In English Report No.(s): DE2005-842122; No Copyright; Avail.: National Technical Information Service (NTIS)

The primary goal of this research, which was sponsored under the Knowledge Base or Core Activities category of IMF solicitation DE-PS07-01ID14123, was to develop a comprehensive methodology for designing and optimizing metallic alloys by combinatorial principles. Because conventional techniques for alloy preparation are unavoidably restrictive in the range of alloy composition that can be examined, combinatorial methods promise to significantly reduce the time, energy, and expense needed for alloy design. Combinatorial methods can be developed not only to optimize existing alloys, but to explore and develop new ones as well. The scientific approach involved fabricating an alloy specimen with a continuous distribution of binary and ternary alloy compositions across its surface an alloy library and then using spatially resolved probing techniques to characterize its structure, composition, and relevant properties. The three specific objectives of the project were (1) to devise means by which simple test specimens with a library of alloy compositions spanning the range of interest can be produced; (2) to assess how well the properties of the combinatorial specimen reproduce those of the conventionally processed alloys; and (3) to devise screening tools which can be used to rapidly assess the important properties of the alloys. As proof of principle, the methodology was applied to the Fe-Ni-Cr ternary alloy system that constitutes many commercially important materials such as stainless steels and the H-series and C-series heat- and corrosion-resistant casting alloys. Three different techniques were developed for making alloy libraries: (1) vapor deposition of discrete thin films on an appropriate substrate followed by use of solid-state diffusion to alloy film and substrate together; (2) co-deposition of the alloying elements from three separate magnetron sputtering sources onto an inert substrate; and (3) localized melting of thin films with a focused electron-beam welding (EBW) system. Each of the techniques was found to have its own advantages and disadvantages. NTIS

Combinatorial Analysis; Design Optimization; Alloying

Source: NASA