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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 37 records · Page 2
All sourcesNASA NTRSDOE OSTI
NASA NTRS1990

Processing effects on the mechanical properties of tungsten heavy alloys

Tungsten heavy alloys exhibit significant mechanical property sensitivities to the fabrication variables. These sensitivities are illustrated in this examination of vacuum sintering and the effects of composition, sintering temperature, and sintering time on the mechanical properties of tungsten heavy alloys. Measurements were conducted to assess the density, strength, hardness, and elongation dependencies. A detrimental aspect of vacuum sintering is matrix phase evaporation, although vacuum sintering does eliminate the need for postsintering heat treatments.

Kishi, Toshihito↗
DOE OSTI2024

Microstructurally-Inspired Strategies to Print Tantalum and Tantalum-Tungsten Alloys

The goal of this project is to investigate strategies to print tantalum and tantalum- tungsten alloys, which are notoriously difficult to print with consistent results because of the sensitivity of the properties to small concentrations of interstitial impurities (particularly oxygen) and microstructure, and hence to processing conditions. The ultimate tensile stress (UTS) for non-additively manufactured Ta as a function of temperature shows a stunning variation. In direct metal laser sintering (DMLS) Ta, a strong dependence of porosity, grain morphology and texture on processing conditions was found.

36 MATERIALS SCIENCE↗
NASA NTRS1966

New tungsten alloy has high strength at elevated temperatures

Tungsten-hafnium-carbon alloy has tensile strengths of 88,200 psi at 3000 deg F and 62,500 psi at 3500 deg F. Possible industrial applications for this alloy would include electrical components such as switches and spark plugs, die materials for die casting steels, and heating elements.

Source record↗
DOE OSTI2026

High temperature stabilization of ultrafine grain tungsten alloys through synergistic compositional complexities

Thermally-stabilized fine-grained microstructures in tungsten provide a pathway to harnessing enhanced properties such as a reduced ductile-to-brittle transition temperature and improved strength while mitigating the adverse effects of grain growth and recrystallization. Here, in this study, we employ a material design strategy that relies on grain boundary segregation in the nanocrystalline state driven by alloy thermodynamics balanced with impurity scavenging through in situ formation of kinetically-stabilizing metal carbides. A W-Ti-Cr alloy is designed through lattice Monte Carlo methods and subsequently synthesized in a single-phase nanocrystalline state, which upon annealing, evolves into an ultrafine grained microstructure containing chromium grain boundary segregation collectively with a dispersed TiX (X=C,O) phase through the reaction of titanium with carbon and oxygen impurities. In situ synchrotron X-ray diffraction experiments demonstrate that increased Ti promotes stabilization across a larger temperature range but with diminishing returns above 10 at.% Ti. Long-term stability was confirmed through the retention of the ultrafine grained microstructure for a total of 8 days (192 h) at 1300 °C without grain/carbide growth and/or recrystallization. Our results demonstrate that, through strategic tailoring of composition and microstructure, one can harness the benefits of both thermodynamic and kinetic stabilization mechanisms, opening pathways for future alloy formulations that expand the window of stability.

36 MATERIALS SCIENCE↗
DOE OSTI2025

Quasi-static to Dynamic Mechanical Response and Microstructure Development of Tantalum-Tungsten Alloys

Lawrence Livermore National Laboratory (LLNL) is interested the quasi-static to dynamic mechanical response and microstructure evolution of tantalum-tungsten (Ta-W) alloys (Ta-2.5W, Ta-5W, and Ta-10W, wt.%) made by conventional wrought processing and additive manufacturing (AM). This work scope was performed at the Colorado School of Mines (Mines) and included quasi-static (e.g., 10 -3 s -1 ) mechanical testing in tension and compression, along with selected high strain rate (Kolsky) pressure bar testing in compression (e.g., 10 3 s -1 ), with and without temperature variations in some instances. Complementary microstructure characterization was performed on undeformed and deformed samples to understand the role of processing on microstructural evolution and the deformation mechanisms that impact the mechanical response with variations in strain rate, temperature, and strain state (e.g., tension versus compression in selected examples). The wrought material provided by LLNL from Viridis Materials was found to have unrecrystallized regions within the microstructure, which led to unexpected results relative to previously reported properties for Ta-W. The AM Ta-2.5W (wt.%) material provided by LLNL was found to have higher compressive strength than wrought Ta-2.5W (wt.%), which is hypothesized to be due to differences in the crystallographic texture between the two materials. This project partially supported several postdocs and graduate students at Mines.

36 MATERIALS SCIENCE↗
NASA NTRS1967

High-strength tungsten alloy with improved ductility

Alloy combines superior strength at elevated temperatures with improved ductility at lower temperatures relative to unalloyed tungsten. Composed of tungsten, rhenium, hafnium, and carbon, the alloy is prepared by consumable electrode vacuum arc-melting and can be fabricated into rod, plate, and sheet.

Klopp, W. D.↗
NASA NTRS1988

Tensile behavior of tungsten and tungsten-alloy wires from 1300 to 1600 K

The tensile behavior of a 200-micrometer-diameter tungsten lamp (218CS-W), tungsten + 1.0 atomic percent (a/o) thoria (ST300-W), and tungsten + 0.4 a/o hafnium carbide (WHfC) wires was determined over the temperature range 1300 t0 1600 K at strain rates of 3.3 X 10 to the -2 to 3.3 X 10 to the -5/sec. Although most tests were conducted on as-drawn materials, one series of tests was undertaken on ST300-W wires in four different conditions: as-drawn and vacuum-annealed at 1535 K for 1 hr, with and without electroplating. Whereas heat treatment had no effect on tensile properties, electropolishing significantly increased both the proportional limit and ductility, but not the ultimate tensile strength. Comparison of the behavior of the three alloys indicates that the HfC-dispersed material possesses superior tensile properties. Theoretical calculations indicate that the strength/ductility advantage of WHfC is due to the resistance to recrystallization imparted by the dispersoid.

Hee, Man Yun↗
NASA NTRS1966

Lower-cost tungsten-rhenium alloys

Tungsten-rhenium alloys with a substantially more dilute rhenium content have ductilities and other mechanical properties which compare favorably with the tungsten-rhenium alloys having much higher concentrations of the costly rhenium.

Klopp, W. D.↗
NASA NTRS1985

Interdiffusional effects between tungsten fibers and an iron-nickel-base alloy

Tungsten fibers in the INCOLOY 903 alloy were annealed for over 100 hours at 1038 C and 1200 C. It was found that interdiffusion results in the formation of a reaction zone. SEM-EDS probe analysis showed that the chemistries across this zone were constant, suggesting the zone was a compound phase. The composition of the compound was estimated to be that of a mu-type phase. The local chemistry (in atomic percent) at the reaction zone/alloy matrix interface was found to be approximately 8 pct W, 1.2 pct Nb, 40 pct Fe, 14 pct Co, and 36 pct Ni. In addition, recrystallization was observed in both the remaining tungsten fiber and the nearby INCOLOY 903 matrix after annealing at 1200 C, but not at 1038 C. The results of this study suggest that reaction zone growth kinetics can be minimized by the reduction of Co and Fe and the increase of W in the matrix alloy.

Caulfield, T.↗