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Results for “PRECIPITATION HARDENING”

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 55 records · Page 3
All sourcesNASA NTRSDOE OSTI
NASA NTRS1977

The effect of microstructure and strength on the fracture toughness of an 18 Ni, 300 grade maraging steel

Fractography and metallographic sectioning were used to investigate the influence of microstructure and strength on the fracture toughness (KIc) and fracture mechanism of an 18 Ni, 300 grade maraging steel. Increased yield strength from 1442 to 2070 MN/m squared through precipitation hardening results in a KIc loss from 143 to 55 MN/m superscript 3/2. Ti (C,N) Ti2S, and TiC inclusions in sizes from 1 to 8, 1 to 15, and 0.1 to 2 microns respectively serve as sites for void nucleation and lead to fracture by the dimpled rupture process in all strength levels considered. TiC nucleated dimples occupy more than half the fracture in all conditions. Void nucleation rate and resultant number of dimples per unit area of fracture increase with increasing yield strength. Average dimple size decreases with increasing strength and/or overaging which follows from the decreasing amount of stable void growth measured by sectioning tensile specimens. Void growth is assisted by crack branching along a path of TiC inclusions. Coalescence occurs in the highest strength materials by a combination of TiC void nucleation and premature separation at strengthening precipitates.

Psioda, J. A.↗
NASA NTRS1970

High-strength magnetic materials

Two new precipitation-hardened magnetic alloys are suitable for operation in 800 to 1600 deg F range. One is a martensitic alloy and the other a cobalt-based alloy. They possess improved creep resistance and have application in high temperature inductors and alternators.

Detert, K.↗
NASA NTRS1971

Metal alloy resistivity measurements at very low temperatures

High speed, automated system accurately measures to approximately one percent in three minutes. System identifies materials having constant thermal or electric conductivity, predicts new material properties, develops alloys in accordance with desired specifications, and develops nondestructive devices for measuring precipitation hardening.

Childs, G. E.↗
NASA NTRS1972

Material variability as measured by low temperature electrical resistivity.

Low temperature electrical resistivity was used to determine the material variability (1) between different manufacturers, (2) between different heats from the same manufacturer, and (3) within a given heat for Al 2024, Al-5% Mg alloys, Inconel 718, A286 stainless, and AISI 316. Generally, the coefficient of variation for solution annealed alloys ranged from 1.2 to 14% between manufacturers, 0.8 to 5.1% between heats, and 0.1 to 1.6% within a heat with stainless steels at the low ends and Al 2024 at the high ends. The variability is increased if the material is in a precipitation-hardened condition. A statistical analysis suggests that the variability within a heat is non-normal.

Clark, A. F.↗
NASA NTRS1975

High-strength alloy with resistance to hydrogen-environment embrittlement

Alloy is precipitation-hardened, high-strength, and low-thermal-expansion materials. It is iron-based and contains nickel and chromium at lower levels than high-strength alloys. It is readily welded and brazed and has good oxidation resistance. Tests indicated there was no reduction of notched or smooth strength.

Mcnamara, T. G.↗
NASA NTRS1973

Evaluation of Stress Corrosion Cracking Susceptibility Using Fracture Mechanics Techniques, Part 1

Stress corrosion cracking (SSC) tests were performed on 13 aluminum alloys, 13 precipitation hardening stainless steels, and two titanium 6Al-4V alloy forgings to compare fracture mechanics techniques with the conventional smooth specimen procedures. Commercially fabricated plate and rolled or forged bars 2 to 2.5-in. thick were tested. Exposures were conducted outdoors in a seacoast atmosphere and in an inland industrial atmosphere to relate the accelerated tests with service type environments. With the fracture mechanics technique tests were made chiefly on bolt loaded fatigue precracked compact tension specimens of the type used for plane-strain fracture toughness tests. Additional tests of the aluminum alloy were performed on ring loaded compact tension specimens and on bolt loaded double cantilever beams. For the smooth specimen procedure 0.125-in. dia. tensile specimens were loaded axially in constant deformation type frames. For both aluminum and steel alloys comparative SCC growth rates obtained from tests of precracked specimens provide an additional useful characterization of the SCC behavior of an alloy.

Sprowls, D. O.↗
NASA NTRS1975

The effect of microstructure and strength on the fracture toughness of an 18 Ni, 300 grade maraging steel

A 300 grade maraging steel was chosen as a vehicle by which to understand the inverse relationship between strength and toughness in high strength alloys such as the 18 Ni maraging steels. The 18 Ni, 300 grade maraging material was a commercial grade consumable-electrode, vacuum arc remelted heat obtained in the form of forged and annealed plate. The matrix contained a population of second-phase impurity inclusions which was a product of the casting and hot working processes. These inclusions did not change with subsequent precipitation hardening. Changes in microstructure resulting in strength increases were brought about by variations in aging temperature and time. Maximum strength was attained in the 300 grade maraging steel by aging at 427 C (800 F) for 100 hours. Tensile, fatigue precracked Charpy impact, and plane-strain fracture toughness tests were performed at room temperature, 20 C (68 F). With increasing strength the fracture toughness decreases as smaller and smaller inclusions act as sites for void initiation.

Psioda, J. A.↗
NASA NTRS1982

Diamond Sheet: A new diamond tool material

Diamond sheet is termed a diamond tool material because it is not a cutting tool, but rather a new material from which a variety of different tools may be fabricated. In appearance and properties, it resembles a sheet of copper alloy with diamond abrasive dispersed throughout it. It is capable of being cut, formed, and joined by conventional methods, and subsequently used for cutting as a metal bonded diamond tool. Diamond sheet is normally made with industrial diamond as the abrasive material. The metal matrix in diamond sheet is a medium hard copper alloy which has performed well in most applications. This alloy has the capability of being made harder or softer if specific cutting conditions require it. Other alloys have also been used including a precipitation hardened aluminum alloy with very free cutting characteristics. The material is suitable for use in a variety of cutting, surfacing, and ring type tools, as well as in such mundane items as files and sandpaper. It can also be used as a bearing surface (diamond to diamond) and in wear resistant surfaces.

Mackey, C. R.↗
NASA NTRS1984

Back stress in dislocation creep. Part 1: Basic concepts and measuring techniques

A theory is proposed whereby the plastic deformation of metal materials is determined by the difference between the applied stress and the back stress which characterizes the resistance of the material to plastic deformation. The back stress is usually equivalent to the internal stress or the friction stress and depends on the magnitude of the applied stress and temperature. The concept of back stress is applied to the case of the dislocation creep of precipitation-hardened or dispersion-strengthened metal materials. An additivity rule is formulated which can be useful in interpreting the creep behavior of such materials.

Cadek, J.↗
NASA NTRS1985

New methods for image collection and analysis in scanning Auger microscopy

While scanning Auger micrographs are used extensively for illustrating the stoichiometry of complex surfaces and for indicating areas of interest for fine point Auger spectroscopy, there are many problems in the quantification and analysis of Auger images. These problems include multiple contrast mechanisms and the lack of meaningful relationships with other Auger data. Collection of multielemental Auger images allows some new approaches to image analysis and presentation. Information about the distribution and quantity of elemental combinations at a surface are retrievable, and particular combinations of elements can be imaged, such as alloy phases. Results from the precipitate hardened alloy Al-2124 illustrate multispectral Auger imaging.

Browning, R.↗
NASA NTRS1989

Compressive strength of a B2 matrix NiAl-Nb intermetallic at 1200 and 1300 K

The effect of a large Nb addition to a NiAl, to a final composition 43.5Ni-45.2Al-0.8Fe-10.5Nb (in at. pct), on the high-temperature compressive strength of NiAl was investigated using cylindrical samples which were compression tested in air at 1200 K and 1300 K under constant-velocity conditions. The compressive strength of the Ni-45Al-10.5Nb was compared to data from all known solid solution-strengthened and/or precipitation-strengthened NiAl-based materials. It was found that, for strain rates higher than 5 x 10 to the -6th/sec, the Ni-45Al-10.5Nb is stronger than NiAl. However, this advantage disappears at lower strain rates. A comparison of NiAl-based materials indicated that a NiAl+TiB2 composite containing 20 vol pct 1-micron-diam particles has a strength superiority over all the solid solution and precipitation-hardened aluminides at strain rates below 10 to the -7th/sec.

Whittenberger, J. Daniel↗
NASA NTRS1990

Solid state processing for high temperature alloys and composites

A variety of solid state powder processing methods have been examined for their potential to produce high temperature materials. These techniques included solid state diffusion, mechanical alloying, reaction milling, and exothermic reactions. While both mechanical alloying and exothermic reactions are capable of producing high temperature composites in addition to yielding solid solution and precipitation hardened alloys, reaction milling can only be used to make composite materials. Although at present this method has only been applied to make carbide strengthened Al, recent work indicates that reaction milling is capable of yielding high strength NiAl-AlN composites.

Whittenberger, J. Daniel↗
NASA NTRS1992

Thermomechanical deformation behavior of a dynamic strain aging alloy, Hastelloy X

An experimental study was performed to identify the effects of dynamic strain aging (solute drag) and metallurgical instabilities under thermomechanical loading conditions. The study involved a series of closely controlled thermomechanical deformation tests on the solid-solution-strenghened nickel-base superalloy, Hastelloy X. This alloy exhibits a strong isothermal strain aging peak at approximately 600 C, promoted by the effects of solute drag and precipitation hardening. Macroscopic thermomechanical hardening trends are correlated with microstructural characteristics through the use of transmission electron microscopy. These observations are compared and contrasted with isothermal conditions. Thermomechanical behavior unique to the isothermal database is identified and discussed. The microstructural characteristics were shown to be dominated by effects associated with the highest temperature of the thermomechanical cycle. Results indicate that the deformation behavior of Hastelloy X is thermomechanically path dependent. In addition, guidance is given pertaining to deformation modeling in the context of macroscopic unified theory. An internal state variable is formulated to qualitatively reflect the isotropic hardening trends identified in the TMD experiments.

Castelli, Michael G.↗
NASA NTRS1991

Slow strain rate 1200-1400 K compressive properties of NiAl-1Hf

Compression tests are conducted on NiAl-1Hf to assess the elevated-temperature creep behavior of this precipitation-hardened aluminide. While the strength is high under fast strain rates (more than 10 exp -5/s), under slower conditions the alloy is weak. Thus, it is unlikely that effective creep resistance can be obtained in NiAl through small Hf additions.

Whittenberger, J. D.↗