Engineering Papers⌕ Search

SEARCH · Engineering Papers

Results for “intermetallic”

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.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 91 records · Page 5
All sourcesNASA NTRSDOE OSTI
NASA NTRS1995

Investigation of Strain Aging in the Ordered Intermetallic Compound beta-NiAl

The phenomenon of strain aging has been investigated in polycrystalline and single crystal NiAl alloys at temperatures between 300 and 1200 K. Static strain aging studies revealed that after annealing at 1100 K for 7200 s (i.e., 2h) followed by furnace cooling, high purity, nitrogen-doped and titanium-doped polycrystalline alloys exhibited continuous yielding, while conventional-purity and carbon-doped alloys exhibited distinct yield points and Luders strains. Prestraining by hydrostatic pressurization removed the yield points, but they could be reintroduced by further annealing treatments. Yield points could be reintroduced more rapidly if the specimens were prestrained uniaxially rather than hydrostatically, owing to the arrangement of dislocations into cell structures during uniaxial deformation. The time dependence of the strain aging events followed at t(exp 2/3) relationship suggesting that the yield points observed in polycrystalline NiAl were the result of the pinning of mobile dislocations by interstitials, specifically carbon. Between 700 and 800 K, yield stress plateaus, yield stress transients upon a ten-fold increase in strain rate, work hardening peaks, and dips in the strain rate sensitivity (SRS) have been observed in conventional-purity and carbon-doped polycrystals. In single crystals, similar behavior was observed; in conventional-purity single crystals, however, the strain rate sensitivity became negative resulting in serrated yielding, whereas, the strain rate sensitivity stayed positive in high purity and in molybdenum-doped NiAl. These observations are indicative of dynamic strain aging (DSA) and are discussed in terms of conventional strain aging theories. The impact of these phenomena on the composition-structure-property relations are discerned. Finally, a good correlation has been demonstrated between the properties of NiAl alloys and a recently developed model for strain aging in metals and alloys developed by Reed-Hill et al.

Weaver, Mark Lovell↗
NASA NTRS1997

BFS Method for Alloys Optimized and Verified for the Study of Ordered Intermetallic Material

The aerospace industry has a need for new metallic alloys that are lightweight and have high strength at elevated temperatures. The BFS (Bozzolo, Ferrante, and Smith) method is a new, computationally efficient and physically sound quantum semi-perturbative approach for describing metals and their defects. Based on a simple interpretation of the alloy formation process that identifies strain and chemical contributions to the energy of the alloy, the method provides an atom-by-atom description of an alloy. Its implementation requires little more than algebra and the solution of transcendental equations. At the NASA Lewis Research Center, we have demonstrated that BFS can investigate the properties of a large number of alloys with a minimum computational effort on low-level computers. This screening allows the selection of the best alloy candidates for a particular application and, therefore, promises large cost savings over current approaches.

Source record↗
NASA NTRS2012

Processing Issues for Preliminary Melts of the Intermetallic Compound 60-NITINOL

The effect of various high temperature heat treatments and cooling rates on the hardness of cast 60-NITINOL (60wt%Ni- 40wt%Ti) was studied. The hardness ranged from approximately 33 HRC for annealed specimens to 63 HRC for water quenched specimens. Aging did not have a further effect on the hardness of the heat-treated and quenched material. The issue of material contamination and its possible effect on quench cracking during heat treatment above 1000 C was explored. The Charpy impact energy of the material was found to be relatively low (ranging from 0.4 to 1.0 J) and comparable to that of cast magnesium. Selection of service environments and applications for this material based on these findings should consider the processing route by which it was produced.

Stanford, Malcolm K.↗
NASA NTRS2012

Addressing Machining Issues for the Intermetallic Compound 60-NITINOL

60-NITINOL (60 wt.% Ni - 40 wt.% Ti) is being studied as a material for advanced aerospace components. Frequent wire breakage during electrical-discharge machining of this material was investigated. The studied material was fabricated from hot isostatically pressed 60-NITINOL powder obtained through a commercial source. Bulk chemical analysis of the material showed that the composition was nominal but had relatively high levels of certain impurities, including Al and O. It was later determined that Al2O3 particles had contaminated the material during the hot isostatic pressing procedure and that these particles were the most likely cause of the wire breakage. The results of this investigation highlight the importance of material cleanliness to its further implementation.

Stanford, Malcolm K.↗
NASA NTRS2015

60NiTi Intermetallic Material Evaluation for Lightweight and Corrosion Resistant Spherical Sliding Bearings for Aerospace Applications

NASA Glenn Research Center and the Kamatics subsidiary of the Kaman Corporation conducted the experimental evaluation of spherical sliding bearings made with 60NiTi inner races. The goal of the project was to assess the feasibility of manufacturing lightweight, corrosion resistant bearings utilizing 60NiTi for aerospace and industrial applications. NASA produced the bearings in collaboration with Abbott Ball Corporation and Kamatics fabricated bearing assemblies utilizing their standard reinforced polymer liner material. The assembled bearings were tested in oscillatory motion at a load of 4.54kN (10,000 lb), according to the requirements of the plain bearing specification SAE AS81820. Several test bearings were exposed to hydraulic fluid or aircraft deicing fluid prior to and during testing. The results show that the 60NiTi bearings exhibit tribological performance comparable to conventional stainless steel (440C) bearings. Further, exposure of 60NiTi bearings to the contaminant fluids had no apparent performance effect. It is concluded that 60NiTi is a feasible bearing material for aerospace and industrial spherical bearing applications.

materials↗
NASA NTRS2020

Creepy (not KREEPy) Gold-Indium Intermetallic Compounds on Secondary Ion Mass Spectrometry Samples

A series of Secondary Ion Mass Spectrometry (SIMS) sessions to measure hydrogen (H) in Martian meteorite minerals was completed using the Cameca 6f SIMS and NanoSIMS 50L at Arizona State University (ASU). During these sessions, a “creeping” phenomenon has occurred, where the edges of samples pressed in indium are covered by a metal alloy. We summarize these observations herein, present a collection of preliminary data, and discuss explanations and concerns for future SIMS work. We conclude the report with a research plan for further study.

Dudley, J. M.↗
NASA NTRS2021

Melt Infiltration Studies of 2D Tyranno SA3(R) Ceramic Matrix Composite Preforms with CrSi2 Intermetallic Alloy

The present paper reports the results of melt infiltrating 2D Tyranno SA3@ fiber woven preforms with molten CrSi2 between 1768 and 1896 K under a vacuum of 1.3 x 10-4 Pa (10-6 torr). The infiltration times varied between 1800 and 7200 s, which did not have any significant effect on the volume fraction of voids filled with the metal. Optical and scanning electron microscopy, back scattered electron imaging, energy dispersion spectroscopy and Raman spectroscopy were used to characterize the infiltrated preforms. A plot of the volume fraction of open voids infiltrated against the absolute melt infiltration temperature showed a sharp peak at 1773 K with almost complete infiltration of the voids at this temperature. The extent of silicide infiltration of the preforms dropped steeply above 1773 K with increasing melt infiltration temperature irrespective of the amount of infiltration time. Above 1805 K, the volume fraction of voids infiltrated with the melt was nearly 0%. It is demonstrated that CrSi2 did not show evidence of a reaction with the SiC fibers. The possibility that a resisting force due to contact angle hysteresis (CAH) may have influenced the diminishing amount of voids filled with increasing temperature above 1773 K was examined. The resistance force was estimated to be extremely small to be consequential. Another possibility that the CrSi2 may have decomposed into Cr(g) and Si(g) in the vacuum melt infiltration furnace appeared to be more plausible based on thermodynamic analyses. An empirical equation is proposed to calculate the amount of remaining charge left to infiltrate the preforms at the infiltration temperature. It is shown that an initial charge of 10 g would rationalize the present observations. While the decomposition of the CrSi2 appeared to mostly explain the present results, some discrepancies were observed, which were inconsistent with the decomposition model.

CrSi2, chromium silicide, ceramic matrix composite↗
NASA NTRS2022

Vacuum Melt Infiltration of 2D Tyranno SA3® Ceramic Matrix Composites with Cr-25(wt.%)Si Intermetallic Alloy

The potential and limitations of vacuum melt infiltrating woven preforms of 2D Tyranno SA3 fibers with Cr-25(wt.%)Si alloy were investigated. Microstructural observations revealed that the volume fractions of open voids infiltrated by the molten metal varied between 3.7 and 10.0% irrespective of the magnitudes of the melt infiltration temperatures and hold times, which was attributed in part to substantial volatilization of the silicide charge based on computational thermodynamics. In the absence of experimental data, poor wettability of the melt could not be ruled out unambiguously. Other possible reasons are carefully examined and discarded. Ring microstructures were observed around the fibers mainly at the outer surfaces of the infiltrated preform, where the BN and chemical vapor infiltrated SiC coatings had vaporized in the high vacuum environment. In contrast, they were absent in the interior of the preform, where the coatings were still present with no evidence of molten metal attack of the coatings. Details of thermodynamic calculations are presented to confirm the volatilization of the BN and CVI SiC coatings thereby resulting in the ring microstructures due to the filling of voids by the molten silicide. It is concluded that successful melt infiltration of Tyranno SA3® with Cr-25%Si can be only achieved under sufficient positive pressure to prevent volatilization of the coatings and the molten silicide.

Cr-25%Si↗
NASA NTRS1997

Design Protocols and Analytical Strategies that Incorporate Structural Reliability Models

Ceramic matrix composites (CMC) and intermetallic materials (e.g., single crystal nickel aluminide) are high performance materials that exhibit attractive mechanical, thermal, and chemical properties. These materials are critically important in advancing certain performance aspects of gas turbine engines. From an aerospace engineers perspective the new generation of ceramic composites and intermetallics offers a significant potential for raising the thrust/weight ratio and reducing NO(sub x) emissions of gas turbine engines. These aspects have increased interest in utilizing these materials in the hot sections of turbine engines. However, as these materials evolve and their performance characteristics improve a persistent need exists for state-of-the-art analytical methods that predict the response of components fabricated from CMC and intermetallic material systems. This need provided the motivation for the technology developed under this research effort. Continuous ceramic fiber composites exhibit an increase in work of fracture, which allows for 'graceful' rather than catastrophic failure. When loaded in the fiber direction these composites retain substantial strength capacity beyond the initiation of transverse matrix cracking despite the fact that neither of its constituents would exhibit such behavior if tested alone. As additional load is applied beyond first matrix cracking, the matrix tends to break in a series of cracks bridged by the ceramic fibers. Any additional load is born increasingly by the fibers until the ultimate strength of the composite is reached. Thus modeling efforts supported under this research effort have focused on predicting this sort of behavior. For single crystal intermetallics the issues that motivated the technology development involved questions relating to material behavior and component design. Thus the research effort supported by this grant had to determine the statistical nature and source of fracture in a high strength, NiAl single crystal turbine blade material; map a simplistic future strength envelope of the material; develop a statistically based reliability computer algorithm; verify the reliability model and computer algorithm-, and model stator vanes for rig tests. Thus establishing design protocols that enable the engineer to analyze and predict the mechanical behavior of ceramic composites and intermetallics would mitigate the prototype (trial and error) approach currently used by the engineering community. The primary objective of the research effort supported by this short term grant is the continued creation of enabling technologies for the macro-analysis of components fabricated from ceramic composites and intermetallic material systems. The creation of enabling technologies aids in shortening the product development cycle of components fabricated from the new high technology materials.

Duffy, Stephen F.↗
NASA NTRS1997

Design Protocols and Analytical Strategies that Incorporate Structural Reliability Models

Ceramic matrix composites (CMC) and intermetallic materials (e.g., single crystal nickel aluminide) are high performance materials that exhibit attractive mechanical, thermal and chemical properties. These materials are critically important in advancing certain performance aspects of gas turbine engines. From an aerospace engineer's perspective the new generation of ceramic composites and intermetallics offers a significant potential for raising the thrust/weight ratio and reducing NO(x) emissions of gas turbine engines. These aspects have increased interest in utilizing these materials in the hot sections of turbine engines. However, as these materials evolve and their performance characteristics improve a persistent need exists for state-of-the-art analytical methods that predict the response of components fabricated from CMC and intermetallic material systems. This need provided the motivation for the technology developed under this research effort. Continuous ceramic fiber composites exhibit an increase in work of fracture, which allows for "graceful" rather than catastrophic failure. When loaded in the fiber direction, these composites retain substantial strength capacity beyond the initiation of transverse matrix cracking despite the fact that neither of its constituents would exhibit such behavior if tested alone. As additional load is applied beyond first matrix cracking, the matrix tends to break in a series of cracks bridged by the ceramic fibers. Any additional load is born increasingly by the fibers until the ultimate strength of the composite is reached. Thus modeling efforts supported under this research effort have focused on predicting this sort of behavior. For single crystal intermetallics the issues that motivated the technology development involved questions relating to material behavior and component design. Thus the research effort supported by this grant had to determine the statistical nature and source of fracture in a high strength, NiAl single crystal turbine blade material; map a simplistic failure strength envelope of the material; develop a statistically based reliability computer algorithm, verify the reliability model and computer algorithm, and model stator vanes for rig tests. Thus establishing design protocols that enable the engineer to analyze and predict the mechanical behavior of ceramic composites and intermetallics would mitigate the prototype (trial and error) approach currently used by the engineering community. The primary objective of the research effort supported by this short term grant is the continued creation of enabling technologies for the macroanalysis of components fabricated from ceramic composites and intermetallic material systems. The creation of enabling technologies aids in shortening the product development cycle of components fabricated from the new high technology materials.

Duffy, Stephen F.↗
NASA NTRS1993

Experimental partitioning of Zr, Ti, and Nb between silicate liquid and a complex noble metal alloy and the partitioning of Ti between perovskite and platinum metal

El Goresy et al.'s observation of Nb, Zr, and Ta in refractory platinum metal nuggets (RPMN's) from Ca-Al-rich inclusions (CAI's) in the Allende meteorite led them to propose that these lithophile elements alloyed in the metallic state with noble metals in the early solar nebula. However, Grossman pointed out that the thermodynamic stability of Zr in the oxide phase is vastly greater than metallic Zr at estimated solar nebula conditions. Jones and Burnett suggested this discrepancy may be explained by the very non-ideal behavior of some lithophile transition elements in noble metal solutions and/or intermetallic compounds. Subsequently, Fegley and Kornacki used thermodynamic data taken from the literature to predict the stability of several of these intermetallic compounds at estimated solar nebula conditions. Palme and Schmitt and Treiman et al. conducted experiments to quantify the partitioning behavior of certain lithophile elements between silicate liquid and Pt-metal. Although their results were somewhat variable, they did suggest that Zr partition coefficients were too small to explain the observed 'percent' levels in some RPMN's. Palme and Schmitt also observed large partition coefficients for Nb and Ta. No intermetallic phases were identified. Following the work of Treiman et al., Jurewicz and Jones performed experiments to examine Zr, Nb, and Ti partitioning near solar nebula conditions. Their results showed that Zr, Nb, and Ti all have an affinity for the platinum metal, with Nb and Ti having a very strong preference for the metal. The intermetallic phases (Zr,Fe)Pt3, (Nb,Fe)Pt3, and (Ti,Fe)Pt3 were identified. Curiously, although both experiments and calculations indicate that Ti should partition strongly into Pt-metal (possibly as TiPt3), no Ti has ever been observed in any RPMN's. Fegley and Kornacki also noticed this discrepancy and hypothesized that the Ti was stabilized in perovskite which is a common phase in Allende CAI's.

Jurewicz, Stephen R.↗
NASA NTRS2015

Mechanical Components from Highly Recoverable, Low Apparent Modulus Materials

A material for use as a mechanical component is formed of a superelastic intermetallic material having a low apparent modulus and a high hardness. The superelastic intermetallic material is conditioned to be dimensionally stable, devoid of any shape memory effect and have a stable superelastic response without irrecoverable deformation while exhibiting strains of at least 3%. The method of conditioning the superelastic intermetallic material is described. Another embodiment relates to lightweight materials known as ordered intermetallics that perform well in sliding wear applications using conventional liquid lubricants and are therefore suitable for resilient, high performance mechanical components such as gears and bearings.

Padula, Santo, II↗
NASA NTRS1987

Development of a new generation of high-temperature composite materials

There are ever-increasing demands to develop low-density materials that maintain high strength and stiffness properties at elevated temperatures. Such materials are essential if the requirements for advanced aircraft, space power generation, and space station plans are to be realized. Metal matrix composites and intermetallic matrix composites are currently being investigated at NASA Lewis for such applications because they offer potential increases in strength, stiffness, and use temperature at a lower density than the most advanced single-crystal superalloys presently available. Today's discussion centers around the intermetallic matrix composites proposed by Lewis for meeting advanced aeropropulsion requirements. The fabrication process currently being used at Lewis to produce intermetallic matrix composites will be reviewed, and the properties of one such composite, SiC/Ti3Al+Nb, will be presented. In addition, the direction of future research will be outlined, including plans for enhanced fabrication of aluminide composites by the arc spray technique and fiber development by the floating-zone process.

Brindley, Pamela K.↗
NASA NTRS1990

Development of a new generation of high-temperature composite materials

Intermetallic matrix composites proposed to meet advanced aeropropulsion requirements are discussed. The powder metallurgy fabrication process currently being used to produce these intermetallic matrix composites will be presented, as will properties of one such composite, SiC/Ti3Al+Nb. In addition, the direction of future research will be outlined, including plans for enhanced fabrication of intermetallic composites by the arc-spray technique and fiber development by the floating-zone process.

Brindley, P. K.↗
NASA NTRS1994

Advanced composites in Japan

The JTEC Panel on Advanced Composites surveyed the status and future directions of Japanese high-performance ceramic and carbon fibers and their composites in metal, intermetallic, ceramic, and carbon matrices. Because of a strong carbon and fiber industry, Japan is the leader in carbon fiber technology. Japan has initiated an oxidation-resistant carbon/carbon composite program. With its outstanding technical base in carbon technology, Japan should be able to match present technology in the U.S. and introduce lower-cost manufacturing methods. However, the panel did not see any innovative approaches to oxidation protection. Ceramic and especially intermetallic matrix composites were not yet receiving much attention at the time of the panel's visit. There was a high level of monolithic ceramic research and development activity. High temperature monolithic intermetallic research was just starting, but notable products in titanium aluminides had already appeared. Matrixless ceramic composites was one novel approach noted. Technologies for high temperature composites fabrication existed, but large numbers of panels or parts had not been produced. The Japanese have selected aerospace as an important future industry. Because materials are an enabling technology for a strong aerospace industry, Japan initiated an ambitious long-term program to develop high temperature composites. Although just starting, its progress should be closely monitored in the U.S.

Diefendorf, R. Judd↗
NASA NTRS1994

Fiber-matrix interphase characterization in composites using ultrasonic velocity data

A nondestructive method is introduced to determine the effective elastic of fiber-matrix interphases from measured composite moduli. The composite moduli are obtained by measuring the angular dependences of ultrasonic longitudinal and transverse phase velocities in planes along and perpendicular to the fibers. Three independent interphase effective moduli are found using micromechanical multiphase models which were applied after averaging composite transverse moduli to account for the composite orthotropy. Sensitivity analysis shows that errors in the calculated interphasial moduli are approximately ten times those in the composite moduli. Experiments are performed on Si3N4 ceramic and Ti-24Al-11Nb intermetallic matrix composites reinforced with carbon coated silicon carbide fibers. The experimental interphasial moduli for the intermetallic composites agree with literature data after accounting for the interphase microstructure. The interphasial moduli for ceramic composites are lower than those for the intermetallic composite due to imperfect mechanical contact between the interphase and the porous matrix. The use of the method to assess the interphase degradation is demonstrated for interphasial oxidation damage. The analysis helps to determine the morphology of the damaged interphase.

Chu, Y. C.↗
NASA NTRS2000

Directionally Solidified NiAl-Based Alloys Studied for Improved Elevated-Temperature Strength and Room-Temperature Fracture Toughness

Efforts are underway to replace superalloys used in the hot sections of gas turbine engines with materials possessing better mechanical and physical properties. Alloys based on the intermetallic NiAl have demonstrated potential; however, they generally suffer from low fracture resistance (toughness) at room temperature and from poor strength at elevated temperatures. Directional solidification of NiAl alloyed with both Cr and Mo has yielded materials with useful toughness and elevated-temperature strength values. The intermetallic alloy NiAl has been proposed as an advanced material to extend the maximum operational temperature of gas turbine engines by several hundred degrees centigrade. This intermetallic alloy displays a lower density (approximately 30-percent less) and a higher thermal conductivity (4 to 8 times greater) than conventional superalloys as well as good high-temperature oxidation resistance. Unfortunately, unalloyed NiAl has poor elevated temperature strength (approximately 50 MPa at 1027 C) and low room-temperature fracture toughness (about 5 MPa). Directionally solidified NiAl eutectic alloys are known to possess a combination of high elevated-temperature strength and good room-temperature fracture toughness. Research has demonstrated that a NiAl matrix containing a uniform distribution of very thin Cr plates alloyed with Mo possessed both increased fracture toughness and elevated-temperature creep strength. Although attractive properties were obtained, these alloys were formed at low growth rates (greater than 19 mm/hr), which are considered to be economically unviable. Hence, an investigation was warranted of the strength and toughness behavior of NiAl-(Cr,Mo) directionally solidified at faster growth rates. If the mechanical properties did not deteriorate with increased growth rates, directional solidification could offer an economical means to produce NiAl-based alloys commercially for gas turbine engines. An investigation at the NASA Glenn Research Center at Lewis Field was undertaken to study the effect of the directional solidification growth rate on the microstructure, room temperature fracture toughness, and strength at 1027 C of a Ni-33Al-31Cr-3Mo eutectic alloy. The directionally solidified rates varied between 7.6 and 508 millimeters per hour Essentially fault-free, alternating (Cr, Mo)/NiAl lamellar plate microstructures (left photograph) were formed during growth at and below 12.7 mm/hr, whereas cellular microstructures (right photograph) with the (Cr, Mo) phase in a radial spokelike pattern were developed at faster growth rates. The compressive strength at 1027 C continuously increased with increasing growth rate and did not indicate a maxima as was reported for directionally solidified Ni-33Al-34Cr. Surprisingly, samples with the lamellar plate microstructure (left photograph) possessed a room-temperature fracture toughness of approximately 12 MPa(sup square root of m), whereas all the alloys with a cellular microstructure had a toughness of about 17 MPa(sup square root of m). These results are significant since they clearly demonstrate that Ni-33Al-31Cr-3Mo can be directionally solidified at much faster growth rates without any observable deterioration in its mechanical properties. Thus, the potential to produce strong, tough NiAl-based eutectics at commercially acceptable growth rates exists. Additional testing and alloy optimization studies are underway.

Whittenberger, J. Daniel↗
NASA NTRS1965

Development of high temperature nickel-base alloys for jet engine turbine bucket applications

A program has been initiated to develop a material with superior properties at elevated temperatures for utilization in turbine blade applications. A nickel-base superalloy can provide the necessary high temperature strength by using the maximum capability of the three available strengthening mechanisms - intermetallic gamma prime precipitation (Ni3Al), solid solution strengthening with refractory and precious metals, and stable carbide formations through the addition of strong carbide forming elements. A stress rupture test at 2000 deg F and 15,000 psi was formulated to approximate the desired properties. By adding varying amounts of refractory metals (Mo, W and Ta) it was possible to statistically analyze the effects of each in a basic superalloy composition containing fixed amounts of Co, Cr, C, B, Sr, and Ni at three separate levels of AL and Ta. Metallographic analysis correlated with the mechanical properties of the alloys; those with few strengthening phases were weak and ductile and those with excessive amounts of intermetallic phases present in undesirable morphologies were brittle.

SUPERALLOY↗