Results for “microstructural properties” — Page 24

NASA NTRS2015

Techniques for Achieving Zero Stress in Thin Films of Iridium, Chromium, and Nickel

We examine techniques for achieving zero intrinsic stress in thin films of iridium, chromium, and nickel deposited by magnetron sputter deposition. The intrinsic stress is further correlated to the microstructural features and physical properties such as surface roughness and optical density at a scale appropriate to soft X-ray wavelengths. The examination of the stress in these materials is motivated by efforts to advance the optical performance of light-weight X-ray space telescopes into the regime of sub-arcsecond resolution through various deposition techniques that rely on control of the film stress to values within 10-100 MPa. A characteristic feature of the intrinsic stress behavior in chromium and nickel is their sensitivity to the magnitude and sign of the intrinsic stress with argon gas pressure and deposition rate, including the existence of a critical argon process pressure that results in zero film stress which scales linearly with the atomic mass of the sputtered species. While the effect of stress reversal with argon pressure has been previously reported by Hoffman and others for nickel and chromium, we report this effect for iridium. In addition to stress reversal, we identify zero stress in the optical functioning iridium layer shortly after island coalescence for low process pressures at a film thickness of approximately 35nm. The measurement of the low values of stress during deposition was achieved with the aid of a sensitive in-situ instrument capable of a minimum detectable level of stress, assuming a 35nm thick film, in the range of 0.40-6.0 MPa for <111> oriented crystalline silicon substrate thicknesses of 70-280 microns, respectively.

X-ray optical thin films↗

NASA NTRS2019

Coordinated Analysis of an Ion Irradiated Carbonaceous Chondrite Suggests Complex Space Weathering Effects

Surfaces of airless planetary bodies are exposed to micrometeorite bombardment and solar wind irradiation which alter the microstructural, compositional, and optical properties of regoliths over time. These processes are collectively known as space weathering, and they complicate the interpretation of remote sensing data and the subsequent characterization of airless surfaces. Within the next 5 years, NASA’s OSIRIS-REx (Origins, Spectral Interpretation, Resource Identification, Security, Regolith Explorer) and JAXA (Japan Aerospace Exploration Agency)’s Hayabusa2 missions will return samples from C-type asteroids Bennu and Ryugu, respectively. Compared to the Moon and S-type asteroids, our understanding of the space weathering of C-complex asteroids is limited. In order to maximize scientific return from remote sensing data and to prepare for the analysis of returned samples from these missions, we must better understand the effects of space weathering on hydrated, organic-rich materials. We can do so by simulating these processes in the laboratory. In this study, we simulate solar wind exposure through ion irradiation of the CM2 carbonaceous chondrite Murchison - a suitable analog for C-complex asteroids. Here, we present coordinated analyses of a sample before and after ion irradiation.

Laczniak, D. L.↗

NASA NTRSDate not supplied

Development and Characterization of the Integrally Stiffened Cylinder (ISC) Process for Launch Vehicles and Aircraft Fuselage Structures

Over the past decade, NASA Langley has led development of the Integrally Stiffened Cylinder (ISC) Process, a near-net shape, flow-forming technology. This innovative process is being evaluated for launch vehicle and commercial aircraft manufacturing. A thick-walled, cylindrical preform is flow-formed in a single operation into a thin-walled barrel with longitudinal stiffeners. The one-piece, stiffened barrels offer a direct replacement for conventional multi-piece welded or riveted structures. A cost-benefit analysis for launch vehicles estimated that the ISC process offers up to a 50% reduction in manufacturing costs and a 10% reduction in mass. NASA, the European Space Agency (ESA), and industry partners have teamed to manufacture 10-ft. diameter aluminum ISCs. The intent is to demonstrate the commercial viability of the process at a scale relevant to the commercial launch and aircraft industries. Development activities will be presented, including process scale-up, formability assessment, microstructural analysis, and mechanical property testing.

ISC, flow forming, near net shape↗

NASA NTRSDate not supplied

Parallelized Carbon Oxidation and Surface Recession Model in Direct-Simulation Monte Carlo Code, SPARTA

Ablative thermal protection system (TPS) materials for spacecraft are composites that often consist of a carbon-based reinforcement and a polymeric matrix. During Earth re-entry, they endure high-temperature oxidation and surface recession. Oxidation is an important mechanism for ablation, sometimes leading to the weakening, spallation, or failure of the oxidized fibers at the surface and in the char layer. However, more details are required including accurate material properties of the fiber microstructure, whether the fibers recede homogenously or localized at pits, and the role of pyrolysis outgassing in order to evaluate the role oxidation plays in the degradation and failure mechanisms of these materials. In this work, we demonstrate a parallelizable oxidation-driven ablation model developed for detailed, large-scale simulations in the DSMC code SPARTA. We also develop robust algorithms which handle the conservation of the surface state after an ablation step. Finally, we verify our model for both simple and more complex chemistry as well as microstructures with reaction statistics, oxidation depth calculations, and detailed visualization of oxidation-induced material recession at the microscale.

V Arias↗

NASA NTRS2006

Phase Stability of a Powder Metallurgy Disk Superalloy

Advanced powder metallurgy superalloy disks in aerospace turbine engines now entering service can be exposed to temperatures approaching 700 C, higher than those previously encountered. They also have higher levels of refractory elements, which can increase mechanical properties at these temperatures but can also encourage phase instabilities during service. Microstructural changes including precipitation of topological close pack phase precipitation and coarsening of existing gamma' precipitates can be slow at these temperatures, yet potentially significant for anticipated disk service times exceeding 1,000 h. The ability to quantify and predict such potential phase instabilities and degradation of capabilities is needed to insure structural integrity and air worthiness of propulsion systems over the full life cycle. A prototypical advanced disk superalloy was subjected to high temperature exposures, and then evaluated. Microstructural changes and corresponding changes in mechanical properties were quantified. The results will be compared to predictions of microstructure modeling software.

Gabb, Timothy P.↗

NASA NTRS2024

Extreme Temperature Additively Manufactured GRX-810 Alloy Development and Hot-fire Testing for Liquid Rocket Engines

Additive manufacturing (AM) has revolutionized component design for liquid rocket engines by offering rapid manufacturing capabilities. This has led to significant opportunities for development and flight programs in the propulsion industry, resulting in cost and schedule savings, as well as performance improvements through new designs and alloy development. A noteworthy example is the GRX-810 oxide dispersion strengthened (ODS) alloy, which was specifically developed for extreme temperatures. This Ni-Co-Cr based alloy was created using integrated computational materials engineering (ICME) techniques to focus on a new class of materials with exceptional temperature and oxidation-resistant properties. The GRX-810 alloy utilizes AM processes to incorporate nano-scale yttria particles throughout its microstructure, resulting in remarkable enhancements. Compared to traditional Nickel-based superalloys, the GRX-810 alloy offers a two-fold increase in tensile strength, 1,000-fold better creep properties, and two-fold improvement in oxidation resistance. NASA successfully demonstrated the development and manufacturing of components using the GRX-810 alloy through laser powder bed fusion (L-PBF) and laser powder directed energy deposition (LP-DED) processes. Extensive efforts were made to model, evaluate metallurgical properties, develop heat treatment processes, characterize the microstructure, and determine mechanical properties. The GRX-810 alloy was specifically designed for aerospace applications, including liquid rocket engine injectors, preburners, turbines, and hot-section components, capable of withstanding temperatures up to 1,100 °C. The objective of this alloy development is to bridge the temperature gap between traditional Nickel-based superalloys and refractory alloys. This paper provides a comprehensive comparison of the GRX-810 alloy with other aerospace alloys, discussing its microstructure, mechanical properties, processing advancements, component development, and hot-fire testing results. The ultimate goal of this development was to elevate the Technology Readiness Level (TRL) of the GRX-810 alloy, enabling its integration into NASA and commercial aerospace applications.

GRX-810↗

NASA NTRS2024

Extreme Temperature Additively Manufactured GRX-810 Alloy Development and Hot-fire Testing for Liquid Rocket Engines

Additive manufacturing (AM) has revolutionized component design for liquid rocket engines by offering rapid manufacturing capabilities. This has led to significant opportunities for development and flight programs in the propulsion industry, resulting in cost and schedule savings, as well as performance improvements through new designs and alloy development. A noteworthy example is the GRX-810 oxide dispersion strengthened (ODS) alloy, which was specifically developed for extreme temperatures. This Ni-Co-Cr based alloy was created using integrated computational materials engineering (ICME) techniques to focus on a new class of materials with exceptional temperature and oxidation-resistant properties. The GRX-810 alloy utilizes AM processes to incorporate nano-scale yttria particles throughout its microstructure, resulting in remarkable enhancements. Compared to traditional Nickel-based superalloys, the GRX-810 alloy offers a two-fold increase in tensile strength, 1,000-fold better creep properties, and two-fold improvement in oxidation resistance. NASA successfully demonstrated the development and manufacturing of components using the GRX-810 alloy through laser powder bed fusion (L-PBF) and laser powder directed energy deposition (LP-DED) processes. Extensive efforts were made to model, evaluate metallurgical properties, develop heat treatment processes, characterize the microstructure, and determine mechanical properties. The GRX-810 alloy was specifically designed for aerospace applications, including liquid rocket engine injectors, preburners, turbines, and hot-section components, capable of withstanding temperatures up to 1,100 °C. The objective of this alloy development is to bridge the temperature gap between traditional Nickel-based superalloys and refractory alloys. This paper provides a comprehensive comparison of the GRX-810 alloy with other aerospace alloys, discussing its microstructure, mechanical properties, processing advancements, component development, and hot-fire testing results. The ultimate goal of this development was to elevate the Technology Readiness Level (TRL) of the GRX-810 alloy, enabling its integration into NASA and commercial aerospace applications.

GRX-810↗

NASA NTRS1986

SiC fiber analysis

Polymer derived Nicalon SiC fibers are known to be thermally unstable at temperatures beyond 1200 C. In an effort to further understand the mechanisms of fiber degradation, Nicalon fibers were heat treated at temperatures up to 2200 C and argon gas pressures varying from 0 to 1360 atm. The effects of gas pressure on the thermal stability of the fibers were determined through property comparisons between the pressure-treated fibers and vacuum-treated fibers. Investigation of the thermal stability included studies of the fiber microstructure and mechanical and physical properties before and after treatments.

Jaskowiak, Martha H.↗

NASA NTRS1992

Effects of casting conditions and deformation processing on A356 aluminum and A356-20 vol. pct SiC composites

The effects of casting conditions and deformation processing on the mechanical properties of unreinforced A356 aluminum and A356-20 vol pct SiC composite were investigated by tensile properties in these compounds fabricated by either sand casting or squeeze casting techniques followed by hot working to 33, 50, 90, and 95 percent reductions. The evolution of the microstructure and values of tensile properties were evaluated for the cast materials in each of the hot worked conditions. It was found that, while the deformation processing of the sand-cast composite resulted in banding of the Al and SiC particles within the microstructure, such features were not observed in the squeeze-cast microstructure. The tensile strengths of the squeeze cast materials was found to be higher than those of the sand cast materials, for both the unreinforced and composite samples, while increased amounts of deformation were found to improve the ductility of the composite.

Rozak, G. A.↗

NASA NTRS1973

The effect of thermal cycling on the structure and properties of a Co, Cr, Ni-TaC directionally solidified eutectic composite

A Co, Cr, Ni-TaC directionally solidified eutectic composite was subjected to thermal fatigue between 427-1093°C. The material suffered degradation in microstructure and elevated temperature mechanical properties. The loss in properties varied with the maximum cycling temperature and number of cycles. This behavior is attributed to the increasing solubility of the TaC in the matrix with temperature from 0.4% at room temperature to 2.2% at 1200°C. During the thermal cycling, the TaC is subjected to solution and reprecipitation which form serrations on the fibers since the easy growth planes of the TaC are not coincident with the fiber faces exposed to the matrix.

Composites↗

NASA NTRS1996

Source of Scatter in the Creep Lives of NiAl(Hf) Single Crystals Revealed

In recent years, there has been an increased emphasis in developing NiAl-based alloys for high- temperature applications in aircraft engines. In comparison to commercial superalloys, binary NiAl has a higher melting temperature, lower density, larger thermal conductivity, and better oxidation resistance. These properties make it a desirable material to replace superalloys as blades and vanes in aircraft engines. Despite this attractive combination of properties, binary NiAl cannot be used as a reliable structural material because of its low-temperature brittleness and poor high-temperature creep strength. GE Aircraft Engines in Cincinnati, Ohio, has recently developed NiAl(Hf) alloys that have creep strengths comparable to commercial superalloys while maintaining the other desirable properties of binary NiAl. The microstructures of these alloys consist of finely distributed G-phase (Ni_(16)Hf_(6)Si_(7)) precipitates, which strengthen the NiAl matrix. However, while the creep properties of these alloys were being evaluated, considerable scatter was observed in the creep lives of specimens tested under identical stress and temperature conditions. Although these alloys had nominally the same composition, the test specimens were obtained from four different ingots (A, B, C, and D) that had been heat treated under similar conditions. The NASA Lewis Research Center began the present study at the request of GE Aircraft Engines under a Space Act Agreement to identify the source of this scatter.

Source record↗

NASA NTRS1995

Superconducting materials processing

The effects of materials processing on the properties and behavior of high temperature yttrium barium copper oxide (YBCO) superconductors were investigated. Electrical, magnetic, and structural characteristics of thin films (300 nm) YBA2CU3O(delta) structures grown by pulsed laser deposition on LaAlO3 and SrTiO3 substrates were used to evaluate processing. Pole projection and thin film diffraction measurements were used to establish grain orientation and verify structural integrity of the samples. Susceptibility magnetization, and transport measurements were used to evaluate the magnetic and electrical transport properties of the samples. Our results verified that an unfortunate consequence of processing is inherent changes to the internal structure of the material. This effect translates into modifications in the properties of the materials, and undesired feature that makes it very difficult to consistently predict material behavior. The results show that processing evaluation must incorporate a comprehensive understanding of the properties of the materials. Future studies will emphasize microstructural characteristics of the materials, in particular, those microscopic properties that map macroscopic behavior.

Hurley, John S.↗

NASA NTRSDate not supplied

Particle-Based Fiber Models of Woven Materials for Earth Entry Thermal Protection

Applications requiring materials with layer-to-layer strength, from basketry to thermal protection systems, use interlaced, three-dimensional woven materials. NASA is developing and deploying woven material heat shields for missions, including Artemis I (3D-MAT for compression pads) and potentially Mars Sample Return - Earth Entry System. These materials are complex, hierarchical and must protect from extreme environments and phenomena, such as deformation, impact and high-enthalpy heating. Woven material performance depends on microstructure, damage and weave geometry. Therefore, fiber-specific models are needed to simulate fiber contacts within the weave hierarchical geometry (fiber to tow to yarn to weave) and the inherent directionality of fibers. Explicit fiber models can simulate how weave microstructure evolution affects thermal and mechanical properties. We parameterize a discrete element bonded particle models (DEM-BPM) of fibers to capture thermal and mechanical behavior within and between fibers, with bonded and contact forces, respectively. We study the proportion of heat transfer and stress via the contact network, fiber bonds and the weave geometry, for example, with respect to yarn warp-weft identity (whether it interlaces weave layers). Our results demonstrate the importance of explicit fiber modeling for connecting microstructure with thermal and mechanical properties.

woven material↗

NASA NTRSDate not supplied

Particle-Based Fiber Models of Woven Materials for Earth Entry Thermal Protection

Applications requiring materials with layer-to-layer strength, from basketry to thermal protection systems, use interlaced, three-dimensional woven materials. NASA is developing and deploying woven material heat shields for missions, including Artemis I (3D-MAT for compression pads) and potentially Mars Sample Return - Earth Entry System. These materials are complex, hierarchical and must protect from extreme environments and phenomena, such as deformation, impact and high-enthalpy heating. Woven material performance depends on microstructure, damage and weave geometry. Therefore, fiber-specific models are needed to simulate fiber contacts within the weave hierarchical geometry (fiber to tow to yarn to weave) and the inherent directionality of fibers. Explicit fiber models can simulate how weave microstructure evolution affects thermal and mechanical properties. We parameterize a discrete element bonded particle models (DEM-BPM) of fibers to capture thermal and mechanical behavior within and between fibers, with bonded and contact forces, respectively. We study the proportion of heat transfer and stress via the contact network, fiber bonds and the weave geometry, for example, with respect to yarn warp-weft identity (whether it interlaces weave layers). Our results demonstrate the importance of explicit fiber modeling for connecting microstructure with thermal and mechanical properties.

woven material↗

NASA NTRS1998

Semiconductors: In Situ Processing of Photovoltaic Devices

Current proposals for developing an extended human presence on the Moon and Mars increasingly consider the processing of nonterrestrial materials essential for keeping the Earth launch burden reasonable. Utilization of in situ resources for construction of lunar and Mars bases will initially require assessment of resource availability followed by the development of economically acceptable and technically feasible extraction processes. In regard to materials processing and fabrication, the lower gravity level on the Moon (0.125 g) and Mars (0.367 g) will dramatically change the presently accepted hierarchy of materials in terms of specific properties, a factor that must be understood and exploited. Furthermore, significant changes are expected in the behavior of liquid materials during processing. In casting, for example, mold filling and associated solidification processes have to be reevaluated. Finally, microstructural development, and therefore material properties, presently being documented through ongoing research in microgravity science and applications, need to be understood and scaled to the reduced gravity environments.

Curreri, Peter A.↗

NASA NTRS1999

In-Situ Production of Solar Power Systems for Exploration

Current proposals for developing an extended human presence, beyond space stations, on the Moon and Mars increasingly consider the processing of non-terrestrial materials essential for keeping the Earth launch burden reasonable. Utilization of in-situ resources for construction of lunar and Mars bases will initially require assessment of resource availability followed by the development of economically acceptable and technically feasible extractive processes. In regard to materials processing and fabrication the lower gravity level on the Moon (0.125 g) and Mars (0.367 g) will dramatically change the presently accepted hierarchy of materials in terms of specific properties, a factor which must be understood and exploited. Furthermore, significant changes are expected in the behavior of liquid materials during processing. In casting, for example, mold filling and associated solidification processes have to be reevaluated. Finally microstructural development and therefore material properties, presently being documented through on-going research in microgravity science and applications, needs to be understood and scaled to the reduced gravity environments. One of the most important elements of a human planetary base is power production. Lunar samples and geophysical measurements returned by the Apollo missions provide detailed data on the composition and physical characteristics of the lunar materials and environment. Based on this knowledge and extrapolations of terrestrial industrial experience it is clear that several types of solar-to-electric converters can be manufactured on the Moon. It is conceivable that well over 90% of a solar-to- electric power system could be made from lunar materials. Production and utilization of photovoltaic devices for solar energy production on Earth is primarily driven by the market economy. On Earth a production plant for photovoltaic devices is intimately linked to the planets massive industrial base. A selection of off the shelf refined materials are available as well as cheap fast transportation on demand. The processes takes place (except for the few seconds reprieve in shot towers etc.) under one gravity, with solar radiation significantly modulated by weather, and under conditions where one atmosphere is free and high vacuum is cumbersome and expensive. Off Earth, on lunar or Mars bases, the cost of photovoltaic power is driven by transport costs - Earth launch, deep space transport, landing on the planetary surface. Thus there is a premium for processes that are materials self-sufficient or for closed loop in-situ processes. The lack of differentiated ores on the Moon, and lack of explored minerals on Mars and interplanetary space give a premium to universal/non-ore-specific mineral extractive processes. Initially a semiconductor/photovoltaic production facility will build on no conveniently located industrial base, further increasing the premium on closed loop self sufficient processes.

Curreri, Peter A.↗

NASA NTRS1998

In situ Resource Utilization for Processing of Metal Alloys on Lunar and Mars Bases

Current plans for practical missions leading to a sustained human presence on our Moon and Mars rely on utilizing their in situ resources. Initially, resource availability must be assessed followed by the development of economically acceptable and technically feasible extractive processes. In regard to metals processing and fabrication, the lower gravity level on the Moon (0.125 g) and Mars (0.369 g) will dramatically change the presently accepted hierarchy of materials in terms of specific properties, a factor which must be understood and exploited. Furthermore, significant changes are expected in the behavior of liquid metals during processing. In metal casting, for example, mold filling and associated solidification processes have to be reevaluated. Finally, microstructural development and therefore material properties, presently being documented through ongoing research in microgravity science and applications, needs to be understood and scaled to the reduced gravity environments. These and other issues are addressed in this paper.

Stefanescu, D. M.↗

NASA NTRS1993

Defects in electro-optically active polymer solids

There is considerable current interest in the application of organic and polymeric materials for electronic and photonic devices. The rapid, non-linear optical (NLO) response of these materials makes them attractive candidates for waveguides, interferometers, and frequency doublers. In order to realize the full potential of these systems, it is necessary to develop processing schemes which can fabricate these molecules into ordered arrangements. There is enormous potential for introducing well-defined, local variations in microstructure to control the photonic properties of organic materials by rational 'defect engineering.' This effort may eventually become as technologically important as the manipulation of the electronic structure of solid-state silicon based devices is at present. The success of this endeavor will require complimentary efforts in the synthesis, processing, and characterization of new materials. Detailed information about local microstructure will be necessary to understand the influence of symmetry breaking of the solid phases near point, line, and planar defects. In metallic and inorganic polycrystalline materials, defects play an important role in modifying macroscopic properties. To understand the influence of particular defects on the properties of materials, it has proven useful to isolate the defect by creating bicrystals between two-component single crystals. In this way the geometry of a grain boundary defect and its effect on macroscopic properties can be determined unambiguously. In crystalline polymers it would be valuable to establish a similar depth of understanding about the relationship between defect structure and macroscopic properties. Conventionally processed crystalline polymers have small crystallites (10-20 nm), which implies a large defect density in the solid state. Although this means that defects may play an important or even dominant role in crystalline or liquid crystalline polymer systems, it also makes it difficult to isolate the effect of a particular boundary on a macroscopically observed property. However, the development of solid-state and thin-film polymerization mechanisms have facilitated the synthesis of highly organized and ordered polymers. These systems provide a unique opportunity to isolate and investigate in detail the structure of covalently bonded solids near defects and the effect of these defects on the properties of the material. The study of defects in solid polymers has been the subject of a recent review (Martin, 1993).

Martin, David C.↗