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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 271 records · Page 15
All sourcesNASA NTRSDOE OSTI
DOE OSTI2019

Microstructure and Properties of Mn-Cu-Based Damping Alloys Prepared by Ball Milling and Hot-Press Sintering

A Mn-Cu-based damping alloy with a nominal composition of 70Mn-24Cu-3Zn-3Al (at.%) was prepared by ball milling of pure elemental powders and subsequent hot-press sintering of powder mixture at 750 and 825 °C for 2 h. For comparison, this alloy was also prepared by induction melting technology and then homogenized at 850 °C for 24 h. Further, they were aged at 430 °C for 2 h. The microstructure, damping capacity and microhardness of the hot-press-sintered and induction-melted alloys have been investigated. The results show that the microstructure of the powder mixture upon ball milling mainly comprises convoluted composite particles containing α-Mn and γ-Cu phases, and isolated α-Mn ones around. The high compactness of the alloys is obtained after hot-press sintering (94.8 and 98.6% at 750 and 825 °C, respectively). At a holding temperature of 750 °C, the microstructure of the alloy is primarily composed of γ-MnCu, γ-CuMn and α-Mn grains. With increasing the target temperature to 825 °C, the single γ-MnCu solid solution has been formed in the alloy by diffusion of Mn etc. into γ-Cu lattices. The hot-press-sintered alloys (especially at 825 °C) possess relatively high damping capacity although which is still lower than that of induction-melted one. In contrast, the microhardness of the hot-press-sintered alloys (especially at 750 °C) is obviously higher than that of the induction-melted one.

36 MATERIALS SCIENCE↗
DOE OSTI2022

Review of the Effects of Polymer Binder Properties on Microstructure and Irreversible Volume Growth of Plastic Bonded Explosives Formulations

The rational design of effective polymeric binders for the formulation of plastic-bonded explosives (PBX) is challenging due to their inherent compositional complexity. The composites comprise irregularly shaped energetic material (EM) powders coated with low weight fractions of polymer via non-equilibrium processes such as slurry coating. Defects can deleteriously affect PBX stability and performance: nano- to micrometer-scale voids can act as loci for hot spots, lowering deflagration and detonation temperatures in unpredictable ways. Furthermore, some nominally desirable polymer properties are at odds with each other: e. g. good flow characteristics are desirable for coating and adhesion, but mechanical stiffness is needed to prevent deformation and cracking of PBX under mechanical stress. Good binder adhesion is critical, but the best means to predict and measure adhesion in PBX is not obvious. Experimental methods of determining binder adhesion on model surfaces may not capture polymer structural configurations relevant to deposition during coating. Molecular dynamics-based computational models have predicted key observables in PBX formulation, suggesting that they may be powerful tools for binder selection. In this review, primarily recent (~2006 and later) literature on polymeric binders for insensitive HE (IHE) is surveyed. We focus on how binder properties influence observable PBX properties as resistance to irreversible volume growth and void formation in PBX formulations mainly (but not exclusively) featuring 1,3,5-triamino-2,4,6-trinitrobenzene (TATB) as the EM (e. g. PBX 9502, LX-17 and others). Conclusions from these studies yield useful guidelines for choosing HE binder candidates, as well as for the general design of highly-filled polymer composite materials. Finally, studies describing challenges in PBX formulation with the newer and more energetically dense high explosive, LLM-105, will be discussed.

adhesion↗
DOE OSTI2019

Significance of Finish Cooling Temperature to Microstructure and Property Relationship of Low-Carbon V-N-Cr Microalloyed High-Strength Steel

Herein, three final cooling temperatures were employed to achieve high strength and toughness communication in the V-N-Cr microalloyed steels. This study shows that V-N-Cr microalloyed steel primarily consisted of ferrite, granular bainite, acicular ferrite, and a small quantity of M/A phase at the final cooling temperature of 600 °C, while the polygonal ferrite, lamellar bainite, granular bainite, and a small fraction of acicular ferrite were obtained at 450 °C. The width of lamellar bainite was ~ 200-400 nm, and acicular ferrite was composed of fine non-parallel ferrite platelet structures with high dislocations densities. As the final cooling temperature decreased further, the microstructure included granular bainite and lath bainite at 350 °C. The nanoscale precipitates of V-N-Cr microalloyed steel were divided into two types, large-scale precipitates near the grain boundary that precipitated at high temperatures and small precipitates of diameter 5-10 nm at low temperatures, which significantly contributed toward strength. The hot rolled low-carbon V-N-Cr microalloy steel exhibited optimal mechanical properties at the final rolling temperature of 830 °C, as well the final cooling temperature was 450 °C. The highest yield strength and tensile strength of V-N-Cr microalloyed steel were 835 MPa and 989 MPa, respectively. The outstanding impact toughness of 161 J tested at − 60 °C was received. The transformation strengthening and precipitation hardening played a crucial role in affecting the thermo-mechanical properties.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Characterization of Radiation Induced Defects Across Scales

The Whole Powder Pattern Modelling (WPPM) approach of diffraction line profile analysis (LPA) was applied for the first time on PuO 2 in order to understand the evolution of the microstructural properties as a function of process conditions. Crystallite size distributions and defect concentrations were determined by WPPM on three different PuO 2 samples - including one with a bimodal distribution and compared to the result of more common LPA analyses used in PuO 2 literature studies (e.g. Scherrer equation, double Voigt method). The conclusion was that a lognormal distribution of spherical crystallites with dislocations most closely represent the microstructure of PuO 2 produced by heating Pu 2 (C 2 O 4 ) 3 (H 2 O) 6 •3H 2 O between 650°C and 850°C. The volume-weighted mean column length (Lvol) parameter obtained from the double Voigt method for the monomodal samples were the same as the Lvol obtained from the WPPM within uncertainty. The two LPA methods did not agree on the Lvol parameters of the bimodal distribution sample with only the WPPM getting values that were consistent with the individual components. The WPPM can potentially provide more insight into future studies of the influences on the microstructure properties of PuO 2 .

36 MATERIALS SCIENCE↗
DOE OSTI2019

Effect of Microstructure and Properties of Ni-WC Composite Coatings on Their Solid Particle Erosion Behavior

Metal matrix composites (MMCs) of WC in Co or Ni matrices are widely used due to their high wear resistance. Previous studies showed that tailoring the mechanical properties through optimum WC content can significantly extend the life cycle of MMCs. In this study, composite coatings of Ni with various WC content ranging from 10 to 55 vol.% were cold sprayed using agglomerated WCNi powders and two different sizes of Ni powders, − 10 + 4 (d{sub 50} = 7 µm) referred to as Ni(7) and − 35 + 15 (d{sub 50} = 25 µm) to as Ni(25). Microstructural characterization, including the deformed structure of Ni splats and retention and distribution of WC, was performed by scanning electron microscopy (SEM). Composite coatings were subjected to solid particle erosion following ASTM G76-13 standard. At low WC content coatings, erosion occurred primarily by plastic deformation of Ni matrices and knocking out of WC particles. At high WC concentrations, network distribution of compacted WCNi particles in the matrices led to a significant drop in erosion rates of coatings, due to a change in erosion mechanism from severe cutting and plowing of Ni and WC dislodging to WCNi splats spalling. Composite coatings sprayed using finer size Ni powder were usually more erosion resistant.

36 MATERIALS SCIENCE↗
DOE OSTI2022

Properties and microstructure evolution of silicon nitride and zirconium nitride following Ni ion irradiation

We report that silicon nitride and zirconium nitride have been proposed as potential materials for multiple nuclear applications (inert matrix fuels, accident tolerant fuels, space nuclear power, fusion reactor design), yet knowledge on their behavior under irradiation remains limited. Ion irradiations were performed using 15 MeV Ni 5+ ions on Si 3 N 4 and ZrN samples, with midrange doses (around 3 µm) from 1 to 50 dpa and temperatures from 300 to 700°C. Volumetric lattice swelling was determined by grazing incidence X-ray diffraction, defect production and evolution were tracked using Transmission Electron Microscopy, and nanoindentation was performed to quantify the ceramics’ mechanical properties evolution. The results from these irradiation studies on nitride ceramics help fill the current gap present in the literature. Behavior consistent with past work on irradiated Si 3 N 4 was observed with respect to mechanical properties and defect formation up to 15 dpa and 500°C. Failure of the grain boundary sintering aid in Si 3 N 4 was observed above these conditions. Different behavior was observed in both nitrides at 50 dpa and 700°C, where lattice swelling increased past potential saturation values. Unreported cavity formation was witnessed in both materials under all irradiation conditions, with stable number density and slight size increase above 15 dpa. The mechanism for the cavity formation remains to be determined.

36 MATERIALS SCIENCE↗
DOE OSTI2018

Effect of Deformation Parameters on Microstructure and Properties During DIFT of X70HD Pipeline Steel

Grain refinement is a critical approach to improve the strength of materials without damaging the toughness. The grains of deformation-induced ferrite are considerably smaller than those of proeutectoid ferrite. Grain refinement is crucial to the application of deformation-induced ferrite. The composition of ferrite and bainite or martensite is important in controlling the performance of X70HD pipeline steel, and cooling significantly influences the control of their ratio and grain size. By analyzing the static and dynamic phase-transition points using Gleeble-3800 thermal simulator, thermal simulations were performed through two-stage deformations in the austenite zone. Ferrite transformation rules were studied with thermal simulation tests under different deformation and cooling parameters based on the actual production of cumulative deformation. The influence of deformation parameters on the microstructure transformation was analyzed. Numerous fine-grain deformation-induced ferrites were obtained by regulating various parameters, including deformation temperature, strain rate, cooling rate, final cooling temperature and other parameters. Results of metallographic observation and microtensile testing revealed that the selection of appropriate parameters can refine the grains and improve the performance of the X70HD pipeline steel.

36 MATERIALS SCIENCE↗
DOE OSTI2014

Effects of helium implantation on the tensile properties and microstructure of Ni₇₃P₂₇ metallic glass nanostructures

We report fabrication and nanomechanical tension experiments on as-fabricated and helium-implanted ~130 nm diameter Ni₇₃P₂₇ metallic glass nano-cylinders. The nano-cylinders were fabricated by a templated electroplating process and implanted with He⁺ at energies of 50, 100, 150, and 200 keV to create a uniform helium concentration of ~3 at. % throughout the nano-cylinders. Transmission electron microscopy (TEM) imaging and through-focus analysis reveal that the specimens contained ~2 nm helium bubbles distributed uniformly throughout the nano-cylinder volume. In-situ tensile experiments indicate that helium-implanted specimens exhibit enhanced ductility as evidenced by a 2-fold increase in plastic strain over as-fabricated specimens, with no sacrifice in yield and ultimate tensile strengths. This improvement in mechanical properties suggests that metallic glasses may actually exhibit a favorable response to high levels of helium implantation.

36 MATERIALS SCIENCE↗
DOE OSTI2022

Time-dependent THMC properties and microstructural evolution of damaged rocks in excavation damage zone

Modeling coupled thermo-hydro-mechanical-chemical (THMC) processes in host rocks near high-level nuclear waste (HLW) repositories at various time scales is an extremely challenging task. The current study integrates experimental, theoretical, and numerical methods in assessing the evolution of excavation damage zone (EDZ) over time and its implication on the long-term migration of hazardous species. Argillite and rock salt and are the focus of this study. The first part of the report presents a novel time-dependent directional microcrack damage theory for generic brittle rocks. It features detailed statistical description of the microcracks within a damaged solid, permitting a direct upscaling of microscale processes such as crack growth kinetics, crack closure/opening, sliding friction to explain the macroscopic creep, nonlinear elasticity, shear dilation, and loading-unloading hysteresis. This provides a basic platform for describing the anisotropic mechanical and transport properties of damaged rocks during excavation and subsequent THMC loadings. The model is validated and numerically implemented to Finite Element (FE) package ABAQUS through the user-defined material (UMAT) interface and have demonstrated great potential in resolving the time-dependent and anisotropic evolution of damage in the EDZ. The second part of the report presents a multi-scale experimental effort in characterizing the thermal, hydraulic, and mechanical properties of Mancos shale and Avery Island salt. For the Mancos shale, triaxial compression tests are performed at different confining pressures and temperatures to probe its thermomechanical properties relevant to HLW repositories. The obtained stress-strain data are interpreted using the proposed directional damage theory. Post-test specimens are subjected to gas permeability tests to reveal the correlation between permeability and the degree of microcracking. At microscale, temperature-controlled nanoindentation tests are performed and found a linear correlation between fracture toughness and elastic modulus from 25°C to 300°C. For Avery Island salt, we have designed and manufactured a novel relative-humidity controlled uniaxial creep device. Long-term creep tests at low stresses (< 5 MPa) are performed at different levels of relative humidity (RH). Besides confirming the much higher creep rates as one would expect through extrapolating the high-stress creep data, the results reveal that the steady-state creep rate of rock salt is strongly dependent on the ambient RH, an aspect that is often neglected in the literature. Both behaviors can be attributed to the pressure-solution creep mechanism which dominates at low stress and high RH levels. The third part of the report explores a set of numerical strategies in modeling the THMC behavior of porous geomaterials. A fully implicit, monolithic FE solution that can flexibly interface with different material models and coupling mechanisms for THMC problems is developed and verified through the ABAQUS user-defined element (UEL) interface. The scheme is used to study the THM response of a hypothetical HLW storage site with reference to an existing in-situ heater test. Strategies for integrating the UEL and the microcrack UMAT are suggested. Another numerical endeavor of this study is to implement a higher-order asymptotic homogenization method to account for the heterogeneous porous structures. The same method is then extended to perform microstructure-informed thermo-mechanical modeling of generalized continua. The above outcomes of this project provide a strong thrust towards enhancing the fundamental understanding and modeling capability of the long-term evolution of host rocks in EDZ, thus helping achieve the design goal of 1-million-year isolation of high-level nuclear wastes.

11 NUCLEAR FUEL CYCLE AND FUEL MATERIALS↗
DOE OSTI2019

Microstructural and Property Evolution of Continuous Columnar-Grained Polycrystalline Copper during Extreme Plastic Deformation at Room Temperature

An extreme extensibility with a true strain of 11.12 has been obtained for continuous columnar-grained (CCG) polycrystalline copper at room temperature, which was cold-drawn from a 10-mm-diameter as-cast rod into a 38.5-μm-diameter ultra-fine wire without any intermediate softening heat treatment. During the extreme plastic deformation, the ultimate tensile stress increased from 140 MPa for as-cast CCG copper to 525 MPa for the deformed sample at a true stain of 11.12, while the relative electrical conductivity maintained a high value of 97.6% IACS. On this basis, CCG copper is an excellent raw material for the fabrication of ultra-fine wires with both high strength and high electrical conductivity. The original columnar grains experienced grain subdivision and formed fibrous grains along the drawing direction with a fibrous longitudinal morphology and curly transverse microstructure at medium to high strain. The subdivision of the fibrous grains then went on as the extreme plastic deformation continued. Large amounts of strain-induced boundaries and microstructural refinement facilitated the storage of abundant glide dislocations created by extreme plastic deformation. Thus, extreme plastic extensibility can be achieved through continuous work hardening of CCG copper.

36 MATERIALS SCIENCE↗
DOE OSTI2015

Microstructures and properties of CH{sub 3}NH{sub 3}PbI{sub 3−x}Cl{sub x} hybrid solar cells

Halide-perovskite CH{sub 3}NH{sub 3}PbI{sub 3} was produced on mesoporous TiO{sub 2} layer by spin-coating a precursor solution of PbCl{sub 2} and CH{sub 3}NH{sub 3}I in dimethylformamide. The role of the annealing process and chlorine (Cl) doping for the perovskite-phase formation was investigated. It was found that crystallization of the perovskite materials was stimulated by the annealing process, and that longer annealing time is necessary for the Cl-doped perovskite compared with that of non-doped perovskite phase.

36 MATERIALS SCIENCE↗
DOE OSTI2017

Mechanical property degradation and microstructural evolution of cast austenitic stainless steels under short-term thermal aging

Mechanical testing and microstructural characterization were performed on short-term thermally aged cast austenitic stainless steels (CASS) to understand the severity and mechanisms of thermal-aging degradation experienced during extended operation of light water reactor (LWR) coolant systems. Four CASS materials – CF3, CF3M, CF8, and CF8M – were thermally aged for 1500 hours at 290 °C, 330 °C, 360 °C, and 400 °C. All four alloys experienced insignificant change in strength and ductility properties but a significant reduction in absorbed impact energy. The primary microstructural and compositional changes during thermal aging were spinodal decomposition of the δ-ferrite into α/ α`, precipitation of G-phase in the δ-ferrite, segregation of solute to the austenite/ ferrite interphase boundary, and growth of M23C6 carbides on the austenite/ferrite interphase boundary. These changes were shown to be highly dependent on chemical composition, particularly the concentration of C and Mo, and aging temperature. A comprehensive model is being developed to correlate the microstructural evolution with mechanical behavior and simulation for predictive evaluations of LWR coolant system components.

36 MATERIALS SCIENCE↗
DOE OSTI2024

3D Printing of Inconel 718 with Enhanced Boron Composition as a Novel Solar Absorber Tube Material in the Concentrated Solar Power (CSP) System

The growing demands for elevated efficiency in the solar energy industry led researchers to focus on the development of functional solar absorber tube material in concentrated solar power (CSP) systems, when molten salts are adopted as the heat transfer fluid. In this study, the typical solar absorber tube material, Inconel 718, was enhanced with boron to achieve a higher solar absorptivity in the visible light spectrum. Combined with an additive manufacturing (AM) method, the boron composition exceeded the traditional manufacturing limit of 60 ppm without microstructural defects. The boron-enhanced Inconel 718 exhibited a high solar absorptivity of nearly 90 % while maintaining a high thermal cycle fatigue resistance after thermal cycling treatment between 550°C and 720°C. The boron composition was increased to the manufacturing failure point, and the effects of different boron compositions on mechanical properties, microstructure, and optical properties were studied. The provided microstructure-property map in this study delivers high potentials of functional AM-printed alloy material in CSP applications.

13 HYDRO ENERGY↗
DOE OSTI2018

Effect of Tool Temperature on Microstructure and Properties of Tailored Hot Stamping Components

Traditional boron steel hot stamping technology can achieve components with full martensite and tensile strength of 1500 MPa. However, fully martensitic hot stamped components exhibit very low level of ductility and are rarely used in energy absorbing structures. Hot stamping with segmented heating and cooling tool can obtain multiphase quenched structures and the tailored mechanical properties. Hot stamping experiment of U-shape component was performed with segmented heating and cooling tool. Mechanical properties of the formed component were measured, and scanning electron microscope and color tint etching were used to quantify the quenched phases achieved under different tool temperatures. The results showed that hardness value decreased from 470 to 230 HV and tensile strength reduced about 50% from 1406 to 730 MPa and elongation increased from 4.19 to 10.20% as tool temperatures increased from 25 to 500 °C. Meanwhile, martensite decreased from 85 to 30% and bainite increased from 12 to 55%, and there was also a small increase in ferrite. In order to get the influence of quenched phases on the strength and hardness of tailored hot stamped component, linear fitting optimization was used to establish mathematical models for area fraction of quenched phases and strength and hardness.

36 MATERIALS SCIENCE↗
DOE OSTI2015

Benefits of utilizing CellProfiler as a characterization tool for U–10Mo nuclear fuel

Automated image processing techniques have the potential to aid in the performance evaluation of nuclear fuels by eliminating judgment calls that may vary from person-to-person or sample-to-sample. Analysis of in-core fuel performance is required for design and safety evaluations related to almost every aspect of the nuclear fuel cycle. This study presents a methodology for assessing the quality of uranium–molybdenum fuel images and describes image analysis routines designed for the characterization of several important microstructural properties. The analyses are performed in CellProfiler, an open-source program designed to enable biologists without training in computer vision or programming to automatically extract cellular measurements from large image sets. The quality metric scores an image based on three parameters: the illumination gradient across the image, the overall focus of the image, and the fraction of the image that contains scratches. The metric presents the user with the ability to ‘pass’ or ‘fail’ an image based on a reproducible quality score. Passable images may then be characterized through a separate CellProfiler pipeline, which enlists a variety of common image analysis techniques. The results demonstrate the ability to reliably pass or fail images based on the illumination, focus, and scratch fraction of the image, followed by automatic extraction of morphological data with respect to fission gas voids, interaction layers, and grain boundaries. - Graphical abstract: Display Omitted - Highlights: • A technique is developed to score U–10Mo FIB-SEM image quality using CellProfiler. • The pass/fail metric is based on image illumination, focus, and area scratched. • Automated image analysis is performed in pipeline fashion to characterize images. • Fission gas void, interaction layer, and grain boundary coverage data is extracted. • Preliminary characterization results demonstrate consistency of the algorithm.

11 NUCLEAR FUEL CYCLE AND FUEL MATERIALS↗
DOE OSTI2018

Effect of tailored martensitic transformation in a thick weld: Residual stresses mitigation, heterogeneous microstructure, and mechanical properties

The residual stresses, microstructural heterogeneities, and mechanical properties were extensively examined in a 25 mm thick weld consisting of two regions which respectively undergo phase transformation at relatively low (100 °C) temperature (LTT) and high (670 °C) temperature (HTT) during cooling. Due to the LTT martensitic transformation, which features a transformation strain of ~4000 με, large compressive residual stress (−510 MPa) was generated as confirmed by neutron diffraction and contour method. Meanwhile, significant heterogeneities were observed in terms of the chemical composition, yield strength, and microhardness across the interface between the LTT and HTT regions. The dependency of martensitic transformation starting temperature (M{sub s}) on chemical composition is empirically formulated, and it reveals that the dependency of M{sub s} on the Ni and Cr compositions becomes stronger when the temperature is lower than 200 °C. The maximum change of residual stresses (σ{sub x}{sup max}) exponentially decreases as M{sub s} decreases in the manner of σ{sub x}{sup max} = 97.5 exp(M{sub s}/227)-649. The fracture behavior was found highly dependent upon the volume fraction of retained austenite influenced by M{sub s}. While a ductile fracture mode was found in the cellular LTT region containing relatively higher amount of retained austenite (~10%), the interface shows transgranular brittle fracture features and sub-cracking due to the relatively small amount of retained austenite and the predominant martensite constituent.

36 MATERIALS SCIENCE↗
DOE OSTI2015

Novel pre-alloyed powder processing of modified alnico 8: Correlation of microstructure and magnetic properties

Progress is reviewed on development of an improved near-final bulk magnet fabrication process for alnico 8, as a non-rare earth permanent magnet with promise for sufficient energy density and coercivity for electric drive motors. This study showed that alnico bulk magnets in near-final shape can be made by simple compression molding from spherical high purity gas atomized pre-alloyed powder. Dwell time at peak sintering temperature (1250 °C) greatly affected grain size of the resulting magnet alloys. This microstructure transformation was demonstrated to be useful for gaining partially aligned magnetic properties and boosting energy product. While a route to increased coercivity was not identified by these experiments, manufacturability of bulk alnico magnet alloys in near-final shapes was demonstrated, permitting further processing and alloy modification experiments that can target higher coercivity and better control of grain anisotropy during grain growth.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗