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Results for “Precipitate crystallography”

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 19 records
All sourcesNASA NTRSDOE OSTI
DOE OSTI2018

A generalized O-element approach for analyzing interface structures

A correct description of interfacial dislocations is critical to the understanding of physical and mechanical properties of the interfaces and their impact on phase transformation and deformation mechanisms. The O-lattice theory provides a general theoretical framework for determining interfacial dislocation structures. However, for systems having an invariant line (IL) or an invariant plane, the O-elements do not always exist in the three-dimensional (3D) space, which impedes the capability of the O-lattice theory to the interfaces in these systems. To determine the dislocation structures in interfaces for which the O-elements do not extend in the 3D space, we introduce a generalized O-element approach by employing the Moore-Penrose pseudoinverse. The generalized O-elements, as the least square solutions to the O-lattice, play a parallel role as that of the ideal O-elements and extend the candidate locations for the coherent regions between dislocations. Worked examples for dislocation structures in both homo-phase and hetero-phase systems are presented. The predicted interface structures are in good agreement with experimental observations and molecular statics (MS)/molecular dynamics (MD) simulations.

36 MATERIALS SCIENCE↗
DOE OSTI2019

Synthesis of greigite (Fe 3 S 4 ) particles via a hydrothermal method

Greigite (Fe 3 S 4 ) particles, with strong ferrimagnetic behavior, have been found to have desirable uses in the areas of biomedical and environmental applications. Size-dependent magnetic properties of greigite can play a crucial role in efficiency of its applications. This study reviews two synthetic approaches to producing such particles. The methods tested within this study include a coprecipitation synthesis and a hydrothermal process. While the coprecipitation method proved to be ineffective at producing greigite, the hydrothermal process showed promise after consistently producing greigite. For the hydrothermal process, the effects of synthesis time, autoclave atmosphere, and polyvinylpyrrolidone (PVP) addition as a capping agent to control particle growth were investigated using X-ray diffractometry (XRD) with Rietveld refinement, vibrating sample magnetometry (VSM), and scanning electron microscopy (SEM). The results show that, while pyrite (FeS2) forms as an impurity phase, increasing the synthesis time up to 18 hours increases the greigite fraction up to 70 wt% and saturation magnetization up to ~ 35 emu/g for the powder synthesized in argon. The SEM micrographs of this sample reveal a mean greigite particle size of ~ 700 nm. It was found that adding PVP brings about a much more uniform microstructure of agglomerated plate-shape particles with nano-sized features.

36 MATERIALS SCIENCE↗
DOE OSTI2025

Material Characterization Report of EBR II Mark IV Fuel Element

The focus of this report is the characterization of an unirradiated as-built fuel element from the Experimental Breeder Reactor II (EBR-II) Mark IV driver fuel design. The fuel in this element is a metallic uranium-zirconium alloy, and the cladding material is HT9 stainless steel. Both the metallic fuel and cladding materials are characterized, including chemical composition, grain size, morphology, phase composition, precipitate composition, crystallography, density, and hardness.

11 - NUCLEAR FUEL CYCLE AND FUEL MATERIALS↗
DOE OSTI2018

Investigations of γ′, γ″ and δ precipitates in heat-treated Inconel 718 alloy fabricated by selective laser melting

Highlights: • The γ austenite matrix shows a fine cellular substructure. • γ′ and three variants of γ″ precipitates around 10–50 nm develop within cellular γ. • Coarser acicular γ″ and plate-like δ occur at grain boundaries and intragranular γ. • The orientation relationships of γ″ with γ, and of δ with γ are observed. - Abstract: Inconel 718 alloy samples were fabricated by selective laser melting (SLM). Microstructure and precipitation in solution-heat-treated- and double-aging-SLM-made Inconel 718 were studied by scanning and transmission electron microscopy. Electron microscope observations showed that disc-shaped and cuboidal γ″, and circular γ′ precipitates with an average size of 10–50 nm developed within cellular γ austenite matrix. The simulated, experimentally observed electron diffraction patterns, and dark-field imaging further revealed that the precipitation of three variants of γ″ in the γ matrix occurred. The coarser acicular γ″, and globular as well as plate-like δ phases precipitated at grain boundaries and also within the interior of austenite matrix. The morphology, distribution and crystallography of these precipitates and their formation mechanisms were analyzed and discussed.

36 MATERIALS SCIENCE↗
DOE OSTI2020

An atom probe tomography and inventory calculation examination of second phase precipitates in neutron irradiated single crystal tungsten

Tungsten is the prime candidate material for the plasma facing divertor system and first wall armor of future nuclear fusion reactors. However, the understanding of the microstructural and chemical evolution of pure tungsten under neutron irradiation is relatively unknown, in part due to a lack of experimental data on this topic. Here, single crystal tungsten has been irradiated in the High Flux Isotope Reactor (HFIR) at Oak Ridge National Laboratory at a nominal temperature of 700–800 °C to damage levels of 0.1 and 1.8 displacements per atom (dpa). Inventory calculations of the neutron irradiation experiments have been used to track isotope generation and decay to inform atom probe tomography (APT) results in the determination of the transmutation-induced precipitate compositions. Furthermore, APT crystallography has been used to show the relationship between precipitates and matrix. The composition of the precipitates is shown to progress towards that of the σ-phase at the highest dose studied, with those precipitates lying along crystallographic planes similar to those of displacement-induced dislocations. This work also sets the framework for APT studies of materials that contain isotopic ratios far from those observed in the natural state.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2023

Influence of Mo Content on the Precipitation Behavior of 13Ni Maraging Ultra-High Strength Steels

This study offers valuable insights into the precipitation behavior of 13Ni maraging steels, emphasizing the role of molybdenum content in their microstructure, strengthening, and precipitate evolution. Precipitate morphology and crystallography were examined using a combination of high-resolution transmission electron microscopy and selected area electron diffraction. Strengthening mechanisms were assessed through Vickers hardness measurements. All the examined samples exhibited a lath martensite microstructure and displayed an increasing hardness over the aging time. The molybdenum content not only influenced the presence of retained austenite in the initial microstructure but also affected the type of precipitates formed during the early aging stages. Initially, Ni 3 Mo precipitates were formed, succeeded by the formation of more stable Fe 2 (Mo,Ti) Laves precipitates. The ultra-high strength of 13Ni maraging steels arises from the combination of the precipitate type and size distribution. The base composition of 13Ni maraging steels achieved a peak hardness of 798 HV1 through the precipitation of Laves Fe 2 (Mo,Ti) phases ranging from 3 to 14 nm in diameter.

13Ni maraging steels↗
NASA NTRS2002

Characterization of the Protein Crystal Growth Apparatus for Microgravity Aboard the Space Station

We have conducted experiments to determine the equilibration rates of some major precipitants used in protein crystallography aboard the International Space Station (ISS). The solutions were placed in the Protein Crystallization Apparatus for Microgravity (PCAM) which mimic Cryschem sitting drop trays. The trays were placed in cylinders. These cylinders were placed inside a Single locker Thermal Enclosure System (STES), and were activated for different durations during the flight. Bumpers pressed against elastomers seal drops in a deactivated state during pre-flight and prior to transfer to the ISS. Activation occurs while in flight on the ISS by releasing the bumpers allowing the drops to be exposed to the reservoir. PCAM was flown to the ISS on STS 100, Flight 6A, on April 19, 2001. Six series of equilibration experiments were tested for each precipitant with a small amount of Green Fluorescent Protein (GFP). Cylinder 10 was never activated, 7 was activated for 40 days, 8 was activated for 20 days, 9 was activated for 10 days, 11 was activated for 4 days and 12 was activated for 2 days. Upon the return to Earth by STS 104 on July 24,2001 the samples were transferred to Marshall Space Flight Center. The samples were then brought to the lab and the volumes of each sample were measured.

Kundrot, Craig E.↗
DOE OSTI2022

Microstructure analysis of laser beam weldments performed on neutron-irradiated 304L steel containing 3 and 8 appm helium

We report that AISI 304 L austenitic stainless steel is one of the major structural materials used in light water reactors (LWRs). In the future, 304 L components may require repair, and several welding techniques have been proposed as candidates. In this study, laser beam welding using the low-energy contribution approach was performed in ~2016 on neutron-irradiated AISI 304 L steel with nominal values of 3 and 8 appm helium (He). The goal was to investigate the impact of helium on the irradiated material weldability and evaluate helium-associated damage. The weld and heat-affected zone (HAZ) microstructure was studied using scanning electron microscopy, electron backscatter diffraction, and transmission electron microscopy (TEM). Analysis of the weldment cross-sections did not reveal severe cracking. Still, evidence of incipient helium-associated damage was observed in the HAZ, manifesting as degraded grain boundaries (GBs) “decorated” by pore chains and mostly small (i.e., ≤ 25-30 µm) scattered cracks. The largest observed crack was ~50 µm in length. Helium-associated damage was localized within ~200-300 µm of the weld pool boundary, and the fraction of the compromised GBs, as a rule, was below ~9-11% of the total GB network. TEM analysis showed significant annealing of the radiation-induced defects at distances up to ~300 µm from the weld pool boundary. Inside the HAZ, the cavities (likely, helium bubbles) tended to form at GBs and inclusions, such as manganese sulfide precipitates in the grain interior. Crystallography analysis of the HAZ damage showed that random high-angle boundaries were most susceptible to helium-associated damage. In contrast, low-angle random boundaries and twin boundaries appeared to be strongly resistant to degradation from the combined effects of helium and welding.

36 MATERIALS SCIENCE↗
DOE OSTI2021

The anion exchange properties of AFm (hydrocalumite-group) minerals defined from solubility experiments and crystallographic information

Solubility experiments with binary series of OH-, Cl-, SO{sub 4}- and CO{sub 3}-AFm were re-examined with a non-ideal, multicomponent solid solution model. The electrical double layer on the mineral's outer surface, which neutralizes about 5% of the anionic charge, can be included. The choice of the end-members in the solid solution and the reaction formulation can help to eliminate the ‘non-ideality’ for OH-SO{sub 4} and Cl-OH exchange. CO{sub 3}-Cl-OH exchange is not ideal in the solubility experiments, nor can it be, because the mineral volume is not a linear combination of the end-members. The solubilities of the end-members are related to the anion charge and inversely to the anion-layer thickness. OH is part of the anion-charge, even when a pure, other anion form is the target of the synthesis. Pure OH-AFm is unstable and converts into hydrogarnet and portlandite, depending on the precipitation rate of hydrogarnet.

36 MATERIALS SCIENCE↗
DOE OSTI2015

Structural characteristics of transition-iron-carbide precipitates formed during the first stage of tempering in 4340 steel

Microstructural and crystallographic characteristics of fine-scale transition-iron-carbide precipitates formed in martensite during tempering of 4340 steel at 200 °C for 3.6 ks were studied via transmission electron microscopy. Precipitates of near-equiaxed shapes and about 10 nm in size were observed, and rows of closely spaced precipitates were aligned predominantly along < 100 > martensite directions. Aggregates of aligned precipitates were up to 150 nm in length, although occasional kinks were present that disrupted the alignment, and some of the adjacent precipitates possessed somewhat different crystallographic orientations. Electron-diffraction results were analyzed in detail and found to be consistent with both epsilon-carbide and eta-carbide phases. Similarities between these two phases were highlighted and discussed. Experimental electron-diffraction data were compared with data from five different unit cells, and each was found to be consistent within uncertainty ranges of ± 0.003 nm for interplanar spacings, ± 2° for angles between plane normals, and a few degrees for the orientation relationship between precipitates and the matrix.

36 MATERIALS SCIENCE↗
DOE OSTI2017

Study on the morphology of bulk hydrides by synchrotron X-ray tomography

Highlights: • The first DCT measurements in zirconium using high energy X-rays is shown. • A modified Hough Transform algorithm brings orientation calculation to pixel level. • The hydride plate normals are clustered in the {0002} pole direction. - Abstract: The morphologies of hydrides was studied using synchrotron X-ray at the European Synchrotron Radiation Facility (ESRF) using Diffraction Contrast Tomography (DCT). Diffraction Contrast Tomography is a relatively new technique that uses simultaneous collection of tomographic and diffraction data to reconstruct the 3D microstructural volume; in this case precipitates and matrix grains, while providing crystallographic orientation of neighbouring matrix grains. Previously the method was limited to light metals such as Al or Mg (due to the use of 8–30 keV X-rays). Here we show the first DCT measurements in a high atomic number metal zirconium using high energy X-rays (60 keV).

36 MATERIALS SCIENCE↗
DOE OSTI2014

Three phase crystallography and solute distribution analysis during residual austenite decomposition in tempered nanocrystalline bainitic steels

Interphase carbide precipitation due to austenite decomposition was investigated by high resolution transmission electron microscopy and atom probe tomography in tempered nanostructured bainitic steels. Results showed that cementite (θ) forms by a paraequilibrium transformation mechanism at the bainitic ferrite–austenite interface with a simultaneous three phase crystallographic orientation relationship. - Highlights: • Interphase carbide precipitation due to austenite decomposition • Tempered nanostructured bainitic steels • High resolution transmission electron microscopy and atom probe tomography • Paraequilibrium θ with three phase crystallographic orientation relationship.

36 MATERIALS SCIENCE↗
DOE OSTI2016

A transmission Kikuchi diffraction study of cementite in a quenched and tempered steel

This is the first transmission Kikuchi diffraction (TKD) study to report the indexing of nano-sized cementite as distinct structures and its orientation relationship with the body-centered cubic matrix in a quenched and tempered steel. Crystallographic analysis via TKD and selected area diffraction returned the well-known Bagaryatskii and Isaichev orientation relationships. However, the indexing of nano-sized cementite via TKD was sensitive to the thickness of the electron transparent region such that TEM remains the most precise method to characterise such precipitates. - Highlights: • Nano-sized cementite in a QT steel has been investigated by TKD and TEM. • Cementite has been indexed as distinct structures via TKD. • Crystallographic analysis returned the Bagaryatskii and Isaichev ORs. • Success of TKD is sensitive to the thickness of the electron transparent region. • TEM remains the most precise technique to characterise nano-sized precipitates.

36 MATERIALS SCIENCE↗
DOE OSTI2018

Microstructure and mechanical properties of intragranular W-Cu/TiC-ZrC composite prepared by reactive melt infiltration at 1300 °C

Highlights: • W-Cu/TiC-ZrC composites with nano W dispersoids were prepared by reactive melt infiltration. • The nano-sized dispersoids were analyzed by TEM in detail. • The intragranular nano W dispersoids and ribbon like precipitates have toughening effects. - Abstract: Newly intragranular W-Cu/TiC-ZrC composites with nano W dispersoids in TiC matrix have been prepared by reactive melt infiltration at 1300 °C for 1 h in vacuum using molten Zr-Cu binary alloys and a (Ti{sub 0.75},W{sub 0.25})C solid solution powder as raw materials. The as-synthesized composites consist of major phases of W, Cu, TiC and ZrC. With the decrease of Zr content from 66 to 21 at.% in the Zr-Cu infiltrator, the reaction formed W phase in the composite has changed from micron-sized intergranular grains to nano-sized rounded inclusions in TiC{sub y} grains. The crystallographic orientation relationship at W and TiC interfaces are detected as:(0 1 1-bar ){sub W}//(1 1 1-bar ){sub TiC}&[0 1 1]{sub W}//[0 1 1]{sub TiC} and (4 1 1){sub W}//(4 2 4){sub TiC}&[0 1 1-bar ]{sub W}//[4 2-bar 3-bar ]{sub TiC}. Nano-sized lamellar structure with both W and Cu rich is detected to have super-lattice structure based on the TiC lattice. The elastic modulus, flexural strength, fracture toughness of the intragranular W-Cu/TiC-ZrC composite infiltrated with Zr{sub 14}Cu{sub 51} melt are 207.5 GPa, 457 MPa and 10.21 MPa∙m{sup 1/2}, respectively. The intragranular nano W dispersoids and ribbon like precipitates hinder crack propagation via crack deflection and bridging.

77 NANOSCIENCE AND NANOTECHNOLOGY↗
DOE OSTI2015

Precipitates in a quasicrystal-strengthened Al–Mn–Be–Cu alloy

In this work, an Al–Mn–Be–Cu alloy was studied containing a primary and eutectic icosahedral quasicrystalline phase in the as-cast microstructure. Special attention was given to a transmission electron microscopy investigation of precipitates formed within the aluminium solid solution (Al{sub ss}) at different temperatures. At 200 °C, only binary Al–Cu precipitates (θ′) were formed. At 300 °C, icosahedral quasicrystalline (IQC) precipitates prevailed with a crystallographic orientation relationship with the Al{sub ss.} The rods of the T-phase (Al{sub 20}Mn{sub 3}Cu{sub 2}) which were precipitated above 400 °C, also had a specific orientation relationship with the Al{sub ss}. The primary and eutectic IQC microstructural constituent started to transform rapidly to the T-phase and Be{sub 4}Al(Mn,Cu) at 500 °C. - Highlights: • In a quasicrystal-strengthened Al-alloy several types of precipitates can form. • At 200 °C, only binary Al–Cu precipitates formed (Al{sub 2}Cu-θ′). • The icosahedral quasicrystalline (IQC) precipitates prevailed at 300 °C. • T-phase (Al{sub 20}Mn{sub 3}Cu{sub 2}) precipitated at temperatures above 400 °C. • The precipitation of different phases did not have a strong effect on hardness.

36 MATERIALS SCIENCE↗
DOE OSTI2015

Evolution of carbides in cold-work tool steels

This study aimed to present the complete history of carbide evolution in a cold-work tool steel along its full processing route for fabrication and application. A sequence of processes from cast to final hardening heat treatment was conducted on an 8% Cr-steel to reproduce a typical commercial processing route in a small scale. The carbides found at each process step were then identified by electron diffraction with energy dispersive spectroscopy in a scanning or transmission electron microscope. After solidification, MC, M{sub 7}C{sub 3} and M{sub 2}C carbides were identified and the last one dissolved during hot compression at 1180 °C. In a subsequent annealing at 870 °C followed by slow cooling, M{sub 6}C and M{sub 23}C{sub 6} were added, while they were dissolved in the following austenitization at 1030 °C. After the final tempering at 520 °C, fine M{sub 23}C{sub 6} precipitated again, thus the final microstructure was the tempered martensite with MC, M{sub 7}C{sub 3} and M{sub 23}C{sub 6} carbide. The transient M{sub 2}C and M{sub 6}C originated from the segregation of Mo and finally disappeared due to attenuated segregation and the consequent thermodynamic instability. - Highlights: • The full processing route of a cold-work tool steel was simulated in a small scale. • The carbides in the tool steel were identified by chemical–crystallographic analyses. • MC, M{sub 7}C{sub 3}, M{sub 2}C, M{sub 6}C and M{sub 23}C{sub 6} carbides were found during the processing of the steel. • M{sub 2}C and M{sub 6}C finally disappeared due to thermodynamic instability.

36 MATERIALS SCIENCE↗
DOE OSTI2014

Impurity precipitation in atomized particles evidenced by nano x-ray diffraction computed tomography

Performances and physical properties of high technology materials are influenced or even determined by their initial microstructure and by the behavior of impurity phases. Characterizing these impurities and their relations with the surrounding matrix is therefore of primary importance but it unfortunately often requires a destructive approach, with the risk of misinterpreting the observations. The improvement we have done in high resolution X-ray diffraction computed tomography combined with the use of an X-ray nanoprobe allows non-destructive crystallographic description of materials with microscopic heterogeneous microstructure (with a grain size between 10 nm and 10 μm). In this study, the grain localization in a 2D slice of a 20 μm solidified atomized γU-Mo particle is shown and a minority U(C,O) phase (1 wt. %) with sub-micrometer sized grains was characterized inside. Evidence is presented showing that the onset of U(C,O) grain crystallization can be described by a precipitation mechanism since one single U-Mo grain has direct orientation relationship with more than one surrounding U(C,O) grains.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗