Engineering Papers⌕ Search

SEARCH · Engineering Papers

Results for “Neutron diffraction”

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 289 records · Page 16
All sourcesNASA NTRSDOE OSTI
DOE OSTI2026

Correlation between microstructure and residual stress formation in friction stir welded armor steels characterized by neutron diffraction

Friction stir welding (FSW) is a solid-state joining process that minimizes the heat-affected zone (HAZ) compared with fusion-based arc welding, making it well suited for joining martensitic armor steels where hardness and ballistic resistance are critical. This study investigates residual stress formation in three defect-free FSW butt-joint configurations relevant to armored-vehicle fabrication: similar rolled homogeneous armor (RHA–RHA, Case 1), similar high-hardness armor (HHA–HHA, Case 2), and dissimilar HHA–RHA (Case 3) joints produced under temperature-controlled conditions (770 °C). Neutron diffraction was employed to quantify the magnitude and spatial distribution of residual stresses in the longitudinal, transverse, and normal directions and to correlate them with weld microstructure and hardness. Tensile residual stresses were concentrated in the softened HAZ, reaching approximately 300 MPa for Case 2 and 400 MPa for Case 1 (≈50–70 % of the base-metal yield strength; ∼581 MPa for RHA and ∼566 MPa for HHA), while compressive residual stresses dominated the stir zone. The spatial extent of tensile stresses scaled with the width of the softened HAZ, which was largest in the dissimilar HHA–RHA joint and smallest in the HHA–HHA joint. Full-width-at-half-maximum (FWHM) analysis revealed low microstrain in overtempered HAZ regions and high microstrain in the stir zone associated with severe plastic deformation and fresh martensite formation. This work demonstrates that residual stress evolution in FSW of martensitic armor steels is governed not primarily by peak temperature or thermal contraction, as inferred from fusion-welding analogies, but by the competition between transformation-induced volumetric expansion and tempering-induced stress relaxation. The relative dominance of these mechanisms is shown to depend on alloy hardenability and local thermal history, leading to more extensive HAZ softening and broader tensile stress regions in the lower-hardenability RHA steel. These findings establish a transferable mechanistic framework for optimizing solid-state joining strategies in high-strength steels and other transformation-hardening alloys beyond armor applications.

Friction stir welding↗
DOE OSTI2015

Structure of 18R shifted hexagonal perovskite La{sub 6}MgTi{sub 4}O{sub 18} revisited by neutron diffraction

The structure of 18-layer shifted B-site deficient hexagonal perovskite La{sub 6}MgTi{sub 4}O{sub 18} compound has been re-examined by neutron powder diffraction. Structural analysis reveals that La{sub 6}MgTi{sub 4}O{sub 18} compound adopts a 18R octahedral-tilted structure with LaO{sub 3} layer stacking sequence of (hhcccc){sub 3} in space group R{sup {sup -}}3, in contrast with the previously proposed R3m. La{sub 6}MgTi{sub 4}O{sub 18} demonstrates partially ordered Mg cation distribution with a preference on the central octahedral sites over the outer octahedral sites in the cubic perovskite blocks isolated by the single vacant octahedral layers between the two consecutive hexagonal layers. The instability of the La{sub 6}MgTi{sub 4}O{sub 18} on alumina ceramic substrate at high temperature and its dependencies of cell parameters and permittivity were characterized as well. - Graphical abstract: 18-layer shifted hexagonal perovskite La{sub 6}MgTi{sub 4}O{sub 18} adopts octahedral-tilted structure in R{sup {sup -}}3 and demonstrates partially ordered Mg distribution in the cubic perovskite blocks isolated by the vacant octahedral layers. - Highlights: • Neutron diffraction reveals an octahedra-tilted structure in R{sup {sup -}}3 for La{sub 6}MgTi{sub 4}O{sub 18}. • Mg/Ti distribution in La{sub 6}MgTi{sub 4}O{sub 18} is partially ordered in the perovskite blocks. • Instability of La{sub 6}MgTi{sub 4}O{sub 18} on alumina ceramic at high temperature is demonstrated.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2018

Quantifying the inter- and intra-granular stresses and their effects on deformation behaviors for the polycrystalline hexagonal beryllium by neutron diffraction

Highlights: • The inter- and intra-granular stresses are quantified for the polycrystalline hexagonal metal beryllium. • Composite behavior of the internal stresses is revealed in the polycrystalline beryllium. • Those internal stresses show the obvious grain-orientation dependence. • Those stresses can be significantly tuned by the temperature and strain rate effects. • The dislocation slip and twinning are quantified together with the inter- and intra-granular stored energies. - Abstract: The internal stresses developing at different length scales play the important role in materials performance. This importance has been well recognized for the cubic metals, however, not for the hexagonal close-packed (hcp) ones. The present work investigates the intergranular and intragranular stresses in the polycrystalline hexagonal beryllium by neutron diffraction. The correlation between those internal stresses and the deformation mechanism is revealed, and the strain rate and temperature effects on those stresses are presented. A composite behavior of intergranular and intragranular stresses is observed, which can be significantly tuned by the temperature and strain rate effects. The intergranular stress and stored energy are large for the soft-oriented grains (SOGs), while the intragranular stress and stored energy are large for the hard-oriented ones (HOGs). Both of those stresses are significantly high for the dynamic strain rate while they are relatively low for the elevated temperature. The large internal stresses in the dynamically compressed specimen should be attributed to the large number of twins and high density of dislocations. Different HOGs-SOGs configurations are proposed on the light of those observations, which might facilitate the properties controlling and extend the application scope for the hcp metal beryllium.

36 MATERIALS SCIENCE↗
DOE OSTI2021

Neutron diffraction illustrates residual stress behavior of welded alloys used as radioactive confinement boundary

Corrosion-resistant welded alloys are frequently used as a leak-tight boundary in critical applications that require confinement of hazardous and/or radioactive substances, including an increasing population of spent nuclear fuel (SNF) canisters. The behavior of residual stresses generated as a result of irregular elastic–plastic deformation during processes such as welding is one of today's key issues to a full understanding of the aging mechanisms that may compromise the confinement boundary. Whether such processes and any subsequent weld repairs, not subjected to post-weld heat treatment, would negatively affect the initial material by introducing through-thickness tensile stresses remains an open question. Here we report the first residual stress measurements using neutron diffraction on the welded joints of a SNF canister. We found significant tensile residual stresses in the as welded sample, indicating that initiation and through-thickness growth of cracks may be possible. Following repair, we observed a stress redistribution and introduction of beneficial compressive stresses. We anticipate our results will improve understanding of confinement susceptibility to aging and guide improvements in repair techniques.

36 MATERIALS SCIENCE↗
DOE OSTI2018

Real-Time In Situ Neutron Diffraction Investigation of Phase-Specific Load Sharing in a Cold-Rolled TRIP Sheet Steel

Real-time in situ neutron diffraction was used to investigate the loading-direction dependence of phase-specific load sharing in a cold-rolled TRIP 780 sheet steel under tension at room temperature. A slightly lower yield stress and relatively faster initial strain hardening were observed for the tension along the rolling direction (RD), than those along the transverse direction (TD) and the diagonal direction (DD). In all three loading directions, the redistribution of inter-phase and inter-granular load sharing occurs upon the yields of the BCC matrix and the FCC phase. The FCC phase is found to yield earlier along the RD than those along the TD and DD. Based on the Hooke’s law and the rule of mixture, it is found that the lattice strains of BCC-(211)/FCC-(311) reflections via single peak fit are better representative of phase elastic strains than the strains calculated via the lattice parameters by Rietveld refinement. The quantitative evolution of phase-specific stress indicates a rapid strain hardening in the FCC phase after yielding during the RD tension. Possible mechanisms of the direction-dependent phase-specific load sharing are discussed in association with the different initial textures in the RD, DD and TD.

Yu, Dunji↗
DOE OSTI2020

Imaging Based Detector with Efficient Scintillators for Neutron Diffraction Measurements

The Anger Camera developed by the detector group at the Oak Ridge National Laboratory was utilized for the present work for its unique advantage of employing multiple modules to obtain large active measurement area for detecting diffracted/scattered thermal neutrons. Considering the relatively small flux associated with diffracted/scattered neutrons, suitable efficiency with high spatial resolution is a requirement for utilizing two-dimensional imaging detectors. The potential to implement pulse shape (in addition to pulse height) discrimination-based scintillators further enhances the ability to detect diffracted neutrons with improved signal to noise ratio. In this paper, initial results associated with 6Li glass-based scintillator will be presented. The authors explored the feasibility of using this system to detect and quantify diffraction peaks and peak shifts at the Neutron Residual Stress Facility (NRSF2), High Flux Isotope Reactor (HFIR) in the Oak Ridge National Laboratory (ORNL). Suitable camera mounting and shielding had to be developed. Reference measurements using polycrystalline powders with known atomic planar spacing will be discussed along with measurement settings associated with expected resolution for peak shift measurements. Initial results are promising and demonstrate that a suitable scintillation-based neutron detecting system is viable for residual stress-based diffraction measurements. Small area detectors are also feasible with suitable consideration to scattering volume and distance to detector.

Seals, Matthew↗
DOE OSTI2018

Non-destructive compositional and microstructural characterization of Sardinian Bronze Age swords through Neutron Diffraction

Highlights: • Determination of the manufacturing technique of some “Sa Idda” swords • New data on their provenience • Determination of: alloy composition, dendritic segregation, mineralization phase - Abstract: The Monte Sa Idda type swords belong to a well characterized typological class, whose origin has long been debated and seems to coincide with the Iberian Peninsula. The name comes from the site of the first discovery of a hoard containing this type of swords, among other bronze artefacts, namely Monte Sa Idda, Decimoputzu-Cagliari, Italy. The swords were produced through fusion inside a casting mould. Such kind of casting mould has not been found in Sardinia, and this may suggests that finished objects were either imported or made using clay or sand casting mould. Moreover, the discovery of these types of sword, in hoards and in votive deposits, raises the problem of their functional use. It is unknown if the blades were intended to be used as weapons, and therefore subjected to cold working necessary for thinning and sharpening of the blade, or as ceremonial objects. In order to answer to these questions, a neutron diffraction experiment was performed on three swords belonging to the Monte Sa Idda type. The results obtained are presented and discussed in the paper.

36 MATERIALS SCIENCE↗
DOE OSTI2012

Evaluation on double-wall-tube residual stress distribution of sodium-heated steam generator by neutron diffraction and numerical analysis

A double-wall-tube is nominated for the steam generator heat transfer tube of future sodium fast reactors (SFRs) in Japan, to decrease the possibility of sodium/water reaction. The double-wall-tube consists of an inner tube and an outer tube, and they are mechanically contacted to keep the heat transfer of the interface between the inner and outer tubes by their residual stress. During long term SG operation, the contact stress at the interface gradually falls down due to stress relaxation. This phenomenon might increase the thermal resistance of the interface and degrade the tube heat transfer performance. The contact stress relaxation can be predicted by numerical analysis, and the analysis requires the data of the initial residual stress distributions in the tubes. However, unclear initial residual stress distributions prevent precious relaxation evaluation. In order to resolve this issue, a neutron diffraction method was employed to reveal the tri-axial (radius, hoop and longitudinal) initial residual stress distributions in the double-wall-tube. Strain gauges also were used to evaluate the contact stress. The measurement results were analyzed using a JAEA's structural computer code to determine the initial residual stress distributions. Based on the stress distributions, the structural computer code has predicted the transition of the relaxation and the decrease of the contact stress. The radial and longitudinal temperature distributions in the tubes were input to the structural analysis model. Since the radial thermal expansion difference between the inner (colder) and outer (hotter) tube reduces the contact stress and the tube inside steam pressure contributes to increasing it, the analytical model also took these effects into consideration. It has been conduced that the inner and outer tubes are contacted with sufficient stresses during the plant life time, and that effective heat transfer degradation dose not occur in the double-wall-tube SG. (authors)

22 GENERAL STUDIES OF NUCLEAR REACTORS↗
DOE OSTI2013

Neutron diffraction study of the formation of ordered antiphase domains in cubic titanium carbide TiC{sub 0.60}

A series of superstructural reflections (described within the sp. gr. Fd3m) are found to be split into three symmetric parts in the neutron powder diffraction pattern of titanium carbide TiC{sub 0.60} annealed at a temperature of 600 Degree-Sign C. No splitting of superstructural reflections is observed in the neutron diffraction pattern of TiC{sub 0.60} annealed at relatively high temperatures (780 Degree-Sign C). This phenomenon can be explained by that fact that the ordering of carbon atoms at relatively high temperatures (780 Degree-Sign C) is accompanied by the formation of randomly oriented rather large antiphase domains (APDs) (450 A). At relatively low temperatures (600 Degree-Sign C), stacking faults arise in the arrangement of partially ordered carbon atoms. In this case, relatively small ordered APDs (290 A) are formed, along with disordered ones.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2021

H-Atom Assignment and Sb–O Bonding of [Mes 3 SbOH][O 3 SPh] Confirmed by Neutron Diffraction, Multipole Modeling, and Hirshfeld Atom Refinement

Neutron wavelength-resolved Laue diffraction experiments permit accurate refinement of the H-atom positions and anisotropic displacement parameters of [Mes 3 SbOH][O 3 SPh]. A multipole-based charge density refinement and a topological analysis of the refined electron density were also performed. Hirshfeld atom refinement (HAR) recovers the neutron-determined H-atom parameters, and the quantum-mechanical electron density used in HAR recovers the electron density topology from the refined multipole model. We report these results confirm that [Mes 3 SbOH][O 3 SPh] does indeed feature a hydroxystibonium cation with a nominal Sb–O single bond and not a stibine oxide with an Sb=O/Sb + –O – bond.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2016

Transformation-induced plasticity in bulk metallic glass composites evidenced by in-situ neutron diffraction

Transformation-induced plasticity in a strain-softening amorphous matrix consisting of austenite B2 phase was studied by in-situ neutron diffraction, coupled with molecular dynamic simulation. It was found that the martensitic transformation from B2 to B19' upon loading commenced at the macroscopic yielding which increased with the decrease of the fraction of the parent austenite B2 phase, and the threshold lattice strain for the martensitic transformation is almost the same in different samples, suggesting that the martensitic transformation in the current glassy matrix is strain-controlled. Analysis of load partition and strain accommodation unveiled that B2 has elastic anisotropy, and the desirable elastic match between B2 and the amorphous matrix ensures a good cooperative deformation. Additionally, molecular dynamic simulation revealed that atoms at the interface between B2 and the amorphous matrix deviated from the standard B2 lattices and acted as nucleation site for the martensitic transformation, eventually giving rise to the strain-controlled martensitic transformation. Our findings provide new insights into the mechanism of phase transformation-mediated plasticity at the microscopic level, and have useful implications for developing novel, high-performance bulk metallic glass composites.

36 MATERIALS SCIENCE↗
DOE OSTI2023

Advancing neutron diffraction for accurate structural measurement of light elements at megabar pressures

Over the last 60 years, the diamond anvil cell (DAC) has emerged as the tool of choice in high pressure science because materials can be studied at megabar pressures using X-ray and spectroscopic probes. In contrast, the pressure range for neutron diffraction has been limited due to low neutron flux even at the strongest sources and the resulting large sample sizes. Here, we introduce a neutron DAC that enables break-out of the previously limited pressure range. Key elements are ball-bearing guides for improved mechanical stability, gem-quality synthetic diamonds with novel anvil support and improved in-seat collimation. We demonstrate a pressure record of 1.15 Mbar and crystallographic analysis at 1 Mbar on the example of nickel. Additionally, insights into the phase behavior of graphite to 0.5 Mbar are described. These technical and analytical developments will further allow structural studies on low-Z materials that are difficult to characterize by X-rays.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2019

Comprehensive study of the magnetic phase transitions in Tb 3 Co combining thermal, magnetic and neutron diffraction measurements

A comprehensive study of the magnetic phase transitions in Tb 3 Co has been undertaken combining different techniques. Using single crystal neutron diffraction in the paramagnetic state a weak crystal structure distortion from the room temperature orthorhombic structure of the Fe 3 C type described with the Pnma space group toward structure with lower symmetry has been observed with cooling below 100 K. At 81 K there is a second order phase transition to an antiferromagnetic incommensurate phase with the propagation vector k = (0.155, 0, 0). As derived from thermal diffusivity measurements, the critical exponents for this transition are very close to the 3D-Heisenberg universality class, proving that the magnetic interactions are short-range but with a deviation from perfect isotropy due to crystal field effects. At T 2 ≈ 70 K there is another magnetic phase transition to a ferromagnetic state whose character is shown to be weakly first order. The low temperature magnetic state has a non-coplanar ferromagnetic structure with strong ferromagnetic components of Tb magnetic moments along the crystallographic c-axis. The application of an external magnetic field B = 2 T along the crystallographic c-axis suppresses the incommensurate antiferromagnetic phase and gives rise to the ferromagnetic phase. The magnetic entropy peak change as well as the refrigerant capacity indicate that Tb 3 Co is a competitive magnetocaloric material in this temperature range.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2013

Powder Neutron Diffraction Study of HoCoGa5

We have studied successive magnetic transitions of HoCoGa5 at TN1 = 9.6 K and TN2 = 7.5 K by using powder neutron diffraction. Apparent superlattice peaks were observed at temperatures below TN1. With further decreases temperature, the patterns exhibit a substantial change at temperatures below TN2. The observed magnetic peaks at 8 K (AntiFerromagnetic InCommensurate (AFIC) phase : TN2 < T < TN1) can be represented by the propagation vector qL = (1/2 0 ) with = 0.35(2). In contrast, the magnetic structure becomes commensurate with qC = (1/2 0 1/2) at 4 K (AntiFerromagnetic Commensurate (AFC) phase : T < TN2). The temperature dependence of magnetic intensity shows an apparent temperature hysteresis at TN2, indicates a first-order transition at TN2. Analysis of the integrated intensity at 4 K reveals that the Ho moment with a size of 8.6(2) B, oriented parallel to the c-axis in the AFC phase. While the successive transitions of HoCoGa5 are different from those of TbCoGa5, the magnetic structure in the AFC phase of HoCoGa5 is the same as the AFTb I of TbCoGa5, and may indicate an additional transition at a lower temperature in HoCoGa5.

Kabayashi, Riki↗
DOE OSTI2011

Neutron diffraction study and superparamagnetic behavior of ZnFe{sub 2}O{sub 4} nanoparticles obtained with different conditions

Spinel-type (S.G.= Fd3-bar m) ZnFe{sub 2}O{sub 4} fine particles with sizes from 4 to 19 nm prepared by solvothermal and microwave-assisted solvothermal methods have been studied by neutron powder diffraction at room temperature. The cation distribution corresponding to mixed spinel structure (Zn{sup 2+}{sub 1-x}Fe{sup 3+}{sub x})[Fe{sup 3+}{sub 2-x}Zn{sup 2+}{sub x}]O{sub 4} along with the unit cell parameter has been estimated after Rietveld refinement of the obtained neutron diffraction data for all the samples. It has been found that the inversion degree parameter (x) takes values between 0.11 and 0.20 depending not only on the particle size but also on the synthesis conditions as well. All the samples behave as superparamagnetic with an effective magnetic moment per particle ({mu}{sub SP}) from 7.0x10{sup 2} to 7.7x10{sup 3} {mu}{sub B}. The sample obtained by microwave assistance displays a different magnetic behavior as the ZFC and FC magnetic susceptibility and the magnetization versus applied field hysteresis loop measured at 5 K suggest. This is related with the dipole interactions that are a consequence of the higher inversion degree and {mu}{sub SP}. - Graphical abstract: ZnFe{sub 2}O{sub 4} nanoparticles of 19 nm obtained by the solvotermal method together with its Rietveld refined pattern. Highlights: > Solvothermally prepared ZnFe{sub 2}O{sub 4} nanoparticles.{yields} Inversion degree obtained after Rietveld refinement of neutron data.{yields} Superparamagnetic behavior.{yields} Dependence with the synthesis conditions.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2026

Uncovering hidden bias in neutron diffraction residual strain measurements

When calculating residual strain via neutron or X-ray diffraction, uncertainties propagated from the peak fit are often inadequate to describe the true scatter of measurements about a singular strain state, such as one that should describe a macroscopic continuum. Because diffraction is inherently a selective process, orientation-dependent scatter arises from the sub-sampling of strong microstructure and strain gradients. This paper investigates the appropriateness of propagated uncertainties with reference to their original intention, i.e. noise about a mean value. Thirty-six unique orientations of strain measurements are taken at multiple locations within an additive friction-stir deposition component with fine-scale gradients (∼200 µm) of plastic strain, texture and residual elastic strain. Multiple strain and stress calculation pathways are compared: direct substitution of three measurements into Hooke's law, direct inversion of any six unique orientations into the strain state tensor and thirty-six measurement least-squares estimation. For the last two cases, the appropriateness of the uncertainty interval is statistically evaluated on the basis of a physical constraint: common agreement under the strain transformation law. For this sample, the direct inversion of six measurements retains a conservative estimate of the uncertainty. However, propagated uncertainties in the least-squares solution greatly underestimate the true experimental scatter. A simple pathway to estimate appropriate uncertainty intervals is suggested. These results demonstrate that the interpretation of uncertainty in residual strain is strongly dependent on intrinsic sample-dependent effects, and that oversampling orientations and statistical analysis can give more accurate results with realistic uncertainties.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Determination of Stress-Free Lattice Spacing (D₀) for Residual Stress Relaxation Measurement in Ni-based Superalloys by Neutron Diffraction

The residual stress and its relaxation in critical engineering components are key to structural materials reliability. The determination of residual stress in bulk engineering structures like Ni-based superalloys can be conducted by measuring the lattice strain with penetrating neutron diffraction. The state-of-the-art engineering diffraction beamline VULCAN at the Oak Ridge National Laboratory (ORNL) Spallation Neutron Source (SNS) provides the critical capability to evaluate the residual strain/stress relaxation in engineering component thanks to the high flux and event data features. By the means of residual stress/strain calculation, it is critical to accurately determine the stress-free lattice spacing d₀, which can be altered by the change of chemistry, unrelieved stress, and measurement scheme. Here we reported d₀ determination for determining residual stress relaxation and distribution in Alloy 718 superalloys after different quenching treatments. Selection of locations for d₀ measurement was discussed by considering the neutron path, attenuation and sample alignment. A dynamic d₀ that resulted from atom diffusion and chemistry change was estimated as function of time for the in-situ relaxation characterization. It demonstrated how the dynamic d₀ values may influence on the strain calculation in different thermally treated samples. The results highlight the importance of dynamic d₀ for in-situ relaxation involving chemical changes and provide guidance to the dynamic d₀ measurement and simulation.

36 MATERIALS SCIENCE↗
DOE OSTI2014

Neutron diffraction studies of a four-coordinated hydride in near square-planar geometry

The structure of a nanospheric polyhydrido copper cluster, [Cu 20 (H) 11 {S 2 P(O i Pr) 2 } 9 ], was determined by single-crystal neutron diffraction. Cu 20 cluster consists of an elongated triangular orthobicupola constructed from 18 Cu atoms that encapsulate a [Cu 2 H 5 } 3- ion in the center with an exceptionally short Cu-Cu distance. The eleven hydrides in the cluster display three different coordination modes to the Cu atoms: Six μ 3 -hydrides in pyramidal geometry, two μ 4 -hydrides in tetrahedral cavity, and three μ 4 -hydrides in an unprecedented near square-planar geometry. The neutron data set was collected on a small crystal of the size 0.20 mm x 0.50 mm x 0.65 mm for seven days using the Spallation Neutron Source TOPAZ single-crystal time-of-flight Laue diffractometer at the Oak Ridge National Laboratory. Furthermore, the final R-factor is 8.64% for 16014 reflections.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗