Time-of-flight neutron transmission diffraction

2001 ◽  
Vol 34 (3) ◽  
pp. 289-297 ◽  
Author(s):  
J. R. Santisteban ◽  
L. Edwards ◽  
A. Steuwer ◽  
P. J. Withers
Keyword(s):  
Time Of Flight ◽  
Neutron Transmission ◽  
Lattice Strains ◽  
Nickel Powders ◽  
Transmission Geometry ◽  
Spallation Source ◽  
The Uk ◽  
Pulsed Neutron

The positions of Bragg edges in neutron transmission experiments can be defined with high accuracy using the time-of-flight (TOF) technique on pulsed neutron sources. A new dedicated transmission instrument has been developed at ISIS, the UK spallation source, which provides a precision of Δd/d≃ 10−5in the determination of interplanar distances. This is achieved by fitting a theoretical three-parameter expression to the normalized Bragg edges appearing in the TOF transmission spectra. The technique is demonstrated by experiments performed on iron, niobium and nickel powders. The applicability of using the instrument for the determination of lattice strains in materials has been investigated using a simplein situloading experiment. Details of the calibration process are presented and the dependence of the resolution and the experimental times required by the transmission geometry on the instrumental variables are studied. Finally, the requirements for a Rietveld-type refinement of transmission data and the advantages and limitations over traditional neutron diffraction peak analysis are discussed.

In situdetermination of stresses from time-of-flight neutron transmission spectra

2003 ◽  
Vol 36 (5) ◽  
pp. 1159-1168 ◽  
Author(s):  
Axel Steuwer ◽  
Javier Roberto Santisteban ◽  
Philip J. Withers ◽  
Lyndon Edwards ◽  
Mike E. Fitzpatrick
Keyword(s):  
Elastic Anisotropy ◽  
Time Of Flight ◽  
Lattice Parameter ◽  
Polycrystalline Materials ◽  
Uniaxial Tensile ◽  
Transmission Spectra ◽  
X Ray Diffraction ◽  
Neutron Transmission ◽  
Pulsed Neutron

The pulsed neutron transmission diffraction technique exploits the sharp steps in intensity (Bragg edges) appearing in the transmitted spectra of thermal neutrons through polycrystalline materials. In this paper the positions of these edges acquired by the time-of-flight (TOF) technique are used to measure accurately the interplanar lattice distances to a resolution of Δd/d≃ 10−4of specimens subjected toin situuniaxial tensile loading. The sensitivity of the method is assessed for elastically isotropic (b.c.c. ferritic) and anisotropic (f.c.c. austenitic) polycrystalline specimens of negligible and moderately textured steels. For the more anisotropic austenitic steel, the elastic anisotropy is studied with regard to a Pawley refinement, and compared with previous results from conventional neutron diffraction experiments on the same material. It is shown that the method can be used to determine anisotropic strains, diffraction elastic constants, the residual and applied stress state as well as the unstrained lattice parameter by recording transmission spectra at different specimen inclinations, by complete analogy with the sin2ψ technique frequently used in X-ray diffraction. The technique is shown to deliver reliable measures of strain even in the case of moderate texture and elastic anisotropy.

Time-of-flight neutron transmission of mosaic crystals

2005 ◽  
Vol 38 (6) ◽  
pp. 934-944 ◽  
Author(s):  
Javier R. Santisteban
Keyword(s):  
Crystal Orientation ◽  
Average Rate ◽  
Time Of Flight ◽  
Incident Beam ◽  
Linear Increase ◽  
Reflection Index ◽  
Neutron Transmission ◽  
Mosaic Crystals ◽  
Definition Of

The energy-dispersive neutron transmission of mosaic crystals presents a series of dips in intensity as a result of reflection in the crystal planes. The positions of these dips can be exploited for the definition of the crystal orientation with a resolution of 1 min of arc. The widths of these dips depend on crystal orientation, on the reflection index, on the mosaicity, and on the incident-beam divergence. The capability of the technique to define the orientation and mosaicity of a Cu crystal has been assessed through time-of-flight experiments. A Cu monochromator has been plastically deformed by uniaxial tensionin situ, and the evolution of crystal orientation and mosaicity was tracked using the technique. Several crystal reflections at different locations of the sample were simultaneously studied during the experiment. A linear increase of mosaicity on deformation at an average rate of ∼5 min per percentage of shear strain was observed. The reorientation of the crystal as a result of the applied load showed variations across the specimen.

In Situ Synchrotron Measurements of Oxide Growth Strains

2005 ◽  
Vol 490-491 ◽  
pp. 287-293 ◽  
Author(s):  
Jonathan Almer ◽  
Geoffrey A. Swift ◽  
John A. Nychka ◽  
Ersan Üstündag ◽  
David R. Clarke
Keyword(s):  
Strain Relaxation ◽  
Relaxation Mechanism ◽  
High Energy ◽  
Oxide Growth ◽  
X Rays ◽  
Pure Alumina ◽  
Transmission Geometry ◽  
Residual Strains

Synchrotron x-rays are used for in situ determination of oxide strain, during oxide formation on a Kanthal A1 FeCrAlZr substrate at 1160°C. The measurements rely on use of high-energy (~80keV) x-rays and transmission geometry, and the methodology of the strain measurements is presented. Oxide growth strains at elevated temperature, relative to pure alumina, were seen to be small, while temperature excursions induced significant strains. Furthermore, significant strain relaxation was observed during isothermal holds, suggesting oxide creep as a major relaxation mechanism. Upon cooling to room temperature, significant residual strains developed, with a corresponding in-plane residual stress of -3.7 GPa.

scholarly journals Experimental determination of precision, resolution, accuracy and trueness of time-of-flight neutron diffraction strain measurements

2020 ◽  
Vol 53 (2) ◽  
pp. 494-511
Author(s):  
I. C. Noyan ◽  
J. R. Bunn ◽  
M. K. Tippett ◽  
E. A. Payzant ◽  
B. Clausen ◽  
...  
Keyword(s):  
Thermal Expansion ◽  
Lattice Strain ◽  
Coefficient Of Thermal Expansion ◽  
Time Of Flight ◽  
Temperature Changes ◽  
Strain Measurements ◽  
Simple Statistical Analysis ◽  
Quantities Of Interest

A simple statistical analysis which yields the precision, resolution, accuracy and trueness of diffraction-based lattice strain measurements is discussed. The procedure consists of measuring the thermal expansion induced in each component of an ideal non-reacting two-component crystalline powder sample in situ. One component, with a high coefficient of thermal expansion (CTE), serves as an internal thermometer. The quantities of interest are obtained by determining the smallest statistically significant thermal lattice strain which can be detected through diffraction analysis in the second, low-CTE, component in response to controlled temperature changes. This procedure also provides a robust check of the alignment of the diffraction system and is able to reveal the presence of systematic errors. The application of this technique to a time-of-flight engineering diffractometer/strain scanner is presented.

scholarly journals Synchrotron Radiation Application for Lattice Strain Measurements

2014 ◽  
Vol 2014 (6) ◽  
pp. 29-38
Author(s):  
Elżbieta Gadalińska ◽  
Andrzej Baczmański ◽  
Kamil Sołoducha
Keyword(s):  
Synchrotron Radiation ◽  
Lattice Strain ◽  
Polycrystalline Materials ◽  
Lattice Strains ◽  
Diffraction Peaks ◽  
Non Destructive ◽  
Initial Results ◽  
Elastic Lattice

Abstract The methods most commonly used for the determination of the elastic lattice deformation and distortion are diffraction methods, which enable to perform measurements of stresses and elastic properties of polycrystalline materials. The main advantages of diffraction methods are associated with their non-destructive character and the possibility to be used for macrostress and microstress analysis of multiphase and anisotropic materials. Diffraction methods enable taking measurements selectively only for a chosen alloy phase. This is very convenient when several phases are present in the sample since measurements of separate diffraction peaks allow the behaviour of each phase to be investigated independently. In this work, a method for analysis of diffraction with synchrotron radiation is described. The methodology is based on the measurements of lattice strains during “in situ” tensile testing for several hkl reflections and for different orientations of the sample with respect to the scattering vector. Some initial results are presented.

High-Resolution Strain Mapping Through Time-of-Flight Neutron Transmission Diffraction

2013 ◽  
Vol 772 ◽  
pp. 9-13 ◽  
Author(s):  
Anton S. Tremsin ◽  
Jason B. McPhate ◽  
John V. Vallerga ◽  
Oswald H.W. Siegmund ◽  
Winfried Kockelmann ◽  
...  
Keyword(s):  
High Resolution ◽  
Spatial Resolution ◽  
Time Of Flight ◽  
Compact Tension ◽  
Strain Mapping ◽  
Neutron Transmission ◽  
Neutron Counting ◽  
Transmission Measurements ◽  
Pulsed Neutron ◽  
Pulsed Neutron Source

The spatial resolution of time of flight neutron transmission diffraction was recently improved by the extension of photon/electron counting technology to imaging of thermal and cold neutrons. The development of novel neutron sensitive microchannel plates enables neutron counting with spatial resolution of ~55 um and time-of-flight accuracy of ~1 us, with efficiency as high as 70% for cold and ~40% for thermal neutrons. The combination of such a high resolution detector with a pulsed collimated neuron beam provides the opportunity to obtain a 2-dimensional map of neutron transmission spectra in one measurement. The results of our neuron transmission measurements demonstrate that maps of strains integrated along the beam propagation direction can be obtained with ~100 microstrain accuracy and spatial resolution of ~100 um providing there are sufficient neutron events collected. In this paper we describe the capabilities of the MCP neutron counting detectors and present the experimental results of 2-dimensional strain maps within austenitic steel compact tension (CT) crack samples measured at the ENGIN-X beamline of the ISIS pulsed neutron source.

scholarly journals Full-pattern analysis of time-of-flight neutron transmission of mosaic crystals

2016 ◽  
Vol 49 (2) ◽  
pp. 348-365 ◽  
Author(s):  
Florencia Malamud ◽  
Javier R. Santisteban
Keyword(s):  
Pattern Analysis ◽  
Bragg Reflection ◽  
Lattice Parameters ◽  
Neutron Transmission ◽  
Iron Nickel ◽  
Mosaic Crystals ◽  
Parameter Measuring ◽  
Natural Pyrite ◽  
Pulsed Neutron

The energy-resolved neutron transmission of mosaic crystals contains a series of dips in intensity, at specific neutron wavelengths defined by the orientation of the specimen in the neutron beam. This article presents a Rietveld type full-pattern analysis of neutron transmission experiments on mosaic crystals performed at spallation pulsed neutron sources. The proposed analysis provides precise and simple determination of lattice parameters, mosaicity, extinction factors and crystal orientation, and is especially suited to investigate the spatial variation of such microstructural information across macroscopic specimens with ∼1 mm resolution. The effect of extinction on the intensity of Bragg reflections has been successfully accounted for by a parameter measuring the ratio of the beam attenuation due to Bragg reflection to the combined attenuation due to absorption and scattering processes. Experiments were performed at the ENGIN-X beamline, ISIS Facility, UK, on several naturally occurring and man-made mosaic crystals, including a copper monochromator at temperatures between 55 and 300 K, an iron–nickel meteorite, and a natural pyrite crystal. Typical experimental resolutions found for lattice parameters and mosaicity are 0.03 and 7%, respectively. The possibilities of the technique for quantitative phase and/or texture analysis of specimens composed of several grains or phases are discussed.

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