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Title: Path length dependent neutron diffraction peak shifts observed during residual strain measurements in U–8 wt% Mo castings

Abstract

This study reports an angular diffraction peak shift that scales linearly with the neutron beam path length traveled through a diffracting sample. This shift was observed in the context of mapping the residual stress state of a large U–8 wt% Mo casting, as well as during complementary measurements on a smaller casting of the same material. If uncorrected, this peak shift implies a non-physical level of residual stress. A hypothesis for the origin of this shift is presented, based upon non-ideal focusing of the neutron monochromator in combination with changes to the wavelength distribution reaching the detector due to factors such as attenuation. The magnitude of the shift is observed to vary linearly with the width of the diffraction peak reaching the detector. Consideration of this shift will be important for strain measurements requiring long path lengths through samples with significant attenuation. This effect can probably be reduced by selecting smaller voxel slit widths.

Authors:
 [1]; ORCiD logo [2]; ORCiD logo [1];  [3]; ORCiD logo [2];  [1]
  1. Univ. of Virginia, Charlottesville, VA (United States). Dept. of Material Science and Engineering
  2. Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)
  3. Y-12 National Security Complex, Oak Ridge, TN (United States)
Publication Date:
Research Org.:
Oak Ridge Y-12 Plant (Y-12), Oak Ridge, TN (United States); Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States). High Flux Isotope Reactor (HFIR)
Sponsoring Org.:
USDOE Office of Science (SC), Basic Energy Sciences (BES) (SC-22); USDOE National Nuclear Security Administration (NNSA)
OSTI Identifier:
1356243
Alternate Identifier(s):
OSTI ID: 1366388
Report Number(s):
MS/GAR-170320
Journal ID: ISSN 1600-5767; JACGAR
Grant/Contract Number:
NA0001942; AC05-00OR22725
Resource Type:
Journal Article: Accepted Manuscript
Journal Name:
Journal of Applied Crystallography (Online)
Additional Journal Information:
Journal Name: Journal of Applied Crystallography (Online); Journal Volume: 50; Journal Issue: 3; Journal ID: ISSN 1600-5767
Publisher:
International Union of Crystallography
Country of Publication:
United States
Language:
English
Subject:
36 MATERIALS SCIENCE; Neutron Diffraction; Residual Stress Mapping; Strain Measurement; U-Mo; Focusing Monochromators; attenuation; Residual Stress Measurement; Focusing Monochromator

Citation Formats

Steiner, M. A., Bunn, J. R., Einhorn, J. R., Garlea, E., Payzant, E. A., and Agnew, S. R.. Path length dependent neutron diffraction peak shifts observed during residual strain measurements in U–8 wt% Mo castings. United States: N. p., 2017. Web. doi:10.1107/S1600576717005295.
Steiner, M. A., Bunn, J. R., Einhorn, J. R., Garlea, E., Payzant, E. A., & Agnew, S. R.. Path length dependent neutron diffraction peak shifts observed during residual strain measurements in U–8 wt% Mo castings. United States. doi:10.1107/S1600576717005295.
Steiner, M. A., Bunn, J. R., Einhorn, J. R., Garlea, E., Payzant, E. A., and Agnew, S. R.. Tue . "Path length dependent neutron diffraction peak shifts observed during residual strain measurements in U–8 wt% Mo castings". United States. doi:10.1107/S1600576717005295. https://www.osti.gov/servlets/purl/1356243.
@article{osti_1356243,
title = {Path length dependent neutron diffraction peak shifts observed during residual strain measurements in U–8 wt% Mo castings},
author = {Steiner, M. A. and Bunn, J. R. and Einhorn, J. R. and Garlea, E. and Payzant, E. A. and Agnew, S. R.},
abstractNote = {This study reports an angular diffraction peak shift that scales linearly with the neutron beam path length traveled through a diffracting sample. This shift was observed in the context of mapping the residual stress state of a large U–8 wt% Mo casting, as well as during complementary measurements on a smaller casting of the same material. If uncorrected, this peak shift implies a non-physical level of residual stress. A hypothesis for the origin of this shift is presented, based upon non-ideal focusing of the neutron monochromator in combination with changes to the wavelength distribution reaching the detector due to factors such as attenuation. The magnitude of the shift is observed to vary linearly with the width of the diffraction peak reaching the detector. Consideration of this shift will be important for strain measurements requiring long path lengths through samples with significant attenuation. This effect can probably be reduced by selecting smaller voxel slit widths.},
doi = {10.1107/S1600576717005295},
journal = {Journal of Applied Crystallography (Online)},
number = 3,
volume = 50,
place = {United States},
year = {Tue May 16 00:00:00 EDT 2017},
month = {Tue May 16 00:00:00 EDT 2017}
}

Journal Article:
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  • This study reports an angular diffraction peak shift that scales linearly with the neutron beam path length traveled through a diffracting sample. This shift was observed in the context of mapping the residual stress state of a large U-8 wt% Mo casting, as well as during complementary measurements on a smaller casting of the same material. If uncorrected, this peak shift implies a non-physical level of residual stress. A hypothesis for the origin of this shift is presented, based upon non-ideal focusing of the neutron monochromator in combination with changes to the wavelength distribution reaching the detector due to factorsmore » such as attenuation. The magnitude of the shift is observed to vary linearly with the width of the diffraction peak reaching the detector. Consideration of this shift will be important for strain measurements requiring long path lengths through samples with significant attenuation. This effect can probably be reduced by selecting smaller voxel slit widths.« less
  • The α-phase transformation kinetics of as-cast U - 8 wt% Mo below the eutectoid temperature have been established by in situ neutron diffraction. α-phase weight fraction data acquired through Rietveld refinement at five different isothermal hold temperatures can be modeled accurately utilizing a simple Johnson-Mehl-Avrami-Kolmogorov impingement-based theory, and the results are validated by a corresponding evolution in the γ-phase lattice parameter during transformation that follows Vegard’s law. Neutron diffraction data is used to produce a detailed Time-Temperature-Transformation diagram that improves upon inconsistencies in the current literature, exhibiting a minimum transformation start time of 40 min at temperatures between 500 °Cmore » and 510 °C. Lastly, the transformation kinetics of U – 8 wt% Mo can vary significantly from as-cast conditions after extensive heat treatments, due to homogenization of the typical dendritic microstructure which possesses non-negligible solute segregation.« less
  • Experiments have been performed recently at Sandia Laboratories to investigate and characterize potential fuel materials for fast burst reactors. A novel technique has been developed to determine the thermomechanical properties of fuel materials under actual use conditions. The Sandia Pulsed Reactor II is used to rapidly fission heat a thin rod of the sample material, supported at its center, thereby inducing longitudinal stress waves in the sample. The dilation history at the ends of the rod and the temperature of the rod are recorded. A measure of the internal friction is determined from the decay of the longitudinal oscillations inducedmore » in the sample. The materials examined include uranium, U-- 0.78 wt percent Ti, U--6 wt percent Mo, and U--10 wt percent Mo. The first two are alpha-phase materials in a wrought condition, while the second two are gamma- phase-stabilized materials in an ''as cast'' condition. The alpha-phase wrought materials had higher internal friction than the gamma-phase ''as cast'' materials, with uranium being the highest by approximately two orders of magnitude as compared to U--10 wt percent Mo, the lowest. (auth)« less