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Title: Analysis of structure and deformation behavior of AISI 316L tensile specimens from the second operational target module at the Spallation Neutron Source

In an earlier publication, tensile testing was performed on specimens removed from the first two operational targets of the Spallation Neutron Source (SNS). There were several anomalous features in the results. First, some specimens had very large elongations (up to 57%) while others had significantly smaller values. Second, there was a larger than the usual amount of data scatter in the elongation results. Third, the stress-strain diagrams of nominally similar specimens spanned a wide range of behavior ranging from expected irradiation-induced hardening to varying levels of force drop after yield point and indirect signs of "traveling deformation wave" behavior associated with strain-induced martensite formation. To investigate the cause(s) of such variable tensile behavior, several specimens from Target 2, spanning the range of observed tensile behavior, were chosen for detailed microstructural examination using electron backscattering analysis (EBSD). It was also shown that the steel employed in the construction of the target contained an unexpected bimodal grain size distribution, containing very large out-of-specification grains surrounded by necklaces of grains of within-specification sizes. The large grains were frequently comparable to the width of the gauge section of the tensile specimen. Moreover, the propensity to form martensite during deformation was shown to be acceleratedmore » by radiation but also to be very sensitive to the relative orientation of the grains with respect to the tensile axis. Specimens having large grains in the gauge that were most favorably oriented for production of martensite strongly exhibited the traveling deformation wave phenomenon, while those specimens with less favorably oriented grains had lesser or no degree of the wave effect, thereby accounting for the larger than expected data scatter.« less
 [1] ;  [1] ;  [2]
  1. Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)
  2. Radiation Effects Consulting, Richland, WA (United States)
Publication Date:
OSTI Identifier:
Grant/Contract Number:
Accepted Manuscript
Journal Name:
Journal of Nuclear Materials
Additional Journal Information:
Journal Volume: 468; Journal ID: ISSN 0022-3115
Research Org:
Oak Ridge National Laboratory (ORNL), Oak Ridge, TN (United States). Center for Nanophase Materials Sciences (CNMS); Spallation Neutron Source
Sponsoring Org:
USDOE Office of Science (SC)
Country of Publication:
United States
36 MATERIALS SCIENCE Spallation Neutron Source; Spallation Target; Tensile Properties; 316L; Deformation Wave; Transformation-induced Plasticity