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Title: α-Phase transformation kinetics of U – 8 wt% Mo established by in situ neutron diffraction

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 °C 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.
Authors:
 [1] ;  [2] ;  [2] ;  [2] ;  [3] ;  [2]
  1. Y-12 National Security Complex, Oak Ridge, TN (United States)
  2. Univ. of Virginia, Charlottesville, VA (United States)
  3. Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)
Publication Date:
OSTI Identifier:
1253990
Report Number(s):
MS/GAR--160503
Journal ID: ISSN 0022-3115
Grant/Contract Number:
NA0001942
Type:
Accepted Manuscript
Journal Name:
Journal of Nuclear Materials
Additional Journal Information:
Journal Volume: 477; Journal Issue: C; Journal ID: ISSN 0022-3115
Publisher:
Elsevier
Research Org:
Oak Ridge Y-12 Plant (Y-12), Oak Ridge, TN (United States)
Sponsoring Org:
USDOE Office of Defense Programs (DP)
Country of Publication:
United States
Language:
English
Subject:
36 MATERIALS SCIENCE U-Mo alloys; neutron diffraction; time-temperature-transformation diagram; transformation kinetics; eutectoid decomposition