Abstract
The elevated temperature phase transformation kinetics of U-6wt pct Nb in both wrought and cast conditions were investigated using in-situ high-energy synchrotron X-ray scattering. The evolution of the phase content, γ-phase composition, and microstructure morphology was determined through the analysis of simultaneously collected wide-angle diffraction and small-angle scattering (SAXS) data. The results of the wide-angle scattering analysis, especially the phase fractions and average composition of the γ-phase, provide model parameters to enable a quantitative analysis using the SAXS data. Greater clarity regarding the kinetics of different precipitation mechanisms, namely the continuous precipitation (CP) of α-U within the γ-phase matrix and the discontinuous (DP) grain boundary precipitation of a lamellar microstructure, consisting of α-U and Nb-rich γ-phase is obtained from the coupled measurement modes. These results indicate that the CP mechanism is responsible for the initial precipitation of α-U at all temperatures considered. Near the nose in the time–temperature-transformation (TTT) diagram at ~ 798 K, both mechanisms are active during the early stages of phase transformation. However, the DP mechanism has an increasingly long incubation period with decreasing temperature below the TTT nose. The average interlamellar spacing obtained from the SAXS analysis increases with time, providing further evidence of the so-called divergent DP behavior previously observed in U-6wt pct Nb alloys.
| Original language | English |
|---|---|
| Pages (from-to) | 707-726 |
| Number of pages | 20 |
| Journal | Metallurgical and Materials Transactions A: Physical Metallurgy and Materials Science |
| Volume | 54 |
| Issue number | 2 |
| DOIs | |
| State | Published - Feb 2023 |
| Externally published | Yes |
Funding
N.P. and S.R.A. would like to thank Dr. Chris Calhoun (University of Cincinnati) for fruitful discussions about the Eshelby analysis of the precipitate coherency strains. This work was supported by the US Department of Energy through both Los Alamos National Laboratory (LANL) and Y-12 National Security Complex. Los Alamos National Laboratory is operated by Triad National Security, LLC, for the National Nuclear Security Administration of U.S. Department of Energy (Contract No. 89233218CNA000001). The research presented in this article was supported by the Science Campaign 4 Program at LANL. Y-12 National Security Complex is operated by Consolidated Nuclear Security, LLC (CNS), for the National Nuclear Security Administration of U.S. Department of Energy (Contract DE-NA-0001942). The research presented in this article was supported under the Plant Directed Research and Development program at Y-12. This research used resources of the Advanced Photon Source, a U.S. Department of Energy (DOE) Office of Science user facility at Argonne National Laboratory and is based on research supported by the U.S. DOE Office of Science-Basic Energy Sciences, under Contract No. DE-AC02-06CH11357. This work of authorship and those incorporated herein were prepared by Consolidated Nuclear Security, LLC (CNS) as accounts of work sponsored by an agency of the United States Government under Contract DE-NA0001942. Neither the United States Government nor any agency thereof, nor CNS, nor any of their employees, makes any warranty, express or implied, or assumes any legal liability or responsibility to any non-governmental recipient hereof for the accuracy, completeness, use made, or usefulness of any information, apparatus, product, or process disclosed, or represents that its use would not infringe privately owned rights. Reference herein to any specific commercial product, process, or service by trade name, trademark, manufacturer, or otherwise does not necessarily constitute or imply its endorsement, recommendation, or favoring by the United States Government or any agency or contractor thereof. The views and opinions of authors expressed herein do not necessarily state or reflect those of the United States Government or any agency or contractor (other than the authors) thereof. N.P. and S.R.A. would like to thank Dr. Chris Calhoun (University of Cincinnati) for fruitful discussions about the Eshelby analysis of the precipitate coherency strains. This work was supported by the US Department of Energy through both Los Alamos National Laboratory (LANL) and Y-12 National Security Complex. Los Alamos National Laboratory is operated by Triad National Security, LLC, for the National Nuclear Security Administration of U.S. Department of Energy (Contract No. 89233218CNA000001). The research presented in this article was supported by the Science Campaign 4 Program at LANL. Y-12 National Security Complex is operated by Consolidated Nuclear Security, LLC (CNS), for the National Nuclear Security Administration of U.S. Department of Energy (Contract DE-NA-0001942). The research presented in this article was supported under the Plant Directed Research and Development program at Y-12. This research used resources of the Advanced Photon Source, a U.S. Department of Energy (DOE) Office of Science user facility at Argonne National Laboratory and is based on research supported by the U.S. DOE Office of Science-Basic Energy Sciences, under Contract No. DE-AC02-06CH11357. This work of authorship and those incorporated herein were prepared by Consolidated Nuclear Security, LLC (CNS) as accounts of work sponsored by an agency of the United States Government under Contract DE-NA0001942. Neither the United States Government nor any agency thereof, nor CNS, nor any of their employees, makes any warranty, express or implied, or assumes any legal liability or responsibility to any non-governmental recipient hereof for the accuracy, completeness, use made, or usefulness of any information, apparatus, product, or process disclosed, or represents that its use would not infringe privately owned rights. Reference herein to any specific commercial product, process, or service by trade name, trademark, manufacturer, or otherwise does not necessarily constitute or imply its endorsement, recommendation, or favoring by the United States Government or any agency or contractor thereof. The views and opinions of authors expressed herein do not necessarily state or reflect those of the United States Government or any agency or contractor (other than the authors) thereof. This document has been authored by Consolidated Nuclear Security, LLC, a contractor of the U.S. Government under contract DE-NA0001942, or a subcontractor thereof. Accordingly, the U.S. Government retains a paid-up, nonexclusive, irrevocable, worldwide license to publish or reproduce the published form of this contribution, prepare derivative works, distribute copies to the public, and perform publicly and display publicly, or allow others to do so, for U. S. Government purposes. On behalf of all authors, the corresponding author states that there is no conflict of interest.