Abstract
First-Passage Kinetic Monte Carlo (FPKMC) simulations of species migration in duplex stainless steels were performed in order to establish relationships between alloy content, segregation behavior, and the formation of Ni–Si–Mn rich particles in cast duplex stainless steels during thermal aging. The Ni–Si–Mn-rich second phase forms after extended aging at reactor operating temperatures and degrades alloy properties. Simulations of Ni–Si–Mn cluster formation were validated through comparison with experimental results obtained through Atom Probe Tomography (APT) on similar alloy compositions, identifying several trends. First, Cu promotes the formation of Ni–Si–Mn clusters, but only when Ni or Mn prefer segregation to the surface of Cu particles; without the segregation of these species, the critical composition for the clusters to form was not achieved. Second, the width of precipitate-denuded zones near γ/δ interfaces increases with decreasing Cu content. This finding was in strong agreement with APT and Scanning Transmission Electron Microscopy results, further validating our model. Finally, our model predicts that Ni–Si–Mn cluster formation will be the most extensive when the Si:Mn ratio is approximately 1:1 and the least extensive when one of these key elements is less concentrated (Mn ≤ 0.5 at.% or Si ≤ 0.5 at.%). The implications of these results on how to improve alloy properties are discussed.
| Original language | English |
|---|---|
| Pages (from-to) | 1-12 |
| Number of pages | 12 |
| Journal | Acta Materialia |
| Volume | 194 |
| DOIs | |
| State | Published - Aug 1 2020 |
Funding
This research was sponsored by U.S. Department of Energy /Office of Nuclear Energy through Light Water Reactor Sustainability Program. Pacific Northwest National Laboratory is operated by Battelle Memorial Institute for the U.S. Department of Energy under Contract no. DEAC05-76RL01830 . APT was performed at PNNL's Environmental Molecular Sciences Laboratory, a Department of Energy - Office of Biological & Environmental Research national scientific user facility. FIB/SEM was performed at PNNL's Radiological Microscopy Suite at the Radiochemical Processing Laboratory and PNNL's Institutional Microscopy Program. This research was also partly sponsored by the Laboratory Directed Research and Development Program of Oak Ridge National Laboratory, managed by UT-Battelle, LLC, for the U. S. Department of Energy under contract number DE-AC05-00OR22725. The authors also thank Dr. Shenyang Hu at Pacific Northwest National Laboratory, for numerous fruitful discussions regarding the computational modeling of Ni-Si-Mn cluster precipitation. This research was sponsored by U.S. Department of Energy/Office of Nuclear Energy through Light Water Reactor Sustainability Program. Pacific Northwest National Laboratory is operated by Battelle Memorial Institute for the U.S. Department of Energy under Contract no. DEAC05-76RL01830. APT was performed at PNNL's Environmental Molecular Sciences Laboratory, a Department of Energy - Office of Biological & Environmental Research national scientific user facility. FIB/SEM was performed at PNNL's Radiological Microscopy Suite at the Radiochemical Processing Laboratory and PNNL's Institutional Microscopy Program. This research was also partly sponsored by the Laboratory Directed Research and Development Program of Oak Ridge National Laboratory, managed by UT-Battelle, LLC, for the U. S. Department of Energy under contract number DE-AC05-00OR22725. The authors also thank Dr. Shenyang Hu at Pacific Northwest National Laboratory, for numerous fruitful discussions regarding the computational modeling of Ni-Si-Mn cluster precipitation.
| Funders | Funder number |
|---|---|
| U.S. Department of Energy | DE-AC05-00OR22725, DEAC05-76RL01830 |
| Battelle | |
| Office of Nuclear Energy | |
| Oak Ridge National Laboratory | |
| Pacific Northwest National Laboratory |