Abstract
Twelve commercial-grade austenitic alloys based on the Ni-Cr-Mo-Fe quaternary system were irradiated using 2 MeV protons at 360 °C to a damage level of 2.5 displacements per atom (dpa). Long-range ordered (Pt2Mo-type) precipitation under proton irradiation was observed, for the first time, in alloys C22, 625, 625P, 625D, 725, and 690. No relevant short-range ordering was observed. These irradiation-enhanced long-range ordered precipitates are coherent with the matrix despite their irregular shape. Of the potential influences on long-range ordering (Ni:Cr, and Ni:(Cr + Mo) ratios, Mo, and iron concentration), Fe content was the strongest by far. The volume fraction of LRO decreases with increasing Fe content by virtue of its role as a stabilizer of the disordered FCC phase, thus reducing the energy savings from ordering. The observed effects of Fe on long-range ordering show qualitative agreement with predictions from thermodynamic modeling. Although solid state diffusion kinetics dominate long-range ordering under purely thermal conditions, ordering under irradiation here (∼ 2.5dpa) is controlled by the thermodynamic driving force. Proton irradiation thus offers a unique approach for studying the low temperature phase transformation in a thermodynamically favored, but kinetically constrained condition.
| Original language | English |
|---|---|
| Pages (from-to) | 446-462 |
| Number of pages | 17 |
| Journal | Acta Materialia |
| Volume | 156 |
| DOIs | |
| State | Published - Sep 1 2018 |
Funding
The authors acknowledge the financial support by EPRI (contracts 10002164 and 10002154 ), and DOE (contract 4000136101 ), and by the U.S. Department of Energy (DOE), Office of Nuclear Energy, Light Water Reactor Sustainability (LWRS) Research and Development Effort, under contract DE-AC05-00OR22725 with UT-Battelle, LLC. The authors also gratefully acknowledge O. Toader, T. Kubley and E. Uberseder at the Michigan Ion Beam Laboratory and D. Woodley at University of Michigan for their assistance with the proton irradiations. M.S acknowledges Dr. A. Hunter at University of Michigan and Dr. J. Wang at Pacific Northwest National Laboratoy for their help with APT experiments and data analysis. M.S also acknowledges Dr. K. Sun for help with the TEM, and Dr. Z. Jiao for stimulating discussion at University of Michigan. Access to the microscopes of the Michigan Center for Materials Characterization (MC 2 ) at University of Michigan is also acknowledged. The authors acknowledge the financial support by EPRI (contracts 10002164 and 10002154), and DOE (contract 4000136101), and by the U.S. Department of Energy (DOE), Office of Nuclear Energy, Light Water Reactor Sustainability (LWRS) Research and Development Effort, under contract DE-AC05-00OR22725 with UT-Battelle, LLC. The authors also gratefully acknowledge O. Toader, T. Kubley and E. Uberseder at the Michigan Ion Beam Laboratory and D. Woodley at University of Michigan for their assistance with the proton irradiations. M.S acknowledges Dr. A. Hunter at University of Michigan and Dr. J. Wang at Pacific Northwest National Laboratoy for their help with APT experiments and data analysis. M.S also acknowledges Dr. K. Sun for help with the TEM, and Dr. Z. Jiao for stimulating discussion at University of Michigan. Access to the microscopes of the Michigan Center for Materials Characterization (MC2) at University of Michigan is also acknowledged.
Keywords
- Irradiation effect
- Long-range ordering (LRO)
- NiCr
- Nickel-base alloy
- Precipitation
- Proton irradiation