Abstract
The attractive mechanical properties and superior resistance to void-swelling make ferritic/martensitic alloys a promising structural material for advanced nuclear reactors. However, one anomaly that has intrigued researchers for more than 50 years is the proportion of two types of dislocation loops in Fe and Fe-Cr alloys with Burger vectors b=½<111> and b=<100>. Although the possible mechanisms responsible for the presence of 〈100〉 loops continue to be the subject of intense modeling studies, there remains incomplete experimental understanding of fundamental irradiation processes in Fe(Cr) alloys. Here, the dose dependence of the irradiation-induced microstructural evolution was examined from 0 to 20 displacement per atom (dpa) in high purity Fe and Fe-10Cr during simultaneous dual-beam (1 MeV Kr + 10 appm He/dpa) irradiation at 435 °C. We experimentally revealed that the mechanism for the formation of 〈100〉 loops may not follow the conventional simple dislocation reaction between two ½<111> loops. Real-time dynamic formation and evolution of defects including black dot loops, loop coarsening, loop decoration, network dislocations, and cavities were demonstrated. Several results indicated that the addition of Cr and He could impede dislocation loop motion. The evolution of the defect size/density and relative fraction of ½<111> vs 〈100〉 loops were quantitatively summarized. With increasing dose, ½<111> loops became the dominant type of loop in both materials. Notably, 〈100〉 loops were predominantly observed near grain boundaries only for pure Fe, while arrays of nanoscale black dot defects composing the 〈100〉 loop strings were observed in plenty in Fe-10Cr.
| Original language | English |
|---|---|
| Article number | 116793 |
| Journal | Acta Materialia |
| Volume | 209 |
| DOIs | |
| State | Published - May 1 2021 |
| Externally published | Yes |
Funding
This research was sponsored by the Office of Fusion Energy Science s, U.S. Department of Energy under grant # DE- SC0006661 with the University of Tennessee ( YRL and SJZ ). The in-situ IVEM ion irradiations and simultaneous TEM observations were supported by the U.S. Department of Energy , Office of Nuclear Energy under DOE Idaho Operations Office Contract DE-AC07-051D14517 as part of a Nuclear Science User Facilities experiment. The fabrication of the Fe-Cr binary alloys has been carried out within the framework of the EUROfusion Consortium and has received funding from the Euratom research and training program 2019–2020 under Grant Agreement No. 633053 . We would like to acknowledge funding from the State of Tennessee and Tennessee Higher Education Commission (THEC) through their support of the Center for Materials Processing. The authors are thankful for the IVEM tandem facility support from Argonne National Laboratory. We acknowledge Peter Baldo for his help on the ion irradiation. We thank Drs. Roger Stoller, Brian Wirth, William Weber, Arunodaya Bhattacharya, and Haixuan Xu for their insightful comments and suggestions. This research was sponsored by the Office of Fusion Energy Sciences, U.S. Department of Energy under grant # DE-SC0006661 with the University of Tennessee (YRL and SJZ). The in-situ IVEM ion irradiations and simultaneous TEM observations were supported by the U.S. Department of Energy, Office of Nuclear Energy under DOE Idaho Operations Office Contract DE-AC07-051D14517 as part of a Nuclear Science User Facilities experiment. The fabrication of the Fe-Cr binary alloys has been carried out within the framework of the EUROfusion Consortium and has received funding from the Euratom research and training program 2019–2020 under Grant Agreement No. 633053. We would like to acknowledge funding from the State of Tennessee and Tennessee Higher Education Commission (THEC) through their support of the Center for Materials Processing.
Keywords
- Dislocation loops
- Helium
- Iron-chromium alloys
- Radiation effects
- in-situ TEM