Methods: The researchers, led by CNL materials engineer Qiang Wang, subjected the CrFeMnNi alloy to irradiation with high-energy protons, at 2 MeV (mega electron volts), under three different conditions: 2.8 dpa (displacements per atom) at 400°C, 2.8 dpa at 600°C, and 16.8 dpa at 400°C. The irradiation-induced microstructural changes were then characterized using scanning transmission electron microscopy combined with energy dispersive X-ray spectrometry and electron energy loss spectroscopy. The synchrotron X-rays of the Canadian Light Source, at the University of Saskatchewan, were used in the microstructure analysis.
Results: Wang and his colleagues gained various insights into how well the HEA stood up under the extreme conditions. They observed that small plate-shaped defects known as Frank loops were more common in the irradiated alloy’s microstructure when it was exposed to the lower temperature, but the loops were larger at the higher temperature. In addition, the metallic components of the alloy started to separate during the irradiation, especially at the higher temperature. Certain parts of the metal lost more manganese, while other parts gained more nickel and iron.
Potential reactor application: Although the microstructure of the irradiated CrFeMnNi alloy showed defects, the defects were fewer than those that develop in stainless steel that is exposed to similar conditions. Thus, the new alloy might function better as a nuclear reactor component than the stainless steel that is currently used in reactors. However, additional research will be needed to further investigate this potential.
Wang commented on the findings by noting, “We did find some advantages [to the CrFeMnNi alloy] and some things we didn’t expect to happen, so obviously this material needs to be better studied to fully understand the applications.” He noted that HEA is “still not code-approved in the nuclear industry, so we don’t know exactly what it will be used for, which is why we are testing the material to see if it can meet those qualifications.”
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