Chromium enrichment on the habit plane of dislocation loops in ion-irradiated high-purity Fe–Cr alloys

• Published in: Acta materialia Vol. 78; pp. 394 - 403
• Main Authors: Bhattacharya, A., Meslin, E., Henry, J., Pareige, C., Décamps, B., Genevois, C., Brimbal, D., Barbu, A.
• Format: Journal Article
• Language: English
• Published: Kidlington Elsevier Ltd 01-10-2014; Elsevier
• Subjects: Applied sciences; Atom-probe tomography; Condensed Matter; Exact sciences and technology; Fe–Cr alloys; Ion irradiation; Materials Science; Metals. Metallurgy; Physics; Probe-corrected STEM–EDS; TEM; Probe-corrected STEM–EDS; Fe–Cr alloys; Ion irradiation; TEM; Atom-probe tomography; Probe-corrected STEM-EDS; Transmission electron microscopy; Chromium alloy; Dislocation loop; Fe-Cr alloys; Atom probe; Dislocation; High purity
• ISSN: 1359-6454; 1873-2453
• DOI: 10.1016/j.actamat.2014.06.050

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Reduced activation high-chromium ferritic/martensitic steels are candidate materials for Generation IV fission and fusion reactors. To gain knowledge about the radiation resistance of these steels in such environments, the first step is to study the Fe–Cr matrix of this material. For that purpose and to understand ballistic damage by neutrons, self-ion irradiations, with and without simultaneous He injection, were performed on a series of high-purity Fe–Cr binary alloys at 773K. Transmission electron microscopy (TEM) analysis revealed “displacement fringe contrast” inside the dislocation loops. This was attributed to the presence of Cr-enriched zones on their habit plane, which is a defect-free region for body-centered cubic Fe-based alloys. A plausible mechanism is discussed to explain the phenomenon, the first step of which would be the radiation-induced segregation of Cr atoms on the dislocation loop core. Energy-dispersive X-ray spectroscopy in scanning TEM mode and atom probe tomography (APT) gave a coherent quantitative estimate of the Cr concentration in these enriched areas. APT study showed that the enrichment was heterogeneous on the loop plane. Upon in situ annealing up to 900K, the loops and the fringes disappeared completely, without leaving a secondary-phase particle, such as carbide, at their position. Fringes were present until the loop disappeared.