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Article Dans Une Revue J.Nucl.Mater. Année : 2021

Helium causing disappearance of a/2<111> dislocation loops in binary Fe-Cr ferritic alloys

Résumé

Single and dual-beam self-ion irradiations were performed at 500°C on ultra-high purity Fe14%Cr alloy to ∼0.33 displacements-per-atom (dpa), and 0 or 3030 atomic-parts-per-million (appm) helium/dpa, respectively. Using transmission electron microscopy, we reveal that helium can drastically modify the dislocation loop Burgers vector in Fe-Cr alloys. Helium co-implantation caused complete disappearance of a/2<111> type dislocation loops, and the microstructure consisted of only a<100> loops. Conversely, a/2<111> type loops were predominant without He co-implantation. The total loop density remained largely unaffected. The results strikingly contrast literature asserting that helium stabilizes a/2<111> type loops in bcc Fe alloys, based on low temperature irradiations. Collectively analyzing the results with literature suggest that the small positive interaction between helium and self-interstitial atoms (SIA) in Fe predicted by atomistic simulations maybe insufficient to holistically explain the dislocation loop microstructure development in presence of helium. Helium-SIA positive binding inadvertently implies elevated a/2<111> loop fraction and higher loop densities that the present results contradict. Helium induced high cavity density causing a preferential loss of highly glissile <111> clusters, leaving the matrix saturated with <100> type clusters is proposed as a potential mechanism. Further, the in-situ irradiations combined with Burgers vector analysis strengthened the evidence of Cr-induced dislocation loop mobility reduction that appears to stabilize the a/2<111> type loops and causes higher loop densities in Fe-Cr alloys.

Dates et versions

hal-04010901 , version 1 (02-03-2023)

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Citer

Arunodaya Bhattacharya, Jean Henry, Brigitte Décamps, Steven J. Zinkle, Estelle Meslin. Helium causing disappearance of a/2<111> dislocation loops in binary Fe-Cr ferritic alloys. J.Nucl.Mater., 2021, 556, pp.153213. ⟨10.1016/j.jnucmat.2021.153213⟩. ⟨hal-04010901⟩
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