A novel displacement cascade driven irradiation creep mechanism in α-zirconium: A molecular dynamics study

JOURNAL OF NUCLEAR MATERIALS

卷:541

Article

Khiara, Nargisse^1,5  Onimus, Fabien¹  Dupuy, Laurent¹  Kassem, Wassim¹  Crocombette, Jean-Paul²  Pardoen, Thomas³  Raskin, Jean-Pierre⁴  Brechet, Yves⁵ 

[1] Univ Paris Saclay, CEA, Serv Rech Met Appl, F-91191 Gif Sur Yvette, France

[2] Univ Paris Saclay, CEA, Serv Rech Met Phys, F-91191 Gif Sur Yvette, France

[3] Catholic Univ Louvain, Inst Mech Mat & Civil Engn, Pl St Barbe 2 L5-02-02, B-1348 Louvain La Neuve, Belgium

[4] Catholic Univ Louvain, Inst Informat & Commun Technol Elect & Appl Math, Pl Levant 2 L5-04-04, B-1348 Louvain La Neuve, Belgium

[5] Univ Grenoble Alpes, Sci & Ingn Mat & Proc SIMAP, 1130 Rue Piscine BP 75, F-38402 St Martin Dheres, France

关键词: Irradiation;    Creep;    Zirconium;    Molecular dynamics;   

DOI  :  10.1016/j.jnucmat.2020.152336

来源: Elsevier

【 摘 要 】

Zirconium alloys used in nuclear reactors undergo irradiation creep, which consists of a visco-plastic deformation activated by irradiation occurring under constant load. However, the fundamental underlying mechanisms have not been unraveled yet. A new high-stress irradiation creep mechanism for recrystallized Zircaloy-4 has recently been proposed based on in situ ion irradiation deformation experiments. A displacement cascade is assumed to induce a direct unpinning of a dislocation from an irradiation defect if the cascade occurs within an effective volume around the pinning point. In the present work, a systematic molecular dynamics study was performed to investigate the effect of a 20 keV cascade occurring near < a >-screw dislocation pinned on an interstitial < a >-loop. The direct release of dislocations by displacement cascades is predicted by the simulations. This release is more likely around the pinning points and with increasing stress, in agreement with experimental observations. The effective volume is roughly estimated for three stress levels equal to 0.897 tau(c), 0.93 tau(c), and 0.977 tau(c) with tau(c) being the critical stress for unpinning (without irradiation). A mechanism is proposed suggesting that unpinning occurs when the displacement cascade encompasses, at its peak of damage, the two pinning points of the dislocation. A methodology requiring acceptable computation time has been implemented to estimate the effective volume for various cascade energies and loop characteristics, faithfully reproducing the MD results. The mean pinning lifetime calculated using the model provides values of the same order of magnitudes as in the in situ deformation experiments under ion irradiation at high stress levels. (C) 2020 Elsevier B.V. All rights reserved.

【 授权许可】

Free