Helical dislocations: Observation of vacancy defect bias of screw dislocations in neutron irradiated Fe-9Cr
Helical dislocations: Observation of vacancy defect bias of screw dislocations in neutron irradiated Fe-9Cr
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DOI：
10.1016/j.actamat.2019.09.031
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发表时间：
2019-12-01
期刊：
影响因子：
9.4
通讯作者：
Roberts, S. G.
中科院分区：
文献类型：
--
作者：
Haley, J. C.;Liu, F.;Roberts, S. G.
我们分析了 Fe9Cr 模型合金在 325 摄氏度下以 1.6 dpa 剂量的中子辐照后的微观结构。螺旋位错是损伤的主要部分；这些是由预先存在的螺旋位错与辐照引起的缺陷的相互作用形成的。我们研究了这些螺旋如何形成的过程，以及它们如何导致位错环的局部聚集。具体来说，我们通过实验表明，空位缺陷与预先存在的螺旋位错的相互作用导致混合螺旋边缘螺旋位错的形成。填隙和空位产生的数量相等，这表明螺旋位错一定起到了空位偏向汇的作用。从理论角度分析了一般螺旋位错，并使用三维离散位错动力学（3D-DDD）开发了空位馈送螺旋位错的形成和增长模型。由于螺旋位错导致空位从局部去除微观结构，这会在位错附近留下较高的填隙过饱和度。我们认为这种过饱和是增强间隙环粗化的原因，导致螺旋位错附近可见间隙簇的比例更高。这些发现为位错如何影响辐射损伤的空间均匀性提供了新的视角。 (C) 2019 Acta Materialia Inc. 由 Elsevier Ltd 出版。
We have analysed the microstructure of a model alloy of Fe9Cr irradiated with neutrons to a dose of 1.6 dpa at 325 degrees C. Helical dislocations comprise a major part of the damage; these formed from the interaction of pre-existing screw dislocations with irradiation-induced defects. We have investigated the process behind how these helices form, and how they cause local clustering of dislocation loops. Specifically, we have shown experimentally that the interaction of vacancy defects with pre-existing screw dislocations causes the formation of mixed screw-edge helical dislocations. Interstitials and vacancies were generated in equal numbers, which shows that the screw dislocations must have acted as vacancy-biased sinks.Helical dislocations in general were analysed from a theoretical perspective, and three Dimensional Discrete Dislocation Dynamics (3D-DDD) was used to develop a model for the formation and growth of a vacancy-fed helical dislocation.Since the helical dislocations cause the removal of vacancies from the local microstructure, this leaves a higher supersaturation of interstitials close to the dislocations. We argue that this supersaturation is responsible for enhanced interstitial loop coarsening, leading to a higher proportion of visible interstitial clusters in the vicinity of helical dislocations. These findings offer a new perspective on how dislocations affect the spatial homogeneity of radiation damage. (C) 2019 Acta Materialia Inc. Published by Elsevier Ltd.