Vacancy effects on one-dimensional migration of interstitial clusters in iron under electron irradiation at low temperatures

Abstract

We performed in situ observation of one-dimensional (1D) migration of self-interstitial atom (SIA) clusters in iron under electron irradiation at 110-300 K using high-voltage electron microscopy. Most 1D migration was stepwise positional changes of SIA clusters at irregular time intervals at all temperatures. The frequency of 1D migration did not depend on the irradiation temperature. It was directly proportional to the damage rate, suggesting that 1D migration was induced by electron irradiation. In contrast, the 1D migration distance depended on the temperature: distribution of the distance ranged over 100 nm above 250 K, decreased steeply between 250 and 150 K and was less than 20 nm below 150 K. The distance was independent of the damage rate at all temperatures. Next, we examined fluctuation in the interaction energy between an SIA cluster and vacancies of random distribution at concentrations 10 −4 -10 −2 , using molecular statics simulations. The fluctuation was found to trap SIA clusters of 4 nm diameter at vacancy concentrations higher than 10 −3 . We proposed that 1D migration was interrupted by impurity atoms at temperatures higher than 250 K, and by vacancies accumulated at high concentration under electron irradiation at low temperatures where vacancies are not thermally mobile.

<i>In-situ</i> study of one-dimensional motion of interstitial-type dislocation loops in hydrogen-ion-implanted aluminum

“…另一方面, 间隙型位错环的一维迁移 研究大部分是基于加速电压为1000 kV或者更高 的超高压电镜而开展的 [16,24−27] . Hamaoka等 [24] 通 过超高压电镜发现硅和铜作为铁中的合金元素 可以降低位错环一维迁移的频率和距离; Hayashi 等 [25] 发现相比于纯金属, 杂质对合金材料中的间 隙原子团簇的一维迁移的影响要小的多; Satoh等 [26] 发现一维迁移的距离与温度有很大关系, 在温度高 的击出阈值仅为16 eV [28] . 因而, 利用普通电镜可 以观察到注氢纯铝中间隙型位错环的一维迁移现 象, 进而研究有关位错环一维迁移的相关问题.…”

Comparison of Influence of the Fast Atom Beam and Ion Beam on the Metal Target

“…erefore, in recent years, simulation methods for the formation of radiation defects have been actively developed. Simulation irradiation of structural materials is carried out using electron beams [16] or ion beams [14,17].…”