FeCr合金中Cr含量对微观结构影响的原子尺度模拟研究

低温辐照脆化是影响铁素体/马氏体（F/M）钢服役的主要问题之一。F/M钢低温辐照脆化的主要机理是辐照产生的纳米缺陷（如位错环、α′相(富Cr团簇)等）阻碍位错运动。本文利用分子动力学方法和迈氏蒙特卡罗方法对F/M钢模型材料--FeCr合金（Fe7%Cr、Fe9%Cr、Fe14%Cr）中Cr元素析出成团簇及在位错环上偏析的机理进行研究，并分析Cr团簇析出与合金成分的关系以及位错环尺寸、位错环类型和合金中Cr含量对位错环上Cr偏析量的影响。模拟结果表明：热力学模拟后，高Cr含量（>9%)的FeCr合金中会析出Cr团簇，且基体内Cr含量越高，析出的Cr团簇尺寸越大；在所研究的3种FeCr合金中，受位错环张应力场作用，合金元素Cr均会在位错环的外围偏析，且FeCr合金中Cr含量越高，Cr在位错环上偏析量越高。低Cr的FeCr合金中Cr对其辐照硬化的影响需考虑位错环上Cr偏析的影响，高Cr的FeCr合金中Cr元素对其辐照硬化的影响需综合考虑Cr团簇及位错环上Cr偏析。

Atomic Scale Simulation Research for Effect of Cr Content on Microstructure in FeCr Alloy

Lower temperature irradiation embrittlement is one primary issue limiting the use of ferritic/martensitic steels. The primary mechanism of lower temperature irradiation embrittlement is the obstruction of dislocation motion by nano-metric defects, such as dislocation loop and α′ precipitate (Cr clusters), induced by irradiation. Using molecular dynamics and Metropolis Monte Carlo (MMC), the mechanism of Cr precipitate and segregation on dislocation loop in FeCr alloys (the models of F/M steels) was studied. On this basis, the dependence of Cr clusters on Cr contents, and the impacts of loop size, loop type and Cr contents in FeCr alloys on the Cr enrichment on loop were explored. The results show that after simulation, Cr clusters were formed in FeCr alloys with higher Cr contents (>9%) and the size of Cr clusters increases with Cr contents in FeCr alloy. For all the studied FeCr alloys here, under the interaction of tensile stress fields, Cr elements can segregate on the outside of dislocation loop after thermodynamics simulation, and enrichment level of Cr on loop increases with the Cr contents in FeCr alloys. For lower Cr contents, the effect of Cr on hardening only needs to consider the Cr segregation on loops, while for higher Cr contents, the influence of Cr contents on the irradiation hardening needs the synthetical study of Cr clusters and Cr segregation on loops.