Solute precipitation on a screw dislocation and its effects on dislocation mobility in bcc Fe
Solute precipitation on a screw dislocation and its effects on dislocation mobility in bcc Fe
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DOI：
10.1016/j.jnucmat.2019.04.007
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发表时间：
2019-06
影响因子：
3.1
通讯作者：
M. I. Pascuet;G. Monnet;G. Bonny;E. Martínez;J.J.H. Lim;Michelle Rovang Burke;L. Malerba
中科院分区：
文献类型：
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作者：
M. I. Pascuet;G. Monnet;G. Bonny;E. Martínez;J.J.H. Lim;Michelle Rovang Burke;L. Malerba
众所周知，反应堆压力容器钢在中子辐照下会硬化和脆化。贝氏体钢辐射脆化的主要机制是位错运动受阻，主要是由于Cu、Ni、Mn、Si和P等溶质原子的团簇或析出。显微组织分析表明，这些团簇或析出物往往优先形成在位错线上，有时完全被偏析的溶质团簇包围。这项工作也提供了这方面的证据，它扩展了先前致力于刃位错的工作，通过研究螺位错周围的这种偏析(BurgersVectOrb= 1/2[111])对位错运动的临界应力的影响。采用方差约束半巨正则系综中的蒙特卡罗算法，通过最小化自由能来研究位错周围原子的修饰。其次，用标准分子动力学方法计算了位错脱离团簇的临界应力，分析了铜、镍、锰和磷在铁基中偏聚的影响。与预期一致，并与以前的工作一致，我们的结果强调，由于分离溶质的存在，触发位错运动所需的应力急剧增加。我们的发现是，溶质装饰的螺位错可以被认为实际上是不移动的，因为它们周围有强烈的偏析。
Reactor pressure vessel steels are well-known to harden and embrittle under neutron irradiation. The primary mechanism of radiation embrittlement for these bainitic steels is the obstruction of dislocation motion, mainly due to clusters or precipitates of solute atoms such as Cu, Ni, Mn, Si and P. Microstructural examinations reveal that these clusters or precipitates are often preferentially formed at dislocation lines, which are sometimes completely surrounded by segregated solute clusters. Evidence of this is provided in this work, too, which extends a previous one dedicated to edge dislocations, by studying the effect of this segregation around screw dislocations (Burgers vectorb= 1/2 [111]) on the critical stress for dislocation motion. A Monte Carlo algorithm in a variance-constrained semi-grand canonical (VC-SGC) ensemble is applied to study the decoration of atoms around dislocations, by minimizing the free energy. Next, the critical stress for dislocation unpinning from the clusters is evaluated by standard molecular dynamics to analyze the effect of Cu, Ni, Mn, and P segregation in the Fe matrix. Consistently with expectations and in agreement with previous work, our results highlight that the required stress for triggering dislocation motion drastically increases due to the presence of segregated solutes. Our finding is that solute-decorated screw dislocations may be considered as practically immobile because of the strong segregation around them.