Department of Chemistry, University of Ottawa, Ottawa, Canada.
J Phys Condens Matter. 2010 Sep 1;22(34):345006. doi: 10.1088/0953-8984/22/34/345006. Epub 2010 Aug 10.
Molecular dynamics simulations were used to model grain boundary sliding in stressed Fe-Ni bicrystals exposed to low energy neutron irradiation. We studied how sliding stress thresholds and sliding mechanisms changed with variations in the Ni boundary morphology and boundary geometry. Simulations corresponding to ordered boundary Ni distributions and coincident-site lattice (CSL) geometries relaxed stress through a dislocation-mediated sliding mechanism. Such a mechanism was found to follow Orowan's law, in which the stress relaxation rate is proportional to the dislocation velocity. Alternatively, simulations of disordered Ni distributions and non-CSL boundary geometries were described by a random shuffling process with time-dependent stress relaxation rate. Nevertheless, irrespective of the stress relaxation process followed by the bicrystals, after reaching equilibrium, the amounts of boundary displacement and stress relaxation were always found to be proportionally related. These observations might prove useful to groups working on building continuum (macroscopic) models of deformations in irradiated materials.
采用分子动力学模拟方法研究了受低能中子辐照的 Fe-Ni 双晶体中晶界滑移。我们研究了晶界形貌和边界几何形状变化对滑移应力阈值和滑移机制的影响。对应有序边界 Ni 分布和共格位错（CSL）结构的模拟通过位错介导的滑移机制来松弛应力。这种机制遵循 Orowan 定律，其中应力松弛速率与位错速度成正比。相反，无序 Ni 分布和非 CSL 边界几何结构的模拟由具有时变应力松弛速率的随机混合过程来描述。然而，无论双晶体遵循哪种应力松弛过程，达到平衡后，边界位移和应力松弛的量总是呈比例关系。这些观察结果可能对致力于构建辐照材料变形的连续（宏观）模型的研究小组有用。
