Previous experimental studies of H permeation in 9%Cr-Fe alloys have found a permeation coefficient 10 times lower and a diffusion coefficient 200 times lower than in pure annealed Fe. In an effort to shed some light on the microscopic origin of these findings, we perform an extensive study of Fe, Cr, and H migration in a high-angle symmetric tilt grain boundary in bcc Fe, both via vacancy and interstitial mechanism. This is undertaken in the framework of transition state theory with the relevant energies obtained from classical interatomic potentials, and partially from Density Functional Theory calculations, in order to check the consistency of structures. Trapping sites for H and possible migration paths are explored. We find that the presence of Cr and its migration via vacancy and interstitials creates the conditions in produce stable preferential trapping sites for H in the grain boundary, that delay the H migration, thereby explaining the experimental results.

以前在9％Cr-Fe合金中进行H渗透的实验研究发现，其渗透系数比纯退火Fe低10倍，扩散系数低200倍。为了阐明这些发现的微观起源，我们通过空位和间隙机制对密闭密炼铁中高角度对称倾斜晶界中的Fe，Cr和H迁移进行了广泛的研究。这是在过渡态理论的框架内进行的，其中从经典的原子间势以及部分地从密度泛函理论计算中获得了相关能量，以检查结构的一致性。探索了H的陷阱站点和可能的迁移路径。