Zhou Xiao, Mousseau Normand, Song Jun
Department of Materials Engineering, McGill University, Montréal, Quebec H3A0C5, Canada.
Département de physique and Regroupement québécois sur les matériaux de pointe, Université de Montréal, C.P. 6128, Succursale Centre-Ville, Montréal, Québec H3C 3J7, Canada.
Phys Rev Lett. 2019 May 31;122(21):215501. doi: 10.1103/PhysRevLett.122.215501.
We perform comprehensive first-principles calculations and kinetic Monte Carlo simulations to explicitly elucidate the distinct roles of grain boundaries (GBs) in affecting hydrogen (H) diffusion in fcc nickel (Ni). We demonstrate the transition between slow and fast H diffusion along the GB with an abrupt change in H diffusivity. Low-angle GBs are shown to comprise isolated high-barrier regions to trap and inhibit H diffusion, with H diffusivity well prescribed by the classical trapping model, while high-angle GBs are shown to provide interconnected low-barrier channels to facilitate H transport. On the basis of the dislocation description of the GB and the Frank-Bilby model, the slow-fast diffusion transition is identified to result from dislocation core overlapping and is accurately predicted. The present Letter provides key mechanistic insights towards interpreting various experimental studies of H diffusion in metals, new critical knowledge for predictive modeling of H embrittlement, and better understanding of the kinetics of H and other interstitial impurities in microstructures.
我们进行了全面的第一性原理计算和动力学蒙特卡罗模拟，以明确阐明晶界（GBs）在影响面心立方镍（Ni）中氢（H）扩散方面的不同作用。我们展示了沿晶界H扩散由慢到快的转变，其扩散率发生了突变。低角度晶界被证明包含孤立的高势垒区域以捕获和抑制H扩散，H扩散率可由经典捕获模型很好地规定，而高角度晶界则被证明提供相互连接的低势垒通道以促进H传输。基于晶界的位错描述和弗兰克 - 比尔比模型，确定慢 - 快扩散转变是由位错核心重叠导致的，并得到了准确预测。本信函为解释金属中H扩散的各种实验研究提供了关键的机理见解，为H脆化的预测建模提供了新的关键知识，并有助于更好地理解微观结构中H和其他间隙杂质的动力学。
