镁晶界的氢致脆化：第一性原理研究。

Hydrogen embrittlement in a magnesium grain boundary: a first-principles study.

机构信息

Department of Energy Science and Technology, Graduate School of Energy Science, Kyoto University, Sakyo-ku, Kyoto, Japan.

出版信息

J Phys Condens Matter. 2012 Feb 29;24(8):085701. doi: 10.1088/0953-8984/24/8/085701. Epub 2012 Jan 26.

DOI:10.1088/0953-8984/24/8/085701

PMID:22277378

Abstract

First-principles fully relaxed tensile and shear test simulations were performed on Σ10(1124)/[1100] tilt Mg grain boundary (GB) models, with and without H segregation, to investigate mechanisms of H embrittlement of Mg. Strengthening as a result of covalent-like characteristics of Mg-H bonds prevailed over weakening of Mg-Mg bonds resulting from charge transfer; as a result, an H atom strengthened the GB. In addition, because the strong Mg-H bonds suppressed macroscopic GB fracture, elongation to failure was not reduced by H segregation. However, the resistance to GB shearing was increased by H segregation. It is therefore suggested that H segregation enhances crack growth at the GB, because dislocation emission from the crack tip is suppressed, resulting in H embrittlement of Mg.

摘要

采用第一性原理方法对Σ10(1124)/[1100]倾斜型镁晶界（GB）模型进行了完全弛豫拉伸和剪切测试模拟，研究了 H 原子对镁脆化的作用机制。结果表明，Mg-H 键的共价特性导致的强化作用超过了电荷转移导致的 Mg-Mg 键弱化作用，因此 H 原子强化了 GB。此外，由于强 Mg-H 键抑制了宏观 GB 断裂，因此 H 原子的偏聚并没有降低镁的断裂伸长率。然而，H 原子的偏聚增加了 GB 的抗剪切能力。因此，H 原子的偏聚增强了 GB 处的裂纹扩展，这是因为抑制了裂纹尖端位错的发射，从而导致了镁的脆化。