金属和合金材料中广泛存在着氢脆现象,即由于氢的渗入使得材料的塑性变形能力显著下降,导致材料倾向于发生脆性或准脆性断裂。尽管氢诱发材料失效的问题被研究了很多年,但微观机理一直存在着广泛争议。本文以近年来的研究结果为基础,提出了“氢化空位”的概念(即氢-空位复合体),认为其是氢致材料失效初期微观结构的最小载体。利用多尺度模拟并结合实验测试,揭示出氢化空位不同于空位的特殊性质,研究了氢环境下在塑性变形中氢化空位的产生、聚集并经过长时间演化形成纳米孔洞的过程,构建出原子尺度事件与微观失效之间的联系。该研究丰富了对氢脆微观机制的理解,同时氢化空位的概念也为揭示氢环境下的其它特殊力学行为提供了思路。

Hydrogen embrittlement, the degradation of mechanical behaviors due to the existence of hydrogen, is an industrially and environmentally critical problem in metals and alloys. Yet the fundamental mechanism(s) of embrittlement are still controversial, and the molecular-level damage events shrouded in mystery. In hydrogen embrittlement phenomena, the molecular-level agents of damage are hypothesized to be hydrogen-vacancy complex (Va+nH→VaH_n), hereupon called hydrogenated vacancy. Contrary to vacancy, hydrogen-vacancy complex has good thermal stability and low diffusivity. When metals undergo plastic deformation at low homologous temperature in the presence of hydrogen, the mechanically driven out-of-equilibrium dislocation processes produce extremely high concentrations of hydrogen-vacancy complexes. Under such high concentrations, these complexes prefer to grow by absorbing additional vacancies and act as the embryos for the formation of proto nano-voids. Our work provides the insight on the microscopic mechanism of hydrogen embrittlement. Moreover, this work also helps understanding some unique mechanical behaviors induced by hydrogen.