First principles study of hydrogen induced the grain boundaries decohesion in fcc Ag

Abstract

Hydrogen embrittlement (HE) is a pervasive but harmful physical (chemical) phenomenon, and it has a profound effect on the mechanical properties of metals. Although the study of HE began as early as the near century and a half ago, the essential mechanism of HE still cannot be completely figured out yet. The metallic-H atoms interaction at the atomistic scale is considered the essence of the HE. Especially the interaction of interstitial H and host atoms at grain boundaries is crucial for revealing the HE mechanism. Here, the first principles simulation is applied to study the effect of the trapped H atoms on the grain boundaries (GBs) cleavage behavior. We construct the GBs with different orientations of the face-cantered cubic (fcc) Argentum (Ag) and conduct the ab initio tensile test for all the GBs. The strength of GBs during cleavage, the distortion of GBs structure, and the electronic structure variation induced by trapped H atoms are analyzed. We find the GBs cleavage strength is generally decreased by trapping H atoms at GBs. The decohesion mechanism is the GBs distortion induced by the local electron density variation of the GBs trapping H atoms.