Atomistic investigation of hydrogen induced decohesion of Ni grain boundaries

JQ Li and C Lu and LQ Pei and C Zhang and R Wang, MECHANICS OF MATERIALS, 150, 103586 (2020).

DOI: 10.1016/j.mechmat.2020.103586

The embrittlement of metallic materials by hydrogen (H) segregation is widely observed, but not understood well on an atomic scale. In the present study, an atomistic investigation of H embrittlement of various grain boundaries (GBs) has been performed by mapping H segregation energy of trapping sites and examining the effect of H segregation on the decohesion of GBs. The simulation results show that under the equilibrium concentration of H atoms typical of embrittlement in Ni, in conjunction with local H diffusion process, the maximum reduction of tensile strength and fracture energy is 6.60% and 15.75% for Sigma 5 (210) < 100 > and Sigma 17 (530) < 100 > GBs, respectively. Inspired by experimental observations of the dislocation structures beneath intergranular failure features, further calculations reveal that the embrittling effect of H atoms in metallic materials can be largely facilitated by the boundary disruption and local stress state concentrated on the GB through the plasticity process. The findings directly provide a picture of H embrittlement arising from the cooperative action of H-induced plasticity and GB decohesion.

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