Influence of hydrogen environment on dislocation nucleation and fracture response of < 1 1 0 > grain boundaries in nickel
JQ Li and C Lu and LQ Pei and C Zhang and R Wang and K Tieu, COMPUTATIONAL MATERIALS SCIENCE, 165, 40-50 (2019).
The segregation of solute H has a profound effect on mechanical properties of grain boundaries (GBs). In this work, systematic molecular dynamics (MD) simulations have been performed to elucidate the influence of H environment on dislocation nucleation process and fracture response of different Ni GBs. The results show that the effect of H on dislocation nucleation depends strongly on GB structures. The presence of H decreases the yield stress required to nucleate dislocations from GBs with C and D structural units (SUs), while increases the yield stress of GBs with E SUs. This difference is attributed to different deformation mechanisms related to the dislocation nucleation from various GBs with H. By analysing the decohesion results, it is found that H has stronger embrittling effect on GBs with E SUs than C and D SUs, originating from the fact that H significantly elongates the Ni-Ni bonds around the open E SUs while slightly expands the compact C and D SUs. These findings present fundamental understanding on H embrittlement mechanism and provide mechanistic insights for engineering microstructure against H embrittlement in metallic materials.
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