The objective is to study the nucleation and growth of helium clusters at grain boundaries (GBs) and their effects on the cohesive strength of GBs in bcc Fe under uniaxial straining.

SUMMARY The effects of helium atoms and the formation of helium clusters on Σ3 {111}, Σ3 {112} and Σ5 {310} symmetric tilt GBs in bcc iron were studied by the molecular dynamics simulation method. We found that helium atoms are deeply trapped at the GBs during annealing at 300 K, and that two or more helium atoms aggregate to form a small helium clusters. The helium atom and small clusters act as a failure initiation site under uniaxial straining. We show that helium atoms decreases cohesive strength and ductility of all the grain boundaries in bcc Fe that were studied.

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