Multiscale simulations elucidate the mechanism of hydrogen embrittlement in high-entropy alloys: from hydrogen trapping and dislocation interaction to microcrack initiation

This work employs an atom-to-continuum (AtC) multiscale framework, integrating molecular dynamics with the finite element method, to elucidate hydrogen embrittlement in an FCC-structured CoCrFeMnNi alloy. The interatomic potentials are rigorously validated against first-principles (DFT) calculations, ensuring accurate cross-scale information transfer. The AtC model efficiently captures the cross-scale mechanical response. Results demonstrate that increasing hydrogen content (0%, 3%, 5%) systematically degrades strength and ductility, inducing a ductile-to-brittle transition. Microscopic analysis reveals that hydrogen segregation at crack tips triggers early microcrack nucleation and propagation through synergistic mechanisms: the dual role of hydrogen-enhanced localized plasticity (enhancing dislocation motion at moderate concentrations and pinning them at high concentrations), stress-induced martensitic transformation (FCC to HCP/BCC), and hydrogen-enhanced void nucleation and growth.