Molecular dynamics study of hydrogen-induced cracking behavior of ferrite-pearlite gas transmission pipeline steel

Hydrogen embrittlement of pipelines depends on the hydrogen-induced cracking behavior of the pipeline steel microstructure. Based on molecular dynamics analysis, the ferrite-cementite (& alpha;-Fe/Fe3C) lamellar atomic structure with the Bagaryatskii orientation relationship was established, and stepwise relaxation of the conjugate gradient energy minimization and constant-temperature and constant-pressure relaxation were performed under NPT (the isothermal-isobaric) conditions. The mechanical property curves of the & alpha;-Fe/Fe3C models were obtained under different cementite terminal plane structures, and the evolution of the atomic structure was analyzed in detail. In addition, the influence of different hydrogen concentrations, different temperatures, different strain rates, changes in voids, and different micro-degrees of freedom on the deformation and failure mechanism of the model was investigated, aiming to provide a reliable way to explore the micro-mechanism of macro-cracking behavior of pipeline steel.