Interaction between Dislocations, Precipitates and Hydrogen Atoms in a 2000 MPa Grade Hot-Stamped Steel

Abstract

Inhibiting the diffusion and aggregation of hydrogen atoms can effectively improve the hydrogen-induced delayed fracture resistance of high strength hot-stamped steel. Here we investigate the interaction between dislocations, precipitates and hydrogen atoms in a 2000 MPa grade hot-stamped steel through a combination of microstructure characterization and hydrogen embrittlement (HE) sensitivity tests. Results show that HE susceptibility indexes increase with the increase of hydrogen charging current density, and the corresponding HE mechanism transfers from hydrogen-enhanced localized plasticity (HELP) dominates to hydrogen-enhanced decohesion (HEDE) dominates. Additionally, dislocations as reversible hydrogen traps with an activation energy of 36.3 kJ/mol, and through calculation, dislocations can carry hydrogen atoms to move when the strain rate is 10^-5 s^-1. We find that dispersed V-rich (Ti, V)C precipitates can refine grain increase reversible hydrogen traps, pin dislocations inhibit H-dislocation interaction, and act as irreversible hydrogen traps to capture hydrogen atoms and, consequently, improve HE resistance.

Keywords: Dislocation, Precipitation, Hydrogen Embrittlement, Hot-Stamped Steel