Interaction between dislocations, precipitates and hydrogen atoms in a 2000 MPa grade hot-stamped steel
Weijian Chen, Weiyan Zhao, Pengfei Gao, Feng Li, Shuang Kuang, Yu Zou, Zhengzhi Zhao
Abstract
Inhibiting the diffusion and aggregation of hydrogen atoms can effectively improve the resistance to hydrogen embrittlement (HE) 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 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. Moreover, we find that dispersed V-rich (Ti, V)C precipitates can refine grain to increase the number of reversible hydrogen traps, pin dislocations to inhibit H–dislocation interaction, and act as irreversible hydrogen traps to capture hydrogen atoms and, consequently, raise the resistance to HE.