Hydrogen behavior during high-temperature plastic deformation in low-alloy steels

Abstract

• Interaction mechanism between thermoplastic deformation and HE. • Cross scale simulation based on MD and DFT. • Proposal and mechanism of hydrogen inhibition recovery. Hydrogen embrittlement of steel has been widely studied; however, the hydrogen behavior during thermoplastic deformation is still unknown. The hydrogen behavior in thermoplastic deformation may have a significant impact on the properties of materials after processing. In this study, hydrogen embrittlement samples were obtained using electrolytic hydrogen charging, and thermoplastic deformation experiments of hydrogen-charged samples at different temperatures were conducted. Hydrogen slightly increased the flow stress, particularly when the deformation temperature was 1123 K. Microstructure characterization revealed that the samples with a high hydrogen content had a higher dislocation density. Molecular dynamics and density functional theory calculations were performed to understand this mechanism. The difference in Gibbs free energy between systems showed that hydrogen reduced the driving force of defect recovery, making recovery more difficult. This microstructure evolution law explained the experimentally observed increase in the dislocation density due to hydrogen. The increase in dislocation density leads to an increase in the flow stress. This study provides useful information and understanding about the behavior of hydrogen during alloy processing. Improving the alloy processing method may be a powerful way to inhibit hydrogen embrittlement.