Experimental and Numerical Investigation of Hydrogen Embrittlement Effect on Microdamage Evolution of Advanced High-Strength Dual-Phase Steel

The effect of hydrogen on the microdamage evolution of 1200M advanced high-strength steel was evaluated by the combination of experimental and numerical approaches. In the experimental section, the tensile test was performed under different testing conditions, i.e., vacuum, in-situ hydrogen plasma charging (IHPC), ex-situ electrochemical hydrogen charging (EEHC), and ex-situ + in-situ hydrogen charging (EIHC) conditions. The post-mortem analysis was conducted on the fracture surface of specimens to illuminate the impact of hydrogen on the microstructure and mechanical properties. The results showed that under all of hydrogen charging conditions, the yield stress and ultimate tensile strength were slightly sensitive to hydrogen, while tensile elongation was profoundly affected. While only ductile dimple features were observed on the fracture surfaces in vacuum condition, the results indicated a simultaneous action of the hydrogen-enhanced decohesion (HEDE) and hydrogen enhanced localized plasticity (HELP) mechanisms of HE, depending on the local concentration of hydrogen under the IHPC and EEHC conditions. At the EIHC condition, the HEDE model was the dominant failure mechanism, which was manifested by the HE-induced large crack. In the numerical approach, a finite-element analysis was developed to include the Gorson–Tvergaard–Needleman (GTN) damage model in Abaqus™ software. To numerically describe the damage mechanism, the GTN damage model was utilized in the 3D finite-element model. After calibration of damage parameters, the predicted damage mechanisms for two testing conditions, i.e., vacuum and EIHC, were compared with experimental results.