On the local evaluation of the hydrogen susceptibility of cold-formed and heat treated advanced high strength steel (AHSS) sheets

Hydrogen embrittlement (HE) is a crucial problem for many advanced high strength steels (AHSS) used in the automotive industry. To contribute to the microstructural understanding on the resistance against hydrogen embrittlement a complex phase (CP) steel and dual phase (DP) steel were investigated systematically in the present work. Both steels have the same tensile strength, but different microstructures. Thermal desorption spectroscopy (TDS) and electrochemical permeation (EP) were used to study the effect of plastic pre-deformation on the chemical diffusivity and solubility. The results were used to parametrize a fully coupled diffusion-mechanical finite element (FE) model. Constant load tests (CLTs) were applied on electrochemical pre-charged notched samples to evaluate the role of hydrogen charging on the mechanical properties. A local evaluation of the CLTs with the fully coupled FE model revealed local limit strain curves (LSC). Comparing these curves yields a very strong effect of the microstructure on the resistivity on hydrogen embrittlement.