Abstract
A cold-rolled third-generation TRIP-assisted advanced high-strength steel (AHSS) of 1000 MPa strength class was investigated to evaluate the influence of hydrogen on its mechanical behavior under slow strain rate testing (SSRT). Hydrogen was introduced electrochemically under controlled conditions, and two levels of diffusible hydrogen were quantified via thermal desorption analysis (TDA). At the lower hydrogen concentration (~0.61 ppm), no significant degradation in tensile properties was observed. In contrast, the higher concentration (~1.16 ppm) resulted in a notable reduction in total elongation, with an embrittlement index of 38.3 %. In TRIP steels, hydrogen reduces the stability of retained austenite, promoting its premature transformation into martensite during plastic deformation. Since martensite has low hydrogen solubility and high hardness, it becomes a preferential site for crack nucleation. This localized hydrogen accumulation, combined with the intrinsic brittleness of martensite, explains the observed reduction in ductility under tensile loading.