Effects of hydrogen on the mechanical properties of QP1180 AHSS

Multiphase steels enable the exploitation of the optimal characteristics of each microstructural component, resulting in a beneficial blend of mechanical strength and ductility and allowing lightweight design and vehicle emissions reduction. Quenching and Partitioning (QP) steels emerged as 3rd generation Advanced High-Strength Steels (AHSS) for automotive applications. Their microstructure is composed of low-carbon martensite and retained austenite, which provides an outstanding balance of strength and ductility but poses significant questions that currently limit its adoption in the automotive industry, primarily due to their inherent vulnerability to Hydrogen Embrittlement (HE) and delayed fracture. In this study, the interaction between hydrogen (H) and QP1180 AHSS was examined. Hydrogen diffusivity and trap energies were evaluated using Devanathan-Stachurski permeation and Thermal Programmed Desorption (TPD) tests. The as-received material did not present high-temperature peaks, suggesting that RA did not trap significant hydrogen in the measured condition. Tensile Slow Strain Rate Tests (SSRT) were conducted on electrochemically hydrogen-charged smooth specimens, with the effective hydrogen content measured via the hot extraction method for each specimen. Fractographic examinations using scanning electron microscopy revealed the influence of hydrogen on fracture behavior, showing a transition from ductile to predominantly brittle fracture modes at elevated hydrogen concentrations.