Dependence of trapping states on the hydrogen content of high-carbon ferrite-austenite dual-phase steel

Abstract

States of hydrogen present in high carbon ferrite (α)-austenite (γ) dual phase steel were analyzed under various hydrogen charging conditions using thermal desorption analysis (TDA). Specimens including 0%γ and 10%γ in α were prepared. The 10%γ specimen consisted of bainitic ferrite and thermally stable retained austenite. When the 10%γ specimen were charged with hydrogen under high fugacity condition, the amount of hydrogen rapidly increased, the end temperature of hydrogen desorption in TDA profile increased, the hydrogen degassing time at 30 ° C increased, and the trap activation energy increased from about 30 kJ/mol to 47 kJ/mol. This 47 kJ/mol value is in excellent agree with the activation energy of hydrogen diffusion in γ phase. These results probably indicated that hydrogen is not absorbed in γ phase but α phase under lower fugacity conditions, i.e., lower amount of hydrogen. In contrast, hydrogen is absorbed in not only α phase but also γ phase under higher fugacity conditions, i.e., higher amount of hydrogen.