Metallographic Analysis of Kinetically Activated Bainite (KAB) Steels

摘要

The current work focuses on a group of steels named KAB (kinetically activated bainite), with accelerated bainite formation kinetics. The bainite formed within the newly developed grades is very fine and exhibits a hardness of up to 66HRC upon oil quenching, which enables the obtainment of tensile strengths beyond 2800?MPa, and grades containing large amount of retained austenite achieve predominantly uniform elongations due to a pronounced TRIP effect, whereas those steels where the bainite reaction approaches completion do not exhibit poor impact properties which are commonly associated with carbide-free lower bainite. This contribution focuses on the microstructural characterization of these steels, using light microscopy, field emission scanning electron microscopy, high-resolution transmission electron microscopy, and the relationship between microstructure and mechanical properties.