Crystallography and Mechanical Properties of Intercritically Annealed Quenched and Partitioned High-Aluminium Steel

The quenching and partitioning response of intercritically annealed steel with aluminum contents in the 2–3 wt.% range and a carbon content of 0.2 wt.% was studied. Two types of morphologies for retained austenite were observed in electron backscatter diffraction studies: blocky, untransformed austenite grains and partially transformed austenite located primarily at prior austenite and packet boundaries. The amount of retained austenite was found to correlate with the initial quench temperature, as well as with the uniform elongation of the specimens in subsequent tensile testing. The transformation characteristics of austenite were rationalized on the basis of prior austenite grain size and inhomogeneous carbon distribution. The martensite transformed during the initial quench was found to favor Σ3 twin-type lath combinations, supplemented by neighboring variants providing self-accommodation.