Application of the Quenching and Partitioning (Q&P) Process to D6AC Steel

Quenching and partitioning (Q&P) was successfully applied to a medium carbon and low alloy martensitic D6AC steel. Fully austenitized samples were quenched to temperatures below the MS temperature (317 degrees C), ranging from 240 to 275 degrees C, and partitioned at the quench temperature for 300 s. While the as quenched sample exhibits a fully martensitic microstructure, all the Q&P processed samples have a retained austenite fraction up to about 6%. These samples were tensile tested at room temperature and their mechanical properties were compared to those obtained from different heat treated D6AC samples. Regardless of the partitioning temperature (equivalent to the quench temperature), the retained austenite in the Q&P processed samples transformed to martensite during the tensile testing, providing additional ductility above 10% of total elongation for the high strength material with a tensile strength around 1 500 MPa.