Bainitic Austempering Incorporating Quenching and Partitioning for Favorable Tuning of Microstructure and Mechanical Properties

A novel aspect of combining bainitic austempering with quenching and the partitioning process is addressed herein to obtain a favorable microstructure with desired mechanical properties. In this regard, Mn–Si–Cr–Al steel is first intercritically annealed at 840 °C and quenched to 140 °C after isothermal treatment at 360 °C for 15 min and then partitioned at 360 °C for 30 min. Multiphase microstructure containing ferrite, bainite, martensite, and retained austenite (RA) is obtained. Uniform elongation and total elongation increase appreciably from 11.5% to 20.5% and 21.0% to 28.3%, respectively, while maintaining near‐identical levels of tensile strength, compared with traditional bainitic austempering. The significant enhancement of tensile properties is attributed to the increase in volume fraction and mechanical stability of RA.