Effect of Quenching and Partitioning with Hot Stamping on Martensite Transformation and Mechanical Properties of AHSS

Two-step quenching and partitioning treatment with hot stamping was applied to advanced high-strength steel (AHSS). The newly treated steel possesses a fine microstructure and typically curved micromorphology. The martensite start temperature of the newly treated steel is increased through the effect of plastic deformation on austenitic microstructure. However, the martensite volume fraction of this steel is deceased because of the enhanced stability of the untransformed austenite after plastic deformation. Consequently, the fraction of retained austenite is increased. The newly treated steel also shows excellent mechanical properties. The volume fraction of retained austenite reaches the highest value of 17.2% when hot stamping is performed at 750 A degrees C. Hence, the steel displays favorable plasticity with an elongation of 14.5%. Moreover, the highest hardness value of 426 HV is obtained when hot stamping is performed at 650 A degrees C. The newly developed process may be employed to develop a new generation of AHSSs.