Influence of Intercritical Heating on the Microstructure and Mechanical Properties of Al-Rich Quenching-Partitioning-Tempering Steel

The microstructure and mechanical properties with traditional and intercritical heating and quenching-partitioning-tempering (referred as Q-P-T and I&Q-P-T, respectively) treatment for the Al-rich steel are revealed through optical microscopy (OM), scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD), electron probe microanalysis (EPMA), and tensile testing. Results indicate that the multiphase microstructures of the Q-P-T and I&Q-P-T-treated steel consist of martensite (M), ferrite (F), and retained austenite (RA). Meanwhile, the I&Q-P-T-treated steel has much more ferrite and relatively less RA than those of the Q-P-T-treated one. During tensile testing, more RA with optimized stability transforms to martensite in the I&Q-P-T-treated specimen, which leads to a more pronounced transformation-induced plasticity (TRIP) effect. Thus, with more ferrite and a remarkable TRIP effect, the elongation and product of strength-elongation of the I&Q-P-T steel are higher than those of the Q-P-T-treated one.