Characteristics of bainitic transformation and its effects on the mechanical properties in quenching and partitioning steels

Viewpoints on Technological Aspects of Advanced High-Strength Bainitic Steels

“…It has been proven that the presence of martensite, even a small amount, prior to the bainitic transformation can accelerate it by suppressing the incubation time, as it provides more nucleation sites [30,51,53,54]. Such a process is fundamentally equivalent to Q&P, as mentioned, implying a competition, at the partitioning stage, between this mechanism and the simultaneous bainitic transformation.…”

“…It has been reported that as the bainitic transformation prevails over the first martensitic transformation (i.e., as the quenching temperature is higher, i.e., closer to M s ), a higher fraction of retained austenite in the form of blocks-implying a lower content of fresh martensite-are present in the final microstructure in an Fe-0.2C-2.82Mn-1.58Si steel. Such a trend is responsible for a higher elongation without compromising the tensile strength [53]. Investigations on the kinetics and microstructures of an Fe-0.28C wt.% high-Si/Al steel isothermically treated at temperatures below M s have shown that the bainitic transformation process was significantly accelerated by the prior formation of athermal martensite, also resulting in a finer microstructure with much better impact toughness and a product of strength and ductility reaching 28.6 GPa % [30,55].…”

Effect of Step Quenching Heat Treatments on the Kinetics of Ferrite Formation and Quenching & Partitioning Modeling for a Commercial C-Mn-Si Steel

“…Chen et al 44 , studying a 0.2C-2.82Mn-1.58Si steel, showed that the occurrence of bainitic transformation in the Q&P process leads to a greater retained austenite fraction due to the optimization of carbon redistribution (which increase the austenite stability) in addition to carbon partition during the transformation 45 . This lead to a significant improvement in uniform and total elongation combined with a high strength, with which other authors also agree [46][47][48][49] .…”

Effect of Quenching Temperature on the Strengthening Mechanism of Low‐Carbon Microalloyed Quenching and Partitioning Steel

“…The Q–P process involves four stages, namely, the full/partial austenitization stage, the initial quenching stage at a temperature between the starting and finishing temperatures of M transformation ( M s and M f ) to form M, the partitioning stage to achieve carbon enriched austenite, and the final quenching stage. [ 3,4 ] During the final cooling to room temperature, some carbon‐rich, stable untransformed austenite is left. It is expected to exert the transformation‐induced plasticity (TRIP) effect during plastic deformation.…”