A carbide-free bainite/martensite/austenite triplex steel with enhanced mechanical properties treated by a novel quenching–partitioning–tempering process

Tempering Behavior of Ductile 1700 MPa Mn–Si–Cr–C Steel Treated by Quenching and Partitioning Process Incorporating Bainite Formation

“…Previously, a QePeT process incorporating the formation of carbide-free bainite during quenching step (abbreviated by BQe PeT process) was proposed [18] . The product of strength and elongation (PSE) could be increased up to 30 GPa%.…”

Very high cycle fatigue behaviors of bainite/martensite multiphase steel treated by quenching-partitioning-tempering process

“…Q&P process was proposed by Speer et al for achieving martensite and austenite multiphase [23][24].The Q&P concept involves an initial cooling step to a quenching temperature (T q ) between the martensite-start (M s ) temperature and the martensite-finish (M f ) temperature, followed by an isothermal holding at T q (or higher than T q ) with purpose of promoting carbon diffuse from martensite to austenite, thereby obtaining more retained austenite at room temperature. It should be noted that the process parameters (e.g., T q ) greatly affect the final morphology and fraction of retained austenite [17,[23][24]. In the present work, a B/M multiphase steel was treated by two bainite-based Q-P-T (BQ-P-T) [25] treatments to obtain different types of retained austenite (with different volume fraction, size and morphology).…”

“…Our previous work indicated that the VHCF properties of the designed bainite/martensite (B/M) multiphase steels are less sensitive to inclusions compared to tempered martensite steels, and "non-inclusion induced crack initiation" could be one of the most important fatigue failure mechanisms in VHCF regime [13][14]16]. By addition of Si, the carbide is replaced by retained austenite in B/M steels [17]. The microstructures of B/M multiphase steels consist of bainitic ferrite, martensite and retained austenite.…”

Stability of Retained Austenite Through a Combined Intercritical Annealing and Quenching and Partitioning (IAQP) Treatment

“…For instance, good combinations of tensile strength (1,000-1,200 MPa) and total elongation (14-20%) were obtained after intercritical annealing and Q&P (IAQP) treatments by Moor et al [7]. Gao et al [11] also improved the mechanical properties of quenching-partitioning-tempering (Q-P-T) steel by introducing carbide-free bainite to achieve a product of strength and elongation to 31.4 GPa%. The elongation of Q-P-T steels as reported was raised without a marked sacrifice of strength, and thus the product of strength and elongation was enhanced as a whole.…”