Near-Ac3 austenitized ultra-fine-grained quenching and partitioning (Q&P) steel

A Study of the Optimum Quenching Temperature of Steels with Various Hot Rolling Microstructures after Cold Rolling, Quenching and Partitioning Treatment

“…A ϕ4 × 10 mm 2 specimen machined from the ingot was heated at 0.05 • C/s to 1000 • C for 10 min followed by cooling at 50 • C/s to room temperature on a dilatometer machine (DIL805A, BAHR-Thermoanalyse GmbH, Hullhorst, Germany). According to previous studies [23,24], treatment at a temperature close to Ac3 can refine the austenite grain size. Thus, the austenitizing parameter of the investigated steel was selected as 820 • C for 5 min.…”

On the Variants of Thermal Process in Developing Strong and Ductile Medium Mn Steel

“…The samples annealed at 800 • C are named "IA-Q&P" steels and those annealed at 900 • C are termed as "Q&P" steels. Note that the annealing at 800 • C is near A c3 ( Figure 1B), which has been reported to have excellent mechanical properties (Cho et al, 2016). The quenching temperature for the IA-Q&P and Q&P process is down to room temperature, at which the martensitic transformation is still not completed (He et al, 2018b).…”

“…Compared with the single IA process, the IA-Q&P process can improve the yield strength without sacrificing the elongation (De Cooman et al, 2016). The soft ferrite matrix of the medium Mn steel produced by the IA process is responsible for the low yield strength, while the steel after IA-Q&P process can possess extra martensite, which can increase the yield strength (Cho et al, 2016;De Cooman et al, 2016). Although the medium Mn steel produced by the IA-Q&P process exhibits better ductility than that fabricated by the single Q&P process owing to the optimal mechanical stability of retained austenite, the former has lower yield strength due to the existence of ferrite phase (Wang X. et al, 2018).…”

Tailor Welded Partition Blanks: New Methods Improve the Ductility of Ultra-high-strength Welded Joint

“…This observation was also suggested that martensite with higher band contrast and larger size was formed during the first quench and then the carbon supersaturated in martensite was partitioned to the surrounding austenite, contributing to its thermal stabilization, whereas fresh martensite with lower band contrast was formed during final quenching, which had higher Kernel average misorientation (upper limit of 5°) than the rest of the microstructure, which was similar with the investigation by Lawrence Cho. 31) Partitioning step in sample B formed tempered equixed martensite, and the slower transformation rate of the martensite-austenite structure would result in the continuous TRIP effect in deformation process. But the content of austenite and its morphology was not satisfied to further improved the ductility of the joint, and Farnoosh 5.…”