Effects of Partitioning Time and Temperature on the Microstructure and Mechanical Properties of a High Strength Microalloyed Steel

In the present study, in a quenching–partitioning (Q–P) process, the effects of partitioning time (Pt) and partitioning temperature (PT) on the mechanical and microstructural properties of a microalloyed Fe-0.21C-1.5Si-2.2Mn-0.054Al-0.08Ti steel were studied. The XRD and SEM results confirmed increases in retained austenite (γR\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$${\gamma }_{\mathrm{R}}$$\end{document}) volume fraction (VγR)\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$${V}_{{\gamma }_{\mathrm{R}}})$$\end{document} and γR\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$${\gamma }_{\mathrm{R}}$$\end{document} carbon concentration by increasing Pt and PT. XRD patterns confirmed reduction in VγR\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$${V}_{{\gamma }_{\mathrm{R}}}$$\end{document} by further increasing the Pt and PT over 500 s and 390 °C, respectively, due to super-saturation of austenite (γ\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$\gamma $$\end{document}) with carbon. PT of 390 °C and Pt of 500 s were recorded as the optimum values for PTs and Pts, which allowed the present steel to obtain higher formability and higher fracture strain characteristics, while retaining higher hardness and strength. The highest yield and tensile strength, hardness and fracture elongation were obtained for the sample partitioned at 390 °C for about 500 s, which were about 741 MPa, 1366 MPa, 322 HB and 25.2%, respectively.