“…From the results of linescan taken from the strip surface to the strip centre, it can be observed that the segregation was uniform from the strip surface to the strip centre in terms of deviation and wavelength (ΔMn = 0.6–0.9 wt-% at a small wavelength). Thus, there was microsegregation of Mn present in the as-cast strip, while there was no macrosegregation, which was different from the distinct macrosegregation observed in Fe–0.05C–12Mn–3Al (wt-%) medium-Mn as-cast strip [16] and Fe–1.27C–28.4Mn–8.3Al (wt-%) high-Mn as-cast strip [20]. Figure 4 OM micrographs of (a) as-cast strip and (d) hot-rolled sheet, SEM micrographs of (b) surface region of as-cast strip, (c) centre region of as-cast strip and (e) hot-rolled sheet, and (f) concentration profile of Mn in the as-cast strip analysed by EPMA.…”
Section: Resultsmentioning
confidence: 99%
“…From the results of linescan taken from the strip surface to the strip centre, it can be observed that the segregation was uniform from the strip surface to the strip centre in terms of deviation and wavelength ( Mn = 0.6-0.9 wt-% at a small wavelength). Thus, there was microsegregation of Mn present in the as-cast strip, while there was no macrosegregation, which was different from the distinct macrosegregation observed in Fe-0.05C-12Mn-3Al (wt-%) medium-Mn as-cast strip [16] and Fe-1.27C-28.4Mn-8.3Al (wt-%) high-Mn as-cast strip [20].…”
Section: As-cast Microstructure and Hot-rolled Sheet Microstructurementioning
A medium-Mn steel (Fe–0.3C–4Mn–1.82Al–0.6Si wt-%) was produced by a novel processing route involving twin-roll strip casting, hot rolling and intercritical annealing (IA). Macrosegregation was absent in the as-cast strip. The microstructure of the as-cast strip consisted of martensite and austenite (∼10 vol.-%), and the solidification structure was characterised by dendritic structure. With an increase in IA temperature from 680 to 725 and to 755°C, austenite fraction in intercritically annealed steels was increased from 22 to 45% and then decreased to 27%. The 710°C intercritically annealed steel yielded excellent mechanical properties with a tensile strength of ∼1007 MPa and total elongation of ∼48%, achieved by a high volume fraction of austenite (∼42%) with appropriate mechanical stability.
“…From the results of linescan taken from the strip surface to the strip centre, it can be observed that the segregation was uniform from the strip surface to the strip centre in terms of deviation and wavelength (ΔMn = 0.6–0.9 wt-% at a small wavelength). Thus, there was microsegregation of Mn present in the as-cast strip, while there was no macrosegregation, which was different from the distinct macrosegregation observed in Fe–0.05C–12Mn–3Al (wt-%) medium-Mn as-cast strip [16] and Fe–1.27C–28.4Mn–8.3Al (wt-%) high-Mn as-cast strip [20]. Figure 4 OM micrographs of (a) as-cast strip and (d) hot-rolled sheet, SEM micrographs of (b) surface region of as-cast strip, (c) centre region of as-cast strip and (e) hot-rolled sheet, and (f) concentration profile of Mn in the as-cast strip analysed by EPMA.…”
Section: Resultsmentioning
confidence: 99%
“…From the results of linescan taken from the strip surface to the strip centre, it can be observed that the segregation was uniform from the strip surface to the strip centre in terms of deviation and wavelength ( Mn = 0.6-0.9 wt-% at a small wavelength). Thus, there was microsegregation of Mn present in the as-cast strip, while there was no macrosegregation, which was different from the distinct macrosegregation observed in Fe-0.05C-12Mn-3Al (wt-%) medium-Mn as-cast strip [16] and Fe-1.27C-28.4Mn-8.3Al (wt-%) high-Mn as-cast strip [20].…”
Section: As-cast Microstructure and Hot-rolled Sheet Microstructurementioning
A medium-Mn steel (Fe–0.3C–4Mn–1.82Al–0.6Si wt-%) was produced by a novel processing route involving twin-roll strip casting, hot rolling and intercritical annealing (IA). Macrosegregation was absent in the as-cast strip. The microstructure of the as-cast strip consisted of martensite and austenite (∼10 vol.-%), and the solidification structure was characterised by dendritic structure. With an increase in IA temperature from 680 to 725 and to 755°C, austenite fraction in intercritically annealed steels was increased from 22 to 45% and then decreased to 27%. The 710°C intercritically annealed steel yielded excellent mechanical properties with a tensile strength of ∼1007 MPa and total elongation of ∼48%, achieved by a high volume fraction of austenite (∼42%) with appropriate mechanical stability.
“…The variation behavior of the strain-hardening rate can be divided into three stages. The first is the sharp decrease stage (stage I), where the negative slope value of the curve is due to the development of moving dislocations and the saturation of dislocation stacks on the sliding surface [27]. After this, a rising and stable stage (stage II) of the strain-hardening rate starts, where the positive slope value of the curves is related to the formation and refinement of deformed microstructures such as unidirectional slip paths or Taylor lattices [21].…”
Section: Effect Of the Thermo-mechanical Process And Nb-v Microalloyi...mentioning
In present study, a novel Nb-V microalloyed Fe–Mn–Al–C steel and a non-microalloyed Fe–Mn–Al–C austenitic steel were treated with different thermo-mechanical processes. The microstructure of the test steels was observed by scanning electron microscope, transmission electron microscope, electron probe micro-analyzer, and X-ray diffractometer. A tensile test was conducted to estimate the mechanical properties of the test steels. Results show that the equiaxed austenitic grains are obtained in both test steels, while hot rolling reduces the grain size significantly. The grain size of the Fe–Mn–Al–C steel decreases by 40%–55% after the addition of Nb-V due to the precipitation of nanoscale (Nb,V)C particles within the austenite matrix. Compared with the solid solution treated specimens, the strength of the hot-rolled or aged specimens is improved. Meanwhile, the strength of the Fe–Mn–Al–C steel with Nb-V microalloying is also increased by 55 MPa due to the precipitation strengthening and fine grain strengthening, while the elongation is decreased. The Nb-V microalloyed Fe–Mn–Al–C steel, after hot rolling + aging treatment, obtains the maximum strength, with the yield and tensile strength of 669 MPa and 1001 MPa, respectively. The strengthening mechanisms that contribute significantly to the yield strength are solid solution strengthening and dislocation strengthening. They are 185 MPa and 211 MPa, respectively, for the Nb-V microalloyed Fe–Mn–Al–C steel at hot rolling + aging conditions. Meanwhile, the segregation of carbon atoms after aging treatment also improves the yield strength significantly.
“…[ 7 ] In the last decade, the studies on Fe–Mn–Al–C low‐density steels emerged in automotive steels, and most of them focused on the dependence of microstructure and mechanical behaviors on annealing and ageing treatments. [ 8–12 ] Zambrano et al found that the precipitation of κ‐carbide can also occur within a few seconds of TMT process in Fe‐11.1Al‐20.7Mn‐1.98Si‐1.55C steel. [ 13 ] The dynamic recrystallization (DRX) behavior of advanced high‐strength steels except novel low‐density steels has been studied extensively, and several flow stress constitutive equations and DRX kinetics have been reported.…”
The flow stress curves of Fe‐31.7Mn‐11.5Al‐0.9C low‐density steel are obtained by a hot‐compression test with a Gleeble‐3500 thermomechanical simulator. It is shown in the results that the dynamic recovery and dynamic recrystallization (DRX) of δ‐ferrite occur preferentially under the same deformation condition, inducing a “yield point‐like” phenomenon in the true stress–strain curves. The Zener–Hollomon parameter is introduced to fit the characteristic parameters used to establish the flow stress model according to Arrhenius hyperbolic sine relationship and Avrami equation, and the DRX activation energy of austenite is 414.12 KJ mol−1. The hot‐processing maps at different true strains are simulated based on the dynamic material model to determine the suitable hot‐rolling process and the optimal hot‐working process selection of high strain rate and high deformation temperature combination, 1100–950 °C/1–0.2 s−1, is recommended.
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