An ultrahigh strength and enhanced ductility cold-rolled medium-Mn steel treated by intercritical annealing

Li, Xuan; Song, Ren‐Jie; Zhou, Naipeng; Li, Jiajia

doi:10.1016/j.scriptamat.2018.05.016

Cited by 80 publications

(20 citation statements)

References 26 publications

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“…When the manganese content rises, the initial microstructure (after cold rolling) changes to low-C martensite [2]. Medium-Mn steels can be obtained as cold-rolled [5] or hot-rolled [6] sheets. For lightweight applications in the automotive industry, cold-rolled coated sheet products are of particular interest.…”

Section: Introductionmentioning

confidence: 99%

“…For lightweight applications in the automotive industry, cold-rolled coated sheet products are of particular interest. In order to obtain the multiphase microstructure consisting of ferrite and austenite or bainite and austenite, intercritical annealing is required [5,7]. These steels can be also produced as hot-rolled sheets for some underbody/suspension applications.…”

Section: Introductionmentioning

confidence: 99%

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Effect of Deformation Temperature on the Portevin-Le Chatelier Effect in Medium-Mn Steel

Grzegorczyk

Kozłowska

Morawiec

et al. 2018

Metals

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Experimental investigations of the plastic instability phenomenon in a hot-rolled medium manganese steel were performed. The effects of tensile deformation in a temperature range of 20-140 • C on the microstructure, mechanical properties, and flow stress serrations were analyzed. The Portevin-Le Chatelier (PLC) phenomenon was observed for the specimens deformed at 60 • C, 100 • C, and 140 • C. It was found that the deformation temperature substantially affects the type and intensity of serrations. The type of serration was changed at different deformation temperatures. The phenomenon was not observed at room temperature. The plastic instability occurring for the steel deformed at 60 • C was detected for lower strain levels than for the specimens deformed at 100 • C and 140 • C. The increase of the deformation temperature to 100 • C and 140 • C results in shifting the PLC effect to a post uniform deformation range. The complex issues related to the interaction of work hardening, the transformation induced plasticity (TRIP) effect, and the PLC effect stimulated by the deformation temperature were addressed. stabilize the retained austenite through its carbon enrichment [8]. An alternative approach is to apply thermomechanical processing (TMP) as direct one-step cooling following the hot rolling. The TMP has the potential for energy savings and high productivity due to the elimination of the need for successive heating [9][10][11]. Chemical composition and processing parameters are designed to obtain the optimal TRIP (Transformation Induced Plasticity) effect, which ensures superior mechanical properties [12,13].Besides the many advantages of this group of steels, some problems during their processing can occur. Medium manganese steels [14-17] and high manganese steels [18][19][20] are prone to plastic instabilities phenomena associated with a serrated flow behavior-Portevin-Le Chatelier (PLC) effect and the appearance of Lüders bands. This is especially the case for cold-rolled steel sheets [21]. Moreover, it critically depends on the carbon level. With a higher C content, a pronounced effect is more visible. The heterogeneous deformation related to the increase in flow stress can lead to numerous cracks during the forming of sheets. Moreover, delayed cracking after deep drawing can appear. Delayed cracking is mostly observed in high-Mn content steels of the high austenite volume fraction. With the increased volume fraction of (retained) austenite, hydrogen embrittlement may be a more important concern. TWIP steels in the last decades have displayed important delayed cracking, which was industrially solved by decreasing the C content, Al alloying, and/or metallurgical processing [22,23]. Medium Mn steels have a less pronounced problem of delayed cracking compared to high-Mn steels [24,25].The PLC effect is commonly known as characteristic serrations which can be observed on a strain-stress curve during a tensile test. The PLC effect has not been fully characterized yet. However, some correlations between the TRIP a...

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Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Effect of Deformation Temperature on the Portevin-Le Chatelier Effect in Medium-Mn Steel

Grzegorczyk

Kozłowska

Morawiec

et al. 2018

Metals

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“…It is worth noting that almost all previous studies on medium-Mn steel were limited to the exploration of microstructure and mechanical properties under the same rolling process. For instance, Song et al reported that 7.75Mn-2.78Al-0.52C wt.% steels processed by cold-rolling exhibited anultimate tensile strength (UTS) of 1090 MPa and a total elongation (TE) of 56.3% [10]. They attributed the excellent performance to the TRIP/TWIP effect, high dislocation density and high fraction of retained austenite.…”

Section: Introductionmentioning

confidence: 99%

Microstructure and Mechanical Properties of Hot- Rolled and Cold-Rolled Medium-Mn TRIP Steels

et al. 2018

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This study investigated the microstructure and mechanical properties of hot-rolled and cold-rolled medium-Mn transformation-induced plasticity (TRIP) steel. The experimental steel, processed by quenching and tempering (Q & T) heat treatment, exhibited excellent mechanical properties for hot-rolled and Q & T steels (strength of 1050–1130 MPa and ductility of 16–34%), as well as for cold-rolled and Q & T steels (strength of 878–1373 MPa and ductility of 18–40%). The mechanical properties obtained after isothermal holding at 775 °C for one hour for cold-rolled/Q & T steel were superior to that of hot-rolled/Q & T steel. Excellent mechanical properties were attributed to the large amount of retained austenite, which produced a discontinuous TRIP effect. Additionally, the differences in mechanical properties correlated with the morphology, stability and content of retained austenite. The cold-rolled sample, quenched from 650 °C (CR 650°C) had extensive TRIP effects in the middle and late stages of the deformation, leading to better mechanical properties. The fracture modes of the hot-rolled sample, quenched from 650 °C, and the cold-rolled sample quenched from 650 °C, were ductile fractures, resulting in excellent ductility.

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“…Due to a relatively low stacking fault energy (SFE) of retained austenite, both twinning-induced-plasticity (TWIP) and transformationinduced-plasticity (TRIP) mechanisms can be triggered during plastic deformation [6]. Researchers have been focusing on improving the mechanical properties [7,8] and understanding the microstructure evolution during deformation for years [9e11]. However, along with the exploitation of such highstrength steels [9,10], hydrogen embrittlement (HE) becomes a severe problem that one should focus on [12,13].…”

Section: Introductionmentioning

confidence: 99%

Insight into hydrogen effect on a duplex medium-Mn steel revealed by in-situ nanoindentation test

Zamanzade

et al. 2019

International Journal of Hydrogen Energy

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An ultrahigh strength and enhanced ductility cold-rolled medium-Mn steel treated by intercritical annealing

Cited by 80 publications

References 26 publications

Effect of Deformation Temperature on the Portevin-Le Chatelier Effect in Medium-Mn Steel

Effect of Deformation Temperature on the Portevin-Le Chatelier Effect in Medium-Mn Steel

Microstructure and Mechanical Properties of Hot- Rolled and Cold-Rolled Medium-Mn TRIP Steels

Insight into hydrogen effect on a duplex medium-Mn steel revealed by in-situ nanoindentation test

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