Impact Toughness of Medium‐Mn Transformation‐Induced Plasticity‐Aided Steels

Sugimoto, Koh‐ichi; Tanino, Hikaru; Kobayashi, Junya

doi:10.1002/srin.201400585

Cited by 45 publications

(47 citation statements)

References 21 publications

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“…A growing interest in medium manganese steels related to their advantageous strength-ductility balance has prompted a better understanding of their behavior during plastic deformation [1][2][3][4]. Medium manganese steels contain 3-12% Mn and other alloying additions, such as Al and Si.…”

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%

“…The tested steel contains~5 wt.% Mn due to its application for hot-rolled products. The higher Mn contents are usually used for cold-rolled products [1,35]. Aluminium was chosen to prevent carbide precipitation.Metals 2019, 9, 2 3 of 13The investigated steel was prepared by vacuum induction melting.…”

mentioning

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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“…The addition of 5% Mn to the base steel decreased both the stretch formability and stretch flangeability of the steel. Figure 12 shows the CIAV at 20°C and the DBTT of TM steels (Steels A and C-H in Table 1) [16,[29][30][31]. From this, it can be seen that when 1%Cr, 1%Cr-0.2%Mo, or 1%Cr-0.2%Mo-1.5%Ni is added to the base steel, the resulting TM steel exhibits a high CIAV ranging from 100 to 120 J/cm 2 , and a low DBTT that ranges from -150 to -130°C.…”

Section: Cold Formabilitymentioning

confidence: 99%

Microstructure and Mechanical Properties of a TRIP-Aided Martensitic Steel

Sugimoto

Srivastava²

2015

Metallogr. Microstruct. Anal.

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This paper deals with the microstructural and mechanical properties of a transformation-induced plasticity-aided martensitic (TM) steel that is expected to serve as an advanced structural steel for automotive applications. The microstructure consisted of a wide lath-martensitestructured matrix and a mixture of narrow lath-martensite and metastable retained austenite of 2-5 vol% (MA-like phase). When 1%Cr and 1%Cr-0.2%Mo were added into 0.2%C-1.5%Si-1.5%Mn steel to enhance its hardenability, the resultant TM steels achieved a superior cold formability, toughness, fatigue strength, and delayed fracture strength as compared to conventional structural steel such as SCM420. These enhanced mechanical properties were found to be mainly caused by (1) plastic relaxation of the stress concentration, which resulted from expansion strain on the strain-induced transformation of the metastable retained austenite, and (2) the presence of a large quantity of a finely dispersed MA-like phase, which suppressed crack initiation or void formation and subsequent void coalescence.

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“…Recently, a high amount of retained austenite can be obtained in different bainitic alloys containing from 1.5 to 8 wt. % of Mn, which is a main austenite stabilizer [8][9][10][11][12][13][14]. These steels are dedicated to the automotive industry for different crash-relevant …”

Section: Introductionmentioning

confidence: 99%

Phase Equilibrium and Austenite Decomposition in Advanced High-Strength Medium-Mn Bainitic Steels

Grajcar

Zalecki

Burian

et al. 2016

Metals

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Abstract:The work addresses the phase equilibrium analysis and austenite decomposition of two Nb-microalloyed medium-Mn steels containing 3% and 5% Mn. The pseudobinary Fe-C diagrams of the steels were calculated using Thermo-Calc. Thermodynamic calculations of the volume fraction evolution of microstructural constituents vs. temperature were carried out. The study comprised the determination of the time-temperature-transformation (TTT) diagrams and continuous cooling transformation (CCT) diagrams of the investigated steels. The diagrams were used to determine continuous and isothermal cooling paths suitable for production of bainite-based steels. It was found that the various Mn content strongly influences the hardenability of the steels and hence the austenite decomposition during cooling. The knowledge of CCT diagrams and the analysis of experimental dilatometric curves enabled to produce bainite-austenite mixtures in the thermomechanical simulator. Light microscopy (LM), scanning electron microscopy (SEM), and transmission electron microscopy (TEM) were used to assess the effect of heat treatment on morphological details of produced multiphase microstructures.

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Impact Toughness of Medium‐Mn Transformation‐Induced Plasticity‐Aided Steels

Cited by 45 publications

References 21 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 a TRIP-Aided Martensitic Steel

Phase Equilibrium and Austenite Decomposition in Advanced High-Strength Medium-Mn Bainitic Steels

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