On the microstructural characteristics influencing the yielding behavior of ultra-fine grained medium-Mn steels

Steineder, Katharina; Križan, Daniel; Schneider, Reinhold; Béal, Coline; Sommitsch, Christof

doi:10.1016/j.actamat.2017.07.056

Cited by 135 publications

(91 citation statements)

References 38 publications

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“…The undesirable yield point phenomenon not is observed in our steel, which is consistent with the tensile behavior of other medium Mn steel with lath-like microstructure [21]. This is because the lath-like microstructure that is elongated in one direction can facilitate the dislocation accommodation and dislocation interactions, and therefore suppresses the yield point phenomenon [21]. The ultra-high yield strength of our steel can be ascribed to the high back-stress developed in present dual-phase heterogeneous structure.…”

Section: Resultssupporting

confidence: 92%

Strong and ductile medium Mn steel without transformation-induced plasticity effect

Huang

2018

Materials Research Letters

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The conventional alloy design of medium Mn steel is to optimize the transformation-induced plasticity (TRIP) effect. Here we show that a dual-phase heterogeneous structure is sufficient to develop a medium Mn steel with high yield strength ( ∼ 1.2 GPa) and large uniform elongation ( ∼ 14.5%). The ultra-high strength is contributed by high back-stress while the large ductility is induced by strain-gradient plasticity and back-stress hardening, both of which are inherent to dual-phase heterogeneous structure. TRIP effect is suppressed during plastic deformation. Therefore, medium Mn steel can be strong and ductile by engineering dual-phase heterogeneous structure without resorting to TRIP effect. IMPACT STATEMENTWe demonstrate that medium Mn steel can be strong and ductile by engineering dual-phase heterogeneous structure without resorting to the conventional transformation-induced plasticity (TRIP) effect. ARTICLE HISTORY

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Section: Resultssupporting

confidence: 92%

Strong and ductile medium Mn steel without transformation-induced plasticity effect

Huang

2018

Materials Research Letters

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“…Steineder et al 's investigation of processing routes on a Fe-6Mn-0.1C (wt pct) alloy revealed that grain morphology, size, and c-austenite stability of medium-Mn steels can influence the extent of yield point elongation. [18] It was noted by Steineder et al that the YPE was influenced by the volume fraction of a-ferrite. Specimens with the highest a-ferrite content, independent of grain morphology, exhibited the greatest yield point elongation and this is consistent with what was described in the previously presented works.…”

Section: A Static Strain Agingmentioning

confidence: 99%

“…[15,16] Baird and Jamieson showed that the addition of N will have a strong effect on the occurrence of static strain aging in ferritic steels. [17] Many of the medium manganese (5 to 10 wt pct) [2,3,[5][6][7][8][9][10][11][12]18] steels proposed for 3rd generation advanced high strength steel application exhibit YPE, and it is noted that the degree of YPE can range from 2 to 10 pct depending upon chemistry and processing prior to mechanical testing. Work by Suh et al [3] on three Fe-0.5Si-5Mn-2Al (wt pct) alloys with carbon contents (0.06 to 0.11 wt pct) exhibited varying degrees of YPE that was dependent upon heat treatment.…”

Section: A Static Strain Agingmentioning

confidence: 99%

Dynamic Strain Aging Phenomena and Tensile Response of Medium-Mn TRIP Steel

Field

Aken

2018

Metall Mater Trans A

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Dynamic strain aging (DSA) and rapid work hardening are typical behaviors observed in medium-Mn transformation-induced plasticity (TRIP) steel. Three alloys with manganese ranging from 10.2 to 13.8 wt pct with calculated room temperature stacking fault energies varying from À 2.1 to 0.7 mJ/m 2 were investigated. Significant serrations were observed in the stress-strain behavior for two of the steels and the addition of 4.6 wt pct chromium was effective in significantly reducing the occurrence of DSA. Addition of chromium to the alloy reduced DSA by precipitation of M 23 (C,N) 6 during batch annealing at 873 K (600°C) for 20 hours. Three distinct DSA mechanisms were identified: one related to manganese ordering in stacking faults associated with e-martensite and austenite interface, with activation energies for the onset and termination of DSA being 145 and 277 kJ/mol. A second mechanism was associated with carbon diffusion in c-austenite where Mn-C bonding added to the total binding energy, and activation energies of 88 and 155 kJ/mol were measured for the onset and termination of DSA. A third mechanism was attributed to dislocation pinning and unpinning by nitrogen in a-ferrite with activation energies of 64 and 123 kJ/mol being identified. Tensile behaviors of the three medium manganese steels were studied in both the hot band and batch annealed after cold working conditions. Ultimate tensile strengths ranged from 1310 to 1404 MPa with total elongation of 24.1 to 34.1 pct. X-ray diffraction (XRD) was used to determine the transformation response of the steels using interrupted tensile tests at room temperature. All three of the processed steels showed evidence of two-stage TRIP where c-austenite first transformed to e-martensite, and subsequently transformed to a-martensite.

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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%

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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On the microstructural characteristics influencing the yielding behavior of ultra-fine grained medium-Mn steels

Cited by 135 publications

References 38 publications

Strong and ductile medium Mn steel without transformation-induced plasticity effect

Strong and ductile medium Mn steel without transformation-induced plasticity effect

Dynamic Strain Aging Phenomena and Tensile Response of Medium-Mn TRIP Steel

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

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