The relative contributions of TWIP and TRIP to strength in fine grained medium-Mn steels

Kwok, Thomas; Gong, Peng; Rose, Rory; Dye, David

doi:10.1016/j.msea.2022.143864

Cited by 22 publications

(14 citation statements)

References 63 publications

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“…Since transformation is unavoidable, the volume fraction of austenite available to twin decreases with increasing strain. Furthermore, Lee et al [28] and Kwok et al [127] also found that due to the fine-grained nature of medium Mn steel microstructures, the capacity for strain hardening by further grain refinement through the dynamic Hall-Petch effect was very limited. When the austenite grain size in medium Mn steels enters the submicron regime, especially in lamellar type microstructures [127], twinning was found to have nearly no effect on strain hardenability.…”

Section: Twip and Stacking Fault Energymentioning

confidence: 99%

“…Furthermore, Lee et al [28] and Kwok et al [127] also found that due to the fine-grained nature of medium Mn steel microstructures, the capacity for strain hardening by further grain refinement through the dynamic Hall-Petch effect was very limited. When the austenite grain size in medium Mn steels enters the submicron regime, especially in lamellar type microstructures [127], twinning was found to have nearly no effect on strain hardenability. Overall, the TWIP effect does not appear to play a significant role in the strain hardening of medium Mn steels.…”

Section: Twip and Stacking Fault Energymentioning

confidence: 99%

“…In medium Mn steels, the TWIP effect was more commonly observed in steels with equiaxed microstructures [28,45,122] as compared to those with lamellar microstructures. In the few studies where twinning was observed in lamellar grains, twins were observed to propagate across the short axis of the lamella rather the long axis [44,127]. This suggests that the mean slip length in lamellar grains is much shorter in lamellar grains compared to equiaxed grains.…”

Section: Twip and Trip Effectsmentioning

confidence: 99%

“…In many instances, medium Mn steels contain both equiaxed and lamellar morphologies, that is, mixed, such as in microstructure G1 in Figure 16 and in Figures 17(a-b) [33,38,43,127]. One possible concern regarding mixed microstructures is that the steel deforms heterogeneously due to the difference in strength between lamellar and equiaxed grains.…”

Section: Mixed Microstructuresmentioning

confidence: 99%

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A review of the processing, microstructure and property relationships in medium Mn steels

Kwok

Dye

2023

International Materials Reviews

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Medium Mn steels are an emerging class of 3rd generation advanced high-strength steels. These steels have received significant attention due to their high strengths, large ductilities and also lower cost compared to their predecessor high Mn Twinning Induced Plasticity (TWIP) steels. Additionally, medium Mn steels have been found to exhibit TWIP and/or Transformation Induced Plasticity (TRIP) effects which can be harnessed to give a high strain hardening rate. Many thermomechanical processing concepts in the literature have been developed, producing multiple microstructure types with differentmechanical properties. The present review therefore aims to summarise the current knowledge of medium Mn steel alloy design especially on the processing, microstructure and property relationships in medium Mn steels. It complements the review of Sun et al. [Physical metallurgy of medium-Mn advanced high-strength steels, Int Mater Rev. 2023.], written independently and in parallel, which focusses more on the phase interfaces and thermodynamics.

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Section: Twip and Stacking Fault Energymentioning

confidence: 99%

Section: Twip and Stacking Fault Energymentioning

confidence: 99%

Section: Twip and Trip Effectsmentioning

confidence: 99%

Section: Mixed Microstructuresmentioning

confidence: 99%

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A review of the processing, microstructure and property relationships in medium Mn steels

Kwok

Dye

2023

International Materials Reviews

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“…Medium Mn steel is one group belonging to the third generation of advanced high strength steels (AHSS) that have received much attention in the last years [1,2]. The motivation for the intensive research regarding these steels is that they exhibit a very interesting combination of mechanical properties that are required to fulfill the actual necessities in the automotive industry regarding weight reduction and safety aspects.…”

Section: Introductionmentioning

confidence: 99%

Effect of the intercritical annealing in the formability and microstructure of a medium Mn steel sheet

Hernández-Rivera

González-Castillo

Azpeitia

et al. 2023

IOP Conf. Ser.: Mater. Sci. Eng.

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A medium Mn steel (MMS) was cast by employing a vacuum induction furnace. After that, the steel was hot rolled (HR) in order to achieve a final thickness of 1.4 mm. The microstructure of the sheet was found to be composed of martensite and a little amount of austenite, the Ultimate Tensile Strength (UTS in this processing condition was close to 1600 MPa and a negligible elongation was found. An intercritical annealing (IA) heat treatment was applied to the steel to promote the austenite reversion and increase its amount and stability. Previous thermodynamic simulations and experimental results were used to determine the temperature and time parameters of the IA. After the steel was subjected to this heat treatment, it exhibited an elongation close to 35% and an UTS close to 1100 MPa. Bendability testing was carried out in that condition in order to correlate it with the microstructural changes in the sheet. It was found that the critical bending angle was higher in the IA condition in comparison with the HR state.

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Carbon in Solution and the Charpy Impact Performance of Medium Mn Steels

Kwok

Worsnop

Douglas

et al. 2023

Metall Mater Trans A

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Carbon is a well known austenite stabiliser and can be used to alter the stacking fault energy and stability against martensitic transformation in medium Mn steels, producing a range of deformation mechanisms such as the Transformation Induced Plasticity (TRIP) or combined Twinning and Transformation Induced Plasticity (TWIP + TRIP) effects. However, the effect of C beyond quasi-static tensile behaviour is less well known. Therefore, two medium Mn steels with 0.2 and 0.5 wt pct C were designed to produce similar austenite fractions and stability and therefore tensile behaviour. These were processed to form lamellar and mixed equiaxed + lamellar microstructures. The low C steel had a corrected Charpy impact energy (KV$$_{10}$$ 10 ) of 320 J cm$$^{-2}$$ - 2 compared to 66 J cm$$^{-2}$$ - 2 in the high C steel despite both having a ductility of over 35 pct. Interface segregation, e.g., of tramp elements, was investigated as a potential cause and none was found. Only a small amount of Mn rejection from partitioning was observed at the interface. The fracture surfaces were investigated and the TRIP effect was found to occur more readily in the Low C Charpy specimen. Therefore it is concluded that the use of C to promote TWIP + TRIP behaviour should be avoided in alloy design but the Charpy impact performance can be understood purely in terms of C in solution.

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The relative contributions of TWIP and TRIP to strength in fine grained medium-Mn steels

Cited by 22 publications

References 63 publications

A review of the processing, microstructure and property relationships in medium Mn steels

A review of the processing, microstructure and property relationships in medium Mn steels

Effect of the intercritical annealing in the formability and microstructure of a medium Mn steel sheet

Carbon in Solution and the Charpy Impact Performance of Medium Mn Steels

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