Design of an Effective Heat Treatment Involving Intercritical Hardening for High Strength/High Elongation of 0.2C–3Al–(6–8.5)Mn–Fe TRIP Steels: Microstructural Evolution and Deformation Behavior

Mou, Yanjie; Li, Zhichao; Zhang, Xiaoteng; Misra, Devesh; Lin, He; Li, Huiping

doi:10.3390/met9121275

Cited by 7 publications

(3 citation statements)

References 38 publications

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“…The martensite in the microstructure was responsible for the low ductility [35]. Mou et al [36] found that lamellar austenite was more likely to cause stress relaxation during martensitic transformation, resulting in low plasticity.…”

Section: Discussionmentioning

confidence: 99%

Susceptibility of High-Manganese Steel to High-Temperature Cracking

2022

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Tests were carried out on two high-Mn steels: 27Mn-4Si-2Al-Nb with Nb microaddition and 24Mn-3Si-1.5Al-Nb-Ti with Nb and Ti microadditions. High-manganese austenitic steels, due to their good strength and plastic properties belong to the AHSS (Advanced High-Strength Steel) group and are used in the automotive industry. The main difficulties faced during the casting of the steel and hot working are hot cracks, which can appear in the surface of the ingot. Cracks on the edges of the sheet after hot rolling are the reason for cutting the edges of the sheet and increasing production costs and material losses. The main reason for the formation of hot cracks is the decrease in metal ductility in the high-temperature brittleness range (HTBR). The width of the HTBR depends on mechanical properties and microstructural factors, i.e., non-metallic inclusions or intermetallic phases at austenite grain boundaries. In this paper, a hot tensile test was performed. The research was performed on the GLEEBLE 3800 thermomechanical simulator. This test allows us to determine the width of the high-temperature brittleness range (HTBR), the Nil Strength Temperature (NST), the Nil Ductility Temperature (NDT), and the Ductility Recovery Temperature (DRT). Hot ductility was determined from the value of the reduction in area R(A). The obtained results make it possible to determine the temperature of the beginning of hot working from the tested high-Mn steels. Fractographic research enabled us to define mechanisms of hot cracking. It was found that hot cracks form as a result of disruptions in the liquid film on crystals’ boundaries.

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Section: Discussionmentioning

confidence: 99%

Susceptibility of High-Manganese Steel to High-Temperature Cracking

2022

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“…A number of studies were devoted toward understanding the factors that affect the stability of austenite, such as carbon content in austenite [27,28], austenite grain size [29,30], austenite morphology [30,31] and Schmidt factor [32,33], but studies on the degree of these factors are rare. From the above analysis, it can be seen that the hot-rolled steel A had an intense TRIP effect during deformation.…”

Section: Discussionmentioning

confidence: 99%

Tuning austenite stability in a medium Mn steel and relationship to structure and mechanical properties

Mou

et al. 2020

Materials Science and Technology

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We study here the underlying factors that govern the stability of austenite in a medium Mn (Fe–0.18C–11Mn–3.8Al) (wt-%) steel. In this regard, a novel heat treatment involving intercritical quenching and tempering was designed to obtain high total elongation (TEL) and high ultimate tensile strength (UTS) in the cold-rolled steel. And the UTS and TEL approached 920–1150 MPa and 35–65%, respectively. The product of TEL and UTS (PSE) exceeded 40 GPa%, with a maximum value of 60 GPa%. A detailed analysis of microstructure before and after tensile deformation revealed that the TRIP effect occurred and the stability of austenite was predominantly governed by the grain sizes of austenite rather than the orientation of austenite grains. The theoretical analysis of work hardening data suggested that the superior elongation of medium Mn TRIP steel is related to the high stability of austenite and the cooperative deformation of ferrite.

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“…Improvement of austenite stability increased the ultimate tensile strength and total elongation of TRIP steel [8]. Furthermore, Mou et al [9] found that lamellar austenite was more likely to cause stress relaxation during martensitic transformation, resulting in a discontinuous TRIP effect and thus higher ductility. Peng et al [10] carried out extension experiment at elevated temperature on Fe-22Mn-0.7C TWIP steel in the temperature range of 700-1250 • C and found that the reduction of area was extremely low, all below 40%.…”

Section: Introductionmentioning

confidence: 99%

Study on High-Temperature Mechanical Properties of Fe–Mn–C–Al TWIP/TRIP Steel

Yang

Zhuang

et al. 2021

Metals

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In this study, high-temperature tensile tests were carried out on a Gleeble-3500 thermal simulator under a strain rate of ε = 1 × 10−3 s−1 in the temperature range of 600–1310 °C. The hot deformation process of Fe–15.3Mn–0.58C–2.3Al TWIP/TRIP at different temperatures was studied. In the whole tested temperature range, the reduction of area ranged from 47.3 to 89.4% and reached the maximum value of 89.4% at 1275 °C. Assuming that 60% reduction of area is relative ductility trough, the high-temperature ductility trough was from 1275 °C to the melting point temperature, the medium-temperature ductility trough was 1000–1250 °C, and the low-temperature ductility trough was around 600 °C. The phase transformation process of the steel was analyzed by Thermo-Calc thermodynamics software. It was found that ferrite transformation occurred at 646 °C, and the austenite was softened by a small amount of ferrite, resulting in the reduction of thermoplastic and formation of the low-temperature ductility trough. However, the small difference in thermoplasticity in the low-temperature ductility trough was attributed to the small amount of ferrite and the low transformation temperature of ferrite. The tensile fracture at different temperatures was characterized by means of optical microscopy and scanning electron microscopy. It was found that there were Al2O3, AlN, MnO, and MnS(Se) impurities in the fracture. The abnormal points of thermoplasticity showed that the inclusions had a significant effect on the high-temperature mechanical properties. The results of EBSD local orientation difference analysis showed that the temperature range with good plasticity was around 1275 °C. Under large deformation extent, the phase difference in the internal position of the grain was larger than that in the grain boundary. The defect density in the grain was large, and the high dislocation density was the main deformation mechanism in the high-temperature tensile process.

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Design of an Effective Heat Treatment Involving Intercritical Hardening for High Strength/High Elongation of 0.2C–3Al–(6–8.5)Mn–Fe TRIP Steels: Microstructural Evolution and Deformation Behavior

Cited by 7 publications

References 38 publications

Susceptibility of High-Manganese Steel to High-Temperature Cracking

Susceptibility of High-Manganese Steel to High-Temperature Cracking

Tuning austenite stability in a medium Mn steel and relationship to structure and mechanical properties

Study on High-Temperature Mechanical Properties of Fe–Mn–C–Al TWIP/TRIP Steel

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