Microstructure–property relationships in TRIP aided medium-C bainitic steel with lamellar retained austenite

Grajcar, A.; Kwaśny, W.; Zalecki, W.

doi:10.1179/1743284714y.0000000742

Cited by 32 publications

(36 citation statements)

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“…3% and 5%, respectively. In order to prevent carbide precipitation, the concept with a higher aluminum content (~1.5%) and Mo addition was applied [29]. Mo was added for solid solution strengthening and to enhance producing bainite-like microstructures [31][32][33].…”

Section: Chemical Compositionmentioning

confidence: 99%

“…Mo can be also added to increase strength by its strong solid solution effect. Moreover, this element affects significantly the austenite decomposition upon cooling and is known as the one, which improves toughness [29,30].Taking into account the increasing interest in medium manganese steels with retained austenite related to their potential application in the automotive industry, the present work focuses on the microstructure-property relationships in thermomechanically processed medium-Mn steels with a high Al content.…”

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confidence: 99%

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confidence: 99%

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Microstructure–Property Relationships in Thermomechanically Processed Medium-Mn Steels with High Al Content

Grajcar

Kilarski²,

Kozłowska

2018

Metals

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Detailed studies on microstructure-property relationships of thermomechanically processed medium-Mn steels with various manganese contents were carried out. Microscopic techniques of different resolution (LM, SEM, TEM) and X-Ray diffraction methods were applied. Static tensile tests were performed to characterize mechanical properties of the investigated steels and to determine the tendency of retained austenite to strain-induced martensitic transformation. Obtained results allowed to characterize the microstructural aspects of strain-induced martensitic transformation and its effect on the mechanical properties. It was found that the mechanical stability of retained austenite depends significantly on the manganese content. An increase in manganese content from 3.3% to 4.7% has a significant impact on the microstructure, stability of γ phase and mechanical properties of the investigated steels. The initial amount of retained austenite was higher for the 3Mn-1.5Al steel in comparison to 5Mn-1.5%Al steel-17% and 11%, respectively. The mechanical stability of retained austenite is significantly affected by the morphology of this phase. case, the phase transformation kinetics depends significantly on the austenite deformation degree [5,8,9]. In case of the first generation AHSSs, the main advantage of the TMP is the ability to refine the ferrite grain size by controlling the austenite pancaking [10,11]. Moreover, the thermomechanical treatment can increase the amount of retained austenite to obtain the optimal TRIP (TRansformation Induced Plasticity) effect [12,13]. In case of medium manganese steels (third generation AHSS), the TMP is also a good alternative for the cold-rolling process [14][15][16]. However, most publications on medium-Mn steels concern the cold-rolling process and subsequent inter-critical heat treatment.Cold-rolled medium-Mn TRIP steels are susceptible to plastic instabilities associated with dynamic strain aging (DSA) and serrated flow (PLC-Portevin-Le Chatelier) effects due to the heat treatment required after cold-rolling. From a technological point of view, the PLC and DSA effects must be avoided. The DSA phenomenon gives rise to non-homogeneous plastic flow during the sheet-forming processes and may lead to surface defects on formed parts [17][18][19]. Our previous reports on thermomechanically processed medium-Mn sheet steels indicate that the problem can be avoided [7].Newly developed fine-grained ferrite-austenite or bainitie-austenite steels contain manganese in a range of 3-12%, while carbon content is ca. 0.1-0.2%. These steels contain also aluminum and silicon (1-3%) additions which delay the carbides formation during the bainitic transformation. The increased Mn amount leads to obtain the high fraction of retained austenite (~10-30%). The Mn addition also increases the carbon solubility and lowers the cementite precipitation temperature [20][21][22]. Al is added to partially replace silicon due to the problems related to galvanizing, hot-rolling and welding [23][24][25]. However, Gir...

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Section: Chemical Compositionmentioning

confidence: 99%

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confidence: 99%

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Microstructure–Property Relationships in Thermomechanically Processed Medium-Mn Steels with High Al Content

Grajcar

Kilarski²,

Kozłowska

2018

Metals

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“…These resulted in a decrease in precipitation strengthening. The kinetic analysis of precipitation during TMCP were completed in a low-carbon microalloyed steel, and there was a bay (local maximum) in the precipitation-time-temperature (PTT) diagram [28][29][30]. It was considered in the present study that precipitation occurred after 600 s at temperatures between 600 • C and 800 • C. Isothermal holding temperature influences the extent of precipitation.…”

Section: The Precipitation Behaviormentioning

confidence: 97%

The Impact of Isothermal Treatment on the Microstructural Evolution and the Precipitation Behavior in High Strength Linepipe Steel

Tian

Wang

et al. 2020

Materials

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Isothermal treatment affects the microstructural evolution and the precipitation behavior of high-strength low alloy (HSLA) steels. In this regard, thermal simulation of different isothermal treatment temperatures was adopted by using a thermomechanical simulator. The results showed that hardness reached the maximum value at 600 °C holding temperature, which was related to a finer grain structure and granular bainite. The strengthening effect of precipitates was remarkable due to the combination of small particle size and small interparticle spacing. It is presumed that the precipitation started after 600 s at 600 °C. Precipitation strengthening continued to exist, even though coarsening of ferrite grains led to softening phenomena when the specimen was isothermally held at 750 °C, which led to relatively high hardness. The precipitates were fcc (Ti, Nb) (N, C) particles, and belonged to MX-type precipitates. Average size of precipitates increased from 3.14 to 4.83 nm when the specimens were isothermally held between 600 °C and 800 °C. Interparticle spacing of precipitates also increased with increasing isothermal treatment temperatures. These led to a reduction in precipitation strengthening. At the same time the polygonal ferrite content increased and ferrite grain size got larger, such that the hardness decreased continuously.

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“…Although perhaps the main feature of multiphase TRIP steels is the austenite transformation into martensite by strain, their overall response is strongly influenced by the intrinsic features of each constituent, especially ferrite and bainite, due to these phases being present in high proportion. Grajcar et al [18], for example, obtained noticeable differences in mechanical properties for a medium carbon TRIP aided steel with Nb and Ti microaddition. These differences were mainly attributed to two factors: (i) the nature of the bainitic-ferritic matrix and (ii) differences in austenite stability due to grain size and shape distribution.…”

Section: Introductionmentioning

confidence: 99%

Microstructure-Based Constitutive Modelling of Low-Alloy Multiphase TRIP Steels

Salinas‐Rodríguez

Celentano

Carvajal

et al. 2019

Metals

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The microstructure of low-alloy multiphase transformation-induced plasticity (TRIP) steels consists of ferrite, bainite, and metastable retained austenite, which can be transformed into martensite by plastic deformation. In some cases, residual martensite can be present in the initial microstructure. The mechanical behavior of these steels depends on the interaction between the intrinsic characteristics of the existing phases and the austenite stability. Due to these factors, the definition of their true stress-strain flow law is complex. This work presents the mechanical characterization of a phenomenological constitutive stress-strain flow law based on the Bouquerel et al. model, as evaluated for three TRIP steels of the same composition but undergoing different heat treatments. Morphological aspects of the existing phases, austenite stability, and suitable mixture laws between phases are considered. The model is found to accurately reproduce a true stress-strain flow law obtained under tensile uniaxial conditions and provide detailed information on the effective stress strain partition between the existing phases.

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Microstructure–property relationships in TRIP aided medium-C bainitic steel with lamellar retained austenite

Cited by 32 publications

References 45 publications

Microstructure–Property Relationships in Thermomechanically Processed Medium-Mn Steels with High Al Content

Microstructure–Property Relationships in Thermomechanically Processed Medium-Mn Steels with High Al Content

The Impact of Isothermal Treatment on the Microstructural Evolution and the Precipitation Behavior in High Strength Linepipe Steel

Microstructure-Based Constitutive Modelling of Low-Alloy Multiphase TRIP Steels

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