A study of microstructure, transformation mechanisms and correlation between microstructure and mechanical properties of a low alloyed TRIP steel

Zaefferer, Stefan; Ohlert, J.; Bleck, Wolfgang

doi:10.1016/j.actamat.2004.02.044

Cited by 425 publications

(270 citation statements)

References 31 publications

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“…Isto era esperado, pois nestas condições supõe-se que a taxa de resfriamento foi menor, ou seja, o material ficou exposto por maior tempo à faixa de temperaturas de formação da bainita. Estes resultados estão de acordo com os encontrados por Zaefferer et al [40] e Jacques [41], onde maiores frações de bainita eram formadas em aços TRIP 800 com o aumento do tempo ou temperatura durante tratamento isotérmico.…”

Section: Resultsunclassified

Avaliação microestrutural e propriedades mecânicas de um aço TRIP soldado a ponto por fricção e mistura mecânica

et al. 2009

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Section: Resultsunclassified

Avaliação microestrutural e propriedades mecânicas de um aço TRIP soldado a ponto por fricção e mistura mecânica

et al. 2009

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“…However, the most important is the mechanical stability of retained austenite, dependent on its carbon content, size, dislocation density, morphology (blocky, interlath), etc. [3][4][5]10 An efficient monitoring of the evolution of retained austenite and strain-induced martensite as a function of strain is crucial for understanding microstructure-property relationships. This approach can be used with typical TRIP-aided ferrite-based steels.…”

Section: Introductionmentioning

confidence: 99%

“…This approach can be used with typical TRIP-aided ferrite-based steels. [1][2][3]16 The aim of the present study is to monitor the evolution of the microstructure of TRIP-aided medium-C bainitic steel.…”

Section: Introductionmentioning

confidence: 99%

“…Dual-phase (DP), complex-phase (CP) and transformation-induced plasticity (TRIP) steels are representatives of the AHSSs containing ferrite as the main structural constituent. [1][2][3] The strain-induced martensitic transformation of retained austenite during cold forming, resulting in additional plasticity, stimulated increased research activities to assess the microstructure-property relationships in TRIP-aided steels. [2][3][4] The demand for ultra-high-strength steels can be satisfied when a soft ferritic matrix is replaced by harder bainite.…”

Section: Introductionmentioning

confidence: 99%

“…[1][2][3] The strain-induced martensitic transformation of retained austenite during cold forming, resulting in additional plasticity, stimulated increased research activities to assess the microstructure-property relationships in TRIP-aided steels. [2][3][4] The demand for ultra-high-strength steels can be satisfied when a soft ferritic matrix is replaced by harder bainite. Hence, a growing importance of the AHSSs containing increased bainite amounts can be observed in [4][5][6][7][8][9] .…”

Section: Introductionmentioning

confidence: 99%

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Microstructure evolution of advanced high-strength TRIP-aided bainitic steel

Grajcar¹

2015

Mater. Tehnol.

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The present work is focused on monitoring the microstructure evolution of the thermomechanically rolled medium-C steel containing Si and Al to prevent the precipitation of carbides. The initial microstructure consists of carbide-free bainite, polygonal ferrite and blocky-type and interlath retained austenite. To monitor the transformation behaviour of the retained austenite transforming into strain-induced martensite, tensile tests were interrupted at particular strains (5 %, 10 %, 15 %, 18.4 %). The amount of the retained austenite determined with XRD and EBSD techniques decreased from 17 % to 6.8 % upon straining, which was related to the transformation-induced plasticity effect. The identification of the retained austenite and strain-induced martensite was carried out using an electron scanning microscope equipped with EBSD (electron backscatter diffraction). It was found that sheet samples are strongly strengthened by the transformation of the blocky retained austenite, whereas the layers and films of the g phase are over-stabilized and they do not transform into martensite. Keywords: AHSS, bainitic steel, retained austenite, thermomechanical treatment, TRIP effect, strain-induced martensite Delo obravnava pregled razvoja mikrostrukture pri termomehanskem valjanju srednje oglji~nega jekla s Si in Al, ki prepre~ita izlo~anje karbidov. Za~etna mikrostruktura je bila iz bainita brez karbidov, poligonalnega ferita ter zaostalega avstenita kockaste oblike in zaostalega avstenita med lamelami. Za spremljanje vedenja zaostalega avstenita pri pretvorbi v deformacijsko induciran martenzit so bili natezni preizkusi prekinjeni pri posameznih raztezkih (5 %, 10 %, 15 %, 18,4 %). Dele`zaostalega avstenita, dolo~en z XRD in EBSD, se je zmanj{al po natezni deformaciji iz 17 % na 6,8 %, kar je posledica vpliva z deformacijo povzro~ene pretvorbe na plasti~nost. Identifikacija zaostalega avstenita in napetostno induciranega martenzita je bila izvr{ena z vrsti~nim elektronskim mikroskopom, opremljenim z EBSD (difrakcija odbitih elektronov). Ugotovljeno je, da se vzorci plo~evine bolj utrjujejo s pretvorbo kockastega zaostalega avstenita, medtem ko so plasti in sloji g-faze bolj stabilizirani in se ne pretvorijo v martenzit.

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Designing Ultrahigh Strength Steels with Good Ductility by Combining Transformation Induced Plasticity and Martensite Aging

et al. 2009

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Steels with a high ultimate tensile strength (UTS) above 1 GPa and good ductility [total elongation (TE) of 15-20% in a tensile test] are of paramount relevance for lightweight engineering design strategies and corresponding CO 2 savings, Figure 1. [1,2] In this work, we report about a novel design approach for precipitation hardened ductile high strength martensitic and austenitic-martensitic steels (up to 1.5 GPa strength). The alloys are characterized by a low carbon content (0.01 wt% C), 9-15 wt% Mn to obtain different levels of austenite stability, and minor additions of Ni, Ti, and Mo (1-2 wt%). The latter are required for creating precipitates during aging heat treatment.Hardening in these materials is realized by combining the TRIP effect with a maraging treatment [transformationinduced plasticity (TRIP); maraging: martensite aging through thermally stimulated precipitation of particles]. The TRIP mechanism is based on the deformation-stimulated athermal transformation of metastable austenite (face centered cubic Fe-Mn phase) into martensite (metastable body centered cubic or orthorhombic Fe-Mn phase) and the resulting matrix and martensite plasticity required to accommodate the transformation misfit. [3][4][5][6][7][8][9][10][11] The maraging treatment is based on hardening the heavily strained martensite through the formation of small intermetallic precipitates (of the order of several nanometers). These particles act as highly efficient obstacles against dislocation motion through the Orowan and Fine-Kelly mechanisms enhancing the strength of the material. [12][13][14][15][16][17] While both types of alloys, i.e., TRIP steels [3][4][5][6][7][8][9][10][11] and maraging steels [12][13][14][15][16][17] have been well investigated, the combination of the two mechanisms in the form of a set of simple Fe-Mn alloys as suggested in this work, namely, the precipitation hardening of transformation-induced martensite by intermetallic nanoparticles, opens a novel and lean alloy path to the development of ultrahigh strength steels that has not been much explored in the past. [18,19] We refer to these alloys as maraging TRIP steels.Related steel design trends that are based on small-scaled second phase precipitates are also pursued by using oxide, [20][21][22][23] nitride, [24,25] or Cu nanosized particles. [26] Other pathways to the design of ultrahigh strength steels have been realized in ultra fine grained materials obtained by advanced thermomechanical processing [27][28][29][30][31][32][33][34] or by accumulative roll bonding. [35] The joint maraging TRIP approach justifies a more detailed study since it opens up a new approach to increase the UTS of conventional steels at relatively lean alloying costs, i.e., without large quantities of expensive alloying elements, owing to the small volume fraction of precipitates required in maraging steels. [12][13][14][15][16][17] The negative side of such strategies lies often in the fact that an increase in tensile strength is typically accompanied by a corresponding dro...

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A study of microstructure, transformation mechanisms and correlation between microstructure and mechanical properties of a low alloyed TRIP steel

Cited by 425 publications

References 31 publications

Avaliação microestrutural e propriedades mecânicas de um aço TRIP soldado a ponto por fricção e mistura mecânica

Avaliação microestrutural e propriedades mecânicas de um aço TRIP soldado a ponto por fricção e mistura mecânica

Microstructure evolution of advanced high-strength TRIP-aided bainitic steel

Designing Ultrahigh Strength Steels with Good Ductility by Combining Transformation Induced Plasticity and Martensite Aging

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