Microstructure based prediction of strain hardening behavior of dual phase steels

Sodjit, Sawitree; Uthaisangsuk, Vitoon

doi:10.1016/j.matdes.2012.05.010

Cited by 206 publications

(81 citation statements)

References 30 publications

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“…It was found that higher amounts of the martensite phase caused finer ferrite grains. 16) In case of the 80% coldrolled samples, dF was smaller and the variation of dF with intercritical holding time was different to that of 50% rolling reduction. After 80% cold-rolling and intercritical annealing for 6, 8, 10 and 12 min, the resulted DP microstructures showed the dF of about 2.86, 2.25, 2.40 and 2.78 μm, respectively.…”

Section: Microstructuresmentioning

confidence: 83%

“…The DP structure became finer with increasing rolling reduction, because of the heavier prior deformation. The dF of the samples decreased by increasing intercritical holding time from 6 to 8 min due to the increase in the VM, 16) and then increased with further annealing time. However, the differences are rather small.…”

Section: Microstructuresmentioning

confidence: 97%

“…16,24) This is a feature in twophase materials which results from the strain gradient between the constituent phases with different deformation behaviours. The geometrically necessary dislocations (GNDs) are required to accommodate this strain gradient and to allow compatible deformation of constituent phases.…”

Section: )mentioning

confidence: 99%

“…As shown in Fig. 12, graphs of UTS and UTS × UE vs. UE has been plotted to compare the DP steels developed in this study with the DP steels from literature 6,10,12,16,18,33) and commercial modern high strength automobile steel, DP980.…”

Section: )mentioning

confidence: 99%

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Strengthening Mechanisms of Ultrafine Grained Dual Phase Steels Developed by New Thermomechanical Processing

2015

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Dual phase (DP) steels have been investigated using a new approach utilizing simple cold-rolling and subsequent intercritical annealing of a martensite-ferrite duplex starting structure. The ferrite grain size and volume fraction of martensite were varied by changing the rolling reduction and intercritical annealing time. Ultrafine grained DP (UFG-DP) steel with an average grain size of about 2 μm was achieved by short intercritical annealing of the 80% cold-rolled duplex microstructure. Tensile testing revealed superior mechanical properties (the ultimate tensile strength of 1 100 MPa and elongation of 13%) for the new DP steel in comparison with the commercially used high strength DP980 steel. The variations in hardness, strength and elongation of the specimens with rolling reduction and intercritical holding time were correlated to microstructural characterizations. The inherent mechanism for strengthening of the DP steel was discussed and the contribution of each strengthening factor was quantitatively calculated. The results showed that the calculated yield strength (430.6 MPa) is very close to the measured value (422 MPa).

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Section: Microstructuresmentioning

confidence: 83%

Section: Microstructuresmentioning

confidence: 97%

Section: )mentioning

confidence: 99%

Section: )mentioning

confidence: 99%

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Strengthening Mechanisms of Ultrafine Grained Dual Phase Steels Developed by New Thermomechanical Processing

2015

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“…Os autores apontam que a martensita afeta a ferrita devido às discordâncias introduzidas nessa estrutura vizinha às ilhas de martensita, como resultado de deformações plásticas associadas à expansão volumétrica da transformação martensítica [13,14]. As discordâncias são requeridas para acomodar este gradiente e para permitir a deformação compatível nas duas fases [15,16]. Considerando os efeitos da direção de laminação prévia aos tratamentos térmicos no comportamento do material, verifica-se que, em geral, apesar de uma pequena superioridade nos valores referentes ao estudo na direção transversal, não foram evidenciadas diferenças significativas entre as direções estudadas.…”

Section: Resultsunclassified

Influência Da Temperatura Intercrítica Na Microestrutura E Nas Propriedades Mecânicas De Um Aço Bifásico

Magalhães¹,

Martins²,

Pinto³

et al. 2018

ABM Proceedings

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6Elaine Carballo Siqueira Corrêa 7 Resumo Nas últimas décadas a crescente demanda por carros mais seguros, econômicos e menos poluentes exigiram das montadoras, siderúrgicas e comunidade científica investimentos na pesquisa e no desenvolvimento de novos materiais, tais como os aços avançados de alta resistência. Dentro deste contexto, neste trabalho foi realizada a análise da microestrutura e das propriedades mecânicas de um aço bifásico na condição inicial e submetido a tratamentos térmicos com aquecimento na região intercrítica e resfriamento brusco. Foram analisadas a proporção dos constituintes na microestrutura e as propriedades mecânicas por meio de microscopia óptica e eletrônica de varredura, de difração de raios X, dureza e de tração. Observou-se, em geral, que o aumento da temperatura intercrítica levou a uma elevação da fração de martensita e, consequentemente, influenciou de forma a aumentar os valores de dureza, resistência mecânica e diminuir a ductilidade. Palavras-chave: Aço bifásico; Tratamento intercrítico; Microestrutura; Propriedades. INFLUENCE OF INTERCRITICAL TEMPERATURE IN THE MICROSTRUCTURE AND THE MECHANICAL PROPERTIES OF A DUAL PHASE STEEL AbstractIn recent decades the increasing demand for safer, economical and less polluting cars demanded of automakers, steelmakers and scientific community investments in research and development of new steels, such as advanced high strength steels. The aim of this work was the analysis of the microstructure and the mechanical behavior of a dual phase steel, in the initial condition and subjected to thermal processing with intercritical heating and quenching. The ferrite-martensite fraction in the material was evaluated by optical and scanning electron microscopy techniques and its influence in the mechanical properties was analyzed through hardness and tensile tests. It was observed that the increase of the intercritical temperature raised the fraction of martensite and thus led to an increase in hardness, yield strength and ultimate tensile strength and to a decrease in the elongation.

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Influences of Microstructure Characteristics on Forming Limit Behavior of Dual Phase Steels

Sirinakorn

Sodjit

Uthaisangsuk

2015

steel research int.

Self Cite

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In the automotive sector, dual phase (DP) steel grades have been increasingly used for various car body parts due to their good combination of strength and formability. To control mechanical and fracture characteristics of the DP steels, effects of martensitic phase fraction, morphology, and phase distribution must be understood. In this work, DP steel sheets with different martensitic phase fractions and ferritic grain sizes were produced through the intercritical annealing process. Likewise, FE simulations of 2D representative volume elements (RVEs) based on real micrograph were performed for all generated DP microstructures. Flow behaviors of single individual phases in the DP steels were described by a dislocation theory and local chemical compositions. Calculated stress–strain responses were verified with experimental results from tensile tests. Subsequently, stretch‐forming tests under different states of stress using the Nakajima samples were carried out for the examined DP steels. Micromechanics RVE models were then applied to predict failure occurrences in the DP microstructures by considering plastic strain instability. Influences of morphologies and properties of constituent phases on localization due to incompatible deformation between martensite and ferrite were discussed with regard to governing stress states.

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Microstructure based prediction of strain hardening behavior of dual phase steels

Cited by 206 publications

References 30 publications

Strengthening Mechanisms of Ultrafine Grained Dual Phase Steels Developed by New Thermomechanical Processing

Strengthening Mechanisms of Ultrafine Grained Dual Phase Steels Developed by New Thermomechanical Processing

Influência Da Temperatura Intercrítica Na Microestrutura E Nas Propriedades Mecânicas De Um Aço Bifásico

Influences of Microstructure Characteristics on Forming Limit Behavior of Dual Phase Steels

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