A novel route for development of ultrahigh strength dual phase steels

Mazaheri, Yousef; Kermanpur, A.; Najafizadeh, A.

doi:10.1016/j.msea.2014.09.058

Cited by 91 publications

(32 citation statements)

References 46 publications

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“…This also was observed in Ref [9]. Furthermore, with decrease in the fraction of martensite regions the overall strength of the material is reduced according to the low of mixtures [28].…”

Section: Discussion 41 the Effect Of Ferrite Fraction On Mechanical supporting

confidence: 73%

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Microstructures and mechanical properties of dual phase steel produced by laboratory simulated strip casting

et al. 2015

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Conventional dual phase (DP) steel (0.08C-0.81Si-1.47Mn-0.03Al wt.%) was manufactured using simulated strip casting schedule in laboratory. The average grain size of prior austenite was 117. ±. 44. μm. The continuous cooling transformation diagram was obtained. The microstructures having polygonal ferrite in the range of 40-90%, martensite with small amount of bainite and Widmanstätten ferrite were observed, leading to an ultimate tensile strength in the range of 461-623. MPa and a corresponding total elongation in the range of 0.31-0.10. All samples exhibited three strain hardening stages. The predominant fracture mode of the studied steel was ductile, with the presence of some isolated cleavage facets, the number of which increased with an increase in martensite fraction. Compared to those of hot rolled DP steels, yield strength and ultimate tensile strength are lower due to large ferrite grain size, coarse martensite area and Widmanstätten ferrite. Abstract: Conventional dual phase (DP) steel (0.08C-0.81Si-1.47Mn-0.03Al wt. %) was manufactured using simulated strip casting schedule in laboratory. The average grain size of prior austenite was 117±44 μm. The continuous cooling transformation diagram was obtained. The microstructures having polygonal ferrite in the range of 40-90 %, martensite with small amount of bainite and Widmanstätten ferrite were observed, leading to an ultimate tensile strength in the range of 461 -623 MPa and a corresponding total elongation in the range of 0.31 -0.10. All samples exhibited three strain hardening stages. The predominant fracture mode of the studied steel was ductile, with the presence of some isolated cleavage facets, the number of which increased with an increase in martensite fraction. Compared to those of hot rolled DP steels, yield strength and ultimate tensile strength are lower due to large ferrite grain size, coarse martensite area and Widmanstätten ferrite. Disciplines Engineering | Science and Technology Studies

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“…This also was observed in Ref [9]. Furthermore, with decrease in the fraction of martensite regions the overall strength of the material is reduced according to the low of mixtures [28].…”

Section: Discussion 41 the Effect Of Ferrite Fraction On Mechanical supporting

confidence: 73%

“…Besides, in some voids the MnS inclusions were observed for all heat treatment conditions (Fig. 16), which could be a site for void formation [6,28].…”

Section: Fractographymentioning

confidence: 93%

Microstructures and mechanical properties of dual phase steel produced by laboratory simulated strip casting

et al. 2015

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“…Uma primeira abordagem envolveu a linearização da curva tensão -deformação reais, considerando o intervalo entre o início da deformação plástica e a carga máxima no ensaio de tração [14]. Nesse caso, o valor de n foi dado pelo coeficiente angular da reta log σ versus log  Ressalta-se que os aços bifásicos possuem uma particularidade, inerente aos aços avançados de alta resistência, que é a possibilidade de observação de mais de uma inclinação na reta representativa da curva log tensão versus log deformação [7,9,16]. Assim, neste trabalho, além da regressão linear considerando um estágio, foi realizada a análise considerando dois estágios de encruamento.…”

Section: Materiais E Métodosunclassified

“…A elevada capacidade de encruamento associada aos aços bifásicos influencia a habilidade desses materiais de exibirem deformação uniforme, ou seja, materiais com alta taxa de encruamento podem ser deformados até magnitude superiores antes de atingir a instabilidade plástica, dando início à estricção. Dessa forma, para processos de fabricação que envolvam deformação plástica, ligas metálicas com esse comportamento são mais atrativas [7,8,9]. Essa alta taxa de encruamento nos aços bifásicos é atribuída basicamente a três fatores: 1) alívio das tensões residuais decorrentes do resfriamento durante a deformação plástica; 2) aumento da densidade de discordâncias na ferrita e 3) incompatibilidade plástica entre a ferrita e a martensita, levando ao desenvolvimento de tensões residuais na primeira [10,11].…”

Section: Introductionunclassified

Efeito Da Temperatura Intercrítica No Expoente De Encruamento De Aços Bifásicos

Magalhães¹,

Martins²,

Aguilar³

et al. 2017

Anais Do Congresso Anual Da ABM

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ResumoAs elevadas taxas de encruamento nos estágios iniciais de deformação plástica observadas para os aços bifásicos constituem uma das principais características que os habilita para aplicação em componentes estruturais na indústria de automóveis. Neste trabalho foi analisada influência de tratamentos intercríticos com aquecimento em temperaturas diversas, seguido de resfriamento brusco, no comportamento em termos de encruamento de um aço bifásico, por meio de dois métodos distintos de determinação do expoente de encruamento. Observou-se que a elevação da temperatura intercrítica influenciou de modo a reduzir o valor do expoente de encruamento, dado que o aumento da temperatura reflete a elevação do percentual de martensita na microestrutura do aço. Além disso, para as diferentes abordagens aplicadas para o cálculo dos valores de n, verificou-se que por meio da técnica de linearização da curva tensão versus deformação foram obtidos valores superiores do expoente de encruamento quando comparada à abordagem utilizando o critério da estricção. Palavras-chave: Aços bifásicos; Tratamento intercrítico; Expoente de encruamento. EFFECT OF THE INTERCRITICAL TEMPERATURE ON THE HARDENING EXPOENT OF DUAL PHASE STEELS AbstractThe high work hardening rates in the early stages of plastic deformation observed in the dual phase steel is one of the most important properties that enables them to be used in structural components in the automobile industry. The aim of this work is to analyze the effects of the intercritical heat treatment at various temperatures followed by quenching on the work hardening behavior of the dual phase steel by different methods for determining the strain hardening exponent n. It was observed that an increase in the intercritical temperature led to the reduction of the strain hardening exponent value. The phenomenon was associated with the increase of the volume fraction of martensite in the steel microstructure. According to the different approaches applied to calculate n value, upper values were found by the curve linearization technique when compared with the approach using the necking criterion.

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“…These, in turn, are dependent on the annealing parameters and alloying elements. So far, some researchers have studied about the effect of the martensite on the properties of ferrite-martensite dual-phase steels, Available online at http://link.springer.com/journal/40195 & Hong-Shuang Di dhshuang@mail.neu.edu.cn 1 including the content [15,16], martensite morphology, distribution martensite and the grain size [17][18][19][20][21][22][23][24]. The tensile properties of DP steels have been investigated widely.…”

Section: Introductionmentioning

confidence: 99%

Effect of Heat-Treatment Schedule on the Microstructure and Mechanical Properties of Cold-Rolled Dual-Phase Steels

Deng

Zhang

2015

Acta Metall. Sin. (Engl. Lett.)

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Low-carbon (0.08 wt% C) steel has been subjected to three different heat treatments to obtain dual-phase steels with different microstructures. An understanding of structure-property was established through tensile tests, in conjunction with scanning electron microscope and transmission electron microscope. The results show that the steel after intermediate quenching (IQ) consisting of fine and fibrous martensite exhibited the intermediate strength, highest elongation and the best comprehensive performance of mechanical properties, whereas the steel subjected to intercritical annealing (IA) produced a network martensite along ferrite grain boundaries, having the lowest strength and intermediate elongation. Besides, step quenching (SQ) resulted in a coarse and blocky ferrite-martensite microstructure showing the worst mechanical properties of the three different heat-treatment conditions. The strain-hardening behavior was studied through the modified CrussardJaoul model, indicating two stages of strain-hardening behavior for all three samples. The highest magnitude of strainhardening ability was obtained by IQ annealing routes. The analysis of the fractured surface revealed that ferrite/martensite interfaces are the most susceptible for microvoid nucleation. However, martensite microcracks were also observed in SQ sample, and the microvoids are nucleated within the ferrite grain in IA sample as well. The variations in strength, elongation, strain-hardening behavior and fracture mechanism of the steel with different heat-treatment schedules were further discussed in relation to the microstructural features.

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A novel route for development of ultrahigh strength dual phase steels

Cited by 91 publications

References 46 publications

Microstructures and mechanical properties of dual phase steel produced by laboratory simulated strip casting

Microstructures and mechanical properties of dual phase steel produced by laboratory simulated strip casting

Efeito Da Temperatura Intercrítica No Expoente De Encruamento De Aços Bifásicos

Effect of Heat-Treatment Schedule on the Microstructure and Mechanical Properties of Cold-Rolled Dual-Phase Steels

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