Microstructure, mechanical properties and fracture behavior of ultra-high strength dual-phase steel

Zhao, Zhengzhi; Tong, Tingting; Liang, Juhua; Yin, Haiqing; Zhang, Aimin; Tang, Di

doi:10.1016/j.msea.2014.09.005

Cited by 63 publications

(28 citation statements)

References 19 publications

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“…Typical round-house engineering stress-strain curves inherent in DP steels [10,26] were also observed in our steel for all four heat treatment conditions (Fig. 14a).…”

Section: Mechanical Propertiessupporting

confidence: 59%

“…In this regard, the finer ferrite grain size the smaller is m 1 . As could be seen from Table 4, DP 40 and DP 50 samples with the lowest average grain sizes ( [26,29,32], resulting in a decrease in strain hardening ability. m 2 increased with a decrease in ferrite fraction, due to a higher restraint from deformation of ferrite grains by martensite regions, which led to a decrease in strain hardening ability.…”

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

confidence: 87%

“…14b and c) due to an increased initial density of dislocations leading to an earlier dislocation immobilisation and pile-up [9,16,26]. The samples with a larger ferrite fraction had a more gradual increase and then a slower decrease in strain hardening exponent.…”

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

confidence: 99%

“…14d. The strain hardening behaviour showed three stages, which is a typical phenomenon for DP steels [5,16,26]. As the modified C-J analysis was unable to fit the flow curve over the entire uniform strain range region, values of strain hardening index m for each strain hardening stage are listed in Table 4.…”

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

confidence: 99%

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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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“…Typical round-house engineering stress-strain curves inherent in DP steels [10,26] were also observed in our steel for all four heat treatment conditions (Fig. 14a).…”

Section: Mechanical Propertiessupporting

confidence: 59%

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

confidence: 87%

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

confidence: 99%

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

confidence: 99%

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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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“…O segundo método utilizado para a determinação do expoente de encruamento foi a análise da deformação uniforme real,ou seja, a partir do critério da formação da estricção descrito por Dieter (1981) [14]. Especificamente nesta abordagem, foi aplicado para a obtenção dos valores de expoente de encruamento o software Origin versão 8.0, utilizando ainda o recurso de tratamento de dados smoothing, com um parâmetro de ajuste de 25 pontos, com objetivo de evitar uma possível propagação de erros das medidas devido à aplicação de diferenciais durante a análise, suavisando o conjunto de dados [17].…”

Section: Materiais E Métodosunclassified

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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Quantitative analysis of martensite and bainite microstructures using electron backscatter diffraction

Wang

Hua

Kong

et al. 2016

Microsc. Res. Tech.

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In the present work, ultra-high-strength steels with multiphase microstructures containing martensite and bainite were prepared by controlling the cooling rate. A new approach was proposed for quantitatively statistical phase analysis using electron backscatter diffraction (EBSD) based on the band contrast which correlates to the quality and intensity of the diffraction patterns. This approach takes advantage of the inherently greater lattice imperfections of martensite, such as dislocations and low-angle grain boundaries, relative to that of bainite. These can reduce the intensity and quality of the EBSD patterns of martensite, which decrease the band contrast. Thus, combined with morphological observations, Gaussian two-peak fitting was employed to analyze the band contrast profile and confirm the ranges of band contrast for the two phases. The volume fractions of bainite and martensite in different samples were determined successfully. In addition, the results show that increased cooling rates improve the proportion of martensite and the ratio of martensite to bainite. Microsc. Res. Tech. 79:814-819, 2016. © 2016 Wiley Periodicals, Inc.

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Microstructure, mechanical properties and fracture behavior of ultra-high strength dual-phase steel

Cited by 63 publications

References 19 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

Quantitative analysis of martensite and bainite microstructures using electron backscatter diffraction

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