Modification of Rule of Mixtures for Estimation of the Mechanical Properties of Dual-Phase Steels

Self Cite

The effect of austenitization and intercritical annealing temperature on mechanical properties and work-hardening response of high-formability dual phase (DP) steel with low C and Mn content is studied. Different mechanisms of microstructural development are characterized. At intercritical temperature range, austenite forms in the ferritic matrix, which will transform to martensite during quenching. However, at austenitization temperatures, the material becomes completely austenitic with low hardenability. As a result, during quenching, there will be some ferrite phase in the martensitic matrix of the resultant DP steel. These differences are found to have important effects on the mechanical properties. The yield strength decreases at low martensite fraction due to the disappearance of the yield-point phenomenon and the presence of martensite-induced dislocations that move at low stresses. However, the yield strength rapidly increases by the dominance of the martensitic matrix at high martensite fractions. Moreover, the dependence of the ultimate tensile strength on martensite volume fraction is discussed based on the work-hardening capacity of the DP steels. Finally, the mechanical properties are summarized by consideration of strength-ductility trade-off seen for DP steels. Figure 8. The strength-ductility balance of DP steels [1] and its extension to high ductility region by including the results of the present study and results of Mirzadeh et al. [24] www.advancedsciencenews.com www.steel-research.de steel research int. 2018, 89, 1700412 www.advancedsciencenews.com www.steel-research.de steel research int. 2018, 89, 1700412

Section: Resultsmentioning

confidence: 98%

Effect of Intercritical Annealing on Mechanical Properties and Work‐Hardening Response of High Formability Dual Phase Steel

Maleki

Mirzadeh

Zamani

2017

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“…For obtaining the slope, the central difference approach based on

n true|_{i} = {\ln σ_{i + 1}^{} - \ln σ_{i - 1}^{}} / {\ln ϵ_{i + 1} - \ln ϵ_{i - 1}}

was utilized. The modified Crussard‐Jaoul analysis was also used for studying the work‐hardening behavior, where it is based on the Swift formula expressed as

ϵ = A + B σ^{p}

, where A , B , and p are constants. Therefore,

σ = \sqrt[p]{(ϵ - A) / B}

, then

d σ / d ϵ = σ / (p (ϵ - A))

, and finally

\ln (d σ / d ϵ) = (1 - p) \ln σ - \ln (p B)

.…”

Section: Methodsmentioning

confidence: 99%

Refinement of Banded Structure via Thermal Cycling and Its Effects on Mechanical Properties of Dual Phase Steel

Ghaemifar

Mirzadeh

2018

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The microstructural refinement by thermal cycling and its effects on the enhancement of mechanical properties and work-hardening response of a typical C-Mn dual phase (DP) steel having the banded ferritic-martensitic morphology is evaluated. It is revealed that the band spacing is reduced by decreasing austenitization temperature and applying thermal cycles to intercritical region, where a saturated spacing will be reached. This results in the enhancement of work-hardening capacity of DP steels as demonstrated based on the instantaneous (incremental) work-hardening rate exponents, modified Crussard-Jaoul analysis, and evaluating the yield ratio after tensile tests. These observations justify the potential of this simple heat treatment route for microstructural control of DP steels. Figure 8. a) Dependence of UTS and total elongation on band spacing and b) Dependence of yield ratio and UTS-YS on band spacing.www.advancedsciencenews.com www.steel-research.de steel research int. 2018, 89, 1700531

“…Mirzadeh et al and Karmakar et al found that changing the initial microstructure can significantly affect the final microstructure and mechanical properties of DP steel. Several researchers attempted to predict the properties of DP steel based on the rule of mixture, the finite element simulation as well as the integrated experimental‐simulation method . On the other hand, the volume fraction and size of the constituent phase for DP steel is mainly determined by the manufacturing processes.…”

Section: Introductionmentioning

confidence: 99%

Effects of Continuous Annealing Process Parameters on the Microstructure and Mechanical Properties of Dual Phase Steel

Kong¹,

Zhang²,

Li³

et al. 2018

Due to the difference in chemistries and manufacturing processes applied, the microstructure and mechanical properties of DP780 steel produced by different production lines may be inconsistent. Annealing experiments are designed and carried out in the laboratory based on the actual industrial production process in order to investigate the effects of continuous annealing process parameters on the microstructure and mechanical properties of DP steel quantitatively. The results show that the effect of intercritical temperature is continuous while the sensitive interval and non-sensitive interval should be considered in terms of the effect of slow cooling temperature, over-aging temperature, and strip speed. The influence degree is defined to quantitatively compare the effects of the influencing factors, which find that the over-aging temperature has the most influential effect on the tensile strength while the effect of the slow cooling temperature ranks second and the intercritical temperature has a minimal impact. The influence degrees on elongation of all the three factors are similar. The results from this study are helpful to efficiently adjust the microstructure and mechanical properties of DP steel.