Isothermal Transformation of a CMnSi Steel Below the MS Temperature

Kim, Donghwi; Speer, John G.; Cooman, Bruno C. De

doi:10.1007/s11661-010-0557-z

Cited by 42 publications

(29 citation statements)

References 25 publications

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“…Depending on the stability of the austenite, during the holding, several other processes may also take place such as growth of martensite i.e. isothermal martensite formation, 25) the appearance of bainite and the precipitation of transition carbides. During holding, martensite will also undergo recovery lowering the final hardness and tensile strength.…”

Section: Phase Transformation Characteristics Hardnessmentioning

confidence: 99%

Effects of Carbon Content and Cooling Path on the Microstructure and Properties of TRIP-aided Ultra-High Strength Steels

Suikkanen¹,

Ristola

Hirvi³

et al. 2013

ISIJ Int.

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The effects of carbon content in the range 0.2-0.4 wt% and thermomechanical treatment parameters on the mechanical properties and microstructures of steels containing 0.5Si-2.0Mn-1.0Al-0.6Cr have been studied in order to help develop an efficient processing route for ultra-high-strength TRIP-aided martensitic-bainitic structural steels. The microstructures consist of granular bainite, lath-like bainite, martensite and up to 23 volume % retained austenite as granular islands and lath-like films. Microsegregation of chromium and manganese results in the formation of martensite-rich bands, the volume fraction of which increases with carbon content. Bands of martensite, induced by the segregation of chromium and manganese, become more prominent with increasing carbon content. Good combinations of tensile strength, elongation and impact toughness can be achieved with 0.2 or 0.3 wt% carbon by thermomechanical rolling followed by water quenching to 150-350°C and isothermal holding for 2 h at the quenching stop temperature. The steel with 0.4 wt% carbon shows high strength and good uniform elongation due to high contents of retained austenite, but its impact toughness is clearly inferior to its lower carbon counterparts. Annealing to alleviate microstructural banding produced a marked improvement in impact toughness.

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Section: Phase Transformation Characteristics Hardnessmentioning

confidence: 99%

Effects of Carbon Content and Cooling Path on the Microstructure and Properties of TRIP-aided Ultra-High Strength Steels

Suikkanen¹,

Ristola

Hirvi³

et al. 2013

ISIJ Int.

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“…Kim et al [13,15,16] state that the nature of the isothermal product obtained in 0.2C-1.5Mn-1.5Si (wt pct) alloys, after applying isothermal treatments below M s , is neither purely martensitic nor purely bainitic. The units of this characteristic product are, for instance, much wider than the laths in athermal martensite, and the boundaries are wavy and contain ledges.…”

Section: Introductionmentioning

confidence: 99%

Effect of Prior Athermal Martensite on the Isothermal Transformation Kinetics Below M s in a Low-C High-Si Steel

Navarro-López

Sietsma

Santofimia

2015

Metall Mater Trans A

111

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A. NAVARRO-LÓ PEZ, J. SIETSMA, and M.J. SANTOFIMIA Thermomechanical processing of Advanced Multiphase High Strength Steels often includes isothermal treatments around the martensite start temperature (M s ). It has been reported that the presence of martensite formed prior to these isothermal treatments accelerates the kinetics of the subsequent transformation. This kinetic effect is commonly attributed to the creation of potential nucleation sites at martensite-austenite interfaces. The aim of this study is to determine qualitatively and quantitatively the effect of a small volume fraction of martensite on the nucleation kinetics of the subsequent transformation. For this purpose, dilatometry experiments were performed at different temperatures above and below the M s temperature for athermal martensite in a low-carbon high-silicon steel. Microstructural analysis led to the identification of the isothermal decomposition product formed above and below M s as bainitic ferrite. The analysis of the transformation processes demonstrated that the initial stage of formation of bainitic ferrite at heat treatments below M s is at least two orders of magnitude faster than above M s due to the presence of martensite.

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“…Dislocation-enhanced Snoek peak was discovered by Magalas et al [51]. The existence of the dislocation-enhanced Snoek peak was confirmed in highpurity fe-C alloys in 2006 [58] in resonant low-frequency internal friction measurements [7][8][9]35,[59][60][61][62][63][88][89][90] and by De Cooman and co-workers using the resonant impulse excitation internal friction technique operating at higher frequencies [27,[64][65][66][67][68]. The presence of the dislocation-enhanced Snoek peak and Snoek-Köster peak was also reported by jung et al [27] in commercial ultra-low carbon bake-hardenable steels.…”

Section: Snoek Peak Dislocation-enhanced Snoek Peak and Snoek-köstermentioning

confidence: 99%

Relationship Between Bake Hardening, Snoek-Köster and Dislocation-Enhanced Snoek Peaks in Coarse Grained Low Carbon Steel

Zhao

Zhang

et al. 2016

Archives of Metallurgy and Materials

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In the present work, specimens prepared from coarse grained low carbon steel with different prestrains were baked and then, their bake hardening (BH) property and internal friction were determined. TeM was used to characterize the dislocation structure in BH treated samples. The measurements of internal friction in prestrained samples and baked samples were carried out using a multifunctional internal friction apparatus. The results indicate that, in coarse grained low carbon steel, the bake hardening properties (BH values) were negative, which were increased by increasing the prestrain from 2 to 5%, and then were decreased by increasing the prestrain from 5 to 10%. In the specimen with prestrain 5%, the BH value reached the maximum value and the height of Snoek-Köster peak was observed to be the maximum alike. With increasing the prestrain, both of the BH value and Snoek-Köster peak heights are similarly varied. It is concluded that Snoek-Köster and dislocation-enhanced Snoek peaks, caused by the interactions between interstitial solute carbon atoms and dislocations, can be used in further development of the bake hardening steels.

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Isothermal Transformation of a CMnSi Steel Below the MS Temperature

Cited by 42 publications

References 25 publications

Effects of Carbon Content and Cooling Path on the Microstructure and Properties of TRIP-aided Ultra-High Strength Steels

Effects of Carbon Content and Cooling Path on the Microstructure and Properties of TRIP-aided Ultra-High Strength Steels

Effect of Prior Athermal Martensite on the Isothermal Transformation Kinetics Below M s in a Low-C High-Si Steel

Relationship Between Bake Hardening, Snoek-Köster and Dislocation-Enhanced Snoek Peaks in Coarse Grained Low Carbon Steel

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