The effect of primary thermo-mechanical treatment on TRIP steel microstructure and mechanical properties

Azizi, Ghavam; Mirzadeh, Hamed; Parsa, Mohammad Habibi

doi:10.1016/j.msea.2015.05.045

Cited by 26 publications

(19 citation statements)

References 4 publications

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“…Figure also shows the microstructures of hot rolled and furnace cooled specimens. Figure d shows a severe ferritic–pearlitic banded structure, which is a result of the chemical segregation of some alloying elements (e.g., Mn) during solidification and subsequent pancaking of the inhomogeneous austenitic during hot rolling . The presence of ill‐defined banded structure in Figure e reveals that 12 h annealing at 1150 °C is not enough to remove chemical homogeneity; whereas by nearly full homogenization as shown in Figure f, the banded structure vanishes completely and the resultant morphology is very similar with the one presented in Figure c.…”

Section: Resultsmentioning

confidence: 72%

Unraveling the Effect of Homogenization Treatment on Decomposition of Austenite and Mechanical Properties of Low‐Alloyed TRIP Steel

Azizi

Mirzadeh

Parsa

2015

steel research int.

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The homogenization treatment is shown to have profound effects on the decomposition of austenite, suppression of microstructural banding, and work-hardening capacity of transformation-induced plasticity (TRIP) steels. Due to the similarity in the activity of carbon in different parts of the parent austenite phase and its extremely coarse grain size, a nearly full homogenization annealing results in the massive-like transformation during subsequent decomposition of austenite at slow cooling rates.

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Section: Resultsmentioning

confidence: 72%

Unraveling the Effect of Homogenization Treatment on Decomposition of Austenite and Mechanical Properties of Low‐Alloyed TRIP Steel

Azizi

Mirzadeh

Parsa

2015

steel research int.

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“…The M s temperature of completely austenitic microstructure can be calculated as 430°C by equation of the form M s = 539-423C -30.4Mn -7.5Si ? 30Al [5]. Based on the lever rule, by intercritical annealing at 790°C, a microstructure consisting of 35% austenite and 65% ferrite is expected to be achieved and the level of carbon in the austenite phase becomes as high as 0.5 wt%.…”

Section: Chemically Inhomogeneous But Microstructurally Homogeneous Smentioning

confidence: 99%

“…However, the high yield strength for the BIT temperature of 400°C can be ascribed to the formation of some martensite during BIT due to the presence of some prior unstable austenite areas with higher M s temperature. The latter is a result of rapid cooling, which disturbs the distribution of carbon during preprocessing and subsequent formation of austenite during intercritical annealing in both lean and rich regions from alloying elements [5].…”

Section: Chemically Inhomogeneous But Microstructurally Homogeneous Smentioning

confidence: 99%

“…During deformation, the metastable retained austenite will transform to martensite (known as TRIP effect), which increases the local strain hardening rate and delays necking [3]. While the distribution of retained austenite in the microstructure (microstructural homogeneity) and its chemical homogeneity regarding the substitutional alloying elements seem to be important factors in the response of TRIP steels [4,5], but these aspects have not been systematically studied yet. The aim of this work is to investigate the effects of microstructural and chemical homogeneity on TRIP effect and the response of TRIP steels during the BIT treatment.…”

Section: Introductionmentioning

confidence: 99%

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Dependency of Deformation Behavior of Retained Austenite in TRIP Steels on Microstructural and Chemical Homogeneity

Azizi

Mirzadeh

Parsa

2015

Acta Metall. Sin. (Engl. Lett.)

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The room-temperature stability of the retained austenite against strain-induced martensitic transformation, its deformation behavior, the response to the bainitic isothermal treatment, the appearance of yield point elongation and other peculiarities of plastic flow, and the mechanical properties of transformation-induced plasticity (TRIP) steel were tailored based on the chemical homogeneity and the relative distribution of the retained austenite, bainite, and ferrite in the microstructure. The presence of ferritic-pearlitic banded structure in the initial microstructure resulted in an inhomogeneous TRIP microstructure, in which the retained austenite and bainite were confined to some bands and it was found to be responsible for the resultant inferior mechanical properties. The appearance of discontinuous yielding for the chemically inhomogeneous material was related to the martensitic transformation of unstable retained austenite at the initial stage of tensile deformation. These results are essential for better understanding of the behavior of advanced high-strength steels and their applications.

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“…Their good mechanical properties result from a complex microstructure containing ferritic matrix, carbide-free bainite and retained austenite [1,2]. Suitable microstructures with proper volume fractions, distributions and morphologies of individual phases and structural components are produced usually by thermo-mechanical treatment [1,3]. Ideal processing parameters vary according to the particular chemical composition of steel.…”

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confidence: 99%

Thermo-Mechanical Treatment of 42sicr and 42mnsi Steels

Kučerová

Jirková

Jandová

2017

Acta Metall Slovaca

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Two high strength low alloyed steels with 0.4%C, 0.6%Mn, 2%Si and either 1.3% of chromium or without chromium were used in this work to evaluate the effect of chromium on the final microstructure obtained by thermo-mechanical processing. Various heating temperatures, cooling rates and bainitic hold temperatures were tested. High strengths around 1700 MPa were achieved for the chromium alloyed steel, however total elongation reached only 9%. Chromiumfree steel turned out to be better suited for TRIP (transformation induced plasticity) processing. The relatively high strengths around 900 MPa were in this case accompanied by very high total elongations exceeding 30%. The final microstructure of chromium-free steel was also more typical for TRIP steel, as it consisted mainly of the mixture of bainite and polygonal ferrite.Keywords: TRIP steel, chromium, thermomechanical processing, scanning electron microscopy 1 Introduction TRIP (transformation induced plasticity) steels are advanced steel grades with high strength and enhanced total elongation and formability. Their good mechanical properties result from a complex microstructure containing ferritic matrix, carbide-free bainite and retained austenite [1,2]. Suitable microstructures with proper volume fractions, distributions and morphologies of individual phases and structural components are produced usually by thermo-mechanical treatment [1,3]. Ideal processing parameters vary according to the particular chemical composition of steel. The most conventional concept is based on C-Mn-Si alloying [1,[4][5]. Further TRIP steel variations were investigated in last decades, testing other alloying elements and their combinations. Silicon was fully or partially replaced by aluminium to improve galvanizing properties of thin sheets for automotive industry [6,7]. Micro alloying by Niobium was designed to refine the final microstructure and increase retained austenite content [8][9][10]. Chromium alloying of medium carbon TRIP steels has not been investigated very thoughtfully [11], probably due to its reputation of a carbide-forming element with a potential to increase the incubation time and decrease the transformation rate of isothermal bainite. The effect of chromium on higher hardenability is usually used in martensite-based steel, primarily to increase the strength [11][12][13]. However, chromium also retards pearlite growth rate and refines the microstructure by reducing the growth rate of prior austenite grain in steels [14][15] and improves corrosion resistance [16], which can be convenient for TRIP steels as well.

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The effect of primary thermo-mechanical treatment on TRIP steel microstructure and mechanical properties

Cited by 26 publications

References 4 publications

Unraveling the Effect of Homogenization Treatment on Decomposition of Austenite and Mechanical Properties of Low‐Alloyed TRIP Steel

Unraveling the Effect of Homogenization Treatment on Decomposition of Austenite and Mechanical Properties of Low‐Alloyed TRIP Steel

Dependency of Deformation Behavior of Retained Austenite in TRIP Steels on Microstructural and Chemical Homogeneity

Thermo-Mechanical Treatment of 42sicr and 42mnsi Steels

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