Effect of austenite grain size and bainite morphology on overall kinetics of bainite transformation in steels

Matsuzaki, Akiyoshi; Bhadeshia, H. K. D. H.

doi:10.1179/026708399101506210

Cited by 108 publications

(74 citation statements)

References 3 publications

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“…Bs temperature variations due to the decrease in PAGS simultaneously influenced bainite transformation kinetics. [13][14][15] However, few researchers have attempted to develop the equations for Bs temperature by considering both chemical composition and PAGS effects. Therefore, in the present study, we developed a simple empirical equation for Bs temperature prediction that includes both the alloying element effect and the PAGS effect based on experimental data obtained from the literature.…”

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confidence: 99%

Prediction of Bainite Start Temperature in Alloy Steels with Different Grain Sizes

2014

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KEY WORDS: bainite start (Bs) temperature; alloying element; prior austenite grain size (PAGS); alloy steels.Bainite microstructure in alloy steels yields materials with an excellent combination of mechanical properties such as high strength and toughness, resistance to creep and fatigue, and hydrogen embrittlement.1,2) During cooling, bainite transformation is initiated at the bainite start (Bs) temperature, which is the highest isothermal temperature at which upper bainite is observed, and ceases when the temperature reaches the martensite start (Ms) temperature. Addition of alloying elements mostly lowers the Bs temperature. Especially, carbon and manganese known as strong austenite stabilizing elements effectively decrease the Bs temperature. Several quantitative investigations have been performed to determine the relationship between the addition of alloying elements and Bs temperature variations in alloy steels. Some empirical equations have been proposed to predict the effect of adding alloying elements to carbon and alloy steels on Bs temperature. [3][4][5][6][7][8][9][10][11][12] Prior austenite grain size (PAGS) can also affect the Bs temperature. Lee et al. 13) reported that Bs temperature decreased with decreasing PAGS. Bs temperature variations due to the decrease in PAGS simultaneously influenced bainite transformation kinetics. [13][14][15] However, few researchers have attempted to develop the equations for Bs temperature by considering both chemical composition and PAGS effects. Therefore, in the present study, we developed a simple empirical equation for Bs temperature prediction that includes both the alloying element effect and the PAGS effect based on experimental data obtained from the literature. We compared the accuracy of our empirical equation with existing equations and verified the performance of our equation using experimental data.Experimental Bs temperature data for carbon and alloy steels were extracted from published time-temperaturetransformation (TTT) diagrams.16) Both chemical composition and PAGS were used to evaluate existing equations and to derive a new equation. We selected the following alloying elements in the present work: C, Mn, Si, Ni, Cr, and Mo.Data for other alloying elements were excluded. The chemical composition range of the selected steels was limited to that of low alloy steels, thus high alloyed steels such as a stainless steel was excluded. Ranges of chemical composition, PAGS, and B s temperature used for equation derivation are summarized in Table 1. The total number of B s data points used in the present work was 97.

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confidence: 99%

Prediction of Bainite Start Temperature in Alloy Steels with Different Grain Sizes

2014

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“…These results are in line with those presented for the normalized samples. It should be noted that bainite nucleates on the parent austenite grains; therefore, and without a doubt, the austenite grain size has an effect on the overall kinetics of the isothermal transformation of bainite [36]. This effect is not accounted for in the theoretical calculations of the type shown in Figure 8 which only consider the chemical composition of the steel.…”

Section: Alloymentioning

confidence: 99%

Vanadium Effect on a Medium Carbon Forging Steel

García‐Mateo

Morales-Rivas

Caballero

et al. 2016

Metals

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“…However, impingement with the boundaries of the austenite grains will inhibit autocatalytic nucleation, 20) and the length of the bainite sub-units will be eventually limited by the size of the austenite grains. 21) Finally, as impingement forces bainite sub-units to grow parallel to each other (as described by Jacques,20) minimisation of the transformation strains by the growth of an optimal combination of different bainite variants is no longer possible, as it would happen in larger grains, 9,22) and some transformation stresses may build up as the reaction proceeds.…”

Section: Transformation In Small Austenite Grainsmentioning

confidence: 99%

A New Physical Model for the Kinetics of the Bainite Transformation

Gaude-Fugarolas

Jacques

2006

ISIJ Int.

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A model describing the bainite reaction is presented that takes into account the effect of very small austenite grain size. This model considers the displacive approach and uses thermodynamic criteria for the description of the nucleation and growth of bainite sub-units forming either at grain boundaries or autocatalytically on previous sub-units. The evolution of the austenite composition with the partitioning and redistribution of carbon is estimated as the transformation proceeds. The size of the sub-units is calculated for each composition and temperature.The transformation kinetics, as well as the incomplete reaction phenomenon, are correctly predicted. Furthermore, the influence of the austenite grain size on the bainite transformation rate is addressed in the case of austenite grains smaller than the length of an unconstrained bainite sub-unit. In this case, the observed enhanced nucleation rate is semi-empirically related to the austenite yield strength. This semi-empirical relationship is corroborated with kinetics data from different alloys.

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Effect of austenite grain size and bainite morphology on overall kinetics of bainite transformation in steels

Cited by 108 publications

References 3 publications

Prediction of Bainite Start Temperature in Alloy Steels with Different Grain Sizes

Prediction of Bainite Start Temperature in Alloy Steels with Different Grain Sizes

Vanadium Effect on a Medium Carbon Forging Steel

A New Physical Model for the Kinetics of the Bainite Transformation

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