Austenite Grain Refinement and Isothermal Growth Behavior in a Low Carbon Vanadium Microalloyed Steel

Yang, Gengwei; Sun, Xinjun; Yong, Qilong; Li, Zhaodong; Li, Xiaoxian

doi:10.1016/s1006-706x(14)60138-2

Cited by 45 publications

(20 citation statements)

References 17 publications

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“…Phenomenological approaches are widely used for their simplicity [8][9][10][11][12][13], the grain diameter following empirical equations of the type:…”

Section: Accepted Manuscriptmentioning

confidence: 99%

Precipitation and grain growth modelling in Ti-Nb microalloyed steels

et al. 2019

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Mechanical properties of microalloyed steels are enhanced by fine precipitates, that ensure grain growth control during subsequent heat treatment. This study aims at predicting austenite grain growth kinetics coupling a precipitation model and a grain growth model. These models were applied to a titanium and niobium microalloyed steel. The precipitate size distributions were first characterized by TEM and SEM and prior austenite grain boundaries were revealed by thermal etching after various isothermal treatments. From CALPHAD database, a solubility product was determined for (Ti,Nb)C precipitates. A numerical model based on the classical nucleation and growth theories was used to predict the time evolution of (Ti,Nb)C size distributions during various isothermal heat treatments. The precipitation model was validated from TEM/SEM analysis. The resulting precipitate size distributions served as entry parameters to a simple grain growth model based on Zener pinning. The pinning pressure was calculated using the whole size distribution. The resulting austenite grain growth kinetics were in good agreement with the experimental data obtained for all investigated heat treatments.

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“…Phenomenological approaches are widely used for their simplicity [8][9][10][11][12][13], the grain diameter following empirical equations of the type:…”

Section: Accepted Manuscriptmentioning

confidence: 99%

Precipitation and grain growth modelling in Ti-Nb microalloyed steels

et al. 2019

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“…Addition of alloying elements, such as V, Ti and Nb, could refine PAGS and the final microstructure by grain growth retardation [17,62,63]. Deformation above the non-recrystallisation temperature can help to reduce the austenite grain size by dynamic/static recrystallisation; and deformation below the non-recrystallisation temperature may increase the amount of crystal defects (dislocations, deformation bands) acting as nucleation sites for ferrite formation, which would refine the low temperature microstructure [38,64].…”

Section: The Approaches To Improve Mechanical Propertiesmentioning

confidence: 99%

Microstructures and mechanical properties of TRIP steel produced by strip casting simulated in the laboratory

Xiong

Kostryzhev

Saleh

et al. 2016

Materials Science and Engineering: A

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Conventional transformation induced plasticity (TRIP) steel (0.17C-1.52Si-1.61Mn-0.03Al, wt%) was produced via strip casting technology simulated in the laboratory. Effects of holding temperature, holding time and cooling rate on ferrite formation were studied via analysis of the continuous cooling transformation diagram obtained here. A typical microstructure for conventional TRIP steels consisting of ~ 0.55 fraction of polygonal ferrite with bainite, retained austenite and martensite was obtained. However, coarse prior austenite grain size of ~80 μm led to large polygonal ferrite grain size of ~17 μm, coarse second phase regions of ~21 μm size, small amount of retained austenite (0.02-0.045) and the presence of Widmanstätten ferrite. Optimisation of the microstructure-property relationship was reached via a variation in the isothermal bainite transformation temperature. The highest retained austenite fraction of 0.045±0.003 with medium carbon content of 1.23±0.01 wt% was obtained after holding at 400 °C, resulting in the highest ultimate tensile strength of 590±35 MPa and largest total elongation of 0.27±0.05. The presence of TRIP effect in the studied steel was revealed through the analysis of strain hardening exponent and modified Crussard-Jaoul model. Effect of processing parameters on retained austenite retention and stress-strain behaviour was discussed. Conventional transformation induced plasticity (TRIP) steel (0.17C-1.52Si-1.61Mn-0.03Al, wt. %) was produced via strip casting technology simulated in the laboratory. Effects of holding temperature, holding time and cooling rate on ferrite formation were studied via analysis of the continuous cooling transformation diagram obtained here. A typical microstructure for conventional TRIP steels consisting of ~ 0.55 fraction of polygonal ferrite with bainite, retained austenite and martensite was obtained. However, coarse prior austenite grain size of ~ 80 μm led to large polygonal ferrite grain size of ~ 17 μm, coarse second phase regions of ~ 21 μm size, small amount of retained austenite (0.02 -0.045) and the presence of Widmanstätten ferrite. Optimisation of the microstructure-property relationship was reached via a variation in the isothermal bainite transformation temperature. The highest retained austenite fraction of 0.045±0.003 with medium carbon content of 1.23±0.01 wt. % was obtained after holding at 400 °C, resulting in the highest ultimate tensile strength of 590±35 MPa and largest total elongation of 0.27±0.05. The presence of TRIP effect in the studied steel was revealed through the analysis of strain hardening exponent and modified Crussard -Jaoul model. Effect of processing parameters on retained austenite retention and stress-strain behaviour was discussed.

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“…This equation was previously used to describe the grain growth of alloys, ceramics and metals. [26][27][28][29][30][31] Given the similar situation, the grain growth of metallic iron phase in coal-based reduction of oolitic iron ore was analysed using Eq. (4).…”

Section: Growth Kineticsmentioning

confidence: 99%