Microstructural evolution and mechanical properties of low-carbon steel treated by a two-step quenching and partitioning process

Yan, Shu; Li, Xianghua; Liu, Wayne J.; Lan, Huifang; Wu, Hongyan

doi:10.1016/j.msea.2015.05.058

Cited by 28 publications

(7 citation statements)

References 27 publications

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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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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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“…Two different forms of retained austenite are described in the literature. On the one hand, film‐like retained austenite between the martensite lathes (interlathe film), respectively, between the bainitic lathes, and, on the other, grains of retained austenite . After the employed heat treatments, retained austenite mainly exists as polygonal shaped grains.…”

Section: Discussionmentioning

confidence: 99%

“…A film‐like formation between the bainite lathes is also known. Despite its higher carbon content, the granular form exhibits a lower stability in comparison to the film‐like retained austenite, such that grains already transform to martensite at lower mechanical loading . In addition, higher ductility can be obtained in TRIP steels possessing film‐like retained austenite, as compared to the granular form…”

Section: Discussionmentioning

confidence: 99%

1‐Step “Quenching and Partitioning” of the Press‐Hardening Steel 22MnB5

Wolf¹,

Nürnberger²,

Rodman³

et al. 2016

steel research int.

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In recent years, high strength steels, particularly press‐hardening steel, have been more extensively employed for manufacturing safety‐relevant structural components in vehicle bodies. These applications require contrasting material properties such as extremely high strengths as well as high forming ductility. Owing to the purely martensitic microstructure, the residual ductility of the conventional press hardened steels is low. Quenching and partitioning heat treatments can fulfil the requirement of an increased residual ductility by stabilizing the retained austenite. Moreover, if the quenching and partitioning heat treatments are carried out after intercritical annealing treatment, then the steel's mechanical properties can be tailored by defining the volume fraction of ferrite in the microstructure. In order to determine the potential of an 1‐step quenching and partitioning heat treatment combined with intercritical annealing processes, elevated contents of retained austenite are produced in ferritic‐martensitic microstructures using the low‐alloyed 22MnB5 steel grade. In addition to a tempered martensitic microstructure, secondary martensite, and a low fraction of retained austenite, the microstructure consists of remaining fractions of ferrite; thus, providing an additional increase in ductility. For this optimized microstructure, a yield stress of 513 MPa and a tensile strength of 1045 MPa are measured with a total elongation of 10.8%.

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“…Although retained austenite is present at a relatively lower fraction, it is an important phase constituent since the transformation induced plasticity (TRIP) effect favors both strength and ductility by improving localized hardening . Heat treatment parameters such as, QT, PT, partitioning time (Pt), and austenitizing temperature are critical in controlling the resulting microstructural evolution and mechanical properties, therefore, they have been extensively studied . Another important factor is chemical composition.…”

Section: Introductionmentioning

confidence: 99%

Effect of Micro‐Alloying Elements on Microstructure and Mechanical Properties in C–Mn–Si Quenching and Partitioning (Q&P) Steels

Yan

Liang

et al. 2018

steel research int.

Self Cite

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The authors design two kinds of Mo–Nb and Ni–Mo–Ti microalloyed steels based on C–Mn–Si steel using quenching and partitioning (Q&P) processing. The results indicate that the addition of microalloying elements increases retained austenite fraction, however, the average carbon concentration in retained austenite is reduced. Nano‐sized NbC and TiC precipitates are separately observed in the Mo–Nb and Ni–Mo–Ti microalloyed steel. Both precipitates can refine prior austenite grains as well as martensite packets and laths. The yield strength of Mo–Nb microalloyed steel treated by Q&P processes is about 87–155 MPa higher than that of the typical C–Mn–Si steel due to precipitation strengthening of NbC and refinement of martensitic structure. However, in the Ni–Mo–Ti microalloyed steel, the increment of yield strength based on precipitation strengthening of TiC is offset by the decrease of solution strengthening due to carbon dilution of the martensitic matrix, and finally the yield strength is not improved. Additionally, although the addition of alloying elements is not associated with strengthening, the product of tensile strength and total elongation (PSE) for both Mo–Nb and Ni–Mo–Ti microalloyed steels approach or exceed 20 GPa%, which indicates a superior comprehensive performance.

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Microstructural evolution and mechanical properties of low-carbon steel treated by a two-step quenching and partitioning process

Cited by 28 publications

References 27 publications

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

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

1‐Step “Quenching and Partitioning” of the Press‐Hardening Steel 22MnB5

Effect of Micro‐Alloying Elements on Microstructure and Mechanical Properties in C–Mn–Si Quenching and Partitioning (Q&P) Steels

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