Effect of austenite stability on the hole expansion behavior of δ-TRIP steels

Xu, Xiaoguang; Xu, Bo; Chen, P.; Liu, R.D.; Wang, G.D.; Yi, Hailong

doi:10.1016/j.mtcomm.2020.101034

Cited by 9 publications

(4 citation statements)

References 25 publications

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“…The smaller the average grain size, the more the plastic deformation can be distributed to more grains, and plastic deformation is more uniform, resulting in a slight stress concentration [14]. The tested steel at the coiling temperature of 520 • C has more retained austenite, and more retained austenite takes place in the TRIP effect during deformation, which further improves the plasticity of the material [10,27]. Therefore, the collaborative effect of ferrite content, average grain size, and TRIP effect contributed to the total elongation of the test steel at the coiling temperature of 520 • C, being slightly higher than that at 480 • C. The ferrite and granular bainite of the test steel at the coiling temperature of 520 • C were uniformly distributed.…”

Section: Effect Of Coiling Temperature On the Strength-plasticity And...mentioning

confidence: 99%

Effect of Coiling Temperature on Microstructure and Properties of Ferritic-Bainitic Dual-Phase Steels

Li,

Zhou,

Liu

et al. 2024

Metals

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In this study, a 780 MPa grade ferritic-bainitic dual-phase steel with excellent matching of strength-plasticity and formability was developed using thermomechanical control processing. Optical microscopy, Scanning electron microscopy, and Electron Backscatter Diffraction techniques were used to characterize the microstructure comprehensively, and the effects of coiling temperature on the microstructure, the strength-plasticity, and hole-expansion ratio of the test steels were thoroughly investigated. The results showed that the test steel had an excellent combination of ferrite and bainite at the coiling temperature of 520 °C, 23.7 and 76.3%, respectively, with a hole expansion ratio of 58.5 ± 2.8%. The uniformity of the microstructure was the key to obtaining a high expansion ratio in ferrite-bainite dual-phase steels. The test steels formed granular bainite at low-temperature coiling, while polygonal ferrite was promoted at high-temperature coiling. The effect of coiling temperature on grain size is small. Dislocations were redistributed during high-temperature coiling, resulting in a decrease in dislocation density. The higher elongation and hole expansion rate at higher coiling temperatures were attributed to increased polygonal ferrite content, reduced grain size, and enhanced TRIP effect. When coiling at low temperatures, the agglomeration of polygonal ferrite or granular bainite tends to result in a non-uniform distribution of the soft and hard phases of the matrix. At the same time, the strong texture parallel to the rolling direction has a significant difference in plasticity in different directions, leading to non-uniform deformation, which is liable to stress concentration, causing crack nucleation and extension in the hole expanding process, thus reducing the hole expansion performance.

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Section: Effect Of Coiling Temperature On the Strength-plasticity And...mentioning

confidence: 99%

Effect of Coiling Temperature on Microstructure and Properties of Ferritic-Bainitic Dual-Phase Steels

Li,

Zhou,

Liu

et al. 2024

Metals

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“…Firstly, in multi-phase TRIP-assisted steels, Kashima et al [219] suggested that the closer in strength between the phases the better the HER and proposed a reverted lamellar morphology without polygonal ferrite to increase stretch flangeablity. In δ -TRIP steels, Xu et al [220] also showed that a high austenite stability was beneficial for HER by reducing the amount of fresh martensite formed at the edge during punching out the initial hole for the hole expansion test. Hole expansion tests are extremely sensitive to edge effects [217] and less martensite at the rim will help to reduce the local strength mismatch between phases at the hole edge.…”

Section: Finishingmentioning

confidence: 99%

A review of the processing, microstructure and property relationships in medium Mn steels

Kwok

Dye

2023

International Materials Reviews

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Medium Mn steels are an emerging class of 3rd generation advanced high-strength steels. These steels have received significant attention due to their high strengths, large ductilities and also lower cost compared to their predecessor high Mn Twinning Induced Plasticity (TWIP) steels. Additionally, medium Mn steels have been found to exhibit TWIP and/or Transformation Induced Plasticity (TRIP) effects which can be harnessed to give a high strain hardening rate. Many thermomechanical processing concepts in the literature have been developed, producing multiple microstructure types with differentmechanical properties. The present review therefore aims to summarise the current knowledge of medium Mn steel alloy design especially on the processing, microstructure and property relationships in medium Mn steels. It complements the review of Sun et al. [Physical metallurgy of medium-Mn advanced high-strength steels, Int Mater Rev. 2023.], written independently and in parallel, which focusses more on the phase interfaces and thermodynamics.

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“…In the material research field, transformation induced plasticity steels have long been recognized as promising materials for automotive industry owing to their unique combination of high strength and ductility [8,9]. The good combination of strength and ductility of transformation induced plasticity steel results from the martensitic transformation of retained austenite during the plastic deformation process, which is called transformation induced plasticity effect [10,11]. To obtain the tubular materials with high strength as well as good plasticity, the authors have been introduced the transformation induced plasticity steel technique into tubular materials research and successfully developed the transformation induced plasticity seamless steel tube with two stage heat treatment using cold drawn steel tube [12,13].…”

Section: Introductionmentioning

confidence: 99%

Microstructure evolution of transformation induced plasticity seamless steel tube in hydraulic free bulge test

Zhang

Kong

et al. 2022

Materialwissenschaft Werkst

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In this study the hydraulic free bulge test with an internal pressure boosting velocities of 0.5 MPa/s and punch feeding speed of 0.2 mm/s was carried out to study the microstructure evolution of the transformation induced plasticity seamless steel tube in the hydroforming process. The microstructure of the selected parts of the tube after the hydraulic free bulge test were investigated with the optical microscope and transmission electron microscope. The transformation rate of the retained austenite to martensite of the selected parts were determined by the x‐ray diffraction. To study the deformation behavior and obtain the stress‐strain state of the tube, the finite element simulation of the hydraulic free bulge test was also carried out. The results show that the retained austenite in the microstructure of all the selected parts transformed to martensite after the hydraulic free bulge test. In the center part of the tube, the highest transformation rate of 82.84 % was obtained. The retained austenites distribute inside of the ferrite grains transform to martensite firstly under the compressive stress and strain state. The retained austenites distribute at the ferrite grain boundaries start to transforme into martensite when the tube is subjected to the tensile stress and strain.

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Effect of austenite stability on the hole expansion behavior of δ-TRIP steels

Cited by 9 publications

References 25 publications

Effect of Coiling Temperature on Microstructure and Properties of Ferritic-Bainitic Dual-Phase Steels

Effect of Coiling Temperature on Microstructure and Properties of Ferritic-Bainitic Dual-Phase Steels

A review of the processing, microstructure and property relationships in medium Mn steels

Microstructure evolution of transformation induced plasticity seamless steel tube in hydraulic free bulge test

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