Temperature Effects on Tensile Deformation Behavior of a Medium Manganese TRIP Steel and a Quenched and Partitioned Steel

Third-generation advanced high-strength steels (AHSS) containing metastable retained austenite are being developed for the structural components of vehicles to reduce vehicle weight and improve crash performance. The goal of this work was to compare the effect of temperature on austenite stability and tensile mechanical properties of two steels, a quenched and partitioned (Q&P) steel with a martensite and retained austenite microstructure, and a medium manganese transformation-induced plasticity (TRIP) steel with a ferrite and retained austenite microstructure. Quasi-static tensile tests were performed at temperatures between −10 and 85 °C for the Q&P steel (0.28C-2.56Mn-1.56Si in wt.%), and between −10 and 115 °C for the medium manganese TRIP steel (0.14C-7.14Mn-0.23Si in wt.%). X-ray diffraction measurements as a function of strain were performed from interrupted tensile tests at all test temperatures. For the medium manganese TRIP steel, austenite stability increased significantly, serrated flow behavior changed, and tensile strength and elongation changed significantly with increasing temperature. For the Q&P steel, flow stress was mostly insensitive to temperature, uniform elongation decreased with increasing temperature, and austenite stability increased with increasing temperature. The Olson–Cohen model for the austenite-to-martensite transformation as a function of strain showed good agreement for the medium manganese TRIP steel data and fit most of the Q&P steel data above 1% strain.

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Effects of Retained Austenite Stability on Mechanical Properties of High Strength TRIP Steel

Advanced Materials Research ◽

10.4028/www.scientific.net/amr.602-604.287 ◽

2012 ◽

Vol 602-604 ◽

pp. 287-293

Author(s):

Zhi Feng Li ◽

Ren Yu Fu ◽

Qing Shan Li

Keyword(s):

Mechanical Properties ◽

Trip Steel ◽

Retained Austenite ◽

Mechanical Stability ◽

High Strength ◽

Tensile Tests ◽

Transformation Kinetics ◽

Austenite Stability ◽

Kinetics Of ◽

Strength And Ductility

Mechanical stability of retained austenite and its effect on mechanical properties of high strength TRIP steel were studied by means of OM, SEM, TEM, XRD, and mechanical testing after various heat treatments. Results revealed that the film-type retained austenite located between bainite laths with high carbon content showed gradual martensitic transformation with strain, demonstrating a good TRIP effect. Samples annealed at 800°C and held at 420°C showed an optimum value of strength and ductility product up to 18381.2MPa%. Transformation kinetics of the retained austenite were evaluated through tensile tests and fitted by the function y=0.86-0.86×exp(-Ax). The fitting results were good.

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Heat Treatment Design for a QP Steel: Effect of Partitioning Temperature

Metals ◽

10.3390/met11071136 ◽

2021 ◽

Vol 11 (7) ◽

pp. 1136

Author(s):

Marcel Carpio ◽

Jessica Calvo ◽

Omar García ◽

Juan Pablo Pedraza ◽

José María Cabrera

Keyword(s):

Retained Austenite ◽

High Strength Steels ◽

High Strength ◽

Tensile Tests ◽

Quenching Temperature ◽

Advanced High Strength Steels ◽

New Family ◽

Automotive Parts ◽

Fresh Martensite ◽

Industry Needs

Designing a new family of advanced high-strength steels (AHSSs) to develop automotive parts that cover early industry needs is the aim of many investigations. One of the candidates in the 3rd family of AHSS are the quenching and partitioning (QP) steels. These steels display an excellent relationship between strength and formability, making them able to fulfill the requirements of safety, while reducing automobile weight to enhance the performance during service. The main attribute of QP steels is the TRIP effect that retained austenite possesses, which allows a significant energy absorption during deformation. The present study is focused on evaluating some process parameters, especially the partitioning temperature, in the microstructures and mechanical properties attained during a QP process. An experimental steel (0.2C-3.5Mn-1.5Si (wt%)) was selected and heated according to the theoretical optimum quenching temperature. For this purpose, heat treatments in a quenching dilatometry and further microstructural and mechanical characterization were carried out by SEM, XRD, EBSD, and hardness and tensile tests, respectively. The samples showed a significant increment in the retained austenite at an increasing partitioning temperature, but with strong penalization on the final ductility due to the large amount of fresh martensite obtained as well.

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A Flow Stress Model of 300M Steel for Isothermal Tension

Materials ◽

10.3390/ma14020252 ◽

2021 ◽

Vol 14 (2) ◽

pp. 252

Author(s):

Rongchuang Chen ◽

Shiyang Zhang ◽

Xianlong Liu ◽

Fei Feng

Keyword(s):

Flow Stress ◽

Constitutive Model ◽

Tensile Deformation ◽

Flow Behavior ◽

Tensile Tests ◽

Uniaxial Tensile ◽

Model Parameters ◽

Average Deviation ◽

Cross Sectional ◽

300M Steel

To investigate the effect of hot working parameters on the flow behavior of 300M steel under tension, hot uniaxial tensile tests were implemented under different temperatures (950 °C, 1000 °C, 1050 °C, 1100 °C, 1150 °C) and strain rates (0.01 s−1, 0.1 s−1, 1 s−1, 10 s−1). Compared with uniaxial compression, the tensile flow stress was 29.1% higher because dynamic recrystallization softening was less sufficient in the tensile stress state. The ultimate elongation of 300M steel increased with the decrease of temperature and the increase of strain rate. To eliminate the influence of sample necking on stress-strain relationship, both the stress and the strain were calibrated using the cross-sectional area of the neck zone. A constitutive model for tensile deformation was established based on the modified Arrhenius model, in which the model parameters (n, α, Q, ln(A)) were described as a function of strain. The average deviation was 6.81 MPa (6.23%), showing good accuracy of the constitutive model.

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Substructure Development and Damage Initiation in a Carbide-Free Bainitic Steel upon Tensile Test

Metals ◽

10.3390/met9121261 ◽

2019 ◽

Vol 9 (12) ◽

pp. 1261

Author(s):

Mari Carmen Taboada ◽

Amaia Iza-Mendia ◽

Isabel Gutiérrez ◽

Denis Jorge-Badiola

Keyword(s):

Retained Austenite ◽

High Strength Steels ◽

High Strength ◽

Tensile Tests ◽

Formation Mechanisms ◽

Tempered Martensite ◽

Damage Initiation ◽

Advanced High Strength Steels ◽

Significant Strength ◽

The Stability

Carbide-free bainitic (CFB) steels belong to the family of advanced high strength steels (AHSS) that are struggling to become part of the third-generation steels to be marketed for the automotive industry. The combined effects of the bainitic matrix and the retained austenite confers a significant strength with a remarkable ductility to these steels. However, CFB steels usually show much more complex microstructures that also contain MA (Martensite–Austenite) phase and auto-tempered martensite (ATM). These phases may compromise the ductility of CFB steels. The present work analyzes the substructure evolution during tensile tests in the necking zone, and deepens into the void and crack formation mechanisms and their relationship with the local microstructure. The combination of FEG-SEM imaging, EBSD, and X-ray diffraction has been necessary to characterize the substructure development and damage initiation. The bainite matrix has shown great ductility through the generation of high angle grain boundaries and/or large orientation gradients around voids, which are usually found close to the bainite and MA/auto-tempered martensite interfaces or fragmenting the MA phase. Special attention has been paid to the stability of the retained austenite (RA) during the test, which may eventually be transformed into martensite (Transformation Induced Plasticity, or TRIP effect).

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The Role of Retained Austenite in Tempered Martensite Embrittlement of 4340 and 300-M Steels Investigated through Rapid Tempering

Metals ◽

10.3390/met11091349 ◽

2021 ◽

Vol 11 (9) ◽

pp. 1349

Author(s):

Virginia K. Euser ◽

Don L. Williamson ◽

Kip O. Findley ◽

Amy J. Clarke ◽

John G. Speer

Keyword(s):

Retained Austenite ◽

High Strength Steels ◽

High Strength ◽

Tensile Tests ◽

Austenite Decomposition ◽

Tempered Martensite ◽

Mechanical Transformation ◽

Fresh Martensite ◽

Rapid Tempering

Tempered martensite embrittlement (TME) is investigated in two medium carbon, high strength steels, 4340 (low silicon) and 300-M (high silicon), via rapid (1, 10, or 100 s) and conventional (3600 s) tempering. Rapid tempering of 4340 diminishes the depth of the TME toughness trough, where improvements in impact toughness correspond to the suppression of retained austenite decomposition. In 300-M, retained austenite decomposition is suppressed to an even greater extent by rapid tempering. While toughness improves overall after rapid tempering, TME severity remains consistent in 300-M across the tempering conditions examined. Through interrupted tensile tests, it was found that the 300-M conditions that exhibit TME are associated with mechanically unstable retained austenite. Unstable retained austenite is shown to mechanically transform early in the deformation process, presumably resulting in fresh martensite adjacent to interlath cementite that ultimately contributes to TME. The present results emphasize the role of both the thermal decomposition and mechanical transformation of retained austenite in the manifestation of TME.

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EFFECT OF C-Mn PARTITIONING ON THE MICROSTRUCTURE AND MECHANICAL PROPERTIES OF TRIP STEEL

Materiali in tehnologije ◽

10.17222/mit.2020.181 ◽

2021 ◽

Vol 55 (2) ◽

pp. 269-275

Author(s):

Cainian Jing ◽

Qiteng Lei ◽

Tao Lin ◽

Daomin Ye ◽

Cong Wu ◽

...

Keyword(s):

Mechanical Properties ◽

Trip Steel ◽

Retained Austenite ◽

Lath Martensite ◽

Tensile Tests ◽

Microstructure And Mechanical Properties

In this paper, the TRIP590 steel was used for C-Mn partitioning. The influence of C-Mn partitioning on the microstructure and mechanical properties of the steel was studied. SEM, EPMA, XRD and tensile tests were used to characterize the microstructure of the tested steel, calculate the content of retained austenite, and analyze the enrichment of C atoms and Mn atoms and mechanical properties. The results show that there was a lot of lath martensite and scattered ferrite in the microstructures of the Q&P steel and C-Mn partitioning steel. After C-Mn partitioning, the content of ferrite was increased. The enrichment of C and Mn in the C-Mn partitioning steel was relatively apparent, and the concentration of the atoms in the center of martensite was significantly higher than at the boundary between martensite and ferrite. Mn-rich areas were also C-rich areas. Compared with the Q&P steel, the C-Mn partitioning steel had a larger amount of retained austenite, higher elongation and PSE.

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Effect of Aluminum and Vanadium on Retained Austenite Stability and Work Hardening in Silicon Free TRIP Steel

Key Engineering Materials ◽

10.4028/www.scientific.net/kem.835.347 ◽

2020 ◽

Vol 835 ◽

pp. 347-352

Author(s):

Ahmed El-Sherbiny ◽

Mohamed Kamal El-Fawkhry ◽

Ahmed Y. Shash ◽

Tarek M. El-Hossainy ◽

Ayman Mohamed Fathy ◽

...

Keyword(s):

Strain Hardening ◽

Trip Steel ◽

Retained Austenite ◽

X Ray Diffraction ◽

Alloying Element ◽

Etching Technique ◽

Complete Replacement ◽

Austenite Stability ◽

Retained Austenite Stability ◽

Strong Candidate

Despite that the conventional CSiMn TRIP steel has a promissing mechanical attributes, it has a limitations on the galvanizability of such grades of steel due to Silicon. Thus, aluminum as a strong candidate for substituting silicon has been introduced in this study accompanied by vanadium as a microalloying element. Microstructure of the studied steel was observed by using OM, and SEM. X-ray diffraction analysis, and tent-etching technique carried out on the studied steel to identify the fractions of the retained Austenite after thermal mechanical process, as well as its morphology. In addition, the mechanical properties in term of strength, ductility, strain hardening, and the rate of strain hardening were studied to define the influenced parameters throughout this alteration. The results refer to the possibility of complete replacement of silicon in TRIP steel with aluminum at the presence of vanadium as a micro alloying element.

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Deformation Behaviour of TRIP Steel Monitored by In Situ Neutron Diffraction

Advanced Materials Research ◽

10.4028/www.scientific.net/amr.939.25 ◽

2014 ◽

Vol 939 ◽

pp. 25-30

Author(s):

Jozef Zrník ◽

Ondrej Muránsky ◽

Petr Sittner

Keyword(s):

Neutron Diffraction ◽

Trip Steel ◽

Retained Austenite ◽

Volume Fraction ◽

Tensile Deformation ◽

Deformation Behaviour ◽

Tensile Load ◽

Ferrite Matrix ◽

Granular Bainite

The paper presents results ofin-situneutron diffraction experiments aimed on monitoring the phase evolution and load distribution in transformation induced plasticity (TRIP) steel when subjected to tensile loading. Tensile deformation behaviour of two TRIP-assisted multiphase steel with slightly different microstructures resulted from different thermo-mechanical treatments applied was investigated byin-situneutron diffraction. The steel with lower retained austenite volume fraction (fγ=0.04) and higher volume fraction of needle-like bainite in the α-matrix exhibits higher yield stress (sample B, 600MPa) but considerably lower elongation in comparison to the steel with higher austenite volume fraction (fγ=0.08), granular bainite and ferrite matrix (sample A, 500 MPa). The neutron diffraction results showed that the applied tensile load is redistributed at the yielding point in a way that the retained austenite bears a significantly larger load than the α-matrix during the TRIP steel deformation. Steel sample with higher volume fraction of retained austenite and less strong ferrite matrix proved to be a better TRIP steel with respect to strength, ductility and the side effect of the strain induced austenite-martensite transformation. The transforming retained austenite in time of loading provides potential for higher ductility of experimental TRIP steel but at the same time acts as a reinforcement phase during the further plastic deformation.TRIP steel, austenite conditioning, austenite transformation, structure, retained austenite, tensile deformation, neutron diffraction, load partitioning, mechanical properties.

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Temperature Development during Step-Wise Tensile Tests on a TRIP Steel

Materials Science Forum ◽

10.4028/www.scientific.net/msf.638-642.3579 ◽

2010 ◽

Vol 638-642 ◽

pp. 3579-3584

Author(s):

Lie Zhao ◽

Corinna Thomser ◽

Kirsten Schneider ◽

Wolfgang Bleck ◽

Jilt Sietsma

Keyword(s):

Trip Steel ◽

Retained Austenite ◽

Room Temperature ◽

Longitudinal Direction ◽

Tensile Tests ◽

Transformation Induced Plasticity ◽

Trip Steels ◽

Loading Process ◽

Temperature Development ◽

The Stability

Temperature development during plastic deformation affects the stability of retained austenite and thus the mechanical properties in transformation-induced plasticity (TRIP) steels. In this work, we used a thermo-camera to monitor the temperature development during a step-wise tensile test of an Al-containing multiphase TRIP steel. The tensile tests were performed by loading the specimen at six straining rates ranging from 5 to 30 s-1 to a stress of 700 MPa and then holding for 15 min, followed by further loading at 50 s-1 until fracture. It is found that temperature increases about 13 – 18 °C during the first loading process and drops back to room temperature with a time-constant of around 2 min. The increment of temperature increases with increasing straining rate. The temperature increases around 30 °C during the second loading process. The distribution of temperature over the specimen surface is found to be rather homogeneous along the longitudinal direction in most cases, except for the ending points of two loading processes. The measurement of temperature development is found to be consistent with previous numerical simulation on the temperature development under constant stress in TRIP steels.

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Microstructure-Tensile Properties Relationship and Austenite Stability of a Nb-Mo Micro-Alloyed Medium-Mn TRIP Steel

Metals ◽

10.3390/met8080615 ◽

2018 ◽

Vol 8 (8) ◽

pp. 615 ◽

Cited By ~ 5

Author(s):

Chunquan Liu ◽

Qichun Peng ◽

Zhengliang Xue ◽

Mingming Deng ◽

Shijie Wang ◽

...

Keyword(s):

Tensile Properties ◽

Trip Steel ◽

Retained Austenite ◽

Temperature Stability ◽

Manganese Steel ◽

Austenite Stability ◽

Fine Grain ◽

Fine Grain Strengthening ◽

Medium Manganese Steel ◽

Lüders Band

This study investigated the microstructure–tensile properties relationship and the retained austenite room temperature stability of a Nb and Mo micro-alloyed medium manganese transformation induced plasticity (TRIP) steel. A number of findings were obtained. Most importantly, the steel after being processed by quenching and tempering (Q & T) exhibited excellent tensile properties, i.e., the strength of 878–1373 MPa, the ductility of 18–40% Mo, and Nb microalloying served to control the fraction of retained austenite and to improve tensile strength by fine grain strengthening. Excellent tensile properties were attributable to the large amount of retained austenite which produced a discontinuous TRIP effect. This effect led to the production a large amount of martensite which relieved the stress concentration, contributing to the coordinated deformation between the phases and thus improving the deformability of the steel. Additionally, the differences in Mn and C contents led to varying degrees of austenite stability and the length of the Lüders band decreased as the inter critical annealing temperature increased. The micro-alloyed medium manganese steel experimented on our study showed considerable improvement in tensile properties in comparison with the 5Mn-0.1C medium manganese steel in previous studies.

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