Mechanical Stability and Deformation-Induced Transformation of Retained Austenite in TRIP Steels at Low Temperatures

2017 ◽  
Vol 741 ◽  
pp. 36-41 ◽  
Author(s):  
Takayuki Yamashita ◽  
Norimitsu Koga ◽  
Osamu Umezawa
Keyword(s):  
Low Temperature ◽  
Work Hardening ◽  
Low Temperatures ◽  
Retained Austenite ◽  
Mechanical Stability ◽  
High Strain ◽  
Volume Fraction ◽  
Trip Steels ◽  
The Stability ◽  
Strength And Ductility

The tensile properties and the stability of retained austenite in TRIP steels with different volume fraction of retained austenite have been studied at low temperature. The steels showed a good valance of strength and ductility at 193 K. Their work-hardening rates were decreased linearly and kept a high value in the high strain regime at 193 K. The retained austenite was mostly transformed into martensite less than 10% strain at 193 K.

Effect of Phosphorus on Microstructure, Mechanical Properties, and Formation of Retained Austenite in TRIP Steels

2012 ◽  
Vol 508 ◽  
pp. 128-132 ◽  
Author(s):  
Eui Pyo Kwon ◽  
Shun Fujieda ◽  
Kozo Shinoda ◽  
Shigeru Suzuki
Keyword(s):  
Mechanical Properties ◽  
Carbon Concentration ◽  
Trip Steel ◽  
Retained Austenite ◽  
Volume Fraction ◽  
Transformation Induced Plasticity ◽  
Trip Steels ◽  
The Stability

In this Study, Influences of P on the Microstructure, Mechanical Properties, and Retained Austenite Characteristics in Transformation Induced Plasticity (TRIP) Steels Were Investigated. Microstructure of 0.2mass%P Containing TRIP Steel Was Inhomogeneous and it Resulted in Deterioration of the Mechanical Properties. Retained Austenite Characteristics such as Volume Fraction and Carbon Concentration Were Also Affected by P. The Stability of Retained Austenite in P Containing TRIP Steel Was Different from that in P-Free TRIP Steel. Such Difference in the Stability of Retained Austenite Was Attributed to the Effect of the Carbon Concentration in Retained Austenite as Well as their Different Microstructure.

Effect of Retained Austenite Stability on Mechanical Properties of 590MPa Grade TRIP Sheet Steels

2010 ◽  
Vol 638-642 ◽  
pp. 3374-3379 ◽  
Author(s):  
Hiroshi Matsuda ◽  
Hisata Noro ◽  
Yasunobu Nagataki ◽  
Yoshihiro Hosoya
Keyword(s):  
Mechanical Properties ◽  
Carbon Content ◽  
Retained Austenite ◽  
High Strain ◽  
Sheet Steels ◽  
Trip Steels ◽  
Austenite Stability ◽  
Retained Austenite Stability ◽  
The Stability ◽  
High Work

Industrial low alloy TRIP sheet steels contain blocky and lath-shaped retained austenite. In the present study, transformation behaviour of blocky and lath-shaped retained austenite during straining was investigated to clarify its effect on mechanical properties. Two types of TRIP steels containing almost the same amount but the different morphology of retained austenite were used. A steel containing large amount of lath-shaped retained austenite exhibits superior ductility, and sustains high work-hardenability in a high strain region. On the contrast, a steel containing large amount of blocky retained austenite exhibits low ductility. 　The work-hardenability increased steeply to the maximum at a low strain region, and then reduced in a high strain region. The stability of the blocky austenite has been found to be poor with respected to martensite transformation. The lath-shaped retained austenite remains until a high strain region whereas the blocky retained austenite transformed into martensite in a low strain region. Carbon content was higher in the lath-shaped retained austenite than in the blocky retained austenite. Stability of retained austenite is, however, inexplicable only by the carbon content, and would be affected by the different morphology and the resulting restraint conditions.

Temperature-Dependent Mechanical Stability of Retained Austenite in Thermomechanically Processed 3Mn Steel

2021 ◽  
Vol 1016 ◽  
pp. 762-767
Author(s):  
Aleksandra Kozłowska ◽  
Adam Grajcar ◽  
Aleksandra Janik ◽  
Krzysztof Radwański
Keyword(s):  
Retained Austenite ◽  
Mechanical Stability ◽  
Electron Backscatter Diffraction ◽  
Tensile Tests ◽  
Trip Effect ◽  
X Ray Diffraction ◽  
Temperature Dependent ◽  
Static Tensile ◽  
The Stability ◽  
Backscatter Diffraction

The temperature-dependent mechanical stability of retained austenite in medium-Mn transformation induced plasticity 0.17C-3.3Mn-1.6Al-1.7Al-0.22Si-0.23Mo thermomechanically processed steel was investigated using scanning electron microscopy (SEM), electron backscatter diffraction (EBSD) and X-ray diffraction (XRD) methods. Specimens were deformed up to rupture in static tensile tests in a temperature range 20–200°C. It was found that deformation temperature affects significantly the intensity of TRIP effect. In case of specimens deformed at temperatures higher than 60°C, a gradual temperature-related decrease in the stability of γ phase was noted. It indicates a progressive decrease of the significance of the TRIP effect and at the same time the growing importance of the thermally activated processes affecting a thermal stability of retained austenite.

Effect of Ausforming Temperature on Bainite Transformation of High Carbon Low Alloy Steel

2015 ◽  
Vol 817 ◽  
pp. 454-459 ◽  
Author(s):  
Jian Guo He ◽  
Ai Min Zhao ◽  
Huang Yao ◽  
Chao Zhi ◽  
Fu Qing Zhao
Keyword(s):  
Low Temperature ◽  
Alloy Steel ◽  
Retained Austenite ◽  
Volume Fraction ◽  
Transformation Rate ◽  
Low Alloy Steel ◽  
High Carbon ◽  
Bainite Transformation ◽  
Electron Backscattered Diffraction ◽  
In Situ Experiments

The effect of ausforming temperature on bainite transformation of high carbon low alloy steel was studied by in situ experiments using a Gleeble 3500 thermal and mechanical testing system. Morphology and crystallography of ausforming bainite were examined by scanning electron microscopy (SEM) and electron backscattered diffraction (EBSD). It has been found that deformation at all temperatures range from 230°C to 600°C can accelerate low temperature bainite transformation, and transformation rate increased with deformation temperature reduced. Quantitative X-ray analysis shows that the volume fraction of retained austenite was about 35.84% after deformation and isothermal transformation for 20 hours, it was approximately the same amount with austempering bainite transformation process (no strain) which austenite volume fraction was about 32.01%. Low temperature bainite formation can be accelerated with a smaller increase amount of retained austenite by deformation at a low temperature range of 230~600 oC.

scholarly journals The Stability of Icosahedral Cd-Yb

2003 ◽  
Vol 805 ◽  
Author(s):  
Günter Krauss ◽  
Sofia Deloudi ◽  
Andrea Steiner ◽  
Walter Steurer ◽  
Amy R. Ross ◽  
...  
Keyword(s):  
Low Temperature ◽  
Ambient Temperature ◽  
Mechanical Stress ◽  
Single Crystals ◽  
High Temperatures ◽  
Low Temperatures ◽  
Ambient Pressure ◽  
X Ray Diffraction ◽  
X Ray ◽  
The Stability

ABSTRACTThe stability of single-crystalline icosahedral Cd-Yb was investigated using X-ray diffraction methods in the temperature range 20 K ≤ T ≤ 900 K at ambient pressure and from ambient temperature to 873 K at about 9 GPa. Single-crystals remain stable at low temperatures and in the investigated HP-HT-regime. At high temperatures and ambient pressure, the quasicrystal decomposes. The application of mechanical stress at low temperatures yields to the same decomposition, the formation of Cd. A reaction of icosahedral Cd-Yb with traces of oxygen or water causing the decomposition seems reasonable, but a low-temperature instability of this binary quasi-crystal cannot be ruled out totally.

scholarly journals Mechanism of the Microstructural Evolution of 18Cr2Ni4WA Steel during Vacuum Low-Pressure Carburizing Heat Treatment and Its Effect on Case Hardness

Materials ◽  
2020 ◽  
Vol 13 (10) ◽  
pp. 2352
Author(s):  
Bin Wang ◽  
Yanping He ◽  
Ye Liu ◽  
Yong Tian ◽  
Jinglin You ◽  
...  
Keyword(s):  
Low Temperature ◽  
Carbon Content ◽  
Retained Austenite ◽  
Mechanical Stability ◽  
Lath Martensite ◽  
Low Pressure ◽  
Low Carbon ◽  
High Carbon ◽  
Carburized Layer ◽  
Martensite Matrix

In this study, vacuum low-pressure carburizing heat treatments were carried out on 18Cr2Ni4WA case-carburized alloy steel. The evolution and phase transformation mechanism of the microstructure of the carburized layer during low-temperature tempering and its effect on the surface hardness were studied. The results showed that the carburized layer of the 18Cr2Ni4WA steel was composed of a large quantity of martensite and retained austenite. The type of martensite matrix changed from acicular martensite to lath martensite from the surface to the core. The hardness of the carburized layer gradually decreased as the carbon content decreased. A thermodynamic model was used to show that the low-carbon retained austenite was easier to transform into martensite at lower temperatures, since the high-carbon retained austenite was more thermally stable than the low-carbon retained austenite. The mechanical stability—not the thermal stability—of the retained austenite in the carburized layer dominated after carburizing and quenching, and cryogenic treatment had a limited effect on promoting the martensite formation. During low-temperature tempering, the solid-solution carbon content of the martensite decreased, the compressive stress on the retained austenite was reduced and the mechanical stability of the retained austenite decreased. Therefore, during cooling after low-temperature tempering, the low-carbon retained austenite transformed into martensite, whereas the high-carbon retained austenite still remained in the microstructure. The changes in the martensite matrix hardness had a far greater effect than the transformation of the retained austenite to martensite on the case hardness of the carburized layer.

Effects of Heat Treatment on Microstructure of High-Strength Manganese-Silicon Steels

2017 ◽  
Vol 270 ◽  
pp. 239-245
Author(s):  
Dagmar Bublíková ◽  
Štěpán Jeníček ◽  
Kateřina Opatová ◽  
Bohuslav Mašek
Keyword(s):  
Heat Treatment ◽  
Cooling Rate ◽  
Microstructure Evolution ◽  
Retained Austenite ◽  
Volume Fraction ◽  
High Strength ◽  
Quenching And Partitioning ◽  
Alloying Additions ◽  
New Procedures ◽  
Strength And Ductility

Today’s advanced steels are required to possess high strength and ductility. This can be accomplished by producing appropriate microstructures with a certain volume fraction of retained austenite. The resulting microstructure depends on material’s heat treatment and alloying. High ultimate strengths and sufficient elongation levels can be obtained by various methods, including quenching and partitioning (Q&P process). The present paper introduces new procedures aimed at simplifying this process with the use of material-technological modelling. Three experimental steels have been made and cast for this investigation, whose main alloying additions were manganese, silicon, chromium, molybdenum and nickel. The purpose of manganese addition was to depress the Ms and Mf temperatures. The Q&P process was carried out in a thermomechanical simulator for better and easier control. The heat treatment parameters were varied between the sequences and their effect on microstructure evolution was evaluated. They included the cooling rate, partitioning temperature and time at partitioning temperature. Microstructures including martensite with strength levels of more than 2000 MPa and elongation of 10–15 % were obtained.

Comparison of the Hardness-Toughness Relationship of Medium-Mn Steels after Q&T and Q&P Treatments*

2021 ◽  
Vol 76 (6) ◽  
pp. 445-457
Author(s):  
R. Schneider ◽  
S. Kaar ◽  
S. Schneider ◽  
D. Krizan ◽  
C. Sommitsch
Keyword(s):  
Tensile Testing ◽  
Retained Austenite ◽  
Room Temperature ◽  
Carbon Diffusion ◽  
Temperature Quenching ◽  
Optimum Parameters ◽  
The Stability ◽  
Relationship Of ◽  
Quenching And Tempering ◽  
Strength And Ductility

Abstract In contrast to quenching and tempering (Q&T), with quenching to room temperature, quenching and partitioning (Q&P) usually applies quenching to a temperature between Ms and room temperature. To stabilize a sufficient amount of retained austenite (RA), carbon diffusion from martensite into austenite and a prevention of cementite formation takes place during the successive partitioning step. Larger amount of RA, and its transformation into martensite during plastic deformation, provides Q&P treated steels with an enhanced combination of strength and ductility. In this investigation, the effect of different Q&T and Q&P treatments on the hardness-toughness relationship was determined. These results are compared with the RA contents and mechanical properties provided by tensile testing. The obtained results clearly demonstrate that the optimum parameters for strength and ductility do not match with the best combinations of hardness and toughness. Furthermore, the stability of the RA plays an important role in the understanding of toughness properties of the investigated Q&P steels.

Transformation Induced Plasticity (TRIP) Effect Used in Forming of Carbon CMnSi Steel

2005 ◽  
Vol 500-501 ◽  
pp. 461-470 ◽  
Author(s):  
Jiří Kliber ◽  
Bohuslav Mašek ◽  
Ondrej Zacek ◽  
H. Staňková
Keyword(s):  
Continuous Casting ◽  
Hot Rolling ◽  
Retained Austenite ◽  
Volume Fraction ◽  
Thermomechanical Processing ◽  
High Strength ◽  
Ferrite Matrix ◽  
Transformation Induced Plasticity ◽  
Trip Steels ◽  
Forming Temperature

Transformation induced plasticity (TRIP) steel combines high strength and high ductility that makes it particularly suitable for forming. Martensite within a ferrite matrix is usually obtained either by continuous casting of slabs followed by hot rolling (which is the fastest method, hence the most economical one, producing, however, relatively thick products) or by the continuous casting of slabs followed by hot rolling, cold rolling and annealing (the method used for thin products). High cooling rates, low coiling temperatures and low reduction during hot deformation were generally found to suppress the formation of polygonal ferrite and promote the presence of retained austenite. This paper focuses on development and modifications of two CMnSi-based TRIP steels with 0,23 % C;1,4 % Mn; 1,9 % Si; ( 0,08 % Nb) by means of laboratory thermomechanical processing. Description of experimental devices for the analysis of transformation plasticity under tensioncompression loading is given. Experiments were carried out on the simulator for thermaldeformation cycles SMITWELD and TANDEM was used for thermomechanical processing on the laboratory rolling mill. The maximum volume fraction of retained austenite and the resulting optimum combination of tensile strength and ductility were achieved in testing heats. Special attention was paid to volume fraction changes of single phases and to changes in morphology of phases. The results suggest that rather short isothermal bainite transformation times are sufficient to obtain TRIP microstructure. The influence of parameters of thermomechanical processing such as the amount of strain, forming temperature and austenitization time and temperature on microstructures of TRIP steels were evaluated.

Microstructure and Mechanical Properties of Cold-Rolled TRIP Steel Sheets

2011 ◽  
Vol 266 ◽  
pp. 280-283 ◽  
Author(s):  
Cai Nian Jing ◽  
Xiao Hui Chen ◽  
Ming Gang Wang ◽  
Qi Zhong Tian ◽  
Zuo Cheng Wang
Keyword(s):  
Retained Austenite ◽  
High Strength ◽  
Transformation Induced Plasticity ◽  
Trip Steels ◽  
Multiphase Microstructure ◽  
Steel Sheets ◽  
High Strength Level ◽  
Cold Rolled ◽  
Level 2 ◽  
Strength And Ductility

Transformation induced plasticity (TRIP) steels have complex multiphase microstructure composed of ferrite, bainite and retained austenite [1]. These metastable retained austenite can transforms into martensite during plastic deformation, which generates a TRIP effect resulting in excellent combination of high strength and ductility even at high strength level [2-5]. For this reason, the TRIP-aided steel sheets are suitable to fabricate automobile parts, as they can offer excellent formability without sacrifice the strength and safety requirement of the steel sheets. As a result, the development of TRIP-aided steels has been a very important issue in the automobile field.

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