Thermal Stability of Retained Austenite in High-carbon Steels during Cryogenic and Tempering Treatments

AbstractAdvanced medium-Mn sheet steels show an opportunity for the development of cost-effective and light-weight automotive parts with improved safety and optimized environmental performance. These steels utilize the strain-induced martensitic transformation of metastable retained austenite to improve the strength–ductility balance. The improvement of mechanical performance is related to the tailored thermal and mechanical stabilities of retained austenite. The mechanical stability of retained austenite was estimated in static tensile tests over a wide temperature range from 20 °C to 200 °C. The thermal stability of retained austenite during heating at elevated temperatures was assessed by means of dilatometry. The phase composition and microstructure evolution were investigated by means of scanning electron microscopy, electron backscatter diffraction, X-ray diffraction and transmission electron microscopy techniques. It was shown that the retained austenite stability shows a pronounced temperature dependence and is also stimulated by the manganese addition in a 3–5% range.

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Effect of Chemistry Modification, Hot Forging and Partitioning on Low Alloy Grade Tool Steel

Key Engineering Materials ◽

10.4028/www.scientific.net/kem.786.75 ◽

2018 ◽

Vol 786 ◽

pp. 75-83

Author(s):

Ahmed Ismail Zaky Farahat ◽

Mohamed Kamal El Fawkhry ◽

Ayman M. Fathy ◽

Taha M. Mattar

Keyword(s):

Thermal Stability ◽

Tool Steel ◽

Retained Austenite ◽

Treatment Process ◽

Hot Forging ◽

Optical Microscope ◽

Isothermal Treatment ◽

The Novel ◽

Slow Cooling ◽

Thermal Stability Of

Development of S6 tool steel has been discussed in this research by conducting a bit modification in the chemical composition using aluminum instead of molybdenum, and micro addition of boron to enhance the marteniste structure. Then, the hardenability and thermal stability have been detected in regarding to S6 tool steel. A novel isothermal treatment process has been suggested to enrich the retained austenite, and thereby, it has been tracked by using XRD, optical microscope, and SEM in conjugation with EDS. The effect of retained on the mechanical properties has been determined. The results ensure that aluminum has inhibited the graphite formation through the slow cooling regime. No change of hardenability or thermal stability of S6 tool steel triggered from adding of aluminum and microaddition of boron. In addition, the novel isothermal process leads to enrichment of retained austenite that has significantly affected on the combination of ductility with strength of the newly designed steel.

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Thermal Stability of Nanocrystalline Structure In X37CrMoV5-l Steel

Archives of Metallurgy and Materials ◽

10.1515/amm-2015-0082 ◽

2015 ◽

Vol 60 (1) ◽

pp. 511-516 ◽

Cited By ~ 1

Author(s):

E. Skołek ◽

S. Marciniak ◽

W.A. Świątnicki

Keyword(s):

Thermal Stability ◽

Retained Austenite ◽

Volume Fraction ◽

Bainitic Ferrite ◽

Nanocrystalline Structure ◽

Thin Layers ◽

Isothermal Quenching ◽

Initial Stage ◽

Increasing Temperature ◽

Thermal Stability Of

AbstractThe aim of the study was to investigate the thermal stability of the nanostructure produced in X37CrMoV5-1 tool steel by austempering heat treatment consisted of austenitization and isothermal quenching at the range of the bainitic transformation. The nanostructure was composed of bainitic ferrite plates of nanometric thickness separated by thin layers of retained austenite. It was revealed, that the annealing at the temperature higher than temperature of austempering led to formation of cementite precipitations. At the initial stage of annealing cementite precipitations occurred in the interfaces between ferritic bainite and austenite. With increasing temperature of annealing, the volume fraction and size of cementite precipitations also increased. Simultaneously fine spherical Fe7C3carbides appeared. At the highest annealing temperature the large, spherical Fe7C3carbides as well as cementite precipitates inside the ferrite grains were observed. Moreover the volume fraction of bainitic ferrite and of freshly formed martensite increased in steel as a result of retained austenite transformation during cooling down to room temperature.

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Thermal Stability of Retained Austenite in TRIP Steel After Different Treatments

Journal of Iron and Steel Research International ◽

10.1016/s1006-706x(08)60013-8 ◽

2008 ◽

Vol 15 (1) ◽

pp. 61-64 ◽

Cited By ~ 14

Author(s):

Wen Shi ◽

Lin Li ◽

Bruno C. De Cooman ◽

Patrick Wollants ◽

Chun-xia Yang

Keyword(s):

Thermal Stability ◽

Trip Steel ◽

Retained Austenite ◽

Thermal Stability Of

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Thermal stability of retained austenite in TRIP steels studied by synchrotron X-ray diffraction during cooling

Acta Materialia ◽

10.1016/j.actamat.2005.08.017 ◽

2005 ◽

Vol 53 (20) ◽

pp. 5439-5447 ◽

Cited By ~ 282

Author(s):

N VANDIJK ◽

A BUTT ◽

L ZHAO ◽

J SIETSMA ◽

S OFFERMAN ◽

...

Keyword(s):

Thermal Stability ◽

Retained Austenite ◽

X Ray Diffraction ◽

X Ray ◽

Trip Steels ◽

Thermal Stability Of

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Thermal Stability of Retained Austenite in TRIP-aided Cold-rolled Steel

Journal of Mechanical Engineering ◽

10.3901/jme.2011.04.066 ◽

2011 ◽

Vol 47 (04) ◽

pp. 66 ◽

Cited By ~ 2

Author(s):

Yuguang ZHANG

Keyword(s):

Thermal Stability ◽

Retained Austenite ◽

Rolled Steel ◽

Cold Rolled Steel ◽

Cold Rolled ◽

Thermal Stability Of

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Thermal Stability of Retained Austenite in Advanced TRIP Steel with Bainitic Ferrite Matrix for Automotive Industries

Materials Science Forum ◽

10.4028/www.scientific.net/msf.1016.429 ◽

2021 ◽

Vol 1016 ◽

pp. 429-434

Author(s):

Eman El-Shenawy ◽

Hoda Refaiy ◽

Hoda Nasr El-Din

Keyword(s):

Mechanical Properties ◽

Thermal Stability ◽

Retained Austenite ◽

Bainitic Ferrite ◽

Residual Austenite ◽

Ferrite Matrix ◽

Sheet Steels ◽

Coiling Process ◽

Hot Rolled ◽

Thermal Stability Of

Multiphase steels consisting of retained austenite and martensite/bainite microstructures such as TRIP, low-temperature-bainite, and Q&P steels are attractive candidates for the new-generation of AHSS. These steels exhibit a remarkable combination of strength and toughness which is essential to meet the objective of weight reduction of engineering-components, while maintaining the compromise of tough-safety requirements. Such good mechanical properties are due to the enhanced work hardening rate caused by austenite-to-martensite transformation during deformation and the strengthening contribution of martensite/bainite. The retained austenite can thermally decompose into more thermodynamically stable phases as a consequence of temperature changes, which is referred to as the thermal stability of retained austenite. TRIP-aided steel is an effective candidate for automotive parts because of safety and weight reduction requirements. The strength–ductility balance of high strength steel sheets can be remarkably improved by using transformation induced plasticity behavior of retained austenite. In manufacturing hot rolled TRIP-aided sheet steels, austenite transforms into bainite during the coiling process. Because black hot coils cool slowly after the coiling process, they are exposed at about 350–450°C for a few hours or days. Therefore, the metastable residual austenite can be decomposed into other phases. This decomposition of residual austenite can produce serious deteriorate of mechanical properties in hot rolled TRIP-aided sheet steels. The present work identified the decomposition behavior and study the thermal stability of retained austenite in the TRIP-aided steel with bainitic/ferrite matrix depending on coiling temperatures and holding times by means of DSC and XRD analysis.

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Thermal stability of retained austenite in Cr–Ni weld metals at low temperatures

Materials Science and Technology ◽

10.1179/1743284712y.0000000194 ◽

2013 ◽

Vol 29 (5) ◽

pp. 594-597 ◽

Cited By ~ 7

Author(s):

H Qiu ◽

J G Qi ◽

L N Wang ◽

F X Yin ◽

K Hiraoka

Keyword(s):

Thermal Stability ◽

Low Temperatures ◽

Retained Austenite ◽

Weld Metals ◽

Thermal Stability Of

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Chemical boundary engineering: A new route toward lean, ultrastrong yet ductile steels

Science Advances ◽

10.1126/sciadv.aay1430 ◽

2020 ◽

Vol 6 (13) ◽

pp. eaay1430 ◽

Cited By ~ 11

Author(s):

Ran Ding ◽

Yingjie Yao ◽

Binhan Sun ◽

Geng Liu ◽

Jianguo He ◽

...

Keyword(s):

Mechanical Properties ◽

Thermal Stability ◽

Grain Size ◽

Grain Boundary ◽

Carbon Steels ◽

Metallic Materials ◽

Grain Boundary Engineering ◽

Design Strategies ◽

Thermal Stability Of ◽

Unique Chemical

For decades, grain boundary engineering has proven to be one of the most effective approaches for tailoring the mechanical properties of metallic materials, although there are limits to the fineness and types of microstructures achievable, due to the rapid increase in grain size once being exposed to thermal loads (low thermal stability of crystallographic boundaries). Here, we deploy a unique chemical boundary engineering (CBE) approach, augmenting the variety in available alloy design strategies, which enables us to create a material with an ultrafine hierarchically heterogeneous microstructure even after heating to high temperatures. When applied to plain steels with carbon content of only up to 0.2 weight %, this approach yields ultimate strength levels beyond 2.0 GPa in combination with good ductility (>20%). Although demonstrated here for plain carbon steels, the CBE design approach is, in principle, applicable also to other alloys.

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