Mechanical and thermal stability of retained austenite in plastically deformed bainite-based TRIP-aided medium-Mn steels

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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Mechanical stability of retained austenite in aluminum-containing medium-Mn steel deformed at different temperatures

Archives of Civil and Mechanical Engineering ◽

10.1007/s43452-021-00177-8 ◽

2021 ◽

Vol 21 (1) ◽

Author(s):

Aleksandra Kozłowska ◽

Krzysztof Radwański ◽

Krzysztof Matus ◽

Ludovic Samek ◽

Adam Grajcar

Keyword(s):

Electron Microscopy ◽

Martensitic Transformation ◽

Deformation Temperature ◽

Retained Austenite ◽

Mechanical Stability ◽

Electron Backscatter Diffraction ◽

Sheet Steel ◽

Tensile Tests ◽

X Ray ◽

Different Temperatures

AbstractThe thermal and mechanical stabilities of retained austenite in aluminum-containing medium-Mn 0.16C–4.7Mn–1.6Al–0.2Si sheet steel were investigated. The strain-induced martensitic transformation in Mn TRIP steel was studied at different temperatures. Static tensile tests were carried out at the temperature ranging from − 60 to 200 °C. The tests allowed to study the influence of the temperature on austenite-to-martensite transformation kinetics. The interrupted tensile tests and corresponding X-ray measurements of retained austenite amount were performed to determine the mechanical stability of retained austenite using the Sugimoto model. The microstructure changes were investigated using scanning electron microscopy (SEM), electron backscatter diffraction (EBSD), X-ray diffraction (XRD) and transmission electron microscopy (TEM) techniques. Observed results reflected the effects of deformation temperature on the mechanical stability of retained austenite and the corresponding response of this phase to martensitic transformation. It was found that an increase in the deformation temperature resulted in the reduced intensity of the TRIP effect due to the higher mechanical stability of retained austenite. At the highest deformation temperature (200 °C), the evidence of thermally activated processes affecting the mechanical behavior was identified.

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Microstructure Evolution and Mechanical Stability of Retained Austenite in Thermomechanically Processed Medium-Mn Steel

Materials ◽

10.3390/ma12030501 ◽

2019 ◽

Vol 12 (3) ◽

pp. 501 ◽

Cited By ~ 3

Author(s):

Adam Grajcar ◽

Andrzej Kilarski ◽

Aleksandra Kozłowska ◽

Krzysztof Radwański

Keyword(s):

Electron Microscopy ◽

Martensitic Transformation ◽

Microstructure Evolution ◽

Retained Austenite ◽

Mechanical Stability ◽

Electron Backscatter Diffraction ◽

Bainitic Ferrite ◽

Tensile Tests ◽

Central Regions ◽

Deformation Level

A microstructure evolution of the thermomechanically processed 3Mn-1.5Al type steel and mechanical stability of retained austenite were investigated during interrupted tensile tests. The microstructural details were revealed using scanning electron microscopy (SEM), electron backscatter diffraction (EBSD), and transmission electron microscopy (TEM) techniques. It was found that the strain-induced martensitic transformation began in central regions of the largest blocky-type grains of retained austenite and propagated to outer areas of the grains as the deformation level increased. At rupture, the mechanical stability showed only boundaries of fine blocky grains of γ phase and austenitic layers located between bainitic ferrite laths. The effects of various carbon enrichment, grain size, and location in the microstructure were considered. The martensitic transformation progress was the highest at the initial stage of deformation and gradually decreased as the deformation level increased.

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

Materials Science Forum ◽

10.4028/www.scientific.net/msf.1016.762 ◽

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.

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Microstructural Features of Strain-Induced Martensitic Transformation in Medium-Mn Steels with Metastable Retained Austenite/ Cechy Mikrostrukturalne Indukowanej Odkształceniem Przemiany Martenzytycznej W Stalach Sredniomanganowych Z Metastabilnym Austenitem Szczątkowym

Archives of Metallurgy and Materials ◽

10.2478/amm-2014-0283 ◽

2014 ◽

Vol 59 (4) ◽

pp. 1673-1678 ◽

Cited By ~ 2

Author(s):

A. Grajcar ◽

A. Kilarski ◽

K. Radwanski ◽

R. Swadzba

Keyword(s):

Electron Microscopy ◽

Retained Austenite ◽

Volume Fraction ◽

Electron Backscatter Diffraction ◽

Bainitic Ferrite ◽

Tensile Tests ◽

Bainitic Steels ◽

Transmission Electron ◽

Strain Induced Martensite ◽

Backscatter Diffraction

Abstract The work addresses relationships between the microstructure evolution and mechanical properties of two thermomechanically processed bainitic steels containing 3 and 5% Mn. The steels contain blocky-type and interlath metastable retained austenite embeded between laths of bainitic ferrite. To monitor the transformation behaviour of retained austenite into strain-induced martensite tensile tests were interrupted at 5%, 10%, and rupture strain. The identification of retained austenite and strain-induced martensite was carried out using light microscopy (LM), scanning electron microscopy (SEM) equipped with EBSD (Electron Backscatter Diffraction) and transmission electron microscopy (TEM). The amount of retained austenite was determined by XRD. It was found that the increase of Mn addition from 3 to 5% detrimentally decreases a volume fraction of retained austenite, its carbon content, and ductility.

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Thermal Stability of Retained Austenite and Properties of A Multi-Phase Low Alloy Steel

Metals ◽

10.3390/met8100807 ◽

2018 ◽

Vol 8 (10) ◽

pp. 807 ◽

Cited By ~ 5

Author(s):

Zhenjia Xie ◽

Lin Xiong ◽

Gang Han ◽

Xuelin Wang ◽

Chengjia Shang

Keyword(s):

Thermal Stability ◽

High Temperature ◽

Alloy Steel ◽

Retained Austenite ◽

Mechanical Stability ◽

Volume Fraction ◽

Low Carbon ◽

Low Alloy Steel ◽

Multi Phase ◽

Thermal Stability Of

In this work, we elucidate the effects of tempering on the microstructure and properties in a low carbon low alloy steel, with particular emphasis on the thermal stability of retained austenite during high-temperature tempering at 500–700 °C for 1 h. Volume fraction of ~14% of retained austenite was obtained in the studied steel by two-step intercritical heat treatment. Results from transmission electron microscopy (TEM) and X-ray diffraction (XRD) indicated that retained austenite had high thermal stability when tempering at 500 and 600 °C for 1 h. The volume fraction was ~11–12%, the length and width remained ~0.77 and 0.21 μm, and concentration of Mn and Ni in retained austenite remained ~6.2–6.6 and ~1.6 wt %, respectively. However, when tempering at 700 °C for 1 h, the volume fraction of retained austenite was decreased largely to ~8%. The underlying reason could be attributed to the growth of austenite during high-temperature holding, leading to a depletion of alloy contents and a decrease in stability. Moreover, for samples tempered at 700 °C for 1 h, retained austenite rapidly transformed into martensite at a strain of 2–10%, and a dramatic increase in work hardening was observed. This indicated that the mechanical stability of retained austenite decreased.

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Microstructure Evolution and Mechanical Stability of Retained Austenite in Medium-Mn Steel Deformed at Different Temperatures

Materials ◽

10.3390/ma12183042 ◽

2019 ◽

Vol 12 (18) ◽

pp. 3042 ◽

Cited By ~ 7

Author(s):

Aleksandra Kozłowska ◽

Aleksandra Janik ◽

Krzysztof Radwański ◽

Adam Grajcar

Keyword(s):

Microstructure Evolution ◽

Retained Austenite ◽

Mechanical Stability ◽

Thermomechanical Processing ◽

Electron Backscatter Diffraction ◽

Tensile Tests ◽

Medium Mn Steel ◽

Different Temperatures ◽

Static Tensile ◽

Xrd Techniques

The temperature-dependent microstructure evolution and corresponding mechanical stability of retained austenite in medium-Mn transformation induced plasticity (TRIP) 0.17C-3.1Mn-1.6Al type steel obtained by thermomechanical processing was investigated using scanning electron microscopy (SEM), electron backscatter diffraction (EBSD), and X-ray diffraction (XRD) techniques. Specimens were deformed up to rupture in static tensile tests in the temperature range 20–200 °C. It was found that an increase in deformation temperature resulted in the reduced intensity of TRIP effect due to the higher stability of retained austenite. The kinetics of strain-induced martensitic transformation was affected by the carbon content of retained austenite (RA), its morphology, and localization in the microstructure.

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Enhanced Dispersion Strengthening of Sm in Mg-10Y-0.5Sm Alloy

Advanced Materials Research ◽

10.4028/www.scientific.net/amr.998-999.51 ◽

2014 ◽

Vol 998-999 ◽

pp. 51-54

Author(s):

Qing Zhang ◽

Quan An Li ◽

Jun Chen ◽

Xing Yuan Zhang

Keyword(s):

Thermal Stability ◽

Tensile Strength ◽

Elevated Temperatures ◽

Tensile Tests ◽

Microstructure Analysis ◽

Dispersion Strengthening ◽

Thermal Stability Of

The enhanced dispersion strengthening of Sm in Mg-10Y-0.5Sm has been investigated by means of microstructure analysis and tensile tests. The results show that Sm addition improves the image of Mg24Y5 phase and causes the formation of fine and dispersed Mg24Y5 phase. Meanwhile, the dissolved Sm increases the thermal stability of Mg24Y5 phase and enhances its dispersion strengthening in the alloy. It leads to the increased tensile strength of the alloy at elevated temperatures.

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Durability of PS-Polyurethane Dedicated for Composite Strengthening Applications in Masonry and Concrete Structures

Polymers ◽

10.3390/polym12122830 ◽

2020 ◽

Vol 12 (12) ◽

pp. 2830

Author(s):

Konrad Kwiecień ◽

Arkadiusz Kwiecień ◽

Teresa Stryszewska ◽

Magdalena Szumera ◽

Marta Dudek

Keyword(s):

Thermal Stability ◽

Mechanical Stability ◽

Concrete Structures ◽

Tensile Tests ◽

Accelerated Weathering ◽

Aqueous Environments ◽

Main Effect ◽

Low Sensitivity ◽

Mineral Fillers ◽

Thermal Stability Of

Polyurethane flexible joints (PUFJ) and fiber reinforced polyurethanes (FRPU) have shown great potential in the repair and protection of masonry and concrete structures. However, some questions have been raised about the durability of such solutions. The accelerated weathering and thermal stability tests carried out so far have shown the mechanical stability of PS-polyurethane in temperatures up to 100 °C and some UV-induced surface degradation. The paper reports the results from tensile tests of PS-polyurethane, used in the technologies mentioned above after being subjected to aging in different corrosive factors, a thermal analysis of unaged polymer which consists of DSC-TGA and dilatometry studies, and SEM-microscopy observation of the specimens with the indication of the elemental composition (EDS). PS-polyurethane showed low sensitivity to weathering with exposition to UV-radiation, some reactiveness to aqueous environments of a different chemical nature, and resistivity to soil and freezing in both air and water. SEM observations indicated changes in the composition of mineral fillers as the main effect of immersion in different water solutions. DSC-TGA studies showed the thermal stability of PS-polyurethane up to 200 °C and degradation proceeding in five stages. Dilatometry studies revealed that the first-degree thermal degradation over 200 °C causes a serious loss of mechanical properties.

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Quasi-Situ Characterization of Retained Austenite Orientation in Quenching and Partitioning Steel via Uniaxial Tensile Tests

Materials ◽

10.3390/ma13204609 ◽

2020 ◽

Vol 13 (20) ◽

pp. 4609

Author(s):

Pengfei Gao ◽

Jie Liu ◽

Weijian Chen ◽

Feng Li ◽

Jingyu Pang ◽

...

Keyword(s):

Mechanical Properties ◽

Retained Austenite ◽

Mechanical Stability ◽

Volume Fraction ◽

Electron Backscatter Diffraction ◽

Early Stage ◽

Tensile Tests ◽

Uniaxial Tensile ◽

Quenching And Partitioning ◽

Austenite Grains

As a representative of the third generation of advanced high strength steel, the quenching and partitioning steel has excellent potential in automobile manufacturing. The characterization and analysis of the mechanical properties and microstructure of the quenching and partitioning steel during deformation is an effective way to explore the microstructure evolution and transformation-induced plasticity effects of complex phase steels. The relationship between the microstructure morphology and mechanical properties of a 1180 MPa-grade quenching and partitioning steel was investigated through interrupted uniaxial tensile tests plus quasi-situ electron backscatter diffraction measurements. A mixture of ferrite, martensite, and retained austenite was observed in the microstructure. It was found that the volume fraction of global retained austenite decreased linearly with the increase of displacement (0 mm–1.05 mm). The evolution of the retained austenite with typical crystal direction ranges with deformation was characterized. Results show that the orientation (111) and (311) account for the highest proportion of retained austenite grains in the undeformed sample and the mechanical stability of the (311) retained austenite grains is the best. Moreover, the retained austenite grains rotated significantly in the early stage of the specimen deformation process (around yielding), and the work hardening of the specimen was weak at this stage, simultaneously.

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Thermal stability and diffusion characteristics of ultrathin amorphous carbon films grown on crystalline and nitrogenated silicon substrates by filtered cathodic vacuum arc deposition

Scientific Reports ◽

10.1038/s41598-021-91903-y ◽

2021 ◽

Vol 11 (1) ◽

Author(s):

Shengxi Wang ◽

Anurag Roy ◽

Kyriakos Komvopoulos

Keyword(s):

Thermal Stability ◽

Amorphous Carbon ◽

Silicon Substrate ◽

Elevated Temperatures ◽

Carbon Films ◽

Vacuum Arc ◽

Cross Sectional ◽

Prolonged Heating ◽

Filtered Cathodic Vacuum Arc ◽

Thermal Stability Of

AbstractAmorphous carbon (a-C) films are widely used as protective overcoats in many technology sectors, principally due to their excellent thermophysical properties and chemical inertness. The growth and thermal stability of sub-5-nm-thick a-C films synthesized by filtered cathodic vacuum arc on pure (crystalline) and nitrogenated (amorphous) silicon substrate surfaces were investigated in this study. Samples of a-C/Si and a-C/SiNx/Si stacks were thermally annealed for various durations and subsequently characterized by high-resolution transmission electron microscopy (TEM) and electron energy loss spectroscopy (EELS). The TEM images confirmed the continuity and uniformity of the a-C films and the 5-nm-thick SiNx underlayer formed by silicon nitrogenation using radio-frequency sputtering. The EELS analysis of cross-sectional samples revealed the thermal stability of the a-C films and the efficacy of the SiNx underlayer to prevent carbon migration into the silicon substrate, even after prolonged heating. The obtained results provide insight into the important attributes of an underlayer in heated multilayered media for preventing elemental intermixing with the substrate, while preserving the structural stability of the a-C film at the stack surface. An important contribution of this investigation is the establishment of an experimental framework for accurately assessing the thermal stability and elemental diffusion in layered microstructures exposed to elevated temperatures.

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