scholarly journals Color Light Metallography Versus Electron Microscopy for Detecting and Estimating Various Phases in a High-Strength Multiphase Steel

Metals ◽  
2021 ◽  
Vol 11 (6) ◽  
pp. 855
Author(s):  
Shima Pashangeh ◽  
Seyyed Sadegh Ghasemi Banadkouki ◽  
Fatemeh Besharati ◽  
Fatemeh Mehrabi ◽  
Mahesh Somani ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
Retained Austenite ◽  
Volume Fraction ◽  
Ammonium Persulfate ◽  
Single Step ◽  
Electron Back Scatter Diffraction ◽  
High Carbon ◽  
Etching Technique ◽  
Multiphase Steel ◽  
Carbon Martensite

In this study, fresh attempts have been made to identify and estimate the phase constituents of a high-silicon, medium carbon multiphase steel (DIN 1.5025 grade) subjected to austenitization at 900 °C for 5 min, followed by quenching and low-temperature bainitizing (Q&B) at 350 °C for 200 s. Several techniques were employed using different chemical etching reagents either individually (single-step) or in combination of two or more etchants in succession (multiple-step) for conducting color metallography. The results showed that the complex multiphase microstructures comprising a fine mixture of bainite, martensite and retained austenite phase constituents were selectivity stained/tinted with good contrasting resolution, as observed via conventional light optical microscopy observations. While the carbon-enriched martensite-retained austenite (M/RA) islands were revealed as cream-colored areas by using a double-step etching technique comprising etching with 10% ammonium persulfate followed by etching with Marble's reagent, the dark gray-colored bainite packets were easily distinguishable from the brown-colored martensite regions. However, the high-carbon martensite and retained austenite in M/RA islands could be differentiated only after resorting to a triple-step etching technique comprising etching in succession with 2% nital, 10% ammonium persulfate solution and then warm Marble’s reagent at 30 °C. This revealed orange-colored martensite in contrast to cream-colored retained austenite in M/RA constituents, besides the presence of brown-colored martensite laths in the dark gray-colored bainitic matrix. A quadruple-step technique involving successive etching with 2% nital, 10% ammonium persulfate solution, Marble’s reagent and finally Klemm’s Ι reagent at 40 °C revealed even better contrast in comparison to the triple-step etching technique, particularly in distinguishing the RA from martensite. Observations using advanced techniques like field emission scanning electron microscopy (FE-SEM) and electron back scatter diffraction (EBSD) failed to differentiate untempered, high-carbon martensite from retained austenite in the M/RA islands and martensite laths from bainitic matrix, respectively. Transmission electron microscopy (TEM) studies successfully distinguished the RA from high-carbon martensite, as noticed in M/RA islands. The volume fraction of retained austenite estimated by EBSD, XRD and a point counting method on color micrographs of quadruple-step etched samples showed good agreement.

scholarly journals Carbon Redistribution and Microstructural Evolution Study during Two-Stage Quenching and Partitioning Process of High-Strength Steels by Modeling

Materials ◽  
2018 ◽  
Vol 11 (11) ◽  
pp. 2302 ◽  
Author(s):  
Yilin Wang ◽  
Huicheng Geng ◽  
Bin Zhu ◽  
Zijian Wang ◽  
Yisheng Zhang
Keyword(s):  
Retained Austenite ◽  
Volume Fraction ◽  
High Strength Steels ◽  
High Strength ◽  
Simulation Method ◽  
Low Carbon ◽  
Two Stage ◽  
Quenching And Partitioning ◽  
Carbon Redistribution ◽  
Carbon Martensite

The application of the quenching and partitioning (Q-P) process on advanced high-strength steels improves part ductility significantly with little decrease in strength. Moreover, the mechanical properties of high-strength steels can be further enhanced by the stepping-quenching-partitioning (S-Q-P) process. In this study, a two-stage quenching and partitioning (two-stage Q-P) process originating from the S-Q-P process of an advanced high-strength steel 30CrMnSi2Nb was analyzed by the simulation method, which consisted of two quenching processes and two partitioning processes. The carbon redistribution, interface migration, and phase transition during the two-stage Q-P process were investigated with different temperatures and partitioning times. The final microstructure of the material formed after the two-stage Q-P process was studied, as well as the volume fraction of the retained austenite. The simulation results indicate that a special microstructure can be obtained by appropriate parameters of the two-stage Q-P process. A mixed microstructure, characterized by alternating distribution of low carbon martensite laths, small-sized low-carbon martensite plates, retained austenite and high-carbon martensite plates, can be obtained. In addition, a peak value of the volume fraction of the stable retained austenite after the final quenching is obtained with proper partitioning time.

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.

Microstructure Characterization of White Layer Formed by Hard Turning and Wire Electric Discharge Machining in High Carbon Steel (AISI 52100)

2011 ◽  
Vol 409 ◽  
pp. 684-689 ◽  
Author(s):  
S. B. Hosseini ◽  
Uta Klement ◽  
J. Kaminski
Keyword(s):  
Electron Microscopy ◽  
Electric Discharge ◽  
Retained Austenite ◽  
Hard Turning ◽  
Flank Wear ◽  
Volume Fraction ◽  
White Layer ◽  
Reference Structure ◽  
Electric Discharge Machining ◽  
Wire Electric Discharge Machining

White layers, formed during hard turning and wire electric discharge machining, were characterized by means of X-ray diffraction, scanning electron microscopy and transmission electron microscopy. Different cutting speeds and flank wear were utilized in order to obtain different thermally and/or plastically deformed white layer. Since the white layer after wire electric discharge machining is mainly thermally induced, it was used as a reference structure. In the investigation, both bainitic and martensitic structures were studied. With a constant flank wear of 0.175 mm the thickness of the white layer increased from 1.5 μm to 3 μm as the cutting speed was increased. In both processes the white layer were characterized by nanosized grains and surface tensile residual stresses. M3C carbides were observed in the hard turned white layer, indicating that the time and temperature needed for completely dissolving the carbides were not reached during cutting. For both materials the white layers formed by wire electric discharge machining consisted of ~ 30 vol. % of retained austenite. Observation regarding the volume fraction of the retained austenite in the white layer formed by hard turning for martensitic material showed an increase in the volume fraction of retained austenite from ~ 2 - 3 vol. % to ~ 6 vol. %, while this observation was not seen in the white layer formed in the bainitic material.

scholarly journals 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

2014 ◽  
Vol 59 (4) ◽  
pp. 1673-1678 ◽  
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.

scholarly journals Investigating the Difference in Mechanical Stability of Retained Austenite in Bainitic and Martensitic High-Carbon Bearing Steels using in situ Neutron Diffraction and Crystal Plasticity Modeling

Metals ◽  
2019 ◽  
Vol 9 (5) ◽  
pp. 482 ◽  
Author(s):  
Rohit Voothaluru ◽  
Vikram Bedekar ◽  
Dunji Yu ◽  
Qingge Xie ◽  
Ke An ◽  
...  
Keyword(s):  
Neutron Diffraction ◽  
Crystal Plasticity ◽  
Retained Austenite ◽  
Mechanical Stability ◽  
Volume Fraction ◽  
High Carbon ◽  
Martensitic Matrix ◽  
Bearing Steels ◽  
In Situ Neutron Diffraction

In situ neutron diffraction of the uniaxial tension test was used to study the effect of the surrounding matrix microstructure on the mechanical stability of retained austenite in high-carbon bearing steels. Comparing the samples with bainitic microstructures to those with martensitic ones, it was found that the retained austenite in a bainitic matrix starts transforming into martensite at a lower strain compared to that within a martensitic matrix. On the other hand, the rate of transformation of the austenite was found to be higher within a martensitic microstructure. Crystal plasticity modeling was used to analyze the transformation phenomenon in these two microstructures and determine the effect of the surrounding microstructure on elastic, plastic, and transformation components of the strain. The results showed that the predominant difference in the deformation accumulated was from the transformation strain and the critical transformation driving force within the two microstructures. The retained austenite was more stable for identical loading conditions in case of martensitic matrix compared to the bainitic one. It was also observed that the initial volume fraction of retained austenite within the bainitic matrix would alter the onset of transformation to martensite, but not the rate of transformation.

scholarly journals Effect of Isothermal Transformation Times below Ms and Tempering on Strength and Toughness of Low-Temperature Bainite in 0.53 C Bainitic Steel

Materials ◽  
2020 ◽  
Vol 13 (10) ◽  
pp. 2418
Author(s):  
Enzuo Liu ◽  
Qiangguo Li ◽  
Sufyan Naseem ◽  
Xuefei Huang ◽  
Weigang Huang
Keyword(s):  
Low Temperature ◽  
Impact Toughness ◽  
Retained Austenite ◽  
Volume Fraction ◽  
Isothermal Transformation ◽  
Electron Back Scatter Diffraction ◽  
Bainitic Steel ◽  
Transmission Electron ◽  
The Impact ◽  
Tempering Process

This study aims to investigate the microstructures, strength, and impact toughness of low-temperature bainite obtained by isothermal transformation at temperature below Ms (Martensite Starting temperature) for different times and tempering process in 0.53 C wt% bainitic steel. By using the optical microscopy, X-ray diffraction (XRD), transmission electron microscopy (TEM), electron back scatter diffraction (EBSD), and mechanical property test, it was found that the microstructures after heat treatment consist of small amounts of martensite, fine bainite, and film retained austenite. After tempered at 250 °C for 2 h, the volume fraction of retained austenite (10.9%) in the sample treated by isothermal transformation at 220 °C for three hours is almost the same as that of the sample without tempering. In addition, the retained austenite fraction decreases with the increase of holding times and is reduced to 6.8% after holding for 15 h. The ultimate tensile strength (1827 MPa), yield strength (1496 MPa), total elongations (16.1%), and impact toughness (up to 58 J/cm2) were obtained by isothermal transformation at 220 °C for three hours and tempered at 250 °C. Whereas, the impact toughness of sample without tempering is 28 J/cm2. After holding for 15 h, the impact toughness raises to 56 J/cm2, while the ductility and strength decreases. These results indicate that the tempering process is helpful to improve the impact toughness of low-temperature bainite.

scholarly journals Enhancing Corrosion Resistance of High-Carbon Steel by Formation of Surface Layers Using Wastes as Input

Metals ◽  
2019 ◽  
Vol 9 (8) ◽  
pp. 902 ◽  
Author(s):  
Handoko ◽  
Pahlevani ◽  
Sahajwalla
Keyword(s):  
Corrosion Resistance ◽  
Laser Scanning ◽  
Volume Fraction ◽  
High Carbon Steel ◽  
Microstructural Analysis ◽  
Electrochemical Corrosion ◽  
Single Step ◽  
Carbon Steels ◽  
Chemical Mapping ◽  
High Carbon

Series of super-hard ceramic layers have been successfully developed on high carbon steels, with a significant improvement of corrosion resistance and hardness, without changing the original properties, which were derived from mixtures of slag (electric arc furnace), waste glass (bottles), and automotive shredder residue (ASR) plastics (polypropylene) via the single step surface modification technique. Microstructural analysis by laser scanning confocal microscopy (LSCM), crystallography analysis by X-ray diffraction (XRD), micro-level chemical analysis by scanning electron microscopy and energy dispersive spectroscopy (SEM and EDS), and depth profile surface analysis with three-dimensional chemical mapping by time-of-flight secondary ion mass spectrometry (TOF-SIMS), followed by electrochemical corrosion test by the Tafel method and hardness test—Vickers hardness measurement. Three areas have been classified, modified surface, interface, and main substrate areas as the synthesis of ceramic layers into surface of the steels that thermodynamically formed during the heat treatment process. Chemical composition analyses have revealed that generated layers consisting of chromium (Cr)- and magnesium (Mg)-based compound have shown an improved corrosion resistance to 52% and hardness to 70% without modifying the initial volume fraction of constituent phases–martensite and retained austenite. These findings have substantially highlighted to the potential use of waste-integrated inputs as raw materials for production in cost-effective way, concurrently decreasing the demand on new resource for coating, alleviating the disadvantageous impact to the environment from waste disposal in landfills.

Microstructure and Mechanical Properties of Medium Manganese Steel Plate with High Strength and Toughness

2016 ◽  
Vol 879 ◽  
pp. 2293-2299
Author(s):  
Ying Zou ◽  
Yun Bo Xu ◽  
Zhi Ping Hu ◽  
Xiao Long Yang ◽  
Xiao Dong Tan ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
Mechanical Properties ◽  
Retained Austenite ◽  
Annealing Temperature ◽  
Steel Plate ◽  
Volume Fraction ◽  
Manganese Steel ◽  
Uniaxial Tensile ◽  
Medium Manganese Steel ◽  
Strength And Toughness

An intercritical annealing process was applied to a medium manganese steel plate (Fe-0.01C-5.3Mn-1.53Si) after the thermo-mechanical controlled processing (TMCP) and ultrafast cooling (UFC). The microstructures were observed by scanning electron microscopy (SEM) equipped with electron backscatter diffraction (EBSD), electron probe micro-analyzer (EPMA) and transmission electron microscopy (TEM). The retained austenite was measured by XRD and mechanical properties were measured by uniaxial tensile and impact tests. The influence of different annealing temperature was compared and the relationship between microstructures and mechanical properties was investigated. Results showed that the microstructures of the medium manganese steel plate were characterized by ultrafine grained lath-like ferrite and retained austenite and the excellent mechanical properties could be obtained at the annealing temperature of 640°C for 5 h. The volume fraction of the retained austenite reached up to 21%, which could significantly increase the elongation compared with the traditional steel plate. The mechanical property results revealed that the steel possessed adequate ultimate tensile strength of 865MPa and excellent impact energy of 121J (-20°C). The outstanding combination of strength and toughness indicates that the steel has a bright application prospect.

Effect of Partitioning of Quenching-Partitioning-Tempering Process on Microstructures and Hardness in High Carbon Steels

2012 ◽  
Vol 538-541 ◽  
pp. 1053-1056
Author(s):  
Yang Zheng Zeng ◽  
Kai Ming Wu ◽  
Feng Hu ◽  
Hua Zheng
Keyword(s):  
Electron Microscopy ◽  
Heat Treatment ◽  
Scanning Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
Retained Austenite ◽  
Carbon Steels ◽  
High Carbon ◽  
Selected Area Electron Diffraction ◽  
Transmission Electron ◽  
Scanning Electron

The effect of partitioning process of quenching-partitioning-tempering (Q-P-T) process on hardness and microstructure were investigated. The 1-step Q-P-T and 2-step Q-P-T heat treatment were designed and carried out. The microstructure and carbides were analyzed by scanning electron microscopy (SEM), transmission electron microscopy (TEM) and selected area electron diffraction (SAED) patterns. Results showed that compared with 1-step Q-P-T heat treatment, more amount of retained austenite was obtained by 2-step Q-P-T heat treatment, however, the carbides were bigger in size and the hardness was lower.

Experimental Study on the Effect of Retained Austenite on the Impact Toughness of a Low-Carbon Martensite Steel

2015 ◽  
Vol 1095 ◽  
pp. 119-123 ◽  
Author(s):  
Liang Gui Peng ◽  
Wei Jie Liu ◽  
Xiang Hua Liu ◽  
Ying Zhi
Keyword(s):  
Retained Austenite ◽  
Volume Fraction ◽  
Low Carbon Steel ◽  
Impact Property ◽  
Low Carbon ◽  
Treatment Processes ◽  
The Common ◽  
The Impact ◽  
Energy Increment ◽  
Carbon Martensite

Effect of various heat treatment processes on the impact property of a low-carbon steel was investigated. Its microstructure and morphology were also observed and characterized. Fraction of retained austenite of the tested steel varied with the change of temperature and holding time of quenching, carbon partitioning and tempering process. After Q&P treatment, the impact property of the tested steel improved with increasing volume fraction of retained austenite. After tempering, the impact property of the tested steel further improved despite the decrease of the fraction of the retained austenite. Experimental results show that the stabilization and fraction of the retained austenite from which the transformation induced plasticity (TRIP) effect originated control the toughness of the tested steel. It should be noted that the common tempering theory is insufficient to explain the current observations for the impact energy increment. Instead, it may be explained by the decomposition of the block-like retained austenite that is generally harmful to the toughness of the steel.

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