1
|
Yang C, Xu T, Zhao H, Hu C, Dong H. Regulation Law of Tempering Cooling Rate on Toughness of Medium-Carbon Medium-Alloy Steel. Materials (Basel) 2023; 17:205. [PMID: 38204058 PMCID: PMC10779875 DOI: 10.3390/ma17010205] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/16/2023] [Revised: 12/25/2023] [Accepted: 12/28/2023] [Indexed: 01/12/2024]
Abstract
Temper embrittlement is a major challenge encountered during the heat treatment of high-performance steels for large forgings. This study investigates the microstructural evolution and mechanical properties of Cr-Ni-Mo-V thick-walled steel, designed for large forgings with a tensile strength of 1500 MPa, under different tempering cooling rates. Optical microscopy (OM), scanning electron microscopy (SEM), and electron backscatter diffraction (EBSD) were employed to analyze the microstructural features. The results demonstrate that the embrittlement occurring during air cooling after tempering is attributed to the concentration of impurities near Fe3C at the grain boundaries. The low-temperature impact toughness at -40 °C after water quenching reaches 29 J due to the accelerated cooling rate during tempering, which slows down the diffusion of impurity elements towards the grain boundaries, resulting in a reduced concentration and dislocation density and an increased stability of the grain boundaries, thereby enhancing toughness. The bainite content decreases and the interface between martensite and bainite undergoes changes after water quenching during tempering. These alterations influence the crack propagation direction within the two-phase microstructure, further modifying the toughness. These findings contribute to the understanding of temper embrittlement and provide valuable guidance for optimizing heat treatment processes to enhance the performance of high-performance steels in large forgings.
Collapse
Affiliation(s)
- Chao Yang
- School of Materials Science and Engineering, Shanghai University, Shanghai 200444, China; (C.Y.); (H.Z.); (H.D.)
| | - Tingting Xu
- Zhongyuan Special Steel Co., Ltd., Jiyuan 459000, China;
| | - Hongshan Zhao
- School of Materials Science and Engineering, Shanghai University, Shanghai 200444, China; (C.Y.); (H.Z.); (H.D.)
- Zhejiang Institute of Advanced Materials, Shanghai University, Jiaxing 314100, China
| | - Chundong Hu
- School of Materials Science and Engineering, Shanghai University, Shanghai 200444, China; (C.Y.); (H.Z.); (H.D.)
- Zhejiang Institute of Advanced Materials, Shanghai University, Jiaxing 314100, China
| | - Han Dong
- School of Materials Science and Engineering, Shanghai University, Shanghai 200444, China; (C.Y.); (H.Z.); (H.D.)
- Zhejiang Institute of Advanced Materials, Shanghai University, Jiaxing 314100, China
| |
Collapse
|
2
|
Królicka A, Caballero FG, Zalecki W, Kuziak R, Rozmus R. Controlling the Thermal Stability of a Bainitic Structure by Alloy Design and Isothermal Heat Treatment. Materials (Basel) 2023; 16:2963. [PMID: 37109799 PMCID: PMC10146538 DOI: 10.3390/ma16082963] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 02/20/2023] [Revised: 04/04/2023] [Accepted: 04/05/2023] [Indexed: 06/19/2023]
Abstract
The aim of this work was to develop a novel bainitic steel that will be specifically dedicated to achieving a high degree of refinement (nano- or submicron scale) along with increased thermal stability of the structure at elevated temperatures. The material was characterized by improved in-use properties, expressed as the thermal stability of the structure, compared to nanocrystalline bainitic steels with a limited fraction of carbide precipitations. Assumed criteria for the expected low martensite start temperature, bainitic hardenability level, and thermal stability are specified. The steel design process and complete characteristics of the novel steel including continuous cooling transformation and time-temperature-transformation diagrams based on dilatometry are presented. Moreover, the influence of bainite transformation temperature on the degree of structure refinement and dimensions of austenite blocks was also determined. It was assessed whether, in medium-carbon steels, it is possible to achieve a nanoscale bainitic structure. Finally, the effectiveness of the applied strategy for enhancing thermal stability at elevated temperatures was analyzed.
Collapse
Affiliation(s)
- Aleksandra Królicka
- Department of Metal Forming, Welding and Technology, Faculty of Mechanical Engineering, Wroclaw University of Science and Technology, 50-371 Wroclaw, Poland
- Department of Physical Metallurgy, National Center for Metallurgical Research (CENIM-CSIC), 28040 Madrid, Spain
| | - Francisca Garcia Caballero
- Department of Physical Metallurgy, National Center for Metallurgical Research (CENIM-CSIC), 28040 Madrid, Spain
| | - Władysław Zalecki
- Łukasiewicz Research Network—Upper Silesian Institute of Technology, 44-121 Gliwice, Poland
| | - Roman Kuziak
- Łukasiewicz Research Network—Upper Silesian Institute of Technology, 44-121 Gliwice, Poland
| | - Radosław Rozmus
- Łukasiewicz Research Network—Upper Silesian Institute of Technology, 44-121 Gliwice, Poland
| |
Collapse
|
3
|
You J, Li Z, Wang J, Li C, Zeng Z, Li S, Huang S. Effect of Complex Strengthening on the Continuous Cooling Transformation Behavior of High-Strength Rebar. Materials (Basel) 2022; 15:8940. [PMID: 36556745 PMCID: PMC9780884 DOI: 10.3390/ma15248940] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 10/11/2022] [Revised: 12/05/2022] [Accepted: 12/09/2022] [Indexed: 06/17/2023]
Abstract
The effects of niobium and composite strengthening on the phase transformation characteristics and precipitation behavior of continuous cooling transformation of high-strength rebar during thermal deformation and subsequent cooling were investigated. The results show that when the cooling rate was within 0.3-5 °C/s, ferrite transformation and pearlite transformation occurred in the experimental steels. The Nb content increased to 0.062 wt.%, and the starting temperature of the ferrite transformation decreased. Meanwhile, the ferrite phase transformation zone gradually expanded, and the pearlite phase transformation zone gradually narrowed with the increase in the cooling rate. When the cooling rate was 1 °C/s, bainite transformation began to occur, and the amount of transformation increased with the increase in the cooling rate. It was found that the main precipitates in the experimental steels were (Nb, Ti, V)C, with an average particle size of about 10-50 nm. When the Nb content was increased to 0.062 wt.% and the cooling rate was increased to 5 °C/s, the ferrite grain size was reduced from 19.5 to 7.5 μm, and the particle size of the precipitate (Nb, Ti, V)C could be effectively reduced. The strength of the steel was significantly improved, but the elongation of the steel was reduced. However, the comprehensive mechanical properties of 0.062 wt.% Nb experimental steel was significantly improved at a cooling rate of 5 °C/s.
Collapse
Affiliation(s)
- Jingtian You
- College of Materials and Metallurgy, Guizhou University, Guiyang 550025, China
- Guizhou Provincial Key Laboratory of Metallurgical Engineering and Process Energy Saving, Guiyang 550025, China
| | - Zhiying Li
- College of Materials and Metallurgy, Guizhou University, Guiyang 550025, China
- Guizhou Provincial Key Laboratory of Metallurgical Engineering and Process Energy Saving, Guiyang 550025, China
| | - Jie Wang
- Shougang Shuicheng Iron and Steel (Group) Co., Ltd., Liupanshui 553000, China
| | - Changrong Li
- College of Materials and Metallurgy, Guizhou University, Guiyang 550025, China
- Guizhou Provincial Key Laboratory of Metallurgical Engineering and Process Energy Saving, Guiyang 550025, China
| | - Zeyun Zeng
- College of Materials and Metallurgy, Guizhou University, Guiyang 550025, China
- Guizhou Provincial Key Laboratory of Metallurgical Engineering and Process Energy Saving, Guiyang 550025, China
| | - Shiwang Li
- College of Materials and Metallurgy, Guizhou University, Guiyang 550025, China
- Guizhou Provincial Key Laboratory of Metallurgical Engineering and Process Energy Saving, Guiyang 550025, China
| | - Sheng Huang
- College of Materials and Metallurgy, Guizhou University, Guiyang 550025, China
- Guizhou Provincial Key Laboratory of Metallurgical Engineering and Process Energy Saving, Guiyang 550025, China
| |
Collapse
|
4
|
Klančnik G, Krajnc L, Nagode A, Burja J. Isothermal Quenching of As-Cast Medium Carbon, High-Silicon AR Steel. Materials (Basel) 2022; 15:5595. [PMID: 36013731 PMCID: PMC9415478 DOI: 10.3390/ma15165595] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 07/08/2022] [Revised: 08/02/2022] [Accepted: 08/09/2022] [Indexed: 06/15/2023]
Abstract
Medium carbon high-silicon abrasion resistant (AR) steel was examined by performing dilatometry, light optical microscopy (LOM), scanning electron microscopy (SEM), and hardness measurements after isothermal bainitization and modified martempering and compared to direct quenching technology. A commercial thermodynamic tool was used for hardness prediction and compared to the measured one and revealed a rather good agreement for direct quenching, as was the case for isothermal holdings near to the martensite start (Ms). The predicted martensite start temperatures were in good agreement with the experimental data, the experimental value was 321 °C, while the predicted values were 324 and 296 °C. However, a higher discrepancy appeared for isothermal holding much above the martensite transition in the bainite region resulting in lower measured hardness compared to the predictions related to the actual kinetics and complexity of the formed final volume percentages of phase constituents such as bainite, martensite, and rest austenite, later as a part of unfinished bainite transformation at studied temperature. The predicted hardness values for quenching, isothermal holding at 280, 300 and 350 °C were 50.6, 50.6, 49.4 and 49.4 HRC, while the measured values were 53.3, 48.3, 48 and 43 HRC, respectively. A very good agreement between the thermodynamic prediction was achieved by comparing the measured Ms concerning prior austenite grain size as one of the crucial parameters for setting a proper heat treatment strategy of various isothermal quenchings making thermodynamic predictions for low alloyed steels a powerful tool for optimizing the heat-treating operations.
Collapse
Affiliation(s)
| | - Luka Krajnc
- Pro Labor d.o.o., Podvin 20, 3310 Žalec, Slovenia
| | - Aleš Nagode
- Department of Materials and Metallurgy, Faculty of Natural Sciences and Engineering, University of Ljubljana, Aškerčeva 12, 1000 Ljubljana, Slovenia
| | - Jaka Burja
- Department of Materials and Metallurgy, Faculty of Natural Sciences and Engineering, University of Ljubljana, Aškerčeva 12, 1000 Ljubljana, Slovenia
- Institute of Metals and Technology, 1000 Ljubljana, Slovenia
| |
Collapse
|
5
|
Steinbacher M, Hoja S. Optimization of Pre-Heat Treatment for Nitriding. Materials (Basel) 2021; 14:7766. [PMID: 34947360 DOI: 10.3390/ma14247766] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 11/19/2021] [Revised: 12/06/2021] [Accepted: 12/09/2021] [Indexed: 11/17/2022]
Abstract
To achieve a core strength that meets the requirements during service life, components to be nitrided are subjected to a pre-heat treatment. Since a higher strength prior to nitriding also has a positive effect on the achievable strength in the nitrided layer, an optimization of the pre-heat treatment may lead to better service characteristics of nitrided components. For this purpose, different optimizations of pre-heat treatment were investigated on the nitriding and quenching and tempering steels EN31CrMoV9 and EN42CrMo4 (AISI4140). One strategy was a change of the austenitization temperature for EN31CrMoV9 from 870 °C to 950 °C in order to solve the coarse carbides of the as-delivered state and realize a finer distribution of the carbides in the quenched and tempered structure. This special treatment lead to a higher hardness compared to the conventional treatment. The second investigated pre-heat treatment variant was a bainitic treatment instead of quenching and tempering. The bainitic initial microstructure increased the diffusion depth compared to conventionally quenched and tempered specimens. In addition the maximum hardness of the nitrided layer, the core hardness was significantly higher on the specimens with the bainitic microstructure. During subsequent nitriding, however, the bainite is tempered and loses some of its hardness.
Collapse
|
6
|
Ruiz-Jimenez V, Jimenez JA, Caballero FG, Garcia-Mateo C. Bainitic Ferrite Plate Thickness Evolution in Two Nanostructured Steels. Materials (Basel) 2021; 14:ma14154347. [PMID: 34361541 PMCID: PMC8347182 DOI: 10.3390/ma14154347] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 07/02/2021] [Revised: 07/29/2021] [Accepted: 07/30/2021] [Indexed: 11/16/2022]
Abstract
Bainitic ferrite plate thickness evolution during isothermal transformation was followed at the same holding temperatures in two nanostructured steels containing (in wt.%) 1C-2Si and 0.4C-3Si. A dynamic picture of how the bainitic transformation evolves was obtained from the characterization of the microstructure present at room temperature after full and partial transformation at 300 and 350 °C. The continuous change during transformation of relevant parameters influencing the final scale of the microstructure, YS of austenite, driving force of the transformation and evolution of the transformation rate has been tracked, and these variations have been correlated to the evolution of the bainitic ferrite plate. Instead of the expected refinement of the plate predicted by existing theory and models, this study revealed a thickening of the bainitic ferrite plate thickness as the transformation progresses, which is partially explained by changes in the transformation rate through the whole decomposition of austenite into bainitic ferrite.
Collapse
|
7
|
Dlouhy J, Podany P, Dzugan J. Copper-Induced Strengthening in 0.2 C Bainite Steel. Materials (Basel) 2021; 14:ma14081962. [PMID: 33919853 PMCID: PMC8070806 DOI: 10.3390/ma14081962] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 01/18/2021] [Revised: 03/31/2021] [Accepted: 04/09/2021] [Indexed: 11/16/2022]
Abstract
Bainitic steels were the focus of this study. These steels have the potential to obtain a good combination of strength, ductility, and edge stretchability, which is a very desirable characteristic in the automotive industry. Cu precipitation potential was investigated during prolonged isothermal bainitization treatment. Precipitation strengthening and ductility were measured using a tensile test, and edge stretchability was measured using a hole expansion test. The microstructure was characterized by high-resolution scanning electron microscopy and an electron backscattered diffraction. Lower bainite was obtained by austenitization treatment and subsequent immersion into a salt bath at 400 °C. Cu precipitation occurred after 120 min of holding in the bath and enhanced the yield stress of the Cu-alloyed steel by 120 MPa as compared with a reference steel without Cu. The strengthening did not affect ductility and decreased the edge stretchability by 10%. Steels with different Mn contents were examined. It was found that the enhancement of Mn content from 1 to 2 wt.% did not boost Cu strengthening ability. This result showed that the presence of Mn did not cause an Mn-Cu precipitation strengthening synergy, observed previously during martensite tempering procedure.
Collapse
|
8
|
Lin M, Zimmermann C, Wang K, Hunkel M, Prahl U, Spatschek R. Modeling Bainitic Transformations during Press Hardening. Materials (Basel) 2021; 14:654. [PMID: 33572594 DOI: 10.3390/ma14030654] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 12/15/2020] [Revised: 01/14/2021] [Accepted: 01/25/2021] [Indexed: 11/16/2022]
Abstract
We revisit recent findings on experimental and modeling investigations of bainitic transformations under the influence of external stresses and pre-strain during the press hardening process. Experimentally, the transformation kinetics in 22MnB5 under various tensile stresses are studied both on the macroscopic and microstructural level. In the bainitic microstructure, the variant selection effect is analyzed with an optimized prior-austenite grain reconstruction technique. The resulting observations are expressed phenomenologically using a autocatalytic transformation model, which serves for further scale bridging descriptions of the underlying thermo-chemo-mechanical coupling processes during the bainitic transformation. Using analyses of orientation relationships, thermodynamically consistent and nondiagonal phase field models are developed, which are supported by ab initio generated mechanical parameters. Applications are related to the microstructure evolution on the sheaf, subunit, precipitate and grain boundary level.
Collapse
|
9
|
Łazarska M, Wozniak TZ, Ranachowski Z, Trafarski A, Marciniak S. The Use of Acoustic Emission and Neural Network in the Study of Phase Transformation below M S. Materials (Basel) 2021; 14:ma14030551. [PMID: 33498855 PMCID: PMC7865756 DOI: 10.3390/ma14030551] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 11/28/2020] [Revised: 01/18/2021] [Accepted: 01/20/2021] [Indexed: 11/16/2022]
Abstract
Acoustic emission and dilatometry were applied to investigate the characteristics of phase transformations in bearing steel 100CrMnSi6-4 during austempering below the martensite start temperature (MS 175 °C) at 150 °C. The aim of this study is to characterize the product of transformation occurring below the MS temperature using various research methods. Analysis of the dilatometric curves shows that, after the formation of athermal martensite below the MS temperature, the austenite continues to undergo isothermal transformation, indicating the formation of bainite. Additionally, tests were carried out with the use of acoustic emission during isothermal hardening of the adopted steel. The obtained acoustic emission signals were analyzed using an artificial neural network. The results, in the form of a graph of the frequency of acoustic emission (AE) event occurrence as a function of time, make it possible to infer about the bainite isothermal transformation. The results of this research may be used in the future to design optimal heat treatment methods and, consequently, may enable desired microstructure shaping.
Collapse
Affiliation(s)
- Małgorzata Łazarska
- Institute of Fundamental Technological Research, Polish Academy of Sciences, Pawińskiego 5B, 02-106 Warszawa, Poland;
- Institute of Materials Engineering, Kazimierz Wielki University, Chodkiewicza 30, 85-064 Bydgoszcz, Poland; (T.Z.W.); (A.T.)
- Correspondence:
| | - Tadeusz Z. Wozniak
- Institute of Materials Engineering, Kazimierz Wielki University, Chodkiewicza 30, 85-064 Bydgoszcz, Poland; (T.Z.W.); (A.T.)
| | - Zbigniew Ranachowski
- Institute of Fundamental Technological Research, Polish Academy of Sciences, Pawińskiego 5B, 02-106 Warszawa, Poland;
| | - Andrzej Trafarski
- Institute of Materials Engineering, Kazimierz Wielki University, Chodkiewicza 30, 85-064 Bydgoszcz, Poland; (T.Z.W.); (A.T.)
| | - Szymon Marciniak
- Faculty of Materials Science and Engineering, Warsaw University of Technology, Wołoska 141, 02-507 Warszawa, Poland;
| |
Collapse
|
10
|
Brykov MN, Petryshynets I, Džupon M, Kalinin YA, Efremenko VG, Makarenko NA, Pimenov DY, Kováč F. Microstructure and Properties of Heat Affected Zone in High-Carbon Steel after Welding with Fast Cooling in Water. Materials (Basel) 2020; 13:ma13225059. [PMID: 33182662 PMCID: PMC7696765 DOI: 10.3390/ma13225059] [Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 09/17/2020] [Revised: 11/03/2020] [Accepted: 11/09/2020] [Indexed: 11/16/2022]
Abstract
The purpose of the research was to obtain an arc welded joint of a preliminary quenched high-carbon wear resistant steel without losing the structure that is previously obtained by heat treatment. 120Mn3Si2 steel was chosen for experiments due to its good resistance to mechanical wear. The fast cooling of welding joints in water was carried out right after welding. The major conclusion is that the soft austenitic layer appears in the vicinity of the fusion line as a result of the fast cooling of the welding joint. The microstructure of the heat affected zone of quenched 120Mn3Si2 steel after welding with rapid cooling in water consists of several subzones. The first one is a purely austenitic subzone, followed by austenite + martensite microstructure, and finally, an almost fully martensitic subzone. The rest of the heat affected zone is tempered material that is heated during welding below A1 critical temperature. ISO 4136 tensile tests were carried out for the welded joints of 120Mn3Si2 steel and 09Mn2Si low carbon steel (ASTM A516, DIN13Mn6 equivalent) after welding with fast cooling in water. The tests showed that welded joints are stronger than the quenched 120Mn3Si2 steel itself. The results of work can be used in industries where the severe mechanical wear of machine parts is a challenge.
Collapse
Affiliation(s)
- Michail Nikolaevich Brykov
- Welding Department, Zaporizhzhia Polytechnic National University, 69063 Zaporizhzhia, Ukraine
- Correspondence:
| | - Ivan Petryshynets
- Institute of Materials Research, Slovak Academy of Sciences, 04001 Kosice, Slovakia; (I.P.); (M.D.); (F.K.)
| | - Miroslav Džupon
- Institute of Materials Research, Slovak Academy of Sciences, 04001 Kosice, Slovakia; (I.P.); (M.D.); (F.K.)
| | | | | | | | - Danil Yurievich Pimenov
- Department of Automated Mechanical Engineering, South Ural State University, Lenin Prosp. 76, Chelyabinsk 454080, Russia;
| | - František Kováč
- Institute of Materials Research, Slovak Academy of Sciences, 04001 Kosice, Slovakia; (I.P.); (M.D.); (F.K.)
| |
Collapse
|
11
|
Long X, Zhang F, Yang Z, Zhang M. Study on Bainitic Transformation by Dilatometer and In Situ LSCM. Materials (Basel) 2019; 12:E1534. [PMID: 31083330 DOI: 10.3390/ma12091534] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 04/11/2019] [Revised: 05/07/2019] [Accepted: 05/09/2019] [Indexed: 11/21/2022]
Abstract
This study investigates the bainitic transformation kinetics of carbide-free bainitic steel with Si + Al and carbide-bearing bainitic steel without Si + Al, as well as the phase transformation and microstructure through in situ high-temperature laser scanning confocal microscopy. Results show that bainitic ferrite plates preferentially nucleate at the grain boundary. New plates nucleate on previously formed ones, including two dimensions which appear on a plane where a three-dimensional space of bainitic ferrite forms. Nucleation on the formed bainitic ferrite is faster than that at the grain boundary in some grains. The bainitic ferrite growth at the austenite grain boundary is longer and has a faster transformation rate. The bainitic ferrite growth on the formed bainitic ferrite plate is shorter and has a slower transformation rate. The location and number of nucleation sites influence the thickness of the bainitic ferrite. The higher the number of plates preferentially nucleating at the original austenite grain boundary, the greater the thickness of the bainitic ferrite.
Collapse
|
12
|
Ben Haj Slama M, Gey N, Germain L, Zhu K, Allain S. Key Parameters to Promote Granularization of Lath-Like Bainite/Martensite in FeNiC Alloys during Isothermal Holding. Materials (Basel) 2018; 11:E1808. [PMID: 30249989 DOI: 10.3390/ma11101808] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 08/31/2018] [Revised: 09/17/2018] [Accepted: 09/21/2018] [Indexed: 11/17/2022]
Abstract
The stability of lath-like microstructures during low-temperature isothermal ageing was analyzed in a Fe5Ni0.33C (in wt %) steel. The microstructures were characterized using Scanning Electron Microscopy (SEM) coupled with Electron Backscatter Diffraction (EBSD). Advanced orientation data processing was applied to quantify the hierarchical and multiscale organization of crystallographic variants subdividing Prior Austenite Grains (PAG) into packets/blocks/sub-blocks. The result shows that ferrite laths of martensite or lower bainite are stable, whatever the ageing temperature (up to 380 °C). On the contrary, a granularization process is triggered when microstructures contain a fraction of upper bainite. This metallurgical evolution corresponds to a rapid and significant change of the ferrite matrix involving a disappearance of 60° disoriented blocks. The phenomenon affects in turn the mechanical properties. The final microstructures obtained after isothermal holding look like granular bainite, which raises some questions about the classification of bainite.
Collapse
|
13
|
Wang Y, Hua J, Kong M, Zeng Y, Liu J, Liu Z. Quantitative analysis of martensite and bainite microstructures using electron backscatter diffraction. Microsc Res Tech 2016; 79:814-9. [PMID: 27338247 DOI: 10.1002/jemt.22703] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/26/2016] [Revised: 06/01/2016] [Accepted: 06/01/2016] [Indexed: 11/07/2022]
Abstract
In the present work, ultra-high-strength steels with multiphase microstructures containing martensite and bainite were prepared by controlling the cooling rate. A new approach was proposed for quantitatively statistical phase analysis using electron backscatter diffraction (EBSD) based on the band contrast which correlates to the quality and intensity of the diffraction patterns. This approach takes advantage of the inherently greater lattice imperfections of martensite, such as dislocations and low-angle grain boundaries, relative to that of bainite. These can reduce the intensity and quality of the EBSD patterns of martensite, which decrease the band contrast. Thus, combined with morphological observations, Gaussian two-peak fitting was employed to analyze the band contrast profile and confirm the ranges of band contrast for the two phases. The volume fractions of bainite and martensite in different samples were determined successfully. In addition, the results show that increased cooling rates improve the proportion of martensite and the ratio of martensite to bainite. Microsc. Res. Tech. 79:814-819, 2016. © 2016 Wiley Periodicals, Inc.
Collapse
Affiliation(s)
- Yongzhe Wang
- The State Key Lab of High Performance Ceramics and Superfine Microstructure, Shanghai Institute of Ceramics, Chinese Academy of Sciences, Shanghai, 200050, China
| | - Jiajie Hua
- The State Key Lab of High Performance Ceramics and Superfine Microstructure, Shanghai Institute of Ceramics, Chinese Academy of Sciences, Shanghai, 200050, China
| | - Mingguang Kong
- Key Laboratory of Materials Physics, Institute of Solid State Physics, Chinese Academy of Science, Hefei, Anhui, 230031, China
| | - Yi Zeng
- The State Key Lab of High Performance Ceramics and Superfine Microstructure, Shanghai Institute of Ceramics, Chinese Academy of Sciences, Shanghai, 200050, China
- CAS Center for Excellence in Superconducting Electronics (CENSE), Shanghai, 200050, China
| | - Junliang Liu
- Research and Development Center, Baoshan Iron and Steel Co Ltd, Shanghai, 201900, China
| | - Ziwei Liu
- The State Key Lab of High Performance Ceramics and Superfine Microstructure, Shanghai Institute of Ceramics, Chinese Academy of Sciences, Shanghai, 200050, China
| |
Collapse
|
14
|
Abstract
Nanotechnology has become an overused adjective, but there has been justified excitement in the context of structural materials. A class of iron alloys has been discovered in which a high density of strong interfaces can be created by heat-treatment alone. The packing of interfaces is so large, and the fact that there is an intrinsic work hardening mechanism in the structure, leads to remarkable properties. The genesis of this structure, its commercialization, the new science associated with the discovery, and its limitations are all explored in this short review.
Collapse
Affiliation(s)
- H K D H Bhadeshia
- University of Cambridge, Materials Science and Metallurgy, Cambridge, UK
| |
Collapse
|
15
|
Ohtsuka H. Structural control of Fe-based alloys through diffusional solid/solid phase transformations in a high magnetic field. Sci Technol Adv Mater 2008; 9:013004. [PMID: 27877922 PMCID: PMC5099791 DOI: 10.1088/1468-6996/9/1/013004] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/10/2007] [Revised: 03/13/2008] [Accepted: 10/29/2007] [Indexed: 06/06/2023]
Abstract
A magnetic field has a remarkable influence on solid/solid phase transformations and it can be used to control the structure and function of materials during phase transformations. The effects of magnetic fields on diffusional solid/solid phase transformations, mainly from austenite to ferrite, in Fe-based alloys are reviewed. The effects of magnetic fields on the transformation temperature and phase diagram are explained thermodynamically, and the transformation behavior and transformed structures in magnetic fields are discussed.
Collapse
Affiliation(s)
- Hideyuki Ohtsuka
- High Magnetic Field Station, National Institute for Materials Science, 3-13 Sakura, Tsukuba, Ibaraki, 305-0003, Japan
| |
Collapse
|