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Bainite

About: Bainite is a research topic. Over the lifetime, 9520 publications have been published within this topic receiving 145305 citations.


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Journal ArticleDOI
TL;DR: In this paper, a quantitative analysis of substructure in the martensite/bainite mixed structure, which is obtained from low-carbon NiCrMoV steels under different cooling conditions, was made by means of optical microscope (OM), scanning electron microscope (SEM), electron backscatter diffraction (EBSD), and transmission electron microscopy (TEM), in order to research the effect on toughness.
Abstract: The quantitative analysis of substructure in the martensite/bainite mixed structure, which is obtained from low-carbon NiCrMoV steels under different cooling conditions, was made by means of optical microscope (OM), scanning electron microscope (SEM), electron backscatter diffraction (EBSD), and transmission electron microscope (TEM), in order to research the effect on toughness. The test results indicate that the toughness of the steel is enhanced with the decrease in the packet and block size under the condition of the same prior austenite grain size mixed with different ratios of martensite and bainite while the lath width is about 0.38 µm. The calculation shows that both the packet and block boundaries have the same hindering effect on crack extension. Furthermore, the effect of the block width on impact energy is much larger than that of the packet. Therefore, the block can be used as microstructural substructure to affect the toughness in low-carbon martensite steels, suggesting that the block size is “the effective grain size” for controlling toughness.

70 citations

Journal ArticleDOI
TL;DR: In this paper, a correlation was confirmed between the good low temperature Charpy toughness of 9Ni steel and the stability of its precipitated austenite against the martensitic transformation.
Abstract: A correlation was confirmed between the good low temperature Charpy toughness of 9Ni steel and the stability of its precipitated austenite against the martensitic transformation. Changes in the microstructure during isothermal tempering were studied in detail. The austenite/martensite interface is originally quite coherent over ∼100 A distances. With further tempering, however, the dislocation structure at the austenite/martensite interface changes, and this change may be related to the increased instability of the austenite particles. The reduction in austenite carbon concentration does not seem large enough to account for the large reduction in austenite stability with tempering time. The strains inherent to the transformation of austenite particles create dislocation structures in the tempered martensite. The large deterioration of the Charpy toughness of overtempered material is attributed, in part, to these dislocation structures.

70 citations

Journal ArticleDOI
TL;DR: In this article, the authors investigated the evolution of bainite in the DLD 12CrNi2 alloy steel process at different laser power of 1800, 2000, and 2200 W and the mechanical properties of as-deposited samples were investigated.
Abstract: In this paper, 12CrNi2 alloy steel samples were successfully fabricated by direct laser deposition (DLD) technology. The evolution of bainite in the DLD 12CrNi2 alloy steel process at different laser power of 1800 W, 2000 W and 2200 W and mechanical properties of as-deposited samples were investigated. The results showed that the middle-upper microstructure of the samples fabricated at different laser power transformed from lath bainite (LB) to granular bainite (GB) with increasing laser power. In addition, granular bainite was divided into blocky granular bainite (GB1) and lath-like granular bainite (GB2) according to different formation mechanisms, and the amount of GB1 increased and GB2 decreased in the range of laser power from 2000 W to 2200 W. No preferred texture was observed in the EBSD maps due to the complex heat flux direction which was resulted in the reciprocating scanning strategy. With the increase of laser power, the proportion of high-angle grain boundaries increased from 33.1% to 46.4% and that of low-angle grain boundaries decreased from 66.9% to 53.6%. The sample fabricated at 2000 W had the highest mean microhardness (331 HV0.2) and the best combination of ultimate tensile strength (757 MPa) and elongation (9.1%). However, the sample fabricated at 2200 W had the best impact toughness (aku = 100.0 J/cm2) because it contained a large amount of GB1 with dispersive and spherical-like island structures. This study provides the theoretical and experimental basis for the design of laser power and controllability of microstructure and properties in the DLD alloy steel process.

70 citations

Journal ArticleDOI
TL;DR: In this paper, the volume fraction of various phases was made for the conventional transformation induced plasticity (TRIP) steel containing silicon, and the microstructures in the TRIP steel were characterized by optical microscopy, scanning electron microscopy and transmission electron microscope, especially, an effective method was developed to identify multi-phase microstructure by atomic force microscopy based on the height difference.
Abstract: Transformation induced plasticity (TRIP) steels exhibit a combination of high strength and ductility due to their multi-phase microstructure, including ferrite, bainite and retained austenite which transforms to martensite under the external stress. The characterization of microstructures is necessary for understanding the relationship between microstructure and property. In the present work, an effort to determine the volume fraction of various phases was made for the conventional TRIP steel containing silicon. The microstructures in the TRIP steel were characterized by optical microscopy, scanning electron microscopy and transmission electron microscopy, especially, an effective method was developed to identify multi-phase microstructures by atomic force microscopy based on the height difference. Furthermore, the stability of retained austenite determining TRIP effect was evaluated by electrical resistance tests and tensile tests. The results show that retained austenite does not generate martensitic transformation at −80 °C and exhibits a good thermodynamic stability, and the transition temperature from stress-induced martensitic transformation to strain-induced martensitic transformation is determined as about −5 °C, and thus strain-induced martensitic transformation over −5 °C (somewhat lower than room temperature) is favorable for the application of TRIP steels in the automobile industry.

70 citations

Journal ArticleDOI
TL;DR: In this article, the mechanical properties of a heat treated dual phase steel were investigated as a function of the martensite volume fraction, and the changes promoted by tempering at 100 C, 200 C and 300 C were measured and investigated.

70 citations


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Performance
Metrics
No. of papers in the topic in previous years
YearPapers
2023211
2022417
2021337
2020425
2019427
2018409