Journal articles: 'Nano-bainite'

1

Zhao, Eric Jiahan, Cheng Liu, and Derek O. Northwood. "Accelerated Nano Super Bainite in Ductile Iron." MRS Advances 3, no. 45-46 (2018): 2789–94. http://dx.doi.org/10.1557/adv.2018.440.

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ABSTRACTA commercial unalloyed ductile iron has been developed to produce a multiphase matrix microstructure consisting of lenticular prior martensite, feathery upper bainite and a nano-scaled super bainite of lath bainitic ferrite and carbon-enriched film retained austenite. Multi-step heat treatment composed of austenizing, rapidly quenching and isothermally holding at low temperature have been developed. A tensile strength of more than 1.6 GPa, a hardness higher than HRC 54, and an elongation in excess of 5%, are achieved. This is attributed to a synergistic multi-phase strengthening effect. The developed nano super bainite exhibits a good balance between strength and toughness. The presence of martensite formed during the quenching prior to the isothermal treatment, accelerates the kinetics of subsequent nano super bainitic transformation by bainitic laths nucleating quickly at the martensite-austenite interfaces.

2

Timokhina, Ilana B., Hossein Beladi, Xiang Yuan Xiong, Elena V. Pereloma, and Peter D. Hodgson. "Nano-Scale Analysis of Nano-Bainite Formed in Advanced High Strength Steels." Materials Science Forum 654-656 (June 2010): 102–5. http://dx.doi.org/10.4028/www.scientific.net/msf.654-656.102.

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The effect of composition and processing schedule on the microstructure of C-Mn-Si-Mo-(Al)-(Nb) steels containing nano-bainite was studied using transmission electron microscopy (TEM) and atom probe tomography (APT). The major phase formed in all steels was nano-bainite. However, the steels with lower carbon and alloying addition content subjected to TMP had better mechanical properties than high alloyed steel after isothermal treatment. The presence of ferrite in the microstructure can improve not only ductility but lead to the formation of retained austenite with optimum chemical stability.

3

Sun, Wei Hua, and Zhi Chao Bi. "Grade E550 Heavy Steel Plate by TMCP for Offshore Energy Exploration." Advanced Materials Research 936 (June 2014): 1146–52. http://dx.doi.org/10.4028/www.scientific.net/amr.936.1146.

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This paper introduces the study and production on steel plate of Grade E550 in60mm thick by Thermo-mechanical processing (TMCP) and tempering for offshoreinfrastructure purpose. The steel plate obtained high strength and goodtoughness in both the base materials and the weld joints. Microstructure and precipitation characteristicswere examined in the plate is comprised of bainite with a small amount ofpre-eutectoid ferrite. Parallel arranged lath bainite characterizes thebainitic structure with high density of dislocations and precipitates. Carbides MxCy averaging 200nm indimension and MC type Carbonitrides in several nano to a dozen nano carbidesdistribute in the bainite ferrite and the bainte lath interfaces. Compatiblemechanical properties were achieved at welded joint. Microstructures were analysed in the welding heataffected zone (HAZ).

4

Pei, Wei, Wei Liu, Yue Zhang, Rongjian Qie, and Aimin Zhao. "Study on Kinetics of Transformation in Medium Carbon Steel Bainite at Different Isothermal Temperatures." Materials 14, no. 11 (May 21, 2021): 2721. http://dx.doi.org/10.3390/ma14112721.

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Ultra-fine carbide-free bainitic (UCFB) steel, also known as nano-bainite (NB) steel, is composed of bainitic ferrite laths with nanoscale thickness and carbon-rich film-like retained austenite located between laths. The bainite transformation kinetic model can accurately describe the bainite transformation kinetics in conventional austempering (CA) processes based on the shear mechanism combined with the dilatometer test. UCFB steels with medium and high carbon composition are designed in this work to systematically study the transformation kinetics of bainite, and the evolution of its microstructure and properties, and reveal the influence of heat treatment processes on the microstructure and properties the UCFB steels. The results show that the activation energy for BF nucleation decreases during the CA process and isothermal transformation temperature decreases. The bainite transformation is first nucleated at the grain boundaries, and then nucleated at the newly formed bainitic ferrite/austenite interface.

5

Mishra, Bidyapati, G. Sukumar, P. P. Senthil, P. R. S. Reddy, B. B. Singh, B. Ramakrishna, K. Siva Kumar, and V. Madhu. "Ballistic Efficacy of Carbide Free High Strength Nano Structured Bainitic Armour Steels." Defence Science Journal 73, No 2 (March 9, 2023): 131–39. http://dx.doi.org/10.14429/dsj.73.18634.

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Carbide free nano-structured bainitic steels typically have strength more than 2.0 GPa and impact toughness of 7 J or less. Most of this class of steels have sluggish kinetics and takes 16-72 h for complete bainitic transformation. The present work discusses key perspectives in developing carbide free nano-structured bainitic steel having strength more than 2.0 GPa and toughness more than 15 J. Further, ballistic evaluation of newly developed carbide free nano-structured bainitic steels having strength more than 2.0 GPa and high toughness of 20 J was carried out to understand the adaptability of these steels in combat vehicle applications. A comparison is made between newly developed high strength and tough carbide free nano-structured bainitic steels with typical martensite based ARMOX 500 class of armour steels. The developed nano-structured bainite showed ballistic performance much superior to ARMOX 500 steel. Monolithic plates of bainite provide complete protection against 7.62 AP projectiles at an areal density of 120 kgm-2. The ballistic efficiency of monolithic plates was further enhanced by using perforated geometrical configurations.

6

YUAN Shao-qiang, 苑少强, 张晓娟 ZHANG Xiao-juan, 郝斌 HAO Bin, and 张济山 ZHANG Ji-shan. "Nano-size precipitation during relaxation and refinement of bainite." Optics and Precision Engineering 21, no. 8 (2013): 1995–99. http://dx.doi.org/10.3788/ope.20132108.1995.

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7

Wang, Jiamei, Xinjie Di, Chengning Li, and Dongpo Wang. "Characterization of nanoscale precipitates and enhanced mechanical properties of high strength weld metals containing Cu additions after PWHT." Metallurgical Research & Technology 119, no. 1 (2022): 119. http://dx.doi.org/10.1051/metal/2022007.

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In order to match rapidly development of high strength low alloy steels, the new metal cored wire contained copper was designed. The multi-pass weld metals were obtained by gas metal arc welding. Results show that microstructure of weld metals is bainite with M-A constituents, and there are nano-9RCu precipitates after PWHT. The weld metal as welded achieves 737 MPa of yield strength (YS) and 1097 MPa of ultimate tensile strength (UTS), with an elongation 8%. After PWHT, the YS and UTS are 725 MPa and 968 MPa, respectively, and elongation increases to 16%. The lower dislocations density and reduction of Cu element at solid solution state hence for the decrease of YS. As well, the nano-Cu precipitates and reduction of effective grain size make it increase. The combined effect of these factors makes YS decrease by only 12 MPa after PWHT. Besides, a good impact performance (46.6 J) can be obtained after PWHT, while it is only 27.7 J of weld metals as welded. The improved toughness of weld metals after PWHT is obtained by the contributions of finer effective grain size, soft bainite, and dispersed nano-9RCu precipitation. The nano-Cu precipitates can improve strength without damage to toughness of weld metal after PWHT.

8

Long, Xiaoyan, Zhao Dai, Wanshuai Wang, Zhinan Yang, Fucheng Zhang, and Yanguo Li. "Carbon Atom Distribution and Impact Toughness of High-Carbon Bainitic Steel." Coatings 14, no. 4 (April 10, 2024): 457. http://dx.doi.org/10.3390/coatings14040457.

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High-carbon nano bainitic steel is currently a hot research topic. The effect of the matrix’s carbon content and carbon atom distribution on the toughness of high-silicon, high-carbon bainitic steel is studied. The microstructure under an incomplete austenitization process consists of undissolved carbides, bainitic ferrite, and retained austenite. Using this process, the carbon content in bainitic ferrite is relatively low. Under the complete austenitization process, the carbon content in the bainite ferrite in the sample is high, and there is more retained austenite in the blocky type. The sample exhibits high impact toughness under an incomplete austenitization process, which is mainly affected by the low carbon content of bainite ferrite, high coordination ability of retained austenite, and high interface density of microstructure. The EBSD results show that the crack easily propagates between parallel bainite laths with low interface density compared with the high interface density perpendicular to the laths.

9

Kumar, Avanish, and Aparna Singh. "Toughness dependence of nano-bainite on phase fraction and morphology." Materials Science and Engineering: A 729 (June 2018): 439–43. http://dx.doi.org/10.1016/j.msea.2018.05.106.

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10

Timokhina, I. B., K. D. Liss, D. Raabe, K. Rakha, H. Beladi, X. Y. Xiong, and P. D. Hodgson. "Growth of bainitic ferrite and carbon partitioning during the early stages of bainite transformation in a 2 mass% silicon steel studied by in situ neutron diffraction, TEM and APT." Journal of Applied Crystallography 49, no. 2 (February 16, 2016): 399–414. http://dx.doi.org/10.1107/s1600576716000418.

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In situ neutron diffraction, transmission electron microscopy (TEM) and atom probe tomography (APT) have been used to study the early stages of bainite transformation in a 2 mass% Si nano-bainitic steel. It was observed that carbon redistribution between the bainitic ferrite and retained austenite at the early stages of the bainite transformation at low isothermal holding occurred in the following sequence: (i) formation of bainitic ferrite nuclei within carbon-depleted regions immediately after the beginning of isothermal treatment; (ii) carbon partitioning immediately after the formation of bainitic ferrite nuclei but substantial carbon diffusion only after 33 min of bainite isothermal holding; (iii) formation of the carbon-enriched remaining austenite in the vicinity of bainitic laths at the beginning of the transformation; (iv) segregation of carbon to the dislocations near the austenite/ferrite interface; and (v) homogeneous redistribution of carbon within the remaining austenite with the progress of the transformation and with the formation of bainitic ferrite colonies. Bainitic ferrite nucleated at internal defects or bainite/austenite interfaces as well as at the prior austenite grain boundary. Bainitic ferrite has been observed in the form of an individual layer, a colony of layers and a layer with sideplates at the early stages of transformation.

11

Rijkenberg, R. Arjan, Maxim P. Aarnts, Floor A. Twisk, Marga J. Zuijderwijk, M. Knieps, and H. Pfaff. "Linking Crystallographic, Chemical and Nano-Mechanical Properties of Phase Constituents in DP and TRIP Steels." Materials Science Forum 638-642 (January 2010): 3465–72. http://dx.doi.org/10.4028/www.scientific.net/msf.638-642.3465.

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This paper discusses practical EBSD strategies for identification and partitioning of phase constituents in DP and TRIP microstructures including martensite, retained-austenite, bainite, intercritical and epitaxial ferrite. EBSD data is complemented with nano-indentation analysis, providing evidence of indentation-induced phase transformation of retained-austenite in TRIP steel and micro-crack initiation at the interface between ferrite and mechanically transformed martensite.

12

Hodgson, Peter D., Ilana Timokhina, Xiang Yuan Xiong, Yoshitaka Adachi, and Hossein Beladi. "Understanding of the Bainite Transformation in a Nano-Structured Bainitic Steel." Solid State Phenomena 172-174 (June 2011): 123–28. http://dx.doi.org/10.4028/www.scientific.net/ssp.172-174.123.

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A 0.79C-1.5Si-1.98Mn-0.98Cr-0.24Mo-1.06Al-1.58Co (wt%) steel was isothermally heat treated at 200°C for 10 days to form a nano-scale bainitic microstructure consisting of nanobainitic ferrite laths with high dislocation density and retained austenite films. The crystallographic analysis using TEM and EBSD revealed that the bainitic ferrite laths are close to the Nishiyama-Wassermann orientation relationship with the parent austenite. There was only one type of packet identified in a given transformed austenite grain. Each packet consisted of two different blocks having variants with the same habit plane, but different crystallographic orientations. The presence of fine C-rich clusters and Fe-C carbides with a wide range of compositions in bainitic ferrite was revealed by Three-dimensional Atom Probe Tomography (APT). The high carbon content of bainitic ferrite compared to the para-equilibrium level of carbon in ferrite, absence of segregation of carbon to the austenite/bainitic ferrite interface and absence of partitioning of substitutional elements between the retained austenite and bainitic ferrite were also found using APT.

13

Xing, X. L., Y. F. Zhou, S. Y. Gao, J. B. Wang, Y. L. Yang, and Q. X. Yang. "Nano-twin in surface modified bainite induced by laser surface modification." Materials Letters 165 (February 2016): 79–82. http://dx.doi.org/10.1016/j.matlet.2015.11.084.

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14

Das, Sourav, Saurabh Kundu, and Arunansu Haldar. "Development of Continuously Cooled High Strength Bainitic Steel through Microstructural Engineering at Tata Steel." Materials Science Forum 702-703 (December 2011): 939–42. http://dx.doi.org/10.4028/www.scientific.net/msf.702-703.939.

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Bainitic steels, which are transformed at very low temperatures, offer an excellent combination of strength and ductility where the strength comes from the nano-structured bainitic plates and thin-film of austenite sandwiched between two bainite sheaves offers the ductility. The main drawback of this structure is the long transformation time which is not ideal for industrial application. Through the microstructural engineering, the extent and kinetics of transformation can be manipulated by judicious selection of alloy composition and process variables. The main challenge is to delay the transformation till the coiling stage and allow the formation of bainite only during the cooling of the coil. In the current work, an approach will be shown, starting from the alloy design based on thermodynamics till the cooling after coiling, which can satisfy the requirements to develop such steel with 1300 MPa UTS combined with 20% elongation (min).

15

Avishan, Behzad, Sahand Golchin, and Sasan Yazdani. "Elongation improvement in nano bainite steel obtained from plastically deformed primary austenite." Philosophical Magazine 100, no. 17 (May 20, 2020): 2244–61. http://dx.doi.org/10.1080/14786435.2020.1764654.

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16

Kumar, Avanish, and Aparna Singh. "Microstructural effects on the sub-critical fatigue crack growth in nano-bainite." Materials Science and Engineering: A 743 (January 2019): 464–71. http://dx.doi.org/10.1016/j.msea.2018.11.114.

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17

Yang, Zhinan, Chunhe Chu, Feng Jiang, Yuman Qin, Xiaoyan Long, Shuli Wang, Da Chen, and Fucheng Zhang. "Accelerating nano-bainite transformation based on a new constructed microstructural predicting model." Materials Science and Engineering: A 748 (March 2019): 16–20. http://dx.doi.org/10.1016/j.msea.2019.01.061.

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18

Timokhina, Ilana, Hossein Beladi, Xiang Yuan Xiong, Yoshitaka Adachi, and Peter D. Hodgson. "Application of Advanced Experimental Techniques for the Microstructural Characterization of Nanobainitic Steels." Solid State Phenomena 172-174 (June 2011): 1249–54. http://dx.doi.org/10.4028/www.scientific.net/ssp.172-174.1249.

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A 0.79C-1.5Si-1.98Mn-0.98Cr-0.24Mo-1.06Al-1.58Co (wt%) steel was isothermally heat treated at 350°C bainitic transformation temperature for 1 day to form fully bainitic structure with nano-layers of bainitic ferrite and retained austenite, while a 0.26C-1.96Si-2Mn-0.31Mo (wt%) steel was subjected to a successive isothermal heat treatment at 700°C for 300 min followed by 350°C for 120 min to form a hybrid microstructure consisting of ductile ferrite and fine scale bainite. The dislocation density and morphology of bainitic ferrite, and retained austenite characteristics such as size, and volume fraction were studied using Transmission Electron Microscopy. It was found that bainitic ferrite has high dislocation density for both steels. The retained austenite characteristics and bainite morphology were affected by composition of steels. Atom Probe Tomography (APT) has the high spatial resolution required for accurate determination of the carbon content of the bainitic ferrite and retained austenite, the solute distribution between these phases and calculation of the local composition of fine clusters and particles that allows to provide detailed insight into the bainite transformation of the steels. The carbon content of bainitic ferrite in both steels was found to be higher compared to the para-equilibrium level of carbon in ferrite. APT also revealed the presence of fine C-rich clusters and Fe-C carbides in bainitic ferrite of both steels.

19

Luo, Quanshun, Haijuan Mei, Matthew Kitchen, Yubi Gao, and Leon Bowen. "Effect of Short-Term Low-Temperature Austempering on the Microstructure and Abrasive Wear of Medium-Carbon Low-Alloy Steel." Metals and Materials International 27, no. 9 (April 16, 2021): 3115–31. http://dx.doi.org/10.1007/s12540-020-00957-6.

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Abstract Nano-bainitic steels have attracted great attention for good wear resistance. In this research, a medium-carbon low-alloyed steel was austempered at a low temperature close to its martensite-start temperature for various times to obtain mixed microstructure of nano-bainite, martensite and retained austenite. The austempered samples were characterised comprehensively by field-emission SEM and quantitative XRD. Its two-body abrasive wear property was evaluated by sliding on a SiC abrasive disc. The results revealed the formation of initial nano-width carbide-free bainitic ferrite (BF) after austempering by 10 min, whereas the BF size and amount both increased with the austempering time. The austempered samples exhibited wear coefficients lower than the quenched martensitic sample by up to 50%. SEM and TEM observations showed wear mechanisms of micro-cutting and ploughing deformation, including the formation of a nano-laminate top layer and bending deformation in the subsurface multiphase microstructure. The decreased wear loss was attributed to the role of retained austenite in the increased plasticity. Graphic abstract

20

Fu, Lihua, Meng Zhou, Yanlin Wang, Yuanan Gao, Yongzhen Zhang, Sanming Du, Yi Zhang, and Yanshan Mao. "The Microstructure Transformations and Wear Properties of Nanostructured Bainite Steel with Different Si Content." Materials 15, no. 18 (September 8, 2022): 6252. http://dx.doi.org/10.3390/ma15186252.

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Nanostructured bainite (NB) bearing steel has excellent strength and ductility combinations, which can improve the fatigue life and wear resistance of bearing steel in harsh conditions. However, the phase transformations and the correlation between the microstructure and wear properties of NB bearing steel are still unclear. In this study, bearing steels with different Si contents (GCr15SiMo and GCr15Si1Mo) were prepared to have nano-bainitic structures, and their microstructure transformations and wear mechanisms were investigated. The results show that the Si element can inhibit the precipitation of carbides and can then promote the block-like retained austenite formation and refine the bainitic ferrite lamellar structure. The impact energy of GCr15Si1Mo is larger than that of GCr15SiMo because the nanostructured bainite and retained austenite are the main toughness phase in these steels. The wear results indicate that the steels which possess appropriate strength and toughness are helpful for improving wear resistance properties. Finally, the wear resistance performance of the GCr15Si1Mo austempered at 210 °C and GCr15SiMo austempered at 230 °C was good in this work.

21

Golchin, Sahand, Behzad Avishan, and Sasan Yazdani. "Effect of 10% ausforming on impact toughness of nano bainite austempered at 300 °C." Materials Science and Engineering: A 656 (February 2016): 94–101. http://dx.doi.org/10.1016/j.msea.2016.01.025.

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22

Zakerinia, Hossein, Ahmad Kermanpur, and Abbas Najafizadeh. "The effect of bainite in producing nano/ultrafine grained steel by the martensite treatment." Materials Science and Engineering: A 528, no. 10-11 (April 2011): 3562–67. http://dx.doi.org/10.1016/j.msea.2011.01.067.

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23

Yang, Z. N., L. Q. Dai, C. H. Chu, F. C. Zhang, L. W. Wang, and A. P. Xiao. "Effect of Aluminum Alloying on the Hot Deformation Behavior of Nano-bainite Bearing Steel." Journal of Materials Engineering and Performance 26, no. 12 (November 28, 2017): 5954–62. http://dx.doi.org/10.1007/s11665-017-3018-7.

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24

Kamikawa, Naoya, Kensuke Sato, Goro Miyamoto, Mitsuhiro Murayama, Nobuaki Sekido, Kaneaki Tsuzaki, and Tadashi Furuhara. "Stress–strain behavior of ferrite and bainite with nano-precipitation in low carbon steels." Acta Materialia 83 (January 2015): 383–96. http://dx.doi.org/10.1016/j.actamat.2014.10.010.

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25

Yu, X. F., Y. H. Wei, D. Y. Zheng, X. Y. Shen, Y. Su, Y. Z. Xia, and Y. B. Liu. "Effect of nano-bainite microstructure and residual stress on friction properties of M50 bearing steel." Tribology International 165 (January 2022): 107285. http://dx.doi.org/10.1016/j.triboint.2021.107285.

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26

Xing, X. L., Y. F. Zhou, Y. L. Yang, S. Y. Gao, X. J. Ren, and Q. X. Yang. "Surface modification of low-carbon nano-crystallite bainite via laser remelting and following isothermal transformation." Applied Surface Science 353 (October 2015): 184–88. http://dx.doi.org/10.1016/j.apsusc.2015.06.109.

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27

Aksenova, K. V., E. N. Nikitina, Yu F. Ivanov, and D. A. Kosinov. "Hardening mechanisms of steels with bainite and martensite structures." Izvestiya Visshikh Uchebnykh Zavedenii. Chernaya Metallurgiya = Izvestiya. Ferrous Metallurgy 61, no. 10 (November 14, 2018): 787–93. http://dx.doi.org/10.17073/0368-0797-2018-10-787-793.

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Martensite and bainite are the most complex structures being formed in steel in heat treatment including the quantitative interpretation. On frequent occasions, the application field of these steels includes the operation at high static and dynamic compression stresses. The thorough and comprehensive analysis of the materials’ structure after different types of treatment enables to use them competently for the manufacturing of the parts and structures providing them with the necessary complex of physical and mechanical properties. The factor determining the mechanical properties of the materials are the structure of solid solution, presence of nano-dimentional particles of the second phases, dislocation substructure, types and location of various boundaries and internal stress fields. For successful control of the formation of structural phase states and mechanical properties of the material it is necessary to know the quantitative laws and the cold hardening mechanisms of steels of different structural classes at active plastic deformation. By methods of transmission electron diffraction microscopy the analysis of cold hardening of 38CrNi3MoV steel with martensite and 30Cr2Ni-2MoV steel with bainite structures at active plastic compression deformation to 26 % and 36 %, respectively, was done in the research. The contributions caused by intraphase boundaries, dislocation substructure, carbide phases, atoms of alloying elements and long-range stress fields are considered. It is established that the substructural hardening (caused by the internal long-range stress fields) and solid solution strengthening (caused by carbon atoms) give largest contribution to cold hardening of 38CrNi3MoV hardened steel. For normalization of 30Cr2Ni2MoV steel hardening also takes place at the expense of the internal stress field’s action, at the penetration of carbon atoms to the ferrite crystal lattice as well as at the structural fragmentation with the deformation degree higher than 26 %. The dislocation substructure and the particles of carbide phase make comparatively small contribution to the hardening of these steels. It is shown that the cause of bainite steel softening at large (more than 15 %) degrees of deformation is connected with the activation of deformation microtwinning process.

28

Guo, Yanbing, Zhuguo Li, Liqun Li, and Kai Feng. "The Effects of Micro-Segregation on Isothermal Transformed Nano Bainitic Microstructure and Mechanical Properties in Laser Cladded Coatings." Materials 13, no. 13 (July 6, 2020): 3017. http://dx.doi.org/10.3390/ma13133017.

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The design of metastable retained austenite is the key issue to obtain nano bainitic steel with high strength and toughness. In this study, nanostructured Fe-based bainitic coatings were fabricated using laser cladding and following isothermal heat treatment. The microstructures and mechanical properties of the laser cladded coating were investigated. The results show that the Mn, Cr, Co, and Al segregated at the solidified prior grain boundaries. The micro-segregation of the solutes strongly influenced the stability of the austenite. As the isothermal temperature decreases, the interface of the bainite and blocky retained austenite approach to the prior interdendritic regions with the decreasing isothermal temperature, and the final volume fraction also decreases. The volume fractions of each phase and microstructure morphology of the coatings were determined by the interdendritic micro-segregation and isothermal temperatures. The stability of the blocky retained austenite distributed at the interdendritic area was lower than that of film and island-like morphology. This phenomenon contributed to the ductile and tough nano bainitic coatings with tunable mechanical properties.

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Zhao, J., T. S. Wang, B. Lv, and F. C. Zhang. "Microstructures and mechanical properties of a modified high-C–Cr bearing steel with nano-scaled bainite." Materials Science and Engineering: A 628 (March 2015): 327–31. http://dx.doi.org/10.1016/j.msea.2014.12.121.

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30

Li, Zhengrong, Zhenhu Lv, Chuangwei Wang, Lei Liu, Kaiyu Cui, and Zhengzhi Zhao. "Effect of Coiling Temperature on Microstructure and Properties of Titanium Strengthened Weathering Building Steel." Metals 13, no. 4 (April 19, 2023): 804. http://dx.doi.org/10.3390/met13040804.

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For weathering steel used in building, it is necessary not only to ensure weather resistance, but also to improve the strength and yield ratio. This study investigates the strengthening effect of Ti microalloying on the tested steel by conducting continuous cooling transformation tests of undercooled austenite and comparative tests of microstructure and performance at different coiling temperatures, with 0.07 wt.% Ti added to the weathering building test steel. The results show that, with an increase in cooling rate (0.1~50 °C/s), the room temperature microstructure of different cooling rates gradually transitions as follows: F + P, F + P + B, F + B and B + M; in addition, the hardness increases. Polygonal ferrite and pearlite were obtained by coiling at 650 °C; quasi-polygonal ferrite, acicular ferrite, pearlite and a small amount of bainite were obtained by coiling at 600 °C; and bainite was obtained by coiling at 550 °C. With a decrease in coiling temperature, the strength of the test steel increased, the yield ratio increased, the elongation after fracture decreased and the elongation at the yield point decreased. Compared with those observed at 650 °C, the nano precipitation phases observed in the sample at 600 °C were smaller in size, higher in number and higher in dislocation density. The combined action of second-phase precipitation strengthening and dislocation strengthening increased the strength and yield ratio of the test steel. This study will be helpful in guiding the improvement of strength grades for weathering steel used in building and industrial production.

31

Kim, Jinhyuk, Gyeongsik Yu, Sangeun Kim, Jinwoo Park, Minkyu Ahn, Jun-Ho Chung, Chang-Hoon Lee, and Chansun Shin. "Microstructural and Mechanical Characterization of Low-Alloy Fire- and Seismic-Resistant H-Section Steel." Metals 14, no. 4 (March 23, 2024): 374. http://dx.doi.org/10.3390/met14040374.

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This study investigates the microstructure and nano-hardness distribution across the thickness of an H-section steel beam, specifically designed for seismic and fire resistance and fabricated using a quenching and self-tempering process. The beam dimensions include a 24 mm thick flange, with flange and web lengths of 300 mm and 700 mm, respectively. Our findings indicate that the mechanical properties across the flange thickness meet the designed criteria, with yield strengths exceeding 420 MPa, tensile strengths of over 520 MPa, and a yield-to-tensile strength ratio below 0.75. Microstructurally, the central part of the flange predominantly consists of granular bainite with a small fraction of martensite–austenite (MA) constituents, while locations closer to the surface show increased acicular ferrite and decreased MA constituents due to faster cooling rates. Furthermore, thermal exposure at 600 °C reveals that while the matrix microstructure remains thermally stable, the MA phase undergoes tempering, leading to a decrease in nano-hardness. These insights underline the significant impact of MA constituents on the elongation properties and stress concentrations, contributing to the overall understanding of the material’s behavior under seismic and fire conditions. The study’s findings are crucial for enhancing the reliability and safety of construction materials in demanding environments.

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Bi, Hong Xia, Ming Hua Tang, Zhi Lan Ren, and Yong Zhou. "Effects of Tempering Temperature on the Microstructure and Mechanical Properties of Low Alloy Ultra-High Strength 45CrNiSiMnMoVA Steel." Materials Science Forum 1036 (June 29, 2021): 11–19. http://dx.doi.org/10.4028/www.scientific.net/msf.1036.11.

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The effects of different tempering temperatures on the microstructure evolution and mechanical properties of the new low-alloy ultra-high-strength 45CrNiSiMnMoVA steel after quenching were investigated by mechanical property tests, SEM and TEM. The results show that a complex phase organization consisting of martensite/ lower bainite of the tested steel after treated at 920°C×1h+(320~380)°C×4h was obtained, and the partition interface of the lath martensite bundle became blurred from clear with the increase of tempering temperature; In the proposed tempering temperature range, the toughness of the alloy has become better while maintain the strength without decreasing basically, and when the tempering temperature is 350°C, the alloy has the optimal comprehensive mechanical properties of strength, plasticity and toughness together. The analysis concluded that the strong toughening of the tested steel was mainly attributed to the coupling effect of the alloying elements in the steel and the composite toughening of the nano-precipitated phases, among other aspects.

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Królicka, Aleksandra, Francisca Garcia Caballero, Władysław Zalecki, Roman Kuziak, and Radosław Rozmus. "Controlling the Thermal Stability of a Bainitic Structure by Alloy Design and Isothermal Heat Treatment." Materials 16, no. 8 (April 7, 2023): 2963. http://dx.doi.org/10.3390/ma16082963.

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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.

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Krupp, Ulrich, Mikhail Solovev, Felix Honecker, Bernhard Adams, and Jan-Christoph Florian. "The Potential of Self-Tempered Martensite and Bainite in Improving the Fatigue Strength of Thermomechanically Processed Steels." MATEC Web of Conferences 165 (2018): 20006. http://dx.doi.org/10.1051/matecconf/2018165020006.

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In contrast to a two-stage hardening and tempering process, the definition of optimized cooling routes after hot working of low-alloy Cr steel allows the adjustments of high-strength microstructures with a sufficient degree of ductility at the same time without any additional heat-treatment. While compressed air cooling after hot forging of micro-alloyed steel grades leads to the formation of lower bainite with finedispersed cementite platelets, quenching by water spray down to the martensite start temperature results in the formation of martensite, that is self-tempered during the subsequent slow-cooling in air. The precipitation of nano-sized cementite precipitates result in superior mechanical properties with respect to impact and tensile testing. Cyclic deformation and crack propagation tests being carried out using resonance testing (100Hz) and ultrasonic fatigue testing (20kHz) systems revealed a pronounced increase in fatigue strength by about 150MPa of the self-tempered martensite condition as compared to the bainitic modification. For the latter one, a steady decrease of the fatigue strength is observed rather than the existence of a real fatigue limit.

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Krupp, Ulrich, Mikhail Solovev, Felix Honecker, Bernhard Adams, and Jan-Christoph Florian. "The Potential of Self-Tempered Martensite and Bainite in Improving the Fatigue Strength of Thermomechanically Processed Steels." MATEC Web of Conferences 165 (2018): 20006. http://dx.doi.org/10.1051/matecconf/201816520006.

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In contrast to a two-stage hardening and tempering process, the definition of optimized cooling routes after hot working of low-alloy Cr steel allows the adjustments of high-strength microstructures with a sufficient degree of ductility at the same time without any additional heat-treatment. While compressed air cooling after hot forging of micro-alloyed steel grades leads to the formation of lower bainite with finedispersed cementite platelets, quenching by water spray down to the martensite start temperature results in the formation of martensite, that is self-tempered during the subsequent slow-cooling in air. The precipitation of nano-sized cementite precipitates result in superior mechanical properties with respect to impact and tensile testing. Cyclic deformation and crack propagation tests being carried out using resonance testing (100Hz) and ultrasonic fatigue testing (20kHz) systems revealed a pronounced increase in fatigue strength by about 150MPa of the self-tempered martensite condition as compared to the bainitic modification. For the latter one, a steady decrease of the fatigue strength is observed rather than the existence of a real fatigue limit.

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López Perrusquia, N., J. A. Ortega Herrera, M. A. Doñu Ruiz, V. J. Cortes Suarez, and L. D. Cruz Rosado. "Characterization Microstructural and Mechanical of X-60 Steel Heat-Treated." MRS Proceedings 1481 (2012): 63–69. http://dx.doi.org/10.1557/opl.2012.1633.

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ABSTRACTIn this paper was study the effect of heat treatment on mechanical properties of an API X-60 steel used for storage and transportation of hydrocarbons.In the first stage evaluation are mechanical properties of steel heat treated by the technique of the three-point test according to ASTM 399-90 was carried out. In the second stage, characterization of the type of failure and microstructure through optical microscopy (OM) was determined; also heat treated samples were then mechanically tested for hardness (HRC) and nano-indentation. The presence of alloying elements by scanning electron microscopy (SEM) and the fracture surfaces generated in the steel with varying times, temperatures and cooling medium generated by different modes of solicitation (Bending), likewise with loading rates were determined. The results revealed a ductile fracture and microstructures (PF) ferrite-pearlite (DP), bainite -ferrite (BF) and martensite-retained and martensite/retained austenite (MA). Finally, this article discusses the effect of heat treatment followed by precipitation hardenable of steel API X-60 on the mechanical properties

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Kwon, Ohjoon, Kyoo Young Lee, Gyo Sung Kim, and Kwang Geun Chin. "New Trends in Advanced High Strength Steel Developments for Automotive Application." Materials Science Forum 638-642 (January 2010): 136–41. http://dx.doi.org/10.4028/www.scientific.net/msf.638-642.136.

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The body design with light weight and enhanced safety is a key issue in the car industry. Corresponding to this trend, POSCO is developing various automotive steel products with advanced performance. Conventional advanced high strength steels such as DP and TRIP steels are now expanding their application since the steels exhibit higher strength and ductility than those of conventional solution and precipitation strengthened high strength steels. Efforts have been made to enhance the mechanical performance of these steels such as ductility, hole expansion ratio, deep drawability, etc. Current research is focused on development of extra- and ultra-AHSS. Extra-AHSS are designed to utilize nano-scale retained austenite embedded in fine bainite and martensite. Ultra-AHSS are designed to have austenite as the major phase, and the ductility is enhanced primarily by continuous strain hardening generated during forming. These steels including extra- and ultra-AHSS are believed to be the next generation automotive steels which will replace the existing high strength steels due to their extremely high strength and ductility combinations.

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Papaefthymiou, Spyros, Marianthi Bouzouni, and Roumen H. Petrov. "Study of Carbide Dissolution and Austenite Formation during Ultra–Fast Heating in Medium Carbon Chromium Molybdenum Steel." Metals 8, no. 8 (August 16, 2018): 646. http://dx.doi.org/10.3390/met8080646.

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In this study, UltraFast Heat Treatment (UFHT) was applied to a soft annealed medium carbon chromium molybdenum steel. The specimens were rapidly heated and subsequently quenched in a dilatometer. The resulting microstructure consists of chromium-enriched cementite and chromium carbides (in sizes between 5–500 nm) within fine (nano-sized) martensitic and bainitic laths. The dissolution of carbides in austenite (γ) during ferrite to austenite phase transformation in conditions of rapid heating were simulated with DICTRA. The results indicate that fine (5 nm) and coarse (200 nm) carbides dissolve only partially, even at peak (austenitization) temperature. Alloying elements, especially chromium (Cr), segregate at austenite/carbide interfaces, retarding the dissolution of carbides and subsequently austenite formation. The sluggish movement of the austenite /carbide interface towards austenite during carbide dissolution was attributed to the partitioning of Cr nearby the interface. Moreover, the undissolved carbides prevent austenite grain growth at peak temperature, resulting in a fine-grained microstructure. Finally, the simulation results suggest that ultrafast heating creates conditions that lead to chemical heterogeneity in austenite and may lead to an extremely refined microstructure consisting of martensite and bainite laths and partially dissolved carbides during quenching.

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Wang, Xiaonan, Yanfeng Zhao, Bingjie Liang, Linxiu Du, and Hongshuang Di. "Study on Isothermal Precipitation Behavior of Nano-Scale (Nb,Ti)C in Ferrite/Bainite in 780 MPa Grade Ultra-High Strength Steel." steel research international 84, no. 4 (December 18, 2012): 402–9. http://dx.doi.org/10.1002/srin.201200195.

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Jia, Decheng, Chunsheng Zhang, Qingchao Wang, Helin Wang, Zhinan Yang, and Fucheng Zhang. "Unleashing the potential of nano-bainite bearing steels: Controllable selection of microstructure evolution enables concurrent improvement of toughness and hardness by pre-cold deformation." Materials Science and Engineering: A 906 (July 2024): 146715. http://dx.doi.org/10.1016/j.msea.2024.146715.

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Hong, Seokmin, Cho-Long Lee, Bong-Sang Lee, Hong-Deok Kim, and Min-Chul Kim. "Effects of Intercritical Heat Treatment on the Temper Embrittlement of SA508 Gr.4N Ni-Cr-Mo High Strength Low Alloy Steels for Reactor Pressure Vessels." Korean Journal of Metals and Materials 61, no. 10 (October 5, 2023): 729–40. http://dx.doi.org/10.3365/kjmm.2023.61.10.729.

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To analyze the effects of intercritical heat treatment on the temper embrittlement of SA508 Gr.4N steels, two model alloys with different phosphorus (P) contents were fabricated. Each sample was heat treated by applying a conventional heat treatment process (quenching-tempering) with/without an intercritical heat treatment process (IHT) and a step-cooling heat treatment for temper embrittlement. Then their microstructure and mechanical properties were evaluated. The microstructure of the SA508 Gr.4N model alloy was composed of tempered lower bainite and martensite, and nano-sized precipitates formed both inside and at boundaries. The grain size was reduced when IHT was applied. There was a small difference in tensile properties according to the heat-treatment conditions and P contents, but the difference in Charpy impact properties was large. The heat treatment for temper embrittlement (TE) increased the impact transition temperature, and a very significant increase was observed in steels with a high P content. The increase in transition temperature owing to TE was reduced when IHT was applied. The fractograph analysis of Charpy fractured specimens at transition temperatures showed that an increase in intergranular fracture was main reason for the TE, and that IHT reduced the formation of intergranular fracture. The AES results showed that P-Ni was segregated at grain boundaries, and the level of segregation was reduced by applying IHT. This occurred because the formation of prior austenite grain boundaries by IHT dispersed the P at grain boundaries, and reduced the amount of P segregation.

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Chhajed, Bhawesh, Kushal Mishra, Kritika Singh, and Aparna Singh. "Corrigendum to “Effect of prior austenite grain size on the tensile properties and fracture toughness of nano-structured bainite” [Materials Characterization, Volume 192, October 2022, 112214]." Materials Characterization 199 (May 2023): 112807. http://dx.doi.org/10.1016/j.matchar.2023.112807.

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Chen, Chih Yuan, Shih Fan Chen, Jer Ren Yang, and Chien Chon Chen. "Precipitation of Nano-Sized Carbides in a Ti-Mo Bearing Steel at a Low Transformation Temperature." Atlas Journal of Materials Science 2, no. 1 (June 14, 2017): 48–53. http://dx.doi.org/10.5147/ajms.v2i1.125.

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While the role of Ti and Mo elements on precipitation strengthening in ferrite grains formed during austenite/ferrite transformation is very clear, some uncertainty still presents concerning influence of microalloying elements on bainite transformation. Therefore, the present study focuses on the precipitation behavior occurred in a Ti-Mo bearing steel during bainitic phase transformation under different heat treatment conditions, and the correlation of the precipitation behavior with hardness distribution. Through the present work, it is expected to achieve a better understanding of low-temperature precipitation behavior to assist metallurgists to find out the reason for maintaining a high hardness by longtime isothermal holding, which can provide insight to design a better quality steel product. Vickers hardness was measured from the 1C-2Ti-2Mo, 1C-2Ti-2Mo and 0.5C-1Ti-2Mo steels treated by isothermal holding at 550 oC for 5 to 60 min. The average Vickers hardness was in the range of 245 - 276, 290 - 335 and 220 - 245, respectively. Therefore, higher hardness can be obtained if the steel containing higher carbon and microalloying elements can form precipitations in the ferrite matrix. On the other hand, increasing Vickers hardness with isothermal holding times indicates a good thermal stability character of complex carbides. The excellent thermal stability can be attributed to the addition of Mo element, which can inhibit the growth of carbides during longtime isothermal holding. Furthermore, the addition of Mo in the steel can avoid annihilation of dislocations during longtime aging. By taking advantages of these two effects, high strength can be achieved for high-strength low-alloy steels containing Mo element. Transmission electron microscopy image showed nano-sized carbides nucleated at dislocations, instead of interfacial precipitations within ferrite grain matrix, because the interface precipitation morphology only occurred accompanying the austenite decomposition reaction. However, the bainitic phase transformation was of a displacive transformation character, thus the complex carbides could not form during the bainitic phase transformation due to a very fast transformation velocity.

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Marcisz, Jarosław, Bogdan Garbarz, Władysław Zalecki, Zofia Kania-Pifczyk, Lech Starczewski, and Marcin Gołuński. "OPTIMISATION OF BALLISTIC PROPERTIES OF NANOSTRUCTURED BAINITIC STEEL PLATES FOR CONTAINER ARMOUR SYSTEM." PROBLEMY TECHNIKI UZBROJENIA 151, no. 3 (January 14, 2020): 97–119. http://dx.doi.org/10.5604/01.3001.0013.7325.

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Abstract: An innovative armour system containing plates made of nanostructured bainite steel is under development to improve operating properties of a light armoured observation-protective container (LAOC) providing the 2nd protection level according to STANAG 4569. Armour system solution of the container has been modified because the new plates have different mechanical and technological properties than currently used armour plates. The paper presents results of investigation of material characteristics and firing tests of plates made of nanostructured steel in the semi-industrial scale. To optimise parameters of heat treatment of the plates the kinetics of phase transformation was examined, and mechanical properties were measured, and changes in microstructure in the area of projectile interaction at firing tests were analysed for different variants of treatment. The reported investigations precede the industrial scale production process for plates made of the new grade steel designed for the armour system of LAOC. Optimisation of mechanical properties of the plates has been carried out by selection of such production parameters as chemical composition of the steel, hot working, interprocess heat treatment and temperature and time of final heat treatment (isothermal annealing). Effect of primary segregation of alloying and residual elements on protective properties of the plates is indicated. As a result of applying the annealing temperature in the range of 210-225°C (Ms temperature is ca. 200°C at cooling rate 1-2°C/s) and time in the range of 120-70 hours respectively, the following properties have been achieved: YS0.2 (yield strength) 1400-1500 MPa; UTS (ultimate tensile strength) 2000-2150 MPa; TE (total elongation) 10-13%, impact toughness KV at room temperature 10-16 J and hardness 590-610 HV (53-54 HRC). Microstructure of the plates consists of carbide free lathy nanobainite and 10-21% (volume fraction) of retained austenite. Plates of thickness 6.3 and 7.5 mm and ammunition type of 5.56x45 mm M193 and 7.62x51 mm API BZ have been used in the firing tests. Based on results of firing tests and microstructure examination in the area of projectile interaction the phenomena have been identified indicating high efficiency of ballistic protection of investigated plates, manifested by high ability to absorption and dissipation of projectile energy without susceptibility to cracking. Based on the results of mechanical properties measurements and firing tests a chemical composition of the nanostructured bainitic steel adjusted for industrial production of plates of thickness in the range of 6-8 mm has been developed. An analysis of container armour system mass reduction possibility, basing on results of investigation of the nano-structured bainite steel plates made in the semi-industrial scale, has been carried out. Basing on the analysis of the container construction and operational conditions some sensitive areas of ballistic protection have been specified to be subjected to firing tests. Ballistic examination will be carried out using the container segments representing the selected sensitive areas.

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Rementeria, Rosalia, Francisca G. Caballero, Lucia Morales-Rivas, and Carlos Garcia-Mateo. "Developing Nanostructured Metal at the Atomic and Nano Scales." AM&P Technical Articles 175, no. 1 (January 1, 2017): 21–24. http://dx.doi.org/10.31399/asm.amp.2017-01.p021.

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Abstract Affordable bulk production of a newly developed nanostructured bainitic steel is possible without using severe deformation or complex heat treatments. This article discusses the characteristics and significance of nanostructured bainite in terms of the transformation mechanism.

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Wang, Jiamei, Chengning Li, Xinjie Di, and Dongpo Wang. "Effect of Cu Content on Microstructure and Mechanical Properties for High-Strength Deposited Metals Strengthened by Nano-Precipitation." Metals 12, no. 8 (August 16, 2022): 1360. http://dx.doi.org/10.3390/met12081360.

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With the rapid development of low-carbon high strength steel, higher requirements are put forward for the matching welding consumables. The deposited metals with 0.62–2.32% Cu addition was prepared by tungsten inert gas welding via metal cored wire. The effect of Cu element on microstructure and mechanical properties of deposited metals were investigated. The multiphase microstructure of deposited metals consists of bainite, martensite, residual austenite, and martensite-austenite constituents. It is found that Cu decreases the start temperature of martensite (Ms) and enlarges the temperature range of bainite from 372 K to 416 K, improving the formation of bainite. With the increase of Cu content, the fraction of martensite decreases and the shape of M-A constituents changes from strip into granular. There are BCC and FCC Cu precipitates in deposited metals. The diameter of Cu precipitates is 14–28 nm, and the volume fraction of it increases with the increase of Cu content. Meanwhile, the deposited metals with 1.79% Cu can achieve a 10% enhancement in strength (yield strength, 873–961 MPa, ultimate tensile strength, 1173–1286 MPa) at little expense of impact toughness (64.56–56.39 J at −20 °C). Cu precipitation can effectively improve the strength of the deposited metals, but it degrades toughness because of lower crack initiation energy. The deposited metal with 1.79% Cu addition shows an excellent strength-toughness balance.

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Wang, Jian Feng, Guang Qiang Li, Ai Da Xiao, and Fu Jie. "Nano-Scaled Fe₃C Precipitates and Precipitation Strengthening in Hot Rolled Low Carbon High Strength Titanium Microalloyed Steel." Advanced Materials Research 146-147 (October 2010): 838–43. http://dx.doi.org/10.4028/www.scientific.net/amr.146-147.838.

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Hot rolled Ti microalloyed steel with polygonal ferrite and granular bainite microstructure and 640 MPa yield strength has been developed in BOF-CSP process. By chemical phase analysis, XRD, EDS and high resolution TEM, the particle size distribution, morphology, composition, crystal structure of precipitates were identified. Results revealed the steel containing Ti exhibits fine and uniformly distributed Fe3C-type carbides, the amount of M3C particles less than 18 nm in size was 0.2565 mass %. The high strength of steel is attributed to the precipitation strengthening effect of Fe3C, the yield strength increment from precipitation strengthening of Fe3C calculated according to the formula by Olson and Ashby-Orowan attained 234.4 MPa.

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Fan, Yanqiu, Changwen Ma, Shaopo Li, and Hai Zhang. "Novel Cu-Rich Nano-Precipitates Strengthening Steel with Excellent Antibacterial Performance." Metals 9, no. 1 (January 7, 2019): 52. http://dx.doi.org/10.3390/met9010052.

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In this study, a certain amount of Cu was added into tentative steel to introduce novel Cu-rich nanoprecipitates, thus enhancing strength yet without sacrificing toughness. This type of precipitates was quite different from previous ε-Cu, and was a novel type of Cu-rich nanoprecipitates, which contained more than 50% Cu. The microstructure, mechanical properties and precipitates of the steels aged at 550 °C for different holding times and were carefully examined. The microstructure of the tested steel was mainly bainite and gradually evolved into equilibrium state after aging. Mechanical properties results showed that after being aged at 550 °C for 10 min, the steel can have an excellent mechanical property combination of strength and toughness. In addition, a large amount of tiny precipitates was uniformly distributed in the matrix of the aging steels, and their size kept at nanoscale. In particular, when the steel was aged at 550 °C for 10 min, it produced the largest number of tiny precipitates of this type. This type of Cu-rich nanoprecipitates emerging from the steel aged at 550 °C for 10 min also brought about a remarkable antibacterial property. It revealed that novel Cu-rich precipitates not only have positive effects on strength and toughness, but also played an important role in antibacterial properties.

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Zhang, Guan-Zhen, Chun-Peng Liu, Si Wu, Sa Zhao, and Bin Zhang. "Rolling Contact Fatigue Damage of High-Speed Railway Wheels With Upper Bainite." Journal of Tribology 144, no. 5 (December 2, 2021). http://dx.doi.org/10.1115/1.4052868.

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Abstract This work investigates the effect of abnormal microstructure on rolling contact fatigue (RCF) damage of high-speed railway wheels under service and the formation mechanism of abnormal microstructure by optical microscopy, scanning electron microscopy, transmission electron microscopy, nano indentation and laser-induced break down spectroscopy. Results show that there are large amounts of upper bainite in the wheel tread, which destroyed the uniformity of the microstructures of the wheel matrix. The bainite is composed of ferrite with high density of dislocations and short bar-shaped cementite. The bainite exhibited higher hardness and elasticity but lower plasticity than the matrix microstructure. The incongruity of plastic deformation between upper bainite and matrix microstructures will lead to stress concentration at boundary of the microstructures, thus accelerating the RCF crack initiation and propagation. The formation of upper bainite is caused by carbon segregation. Segregation of carbon element will make the continuous cooling transformation (CCT) curve shift to the right significantly, thus increasing the probability of bainite transformation in segregation zone at higher cooling rate. Therefore, large amounts of upper bainite were formed at wheel tread.

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Chinara, M., B. Jayabalan, B. Bhattacharya, A. Durga Vara Prasad, S. Chatterjee, and S. Mukherjee. "Low cycle fatigue behaviour study of a nano precipitate strengthened Ferrite-Bainite 780 steel." International Journal of Fatigue, October 2022, 107294. http://dx.doi.org/10.1016/j.ijfatigue.2022.107294.

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Journal articles on the topic 'Nano-bainite'

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