Investigation of abnormal effect of dual-phase ferritic-bainitic microstructures on modification of mechanical properties of MO40 low alloy steel in comparison with full bainitic conditions
Subject Areas : journal of New MaterialsAbbas Yazdizade Khalili 1 , sadegh ghasemi banadkouki 2 , Hamid Reza Karimi Zarchi 3 , masoud mosallaee pour 4
1 - Yazd University
2 - department of mining and metallurgical engineering, yazd university, yazd, iran
3 - Mining Technologies Research Center, Department of Mining and Metallurgical Engineering, Yazd University, University Blvd, Safayieh, Yazd, PO Box: 98195 – 741, Iran
4 - yazd univesity
Keywords: MO40 low alloy steels, Step quenching heat treatment, Dual phase ferritic-bainitic microstructures, Interaction between bainite crystals and ferrite phase, Abnormal mechanical properties,
Abstract :
The purpose of this research is to investigate microstructural features and mechanical properties of MO40 low alloy steel under dual-phase ferritic-bainitic in comparison with those of full bainitic conditions. To do so, various heat treatment cycles including Austenitizing the samples at 860°C for 50 minutes, step quenching in primary 620°C salt bath for different duration times of 1 to 10 minutes, quenching in secondary 350°C salt bath for 30 minutes and then water quenching to room temperature in order to develop dual-phase ferritic-bainitic microstructures in the samples. The isothermal heat treatment in primary 620°C salt bath for various duration times was used in order to develop different volume fractions of ferritic phase in the microstructures, then the secondary 350°C salt bath was used for subsequent transformation of remaining prior austenite to bainite. Tensile test, micro and macro hardness testers, optical metallography and FE-SEM equipped with EDS were used for investigation of variations of mechanical properties and microstructural features. The experimental results show that there is a non-linear and abnormal relationship between the mechanical properties of dual-phase ferritic-bainitic samples and variations of ferrite and bainite volume fractions. The mechanical properties of dual-phase ferritic-bainitic samples involving 8-12 vol% grain boundary ferrite in the vicinity of bainite is considerably higher than other dual phase ferritic-bainitic samples and even full bainitic ones. This improvement in mechanical properties of dual-phase ferritic-bainitic samples involving 8-12 vol% ferrite is originating from interaction of bainite crystals on grain boundary ferrite.
1- T. Baudin, C. Quesne, J. Jura, R. Penelle, Microstructural characterization in a hot-rolled, two-phase steel, Mater. Charact. 47 (2001) 365–373.
2- A. Das, M. Ghosh, S. Tarafder, S. Sivaprasad, D. Chakrabarti, Micromechanisms of deformation in dual phase steels at high strain rates, Mater. Sci. Eng. A. 680 (2017) 249–258.
3- H. Ashrafi, M. Shamanian, R. Emadi, N. Saeidi, A novel and simple technique for development of dual phase steels with excellent ductility, Mater. Sci. Eng. A. 680 (2017) 197–202.
4- F. Rieger, M. Wenk, S. Schuster, T. Böhlke, Mechanism based mean-field modeling of the work-hardening behavior of dual-phase steels, Mater. Sci. Eng. A. 682 (2017) 126–138..
5- R.R. Mohanty, O.A. Girina, N.M. Fonstein, Effect of Heating Rate on the Austenite Formation in Low-Carbon High-Strength Steels Annealed in the Intercritical Region, Metall. Mater. Trans. A. 42 (2011) 3680.
6- R. Khondker, A. Mertens, J.R. McDermid, Effect of annealing atmosphere on the galvanizing behavior of a dual-phase steel, Mater. Sci. Eng. A. 463 (2007) 157–165.
7- م. کاشفی و ص. قاسمی، مقایسه ریزساختار و رفتار مکانیکی فولاد MO40 در شرایط دوفازی فریتی- مارتنزیتی و کوئنچ مستقیم بازگشت داده شده، مجله مواد نوین، جلد 9، شماره 1، پاییز 97.
8- A. Fallahi, Microstructure-properties correlation of dual phase steels produced by controlled rolling process, Mater. Sci. Technol. 01 (2002) 451–454.
9- A. Bag, K.K. Ray, E.S. Dwarakadasa, Influence of martensite content and morphology on the toughness and fatigue behavior of high-martensite dual-phase steels, Metall. Mater. Trans. A. 32 (2001) 2207–2217.
10- A. Bag, K.K. Ray, E.S. Dwarakadasa, Influence of martensite content and morphology on tensile and impact properties of high-martensite dual-phase steels, Metall. Mater. Trans. A. 30 (1999) 1193–1202.
11- P. Movahed, S. Kolahgar, S.P.H. Marashi, M. Pouranvari, N. Parvin, The effect of intercritical heat treatment temperature on the tensile properties and work hardening behavior of ferrite–martensite dual phase steel sheets, Mater. Sci. Eng. A. 518 (2009) 1–6.
12- E. Fereiduni, S.S.G. Banadkouki, Improvement of mechanical properties in a dual-phase ferrite–martensite AISI4140 steel under tough-strong ferrite formation, Mater. Des. 56 (2014) 232–240.
13- S.S.G. Banadkouki, E. Fereiduni, Effect of prior austenite carbon partitioning on martensite hardening variation in a low alloy ferrite–martensite dual phase steel, Mater. Sci. Eng. A. 619 (2014) 129–136.
14- E. Fereiduni, S.S.G. Banadkouki, Reliability/unreliability of mixture rule in a low alloy ferrite–martensite dual phase steel, J. Alloys Compd. 577 (2013) 351–359.
15- N. Saeidi, A. Ekrami, Comparison of mechanical properties of martensite/ferrite and bainite/ferrite dual phase 4340 steels, Mater. Sci. Eng. A. 523 (2009) 125–129.
16- A. Kumar, S.B. Singh, K.K. Ray, Influence of bainite/martensite-content on the tensile properties of low carbon dual-phase steels, Mater. Sci. Eng. A. 474 (2008)270–282.
17- م. خاکیان، ارتباط ریزساختار و خواص مکانیکی فولاد AISI 4340 در شرایط دوفازی فریتی- ببینیتی، دانشگاه صنعتی شریف، 1385.
18- M. Sudo, S. Hashimoto, S. Kambe, Niobium bearing ferrite-bainite high strength hot-rolled sheet steel with improved formability, Trans. Iron Steel Inst. Japan. 23 (1983) 303–311.
19- G.F. Vander voort, "Atlas of Time-Temprature Digrams for Irons and Steels" ASM International, 1991.
20- N.C. Goel, S. Sangal, K. Tangri, A theoretical model for the flow behavior of commercial dual-phase steels containing metastable retained austenite: Part I. derivation of flow curve equations, Metall. Trans. A. 16 (1985) 2013–2021.
21- V. Singh, "physical metallurgy" Lomus Offset Press, Delhi-110006, PP. 617.
22- C. Garcia-Mateo and F. G. Caballero, “Ultra-high-strength Bainitic steels”, ISIJ International, 2005, vol. 45, no. 11, pp. 1736-1740.
23- N. Anand et al., “Microstructural dependence of work hardening behavior in Martensite-Ferrite microalloyed steels”, ASM International, Journal of Materials Engineering and Performance, 2015, vol. 24(1), pp. 517-528.
24- Y. Mazaheri et al.,” A novel route for development of ultrahigh strength dual phase steels”, Elsevier, Journal of Materials Science and Engineering A, 2014, vol. A 619, pp. 1-11.
_||_