Superior improvement of tensile properties in a low alloy medium silicon DIN 1.5025 steel under single step quenching and partitioning heat treatment compared to fully martensitic conditions

Document Type : Research Paper

Authors

• Shima Pashangeh ¹
• sadegh ghasemi banadkouki ²

¹ Mining Technologies Research Center, Department of Mining and Metallurgical Engineering, Yazd University, Yazd, Iran

² department of mining and metallurgical engineering, yazd university, yazd, iran

Abstract

Advanced High Strength Steels (AHSS) are the result of a great effort by researchers to design and develop high strength steels with good formability, which can be replaced by the conventional quenched and tempered steels. In fact, this group of steels is hardened by controlling the phase transformation of austenite to different phases, which is quite different from conventional quenching and tempering steels with fully martensitic microstructure. In the present study, the tensile behavior of low alloy medium silicon DIN 1.5025 steel has been investigated under one step quenching and partitioning heat treatment (Q&P) at quenching temperature 250oC (below the martensitic start temperature: 275oC) for different partitioning times ranged from 5s to 1h compared to direct quenching condition. Microstructural studies, as well as changes in mechanical properties, were carried out by using laser and scanning electron microscopes, along with X-ray diffraction pattern and tensile and hardness tests, respectively. Microstructural studies indicate the formation of microcomposite microstructures containing carbide free bainite-martensite-retained austenite during Q&P heat treatment compared to fully martensitic microstructures. The results indicated that the retained austenite volume fraction increasing up to a maximum value of 17.8% after partitioning for 600s resulted in a superior improvement in the tensile behavior of the microcompositic samples. Superior improvement of mechanical behavior with respect to the partitioning time of microcompositic specimens indicates the beneficial effect of retained austenite phase on tensile properties according to the transformation induced plasticity effect (TRIP) mediated by the transformation of retained austenite to martensite during the tensile test.

Keywords

• low alloy medium silicon DIN 1.5025 steel
• direct water quenching
• quenching and partitioning
• bainite-martensite-retained austenite microcompositic microstructure
• TRIP effect

20.1001.1.22285946.1399.10.40.5.4

---

References

[1]        R.T. Howard, M.Cohen "Austenite transformation above and within the martensite range", Trans AIME, Vol. 176, pp.4, 1948. 

 [2]       D.H. Kim, J.G. Speer, H.S. Kim, B.C. De Cooman, "Observation of an isothermal transformation during quenching and partitioning processing", Metallurgical and Materials Transactions A, Vol. 40, pp. 2048-60, 2009.           

[3]        A. Navarro-Lopez, J. Sietsma, M.J. Santofimia, "Effect of prior athermal martensite on the isothermal transformation kinetics below M_s in a low-C high-Si steel", Metallurgical and Materials Transactions A, Vol.47, pp. 1028-39, 2016.     

[4] ع. یزدی­زداه خلیلی، ص. قاسمی، ح. م. کریمی، م. مصلایی­پور، "بررسی تاثیر نامتعارف میکروساختارهای دوفازی فریتی- بینیتی بر اصلاح خواص مکانیکی فولاد کم‌آلیاژ MO40 در مقایسه با شرایط تمام بینیتی"، مجله مواد نوین، جلد 10، شماره 1، پاییز 98.     
           

 [5]        E.P. Da Silva, D. De Knijf, W. Xu, C. Fjer, Y. Houbaert, J. Sietsma, et al. "Isothermal transformations in advanced high strength steels below martensite start temperature", Materials Science and Technology, Vol.31, pp. 808-16, 2015.

[6]         S. Samanta, P. Biswas, S. Giri, S.B. Singh, S. Kundu, "Formation of bainite below the M_s temperature: Kinetics and crystallography", Acta Mater. Vol. 105, pp. 390-403, 2016.   

 [7]        Y.H. Jiang, R.F. Zhou, D. Lu, Z.H. Li, "Microstructures and properties of a bainite and martensite dual-phase cast steel fabricated by combination of alloying and controlled cooling heat treatment", Materials Science Forum, Vol. 475, pp. 93-6, 2005.      

[8]         S.M.C. Van Bohemen, M.J. Santofimia, J. Sietsma, "Experimental evidence for bainite formation below M_s in Fe-0.66C", Scripta Materialia, Vol. 5, pp. 488-91, 2008.         

[9]         I.A. Yakubtsov, G.R. Purdy, "Analyses of transformation kinetics of carbide-free bainite above and below the athermal martensite-start temperature", Metallurgical and Materials Transactions A, Vol. 43, pp. 437-46, 2012.        

[10]       J.C. Hell, M. Dehmas, S. Allain, J.M. Prado, A. Hazotte, J.P. Chateau, "Microstructure-properties relationships in carbide-free bainitic steels", ISIJ International, Vol. 51, pp. 1724-32, 2011.

 [11]      J. Sun, H. Yu, S. Wang, Y. Fan, "Study of microstructural evolution, microstructure-mechanical properties correlation and collaborative deformation-transformation behavior of quenching and partitioning (Q&P) steel", Materials Science and Engineering: A, Vol. 596, pp. 89-97, 2014.    

 [12]      F. HajyAkbary, J. Sietsma, G. Miyamoto, N. Kamikawa, R.H. Petrov, T. Furuhara, et al. "Analysis of the mechanical behavior of a 0.3 C-1.6 Si-3.5 Mn (wt%) quenching and partitioning steel", Materials Science and Engineering: A, Vol. 677, pp.505-14, 2016.       

 [13]      D. Kim, J.G. Speer, B.C. De Cooman, "Isothermal transformation of a CMnSi steel below the M_s temperature", Metallurgical and Materials Transactions A, Vol. 42, pp. 1575-85, 2011.      

 [14]      M. Oka, H.Okamoto, "Swing back in kinetics near M_s in hypereutectoid steels", Metallurgical and Materials Transactions A, Vol.19, pp. 447-52, 1988.

 [15]     L. Zhao, L. Qian, J. Meng, Q. Zhou, F. Zhang, "Below-M_s austempering to obtain refined bainitic structure and enhanced mechanical properties in low-C high-Si/Al steels", Scripta Materialia, Vol.112, pp.96-100, 2016.      

 [16]     J. Feng, T. Frankenbach, M.Wettlaufer, "Strengthening 42crmo4 steel by isothermal transformation below martensite start temperature', Materials Science and Engineering: A, Vol.683, pp. 110-5, 2017.      

 [17]     J. Tian, G. Xu, M. Zhou, H.Hu, "Refined Bainite Microstructure and Mechanical Properties of a High Strength Low Carbon Bainitic Steel Treated by Austempering Below and Above M_s", Steel Research International, Vol. 89, pp. 1-10, 2018.          

 [18]     Y. Toji, H. Matsuda, D. Raabe, "Effect of Si on the acceleration of bainite transformation by pre- existing martensite", Acta Materialia, Vol. 116, pp. 250-6, 2016.      

[19]      M. Somani, D. Porter, L. Karjalainen, D. Misra, "on the decomposition of austenite in a high-silicon steel during quenching and partitioning", Materials Science and Technology, Vol. 28  pp. 1013-20,  2012.

 [20]     X.Y. Long, J. Kang, B. Lv, F.C. Zhang, "Carbide-free bainite in medium carbon steel", Materials & Design, Vol. 64, pp.237-45, 2014.     

[21]      X. Tan, Y. Xu, X. Yang, D. Wu, "Microstructure – properties relationship in a one-step quenched and partitioned steel", Materials Science & Engineering A, Vol. 589, pp. 101-11, 2014.

[22]      R. Jafari  S. Kheirandish  S. Mirdamadi, "Effects of partitioning parameters in quenching and partitioning on microstructure and mechanical properties of an ultra-high low- alloy steel", Materials Science and Engineering Technology,  Vol. 49, pp. 1381-91,  2018.

[23]      D. Krizan, B.C.De, "Analysis of the Strain-Induced Martensitic Transformation of Retained Austenite in Cold Rolled Micro-Alloyed TRIP Steel", Steel research international, Vol. 79, pp. 513-22, 2008.

 [24]     E.D.E. Moor, S. Lacroix, A.J. Clarke, J. Penning, J.G. Speer, "Effect of Retained Austenite Stabilized via Quench and Partitioning on the Strain Hardening of Martensitic Steels", Metallurgical and Materials Transactions A, Vol. 39, pp. 2586-95, 2008.