Effect of Cooling Rates in Coiling Process on Microstructures and Mechanical Properties in Al-Bearing Hot-Rolled TRIP Steel

doi:10.1007/s40195-018-00868-x

Abstract

Abstract:

In this study, the effect of cooling rates on microstructures and mechanical properties in a Al-bearing hot-rolled transformation-induced plasticity steel was investigated. The experiments were carried out using hot simulation machine and hot rolling mill, where the samples were cooled at different cooling rates. The results showed that with the increase in cooling rates, film-like retained austenite gradually disappeared and only blocky retained austenite was retained at higher cooling rates. The volume fraction of retained austenite was 9-11% at cooling rates of 0.05-1 °C/s and 4-6% at cooling rates of 5-10 °C/s. In addition, martensite/austenite island was observed because of the heterogeneous carbon distribution. The samples cooled at 0.05 °C/s and 0.5 °C/s exhibited excellent mechanical properties, with tensile strengths of 712 MPa and 726 MPa, total elongations of 42% and 36% and strength and ductility balances of 29.91 GPa% and 26.15 GPa%, respectively. During plastic deformation, the instantaneous work hardening exponent of the sample cooled at 0.05 °C/s increased continuously until it reached the maximum value, while the instantaneous work hardening exponent of the sample cooled at 0.5 °C/s remained stable.

Key words: Hot-rolled TRIP steels, Cooling rate, Microstructures, Mechanical properties, Work hardening behavior

Xiao-Hui Wang, Jian Kang, Yun-Jie Li, Guo Yuan, R. D. K. Misra, Guo-Dong Wang. Effect of Cooling Rates in Coiling Process on Microstructures and Mechanical Properties in Al-Bearing Hot-Rolled TRIP Steel[J]. Acta Metallurgica Sinica (English Letters), 2019, 32(10): 1207-1218.

Figures/Tables 11

Table 1 Chemical composition of the experimental steel (wt%)

C	Mn	Al	Si	S	P	Fe
0.218	1.52	1.10	0.547	0.004	0.027	Bal.

Fig. 1 Ferrite transformation temperature of the experimental steel in equilibrium and undercooled states: a volume fractions of phases versus temperature; b dilatation versus temperature

Fig. 2 Schematic diagram of processing route

Fig. 3 Microstructures of the experimental steel cooled from 400 °C at different cooling rates: a 0.05 °C/s; b 0.1 °C/s; c 0.5 °C/s; d 1 °C/s; e 5 °C/s; f 10 °C/s. PF is polygonal ferrite, BF is bainitic ferrite, RA is retained austenite and M is martensite

Fig. 4 Carbon distribution of the experimental steel cooled from 400 °C at different cooling rates: a 0.5 °C/s; b 1 °C/s; c 5 °C/s; d 10 °C/s. PF is polygonal ferrite, BF is bainitic ferrite, RA is retained austenite and M is martensite

Fig. 5 EBSD images of the experimental steel cooled from 400 °C at different cooling rates: a 0.5 °C/s; b 1 °C/s; c 5 °C/s; d 10 °C/s. PF is polygonal ferrite, BF is bainitic ferrite, RA is retained austenite and M is martensite

Fig. 6 TEM images of the experimental steel cooled from 400 °C at the cooling rate of 0.05 °C/s: a film-like retained austenite in bright field; b film-like retained austenite in dark field; c film-like retained austenite in SAED pattern; e blocky retained austenite in bright field; f blocky retained austenite in dark field; g blocky retained austenite in SAED pattern. PF is polygonal ferrite, BF is bainitic ferrite and RA is retained austenite

Fig. 7 TEM images of the experimental steel cooled from 400 °C at the cooling rate of 5 °C/s: a martensite in bright field; b martensite in dark field; c martensite in SAED pattern. PF is polygonal ferrite and M is martensite

Fig. 8 TEM images of the experimental steel cooled from 400 °C at the cooling rate of 0.5 °C/s: a martensite/austenite island in bright field; b martensite/austenite island in dark field; c martensite/austenite island in SAED pattern. PF is polygonal ferrite, RA is retained austenite and M is martensite

Fig. 9 Volume fraction and carbon content of retained austenite at different cooling rates: a XRD curves; b austenite diffraction peaks; c the volume fraction of retained austenite; d the carbon content of retained austenite

Fig. 10 Hardness and mechanical properties of the experimental steel at different cooling rates: a hardness of experimental steel; b engineering strain and engineering stress curves; c instantaneous work hardening exponent during dislocations interaction; d instantaneous work hardening exponent during plastic deformation

References

[1]	C. Wang, H. Ding, M. Cai, B. Rolfe, Mater. Sci. Eng. A 610, 65 (2014)
[2]	M. De Meyer, B.C. De Cooman, D. Vanderschueren, Iron Steelmak. 27, 55(2000)
[3]	J. Mahieu, B.C. De Cooman, J. Maki, S. Claessens, Iron Steelmak. 29, 29(2002)
[4]	B. Mintz, Int. Mater. Rev. 46, 169(2001)
[5]	K. Zhu, C. Mager, M. Huang, J. Mater. Sci. Technol. 33, 12(2017)
[6]	V.S.Y. Injeti, Z.C. Li, B. Yu, R.D.K. Misra, Z.H. Cai, H. Ding, J. Mater. Sci. Technol. 34, 745(2018)
[7]	H.Q. Huang, H.S. Di, N. Yan, J.C. Zhang, Y.G. Deng, R.D.K. Misra, J.P. Li, Acta Metall. Sin. (Engl. Lett.) 31, 503(2018)
[8]	P.J. Jacques, E. Girault, A. Mertens, B. Verlinden, J. Van Humbeeck, F. Delannay, ISIJ Int. 41, 1068(2001)
[9]	D.W. Suh, S.J. Park, C.S. Oh, S.J. Kim, Scr. Mater. 57, 1097(2007)
[10]	J. Mahieu, B.C. De Cooman, J. Maki, Mater. Trans. A 33, 2573 (2002)
[11]	Y.J. Li, J. Kang, W.N. Zhang, D. Liu, X.H. Wang, G. Yuan, Mater. Sci. Eng. A 710, 181 (2018)
[12]	J. Chiang, J.D. Boyd, A.K. Pilkey, Mater. Sci. Eng. A 638, 132 (2015)
[13]	J. Chiang, B. Lawrence, J.D. Boyd, A.K. Pilkey, Mater. Sci. Eng. A 528, 4516 (2011)
[14]	A.Z. Hanzaki, R. Pandi, P.D. Hodgson, S. Yue, Metall. Mater. Trans. A 24, 2657 (1993)
[15]	S.M.K. Hosseini, A.Z. Hanzaki, M.J.Y. Panah, Mater. Sci. Eng. A 374, 122 (2004)
[16]	H.S. Wang, J. Kang, W.X. Dou, Y.X. Zhang, G. Yuan, G.M. Cao, R.D.K. Misra, G.D. Wang, Mater. Sci. Eng. A 702, 350 (2017)
[17]	N.H.V. Dijk, A.M. But, L. Zhao, J. Sietsma, S.E. Offerman, J.P. Wright, Acta Mater. 53, 5439(2005)
[18]	D.J. Dyson, B. Holmes, ISIJ Int. 208, 469(1970)
[19]	J.H. Hollomon, J. Member, Metall. Technol. 12, 268(1945)
[20]	F.H. Akbary, J. Sietsma, G. Miyamoto, T. Furuhara, M.J. Santofimia, Acta Mater. 104, 72(2016)
[21]	Z.Q. Liu, G. Miyamoto, Z.G. Yang, T. Furuhara, Acta Mater. 61, 3120(2013)
[22]	X.C. Xiong, B. Chen, M.X. Huang, Scr. Mater. 68, 321(2013)
[23]	Y.J. Li, D. Chen, X.L. Li, Steel Res. Int. 88, 11(2017)
[24]	C. Wang, X. Wu, J. Liu, N. Xu, Mater. Sci. Eng. A 438, 267 (2006)
[25]	E.J. Seo, L. Cho, Y. Estrin, B.C. De Cooman, Acta Mater. 113, 124(2016)
[26]	G.A. Thomas, J.G. Speer, D.K. Matlock, Metall. Mater. Trans. A 42A, 3652 (2011)
[27]	J. Zhao, W. Hu, X. Wang, J. Kang, G. Yuan, H. Di, R.D.K. Misra, Mater. Sci. Eng. A 666, 214 (2016)
[28]	A. Mertens, E.M. Bellhouse, J.R. Mcdermid, Mater. Sci. Eng. A 608, 249 (2014)
[29]	E.M. Bellhouse, J.R. Mcdermid, Metall. Mater. Trans. A 41, 1460 (2010)
[30]	J.R. Mcdermid, H.S. Zurob, Y. Bian, Metall. Mater. Trans. A 42, 3627 (2011)
[31]	E. Pereloma, H. Beladi, L. Zhang, I. Timokhina, Metall. Mater. Trans. A 43, 3958 (2012)
[32]	L. Li, X. Zhang, W. Yang, Metall. Mater. Trans. A 44, 4337 (2013)
[33]	D. De Knijf, T. Nguyen-minh, R.H. Petrov, L.A.I. Kestens, J.J. Jonas, J. Appl. Cryst. 47, 1261(2014)