Effect of substitution of Si by Al on the microstructure and mechanical properties of bainitic transformation-induced plasticity steels

doi:10.1016/j.jmst.2017.09.002

摘要/Abstract

Abstract:

The effect of partial or full substitution of Si by Al on the microstructure and mechanical properties has been extensively studied in multi-phase transformation-induced plasticity (TRIP) steels with polygonal ferrite matrix, but rarely studied in bainitic TRIP steels. The aim of the present study is to properly investigate the effect of Al and Si on bainite transformation, microstructure and mechanical properties in bainitic steels in order to provide guidelines for the alloying design as a function of process parameters for the 3rd generation advanced high strength steels (AHSS). It is shown from the dilatometry study, microstructural investigations and tensile properties measurements that the Al addition results in an acceleration whereas Si addition leads to a retardation in bainite transformation kinetics. The addition of Al retards the decomposition of austenite into pearlite and carbides at holding temperatures higher than 450 °C whereas Si retards the decomposition of austenite into carbides at temperatures lower than 450 °C. Consequently, the Al-added bainitic steel has a better strength-elongation combination at bainitic holding temperatures higher than 450 °C while Si-added steel has a better strength-elongation combination at temperatures lower than 450 °C. The higher yield strength of Al-added steel is mainly attributed to its finer bainitic lath. The higher tensile strength of Si-added steel is not only related to the stronger contribution of Si on work hardening during deformation, but also due to the higher volume fraction of martensite or martensite/austenite (MA) blocks in all heat treatment conditions, as well as the lower mechanical stability of retained austenite in this steel.

Key words: TRIP steel, Bainite transformation kinetics, Carbide free bainite, Mechanical properties, AHSS

. [J]. 材料科学与技术, 2017, 33(12): 1475-1486.

Zhu Kangying, Mager Coralie, Huang Mingxin. Effect of substitution of Si by Al on the microstructure and mechanical properties of bainitic transformation-induced plasticity steels[J]. J. Mater. Sci. Technol., 2017, 33(12): 1475-1486.

图/表 16

Table 1 Chemical compositions of the steels (in wt%).

Steel	C	Mn	Si	Al	P	S	N
Ref	0.25	2.07	0.098	0.021	0.023	<0.002	0.0033
0.5Al	0.247	2.07	0.083	0.53	0.025	0.0022	0.0038
1Al	0.256	2.07	0.085	1.01	0.026	0.002	0.0041
1.5Al	0.249	2.07	0.084	1.54	0.028	0.0021	0.0032
1Si	0.252	2.07	1.09	0.023	0.025	<0.002	0.0036

Table 2 Bs temperatures of the different steels (°C).

	0Al	0.5Al	1Al	1.5Al	1Si
Experimental	585 ± 5	605 ± 5	615 ± 5	625 ± 5	560 ± 5
Calculated	582	607	617	625	560

Fig. 1. Transformation kinetics at (a) 550 °C, (b) 500 °C, (c) 450 °C and (d) 400 °C after a soaking at 1100 °C for 5 min for the five steels.

Fig. 2. TTT diagram at 5% bainite transformation for 1Al and 1Si showing the effect of soaking temperature (1100 °C vs. 950 °C) on bainite transformation kinetics.

Fig. 3. Calculated driving force for nucleation in the different steels using Bhadeshia’s program.

Fig. 4. Optical microstructure of (a) Ref, (b) 1Al and (c) 1Si steels subjected to a soaking at 1100 °C for 5 min followed by an isothermal holding at 550 °C for 20 min.

Fig. 5. Optical microstructure of (a) 0.5Al, (b) 1Al, (c) 1.5Al and (d) 1Si subjected to a soaking at 1100 °C for 5 min followed by an isothermal holding at 500 °C for 20 min.

Fig. 6. SEM observations of the microstructures of (a) 0.5Al and (b) 1.5Al steels after soaking at 1100 °C followed by isothermal holding at 500 °C for 20 min, as well as (c) 1Al and (d) 1Si steels after soaking at 950 °C for 5 min followed by isothermal holding at 500 °C for 150 s. The yellow arrows indicating the locations of pearlite (P), M showing the martensite islands formed upon final cooling.

Table 3 Retained austenite fraction (γ%) and the C content in retained austenite (C%) measured at room temperature using X-ray diffraction in 1Al and 1Si steels after soaking at 950 °C for 5 min followed by a bainitic holding at different temperatures for different times.

Steel	Bainitic holding temperature (°C)	Holding time (s)	γ%	C%
1Al	500	100	12.7	0.92
	500	600	6.8	0.82
	450	100	12.7	1.17
	450	600	12.7	1.04
	400	150	5	1.16
	400	600	1.4	-
1Si	500	200	4.7	0.67
	450	150	14.7	0.98
	450	600	8.8	0.85
	400	600	9.8	1.02

Fig. 7. SEM observations of the microstructures of (a) 0.5Al, (b) 1Al, (c) 1.5Al and (d) 1Si steels after soaking at 1100 °C for 5 min followed by isothermal holding at 450 °C for 20 min. Areas delineated by yellow lines indicate the locations of pearlite (P) and MA shows the martensite-austenite islands.

Fig. 8. SEM observations of the microstructures of (a) 1Al and (b) 1Si steels after soaking at 950 °C for 5 min followed by isothermal holding at 450 °C for 10 min. Areas surrounded by yellow lines indicate the location where retained austenite decomposed into pearlite (P) and carbides during holding and M indicates the martensite island.

Fig. 9. SEM observation of the microstructures of (a) 1Al and (b) 1Si steels after soaking at 950 °C for 5 min followed by isothermal holding at 400 °C for 10 min. Yellow arrows indicate the locations of martensite-austenite islands (MA).

Fig. 10. Intercepted lath size as a function of the threshold misorientation to define a grain boundary in 1Al and 1Si steels after soaking at 950 °C followed by isothermal holding at 450 °C and 400 °C for 10 min.

Fig. 11. Superimposition of EBSD band contrast map with IPF color showing the microstructure 1Si steel subjected to a soaking at (a) 950 °C and (b) 1100 °C for 5 min and an isothermal holding at 450 °C for 10 min, with yellow arrows indicating the area of martensite (M) or MA islands, (c) intercepted lath size as a function of threshold misorientation to define grain boundaries in 1Al steel after soaking at 950 °C and 1100 °C for 5 min and isothermal holding at 400 °C and 450 °C for 10 min.

Fig. 12. (a) Yield strength (YS) and ultimate tensile strength (UTS), (b) uniform elongation (Uel) and total elongation (Tel), (c) yield strength-uniform elongation product (YS × Uel) and ultimate tensile strength-total elongation product (UTS × Tel) as a function of bainitic isothermal holding temperature for 1Al and 1Si steels.

Fig. 13. Engineering stress-strain curves of 1Al and 1Si steels after soaking at 950 °C for 5 min followed by isothermal holding at (a) 400 °C and (b) 500 °C for different times and the correponding n value at (c) 400 °C and (d) 500 °C holding temperatures. n=1σ·dσds’, where σ is the stress and ε is the strain.

参考文献

[1]	L. Barbé, K. Verbeken, E. Wettinck, ISIJ Int., 46(2006), pp. 1251-1257
[2]	B. Mintz, Int. Mater. Rev., 46(2001), pp. 169-197
[3]	J. Mahieu, S. Claessens, B.C. De Cooman, Proc. of 5th Int. Conf. on Zinc and Zinc Alloy Coated Steel Sheet (Galvatech 2001), Brussels, Belgium(2001), pp. 644-651
[4]	M. De Meyer, B.C.De Cooman, D.Vanderschueren, Iron Steelmaker, 27(2000), pp. 55-63
[5]	J. Mahieu, B.C.De Cooman, J.Maki, S. Claessens, Iron Steelmaker, 29(2002), pp. 29-34
[6]	P.J. Jacques, E. Girault, A. Mertens, B. Verlinden, J. Van Humbeeck, F. Delannay, ISIJ Int., 41(2001), pp. 1068-1074
[7]	D.W. Suh, S.J. Park, C.S. Oh, S.J.Kim, Scr. Mater., 57(2007), pp. 1097-1100
[8]	M. De Meyer, D. Vanderschueren, B.C.De Cooman, ISIJ Int., 39(1999), pp. 813-822
[9]	J. Mahieu, J. Maki, B.C.De Cooman, S. Claessens, Metall. Mater. Trans. A, 33A(2002), pp. 2573-2580
[10]	E. Girault, A. Mertens, P. Jacques, Y. Houbaert, B. Verlinden, J.V.Humbeeck, Scr. Mater., 44(2001), pp. 885-892
[11]	K. Sugimoto, B. Yu, Y. Mukai, S. Ikeda, ISIJ Int., 45(2005), pp. 1194-1200
[12]	M. Gomez, C. Garcia, A. DeArdo, D. Haezebrouck,Microstructural evolution during continuous galvanizing and final mechanical properties of high Al-low Si TRIP steels,Materials Science and Technology (MS&T), September 16-20, 2007, Detroit, Michigan(2007), pp. 1-14
[13]	R. Pradhan, J.P.Wise, Mech. Work. Steel Process. Conf. Proc., 41(2003), pp. 153-171
[14]	F.B.Pickering, Physical Metallurgy and the Design of Steels, Applied Science Ltd., London(1978), p. 4
[15]	I. Tsukatani, S. Hashimoto, T. Inoue, ISIJ Int., 31(1991), pp. 992-1000
[16]	M. Gomez, C.I. Garcia, D.M. Haezebrouck, A.J.Deardo, ISIJ Int., 49(2009), pp. 302-311
[17]	K. Zhu, H. Chen, J.P. Masse, O. Bouaziz, G. Gachet, Acta Mater., 61(2013), pp. 6025-6036
[18]	J.B. Seol, D. Raabe, P.P. Choi, Y.R. Im, C.G.Park, Acta Mater., 60(2012), pp. 6183-6199
[19]	T. Hojo, K. Sugimoto, Y. Mukai, S. Ikeda, ISIJ Int., 48(2008), pp. 824-829
[20]	D.J. Dyson, B. Holmes, J. Iron Steel Inst., 208(1970), pp. 469-474
[21]	S.M.C. van Bohemen, Mater. Sci. Technol., 28(2012), pp. 487-495
[22]	S.K. Liu, J. Zhang, Metall. Trans. A, 21(1990), pp. 1517-1525
[23]	M. Peet, H.K.D.H. Bhadeshia,Program MAP_STEEL_MUCG83,(2017),
[24]	D. Raabe, M. Herbig, S. Sandlobes, Y. Li, D. Tytko, M. Kuzmina, D. Ponge, P.P.Choi, Curr. Opin. Solid State Mater. Sci., 18(2014), pp. 253-261
[25]	H. Xue, T.N.Baker, Mater. Sci. Technol., 9(1993), pp. 424-429
[26]	J. Barford, W.S.Owen, Metal Sci. Heat Treat., 4(1962), pp. 359-360
[27]	M. Umemoto, K. Horiuchi, I. Tamura, Tetsu-to-Hagane, 68(1982), pp. 461-470
[28]	C.A. D?cker, M. Green, J.L. Collet, K. Zhu, N. Kwiaton, R. Kuziak, Z.I. Olano, C. Stallybrass, C. Luo,Bainitic Hardenability -Effective Use of Expensive and Strategically Sensitive Alloying Elements in High Strength Steels, RFCS Contract RFSR-CT-2007-00023, Final Report,(2010)
[29]	S.J. Lee, J.S. Park, Y.K.Lee, Scr. Mater., 59(2008), pp. 87-90
[30]	E.S. Davenport, R.A. Grange, R.J.Hafsten, Trans AIME, 145(1941), pp. 301-314
[31]	S. Yamamoto, H. Yokoyama, K. Yamada, M. Niikura, ISIJ Int., 35(1995), pp. 1020-1026
[32]	L.W. Graham, H.J.Axon, J. Iron Steel Inst., 191(1959), pp. 361-365
[33]	A. Matsuzaki, H.K.D.H. Bhadeshia, Mater. Sci. Technol., 15(1999), pp. 518-522
[34]	H.L. Yi, Z.Y. Hou, Y.B. Xu, D. Wu, G.D.Wang, Scr. Mater., 67(2012), pp. 645-648
[35]	S. Liu, F.C. Zhang, Z.N. Yang, M. Wang, C.L.Zheng, Mater. Des., 93(2016), pp. 73-80
[36]	E.M. Bellhouse, J.R.McDermid, Metall. Mater. Trans. A, 41A(2010), pp. 1460-1473
[37]	B. Mintz, W.D. Gunawardana, H. Su, Mater. Sci. Technol., 24(2008), pp. 596-600
[38]	T. Nakagaito, H. Matsuda, S. Matsuoka, Y. Tanaka, Tetsu-to-Hagané, 97(2011), pp. 35-43
[39]	G.R. Lehnhoff, K.O. Findley, B.C.De Cooman, Scr. Mater., 92(2014), pp. 19-22
[40]	A. Dumay, J.P. Chateau, S. Allain, S. Migot, O. Bouaziz, Mater. Sci. Eng. A, 483-484(2008), pp. 184-187
[41]	E. Jimenez-Melero, N.H. van Dijk, L.Zhao, J. Sietsma, S.E. Offerman, J.P. Wright, S. van der Zwaag, Acta Mater., 57(2009), pp. 533-543
[42]	P.J. Jacques, J. Ladriere, F. Delannay, Metall. Mater. Trans. A, 32A(2001), pp. 2759-2768
[43]	B. Timokhina, P.D. Hodgson, E.V.Pereloma, Metall. Mater. Trans. A, 35A(2004), pp. 2331-2341
[44]	F.G. Caballero, C. Garcia-Mateo, J. Chao, M.J. Santofimia, C. Capdevila, C.G. de Andres, ISIJ Int., 48(2008), pp. 1256-1262
[45]	O. Matsumu, Y. Sakuma, Y. Ishii, J. Zhao, ISIJ Int., 32(1992), pp. 1110-1116
[46]	K. Sugimoto, J. Sakaguchi, T. Iida, T. Kashima, ISIJ Int., 40(2000), pp. 920-926
[47]	K. Sugimoto, A. Kanda, R. Kikuchi, S. Hashimoto, T. Kashima, S. Ikeda, ISIJ Int., 42(2002), pp. 450-455
[48]	G. Gao, H. Zhang, X. Gui, Z. Tan, B. Bai, J. Mater. Sci. Technol., 31(2015), pp. 199-204