Controlling Carbide Evolution to Improve the Ductility in High Specific Young’s Modulus Steels

doi:10.1007/s40195-022-01390-x

Abstract

Abstract:

A high specific Young’s modulus steel could be achieved by introducing a large fraction of kappa-carbides (κ-carbide), and its ductility was improved by efficiency divorced eutectoid transformation (DET) treatment. For this steel, carbon and aluminum contents affect not only the carbide fraction, but also the type and morphology of carbides, and consequently the mechanical properties. In this work, the alloy was designed by considering both the carbide morphology and Young’s modulus, and the carbides in the high specific Young’s modulus steels were adjusted by controlling carbon content in a suitable range for achieving a good combination of strength and ductility. The detailed microstructure evolution process during DET reaction was studied, and it was found that a higher austenitizing temperature and the cooling rate lower than 300 ℃ h^-1 are suitable. The blocky carbides could be avoided by designing the carbon content in a limited content range. The microstructure-property relationship of the experimental steels was also discussed for giving an impetus to the future development of high specific Young’s modulus steels.

Key words: κ carbide, High aluminum, High carbon, Divorced eutectoid transformation, Ductility

Peng Chen, Xin Xu, Chao Lin, Fuming Yang, Jiachen Pang, Xiaowu Li, Hongliang Yi. Controlling Carbide Evolution to Improve the Ductility in High Specific Young’s Modulus Steels[J]. Acta Metallurgica Sinica (English Letters), 2022, 35(10): 1703-1711.

Figures/Tables 10

Table 1 Actual chemical compositions of experimental alloys and the specific Young’s modulus of hot-rolled alloys

Alloys	Al (wt%)	C (wt%)	Fe (wt%)	Calculated specific Young’s modulus (GPa g^-1 cm³)
A	4.7	1.4	Balance	29.2
B	7.4	1.0	Balance	27.6
C	7.2	1.4	Balance	28.6

Table 2 Parameters of DET heat treatment

Samples	Austenitizing temperature (℃)	Finishing temperature of slow cooling (℃)	Cooling rate (℃ h^-1)
A	825-700	825	700	50
	825-720	825	720	50
	825-740	825	740	50
	825-760	825	760	50
B	880-700	880	700	50
	880-720	880	720	50
	880-740	880	740	50
	880-760-I	880	760	50
	880-760-II	880	760	300
	880-760-III	880	760	1200
C	900-720	900	720	90
	860-740	860	740	90
	900-740	900	740	90

Fig. 1 Effect of alloy elements on the aluminum content in ferrite and specific Young’s modulus: a Fe-1.4C-xAl wt%; b Fe-xC-7Al wt%

Fig. 2 Hot-rolled microstructures in alloys A a, B b and C c, as well as their tensile properties d. XRD patterns are inserted in a-c, and elements distribution analysis along the red arrow is inserted in a

Fig. 3 SEM images showing the microstructures in alloy-C treated by quenching after austenitizing at 860 ℃ for 40 min a and 900 ℃ for 40 min b, and heat-treated by DET of 860-740 c and 900-740 d

Fig. 4 SEM images showing the microstructures in the alloys heat-treated by DET with different finishing temperatures of slow cooling and slow cooling rates: a A-825-700; b A-825-720; c A-825-740; d B-880-700; e B-880-720; f B-880-740; g B-880-760-I; h B-880-760-II; i B-880-760-III

Fig. 5 Tensile stress-strain curves of selected heat-treated alloys

Fig. 6 Elements distribution analysis and XRD pattern of the spheroidized sample A-825-720: a SEM micrograph; b carbon distribution; c aluminum distribution; d XRD pattern

Fig. 7 SEM microstructures at the region near the fracture: a A-825-720, b B-880-720

Fig. 8 Calculated equilibrium phase fraction as a function of temperature in Fe-5Al-xC a), Fe-6Al-xC b, Fe-7Al-xC c, and Fe-8Al-xC d in wt%; e carbon content range at given aluminum content

References 27

[1]	S. Chen, R. Rana, A. Haldar, R.K. Ray, Prog. Mater. Sci. 89, 345 (2017)
[2]	F.D.R. Bonnet, V. Daeschler, G. Petitgand, Can. Metall. Quart. 53, 243 (2014)
[3]	H. Springer, R. Aparicio Fernandez, M.J. Duarte, A. Kostka, D. Raabe, Acta Mater. 96, 47 (2015)
[4]	P. Chen, J. Fu, X. Xu, C. Lin, J.C. Pang, X.W. Li, R.D.K. Misra, G.D. Wang, H.L. Yi, J. Mater. Sci. Technol. 87, 54 (2021)
[5]	J.H. Whiteley, J. Iron Steel Inst. 105, 339 (1922)
[6]	T. Oyama, O.D. Sherby, J. Wadsworth, B. Walser, Scr. Metall. 18, 799 (1984)
[7]	E.M. Taleff, C.K. Syn, D.R. Lesuer, O.D. Sherby, Metall. Mater. Trans. A 27, 111 (1996)
[8]	C.K. Syn, D.R. Lesuer, O.D. Sherby, Metall. Mater. Trans. A 25, 1481 (1994)
[9]	D. Connetable, P. Maugis,Intermetallics 16, 345 (2008)
[10]	M. Palm, G. Inden,Intermetallics 3, 443 (1995)
[11]	D. Connetable, J. Lacaze, P. Maugis, B. Sundman,Calphad 32, 361 (2008)
[12]	K. Chin, H. Lee, J. Kwak, J. Kang, B. Lee, J. Alloys Compd. 505, 217 (2010)
[13]	P. Chen, X.W. Li, H.L. Yi,Metals 10, 1021 (2020)
[14]	N. Jiyoung, K. Hanchul, J. Korean Phys. Soc. 58, 285 (2011)
[15]	J. Lee, N.J. Kim, J.Y. Jung, E.S. Lee, S. Ahn, Scr. Mater. 39, 1063 (1998)
[16]	R. Rana, C. Liu, Can. Metall. Quart. 53, 300 (2014)
[17]	S.F. Pugh, Philos. Mag. 45, 823 (1954)
[18]	V.A. Andryushchenko, V.G. Gavrilyuk, V.M. Nadutov, Phys. Met. Metallogr. 60, 50 (1985)
[19]	J. Yang, P. La, W. Liu, Y. Hao, Mater. Sci. Eng. A 382, 8 (2004)
[20]	L.J. Huetter, H.H. Stadelmaier, Acta Metall. 6, 367 (1958)
[21]	W.K. Choo, K.H. Han, Metall. Mater. Trans. A 16, 5 (1985)
[22]	Engineering toolbox, (2003), Young's Modulus, tensile and yield strength for common materials. https://www.engineeringtoolbox.com/young-modulus-d_417.html. Accessed 20 Sep 2020
[23]	P. Chen, X.C. Xiong, G.D. Wang, H.L. Yi, Scr. Mater. 124, 42 (2016)
[24]	D. Bergner, Y. Khaddour, Defect Diffus. Forum 95-98, 709 (1993)
[25]	J.C. Pang, W.F. Yang, G.D. Wang, S.J. Zheng, R.D.K. Misra, H.L. Yi, Scr. Mater. 209, 114395 (2022)
[26]	B. Mintz, W.D. Gunawardana, H. Su, Mater. Sci. Technol. 24, 596 (2008)
[27]	K. Wallin, T. Saario, K. Törrönen, Int. J. Fract. 32, 201 (1986)