Precipitation Behavior of Primary Carbides in Medium Carbon Nb-Alloyed Steel

doi:10.11900/0412.1961.2023.00053

Acta Metall Sin

2025, Vol. 61

Issue (4): 653-664 DOI: 10.11900/0412.1961.2023.00053

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Precipitation Behavior of Primary Carbides in Medium Carbon Nb-Alloyed Steel

LIANG Xuan¹^,², HOU Tingping¹^,²(

), ZHANG Dong¹^,², TAN Xinyang¹^,², WU Kaiming¹^,²(

)

1 State Key Laboratory of Refractories and Metallury, Wuhan University of Science and Technology, Wuhan 430081, China
2 Hubei Collaborative Innovation Center for Advanced Steels, Wuhan University of Science and Technology, Wuhan 430081, China

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LIANG Xuan, HOU Tingping, ZHANG Dong, TAN Xinyang, WU Kaiming. Precipitation Behavior of Primary Carbides in Medium Carbon Nb-Alloyed Steel. Acta Metall Sin, 2025, 61(4): 653-664.

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Abstract

High-performance steels containing niobium have widespread use in high-end manufacturing sectors such as aerospace, automotive, energy, and construction engineering. Due to its capacity as a strong carbide-forming element, Nb favors the formation of NbC. These carbides, dispersed within the matrix, significantly contribute to precipitation strengthening, precipitation hardening, and grain refinement. In addition, Nb serves as a positive segregation element. When steel solidifies from its molten state, Nb segregates in the liquid phase and forms primary NbC carbides. These carbides significantly affect the mechanical properties of steel. Herein, to investigate the effect of Nb content on primary carbides in medium-carbon Nb-alloyed steel, the microstructure including the morphology, size, and distribution of niobium and carbon was characterized through SEM and TEM. To further understand the role of lattice vibrations and electrons at different temperatures, the first principle calculations with quasi-harmonic Debye model were combined to study the evolution of thermodynamic parameters. Primary carbides form because of solute segregation at the solid-liquid interface. For a more detailed investigation, a solute microsegregation model coupled with solidification phase transition was developed. This model was adopted to quantitatively analyze the effects of solidification phase transition and Nb content on solute microsegregation. The experiments yielded the following results: with increasing Nb content, the morphology of primary carbides shifted from spherical to polyhedral geometry. Furthermore, a distinct zonal distribution of primary carbides was observed. The laws of thermodynamics indicate that the increase in free energy change due to electrons at different temperatures is compensated by the decrease in free energy change arising from lattice vibrations, indicating the key role of lattice vibrations in maintaining the stability of NbC. The Gibbs free energy change at different temperatures was negative, indicating the thermostatic stability of NbC. Furthermore, the absence of imaginary frequency in the phonon spectrum indicates the dynamic stability of NbC. From a microsegregation viewpoint, the mass fraction of solute carbon decreases while that of the solute Nb increases at the solidification front during the phase transition from L + δ to L + γ. As the Nb content increases, the solid fraction of the solidification phase transition increases. Increased Nb content promotes the precipitation of primary carbides at low solid fractions.

Key words: Nb-alloyed steel primary carbide thermodynamic mechanism first principle calculation microsegregation solidification phase transition

Received: 13 February 2023

ZTFLH:

O614.51

Fund: National Natural Science Foundation of China(12174296, U1532268, U20A20279);Key Research and Development Program of Hubei Province(2021BAA057);Excellent Young and Middle-aged Science and Technology Innovation Team in Colleges, Universities of Hubei Province(T201903);Zhejiang Provincial Leading Innovation and Entrepreneurship Team(2021R01020)

Corresponding Authors: HOU Tingping, professor, Tel: 18140522212, E-mail: houtingping@wust.edu.cn;
WU Kaiming, professor, Tel: 13100610041, E-mail: wukaiming@wust.edu.cn

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https://www.ams.org.cn/EN/10.11900/0412.1961.2023.00053 OR https://www.ams.org.cn/EN/Y2025/V61/I4/653

Table 1 Chemical compositions of the tested steels

Fig.1 Crystal structures of NbC (a), Nb (b), and C (c)

Element	$D 0 δ$	$Q δ$	$D 0 γ$	$Q γ$	$k δ / L$	$k γ / L$
C	0.0127	81370.80	0.0761	134557.44	0.19	0.340
Nb	50.2000	251960.48	0.8300	266478.96	0.40	0.220
Mn	0.7600	224429.76	0.0550	249366.40	0.76	0.780

Table 2 Diffusion constants, diffusion activation energies, and equilibrium partition coefficients of solute elements^[33]

Fig.2 SEM images of steels with different Nb contents
(a) 0.1Nb (b) 0.6Nb (c) 1.1Nb (d) 1.6Nb

Fig.3 Bright-field TEM image of the carbide (a) and element distributions of Nb (b) and C (c)

Table 3 Optimized lattice constants, cell angles and formation energy of NbC, Nb, and C at 0 K, 0 Pa

Fig.4 Calculated phonon dispersion spectra (a) and total or partial density of states (TDOS, PDOS) (b) for NbC

Fig.5 TDOS and PDOS for NbC (a), and TDOS for Nb (b) and C (c)

Fig.6 Calculated Gibbs free energies including the lattice vibrational and electronic contributions (G_vib, G_el) as a function of temperature for NbC

Fig.7 Change in Gibbs free energies related to lattice vibrations and electrons (ΔG_vib,ΔG_el) (a) and dependence of change in total Gibbs free energy on temperature for NbC (ΔG) (b)

Fig.8 Effect of Nb content on phase transformation during solidification process by Thermo-Calc calculation
(a) 0.1Nb (b) 0.6Nb (c) 1.1Nb (d) 1.6Nb

Table 4 Temperature ranges of three-phase coexistence (ΔT_{L +}_δ₊_γ ) and carbides precipitation temperature (T_start) for medium carbon steels with different Nb contents

Fig.9 Variation of solute equilibrium partition coeffici-ents k_C (a) and k_Nb (b) with temperature for 1.6Nb steel

Fig.10 Effects of phase transition on solute segregation in 0.1Nb steel (f_s is the solid phase volume fraction, w(C) $L, f s$ and w(Nb) $L, f s$ are the concentrations of C and Nb in the residual liquid of steel, respectively)
(a) C (b) Nb

Fig.11 Effects of Nb content on segregation ratios of C (a) and Nb (b) ( $f s δ / γ$ is the solid fraction of NbC carbide when L + δ→L + γ phase transition occurs, w(M) $L, 0$ (M = C, Nb) is the initial mass fraction of M in liquid phase. Different colors of f_s represent different steels)

Fig.12 Curves of actual solubility product and equilibrium solubility product at solidification front against solid fraction (The vertical coordinate on the right represents the temperature of the liquid at the solidification front under different solid fractions; $f s N b C$ is the solid fraction of NbC carbide at the beginning stage)
(a) 0.1Nb (b) 0.6Nb (c) 1.1Nb (d) 1.6Nb

$f s$	$w (C) L, f s$				$w (N b) L, f s$
	0.1Nb	0.6Nb	1.1Nb	1.6Nb	0.1Nb	0.6Nb	1.1Nb	1.6Nb
0.380	0.289	0.289	0.289	0.289	0.130	0.780	1.432	2.084
0.516	0.344	0.344	0.344	0.344	0.146	0.879	1.612	-
0.689	0.369	0.369	0.453	0.453	0.240	1.440	-	-
0.948	0.547	0.546	0.548	0.549	0.684	-	-	-

Table 5 Mass fractions of solute elements C and Nb in liquid at solidification front when

f s = f s N b C

Fig.13 Effects of NbC precipitation on solute concentrations of C (a) and Nb (b) for 0.1Nb steel

1	Yang Y. All-optical photodetector based on photothermal effect of MXene Nb₂CT _x [D]. Tianjin: Tianjin University of Technology, 2022
	杨洋. 基于碳化铌光热效应的全光探测器的研究 [D]. 天津: 天津理工大学, 2022
2	Chu S J, Mao B, Hu G K. Microstructure control and strengthening mechanism of high strength cold rolled dual phase steels for automobile applications [J]. Acta Metall. Sin., 2022, 58: 551 doi: 10.11900/0412.1961.2022.00061
	储双杰, 毛博, 胡广魁. 汽车用先进高强度冷轧双相钢的显微组织调控和强韧化机理 [J]. 金属学报, 2022, 58: 551 doi: 10.11900/0412.1961.2022.00061
3	Li Z Y, Li C R, Zeng Z Y, et al. Thermodynamic study of carbide and nitride precipitation of niobium in 500 MPa high-strength anti-seismic rebars [J]. J. Iron Steel Res., 2020, 32: 727
	黎志英, 李长荣, 曾泽芸等. 高强抗震钢筋中铌的碳、氮化物析出热力学研究 [J]. 钢铁研究学报, 2020, 32: 727 doi: 10.13228/j.boyuan.issn1001-0963.20190238
4	Zhou J, Hu C Y, Hu F, et al. Insight into the effect of Nb microalloying on the microstructure-property relationship of a novel wire rod [J]. J. Mater. Res. Technol., 2022, 16: 276 doi: 10.1016/j.jmrt.2021.11.144
5	Su X, Wang H X, Zhu M, et al. In-situ observation for effect of niobium on pearlite transformation in high-carbon steels [J]. Iron Steel, 2022, 57(4): 88
	苏雪, 王厚昕, 朱敏等. 原位观察铌对高碳钢珠光体相变的影响 [J]. 钢铁, 2022, 57(4): 88
6	Tian J Y, Wang H X, Zhu M, et al. Improving mechanical properties in high-carbon pearlitic steels by replacing partial V with Nb [J]. Mater. Sci. Eng., 2022, A834: 142622
7	Zhang Y, Li X X, Wei K, et al. Element segregation in GH4169 superalloy large-scale ingot and billet manufactured by triple-melting [J]. Acta Metall. Sin., 2020, 56: 1123 doi: 10.11900/0412.1961.2020.00101
	张勇, 李鑫旭, 韦康等. 三联熔炼GH4169合金大规格铸锭与棒材元素偏析行为 [J]. 金属学报, 2020, 56: 1123
8	Xie Y, Cheng G G, Chen L, et al. Characteristics and generating mechanism of large precipitates in Nb-Ti-microalloyed H13 tool steel [J]. ISIJ Int., 2016, 56: 995
9	Jiang Q C, Sui H L, Guan Q F. Thermal fatigue behavior of new type high-Cr cast hot work die steel [J]. ISIJ Int., 2004, 44: 1103
10	Tchuindjang J T, Lecomte-Beckers J. Fractography survey on high cycle fatigue failure: Crack origin characterisation and correlations between mechanical tests and microstructure in Fe-C-Cr-Mo-X alloys [J]. Int. J. Fatigue, 2007, 29: 713
11	Jang J H, Lee C H, Heo Y U, et al. Stability of (Ti, M)C (M = Nb, V, Mo and W) carbide in steels using first-principles calculations [J]. Acta Mater., 2012, 60: 208
12	Fang C M, van Huis M A, Zandbergen H W. Structural, electronic, and magnetic properties of iron carbide Fe₇C₃ phases from first-principles theory [J]. Phys. Rev., 2009, 80B: 224108
13	Zhang D, Zheng H, Hou T P, et al. Hardness increases due to (Fe, Cr)₂C carbide precipitated during natural aging in high chromium cast iron [J]. Vacuum, 2023, 209: 111766
14	Klymko T, Sluiter M H F. Computing solubility products using ab initio methods precipitation of NbC in low alloyed steel [J]. J. Mater. Sci., 2012, 47: 7601
15	Arroyave R, Shin D, Liu Z K. Ab initio thermodynamic properties of stoichiometric phases in the Ni-Al system [J]. Acta Mater., 2005, 53: 1809
16	Shang S L, Wang Y, Kim D, et al. First-principles thermodynamics from phonon and Debye model: Application to Ni and Ni₃Al [J]. Comput. Mater. Sci., 2010, 47: 1040
17	Voller V R. Modeling micro scale phenomena for application in solidification process simulations [A]. Proceedings of the Second International Conference on Processing Materials for Properties [C]. San Francisco: TMS, 2000: 1011
18	Scheil E. Bemerkungen zur Schichtkristallbildung [J]. Int. J. Mater. Res., 1942, 34(3): 70
19	Brody H D, Flemings M C. Solute redistribution in dendritic solidification [J]. Trans. Met. Soc. AJIME, 1966, 236: 615
20	Ohnaka I. Mathematical analysis of solute redistribution during solidification with diffusion in solid phase [J]. Trans. ISIJ, 1986, 26: 1045
21	Clyne T W, Kurz W. Solute redistribution during solidification with rapid solid state diffusion [J]. Metall. Trans., 1981, 12A: 965
22	Voller V R, Beckermann C. Approximate models of microsegregation with coarsening [J]. Metall. Mater. Trans., 1999, 30A: 3016
23	Voller V R, Beckermann C. A unified model of microsegregation and coarsening [J]. Metall. Mater. Trans., 1999, 30A: 2183
24	Liang X, Hou T P, Zhang D, et al. New evaluation of the thermodynamics stability for bcc-Fe [J]. J. Phys.: Condens. Matter., 2022, 34: 455801
25	Otero-de-la-Roza A, Luaña V. G_IBBS2: A new version of the quasi-harmonic model code. I. Robust treatment of the static data [J]. Comput. Phys. Commun., 2011, 182: 1708
26	Otero-de-la-Roza A, Abbasi-Pérez D, Luaña V. G_IBBS2: A new version of the quasiharmonic model code. II. Models for solid-state thermodynamics, features and implementation [J]. Comput. Phys. Commun., 2011, 182: 2232
27	Wolverton C, Zunger A. First-principles theory of short-range order, electronic excitations, and spin polarization in Ni-V and Pd-V alloys [J]. Phys. Rev., 1995, 52B: 8813
28	Kresse G, Furthmüller J. Efficiency of ab-initio total energy calculations for metals and semiconductors using a plane-wave basis set [J]. Comput. Mater. Sci., 1996, 6: 15
29	Blöchl P E. Projector augmented-wave method [J]. Phys. Rev., 1994, 50B: 17953
30	Togo A, Tanaka I. First principles phonon calculation in materials science [J]. Scr. Mater., 2015, 108: 1
31	Guo W, Long M J, Wu J L, et al. Effect of solute partition coefficient and TiN precipitation on micro-segregation of 22MnB5 steel [J]. Iron Steel, 2022, 57(3): 44
	郭伟, 龙木军, 吴家璐等. 22MnB5钢溶质分配系数及TiN析出对微观偏析的影响 [J]. 钢铁, 2022, 57(3): 44
32	Won Y M, Thomas B G. Simple model of microsegregation during solidification of steels [J]. Metall. Mater. Trans., 2001, 32A: 1755
33	Fu Y X, Zhu L G, Sun L G, et al. Calculation of high temperature solidification characteristics and high temperature physical properties of high strength steel containing niobium [J]. Steelmaking, 2020, 36(2): 34
	付雨潇, 朱立光, 孙立根等. 含Nb高强钢高温凝固特性与物性参数的计算 [J]. 炼钢, 2020, 36(2): 34
34	Chen M W, Wang Z D. The evolution and morphological stability of a particle in a binary alloy melt [J]. J. Cryst. Growth, 2023, 607: 127113
35	Villars P, Calvet L D. Pearson's Handbook of Crystallographic Data for Intermetallic Phases [M]. Metals Park: American Society for Metals, 1985: 1
36	Nartowski A M, Parkin I P, MacKenzie M, et al. Solid state metathesis routes to transition metal carbides [J]. J. Mater. Chem., 1999, 9: 1275
37	Singh D J, Klein B M. Electronic structure, lattice stability, and superconductivity of CrC [J]. Phys. Rev., 1992, 46B: 14969
38	Zhao C C, Xing X L, Guo J, et al. Micro-properties of (Nb, M)C carbide (M = V, Mo, W and Cr) and precipitation behavior of (Nb, V)C in carbide reinforced coating [J]. J. Alloys Compd., 2019, 788: 852
39	Wang R, Wang S F, Wu X Z. Ab initio study of the thermodynamic properties of rare-earth-magnesium intermetallics MgRE (RE = Y, Dy, Pr, Tb) [J]. Phys. Scr., 2011, 83: 065707
40	Gui L T, Long M J, Huang Y W, et al. Effects of inclusion precipitation, partition coefficient, and phase transition on microsegregation for high-sulfur steel solidification [J]. Metall. Mater. Trans., 2018, 49B: 3280
41	Zhang X W, Zhang L F, Yang W, et al. Thermodynamics and dynamics of MnS inclusions precipitation during solidification process in heavy rail steels [J]. Iron Steel, 2016, 51(9): 30
	张学伟, 张立峰, 杨文等. 重轨钢中MnS析出热力学和动力学分析 [J]. 钢铁, 2016, 51(9): 30 doi: 10.13228/j.boyuan.issn0449-749x.20160079
42	Chen J X. Data Manual of Common Steelmaking Charts [M]. Beijing: Metallurgical Industry Press, 1984: 565
	陈家祥. 炼钢常用图表数据手册 [M]. 北京: 冶金工业出版社, 1984: 565
43	Liu Z Z, Wei J, Cai K K. A coupled mathematical model of microsegregation and inclusion precipitation during solidification of silicon steel [J]. ISIJ Int., 2002, 42: 958

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