Investigation on Strengthening Mechanism of China Low-Activation Ferrite Steel upon Thermo-Mechanical Treatment

doi:10.1007/s40195-023-01629-1

Abstract

Abstract:

The objective of this study was to investigate the influence of strengthening mechanisms on the high-temperature mechanical properties of China low-activation ferrite (CLF-1) steel, which underwent thermodynamic design and thermo-mechanical treatment (TMT). The microstructure characterization in the normalized and tempered condition and the TMT condition was carried out using optical microscopy, X-ray diffractometer, and scanning electron microscopy with electron backscatter diffraction. High-resolution transmission electron microscopy was employed to determine the crystallographic structures of precipitated phases. The results indicated that the addition of Ti led to an increase in the allocation of C in MC phase and an enhancement in the content of MC phase. Compared to CLF-P steel in the normalized and tempered condition, a 1.5-fold increase in dislocation density and an order of magnitude improvement in MX phase density were achieved after TMT. The formation of high-density nano-scale MC phases during TMT played a significant role in precipitation strengthening due to their favorable coherent relationship with the matrix and low interfacial free energy. The excellent high-temperature mechanical properties observed in CLF-P steel after TMT can be attributed to the combined effects of precipitation strengthening, dislocation strengthening, and lath strengthening.

Key words: China low-activation ferrite (CLF-1) steel, Thermo-mechanical treatment, MC phase, Crystallographic structure, Strengthening mechanism

Dongtian Yang, Liangyin Xiong, Hongbin Liao, Guoping Yang, Xiaoyu Wang, Shi Liu. Investigation on Strengthening Mechanism of China Low-Activation Ferrite Steel upon Thermo-Mechanical Treatment[J]. Acta Metallurgica Sinica (English Letters), 2024, 37(2): 373-387.

Figures/Tables 21

Table 1 Chemical composition of CLF-1 steel and CLF-P steel (wt%)

	Fe	Cr	W	Mn	Ta	V	C	N	Ti
CLF-1	Bal	8.5	1.5	0.5	0.08	0.24	0.1	0.15	-
CLF-P	Bal	8.46	1.56	1.55	0.05	0.31	0.11	-	0.29

Fig. 1 Phase fraction plots: variations of equilibrium precipitated phases in a CLF-1 steel; b CLF-P steel with temperature

Fig. 2 Allocations of elements in precipitates: a variations of allocation of C element in M23C6, MC, matrix with temperature; b variations of allocation of Ti, Ta, V and W element in MC phase of CLF-P steel with temperature

Fig. 3 a, d and g Optical micrographs, b, e and h SEM images and c, f and i TEM images of the CLF-1 steel a-c and CLF-P steel d-i

Table 2 Comparison of microstructural components and predicted strengthening contributions at 25 °C and 650 °C for CLF-P steel in N + T and TMTT70 conditions

Microstructure		N + T		TMTT70
Temperature		25 °C	650 °C	25 °C	650 °C
Coarse particles (M₂₃C₆)	Size, nm	106.85 ± 30.19		97.55 ± 44.52
	Density, m⁻³	2.9 × 10¹⁹		3.08 × 10¹⁹
	Δσ_ppt, MPa	103.12	73.64	101.54	72.51
Fine particles (MC)	Size, nm	16.19 ± 9.64		11.42 ± 4.88
	Density, m⁻³	4.19 × 10²⁰		3.36 × 10²¹
	f_v, %	0.13%		0.5%
	Δσ_ppt, MPa	91.32	65.21	253.9	181.31
Dislocations	Density, m⁻²	2.18 × 10¹⁴		4.4 × 10¹⁴
Dislocations	Δσ_disl, MPa	216.23	154.41	307.2	219.37
Lath subgrains	Width, nm	287 ± 80		188 ± 57
Lath subgrains	Δσ_sgb, MPa	204.11	145.76	311.6	222.51
Grains	Size, μm	12.07 ± 4.99		70.67 ± 15.65
Grains	Δσ_gb, MPa	73.85	52.74	30.52	21.8
Total strength (Δσ)		466.93	333.44	626.79	447.59

Fig. 4 Electron backscatter diffraction images (left side) and KAM maps (right side) of CLF-P steel in a, b N + T, c, d TMTT70 conditions

Fig. 5 Pole figure densities of CLF-P steel in a N + T, b TMTT70 conditions

Fig. 6 KAM distribution profiles of CLF-P steel in N + T and TMTT70 conditions

Fig. 7 X-ray diffraction patterns of CLF-P steel under different conditions: a matrix phase including full width at half maxima, b matrix phase of the crystal face (200)

Table 3 Average dislocation density in CLF-P steel of different conditions as determined from modified Williamson-Hall method

Conditions	Dislocation density (m⁻²)
Normalized and tempered	3.19 × 10¹⁴
TMT at 973 K	12.52 × 10¹⁴
TMT and tempered at 1013 K	4.66 × 10¹⁴

Fig. 8 TEM bright-field images of CLF-P steel: a N + T condition, b TMTT70 condition

Fig. 9 Bright-field images of CLF-P steel in TMTT70 condition: a illustration A in Fig. 8b, b illustration B in Fig. 8b

Fig. 10 HRTEM images of a MC phase (TiC) in the TMTT70 condition, b corresponding FFT patterns

Fig. 11 HRTEM image of a and b M23C6 phase in the TMTT70 condition and c corresponding FFT patterns

Fig. 12 HRTEM images of a and b Laves phase in the TMTT70 condition, c corresponding FFT patterns

Table 4 Measured and calculated inter-planar distances (d) and angles (α) of the TiC particle in Fig. 10a

	d₁{020} (Å)	d₂{1 \(\overline{1 }1\)} (Å)	d₃{111} (Å)	α₁₂ (°)	α₂₃ (°)	α₁₃ (°)
Measured	2.133	2.492	2.596	123.33	69.43	55
TiC	2.165	2.450	2.450	125.26	70.53	54.74

Table 5 Measured and calculated inter-planar distances (d) and angles (α) of the M23C6 particle in Fig. 11a

	d₁{\(\overline{2 }00\)} (Å)	d₂{ \(0 \overline{4 }\overline{2 }\)} (Å)	d₃{\(\overline{2 }\overline{4 }\overline{2 }\)} (Å)	α₁₂ (°)	α₂₃ (°)	α₁₃ (°)
Measured	5.543	2.499	2.224	90.50	25.10	64.40
\({M}_{23}{\mathrm{C}}_{6}\)	5.319	2.379	2.171	90	24.09	65.91

Table 6 Measured and calculated inter-planar distances (d) and angles (α) of the Laves particle in Fig. 12a

	d₁{ \(10 \overline{1 } 1\) } (Å)	d₂{ \(0 \overline{1 }10\)} (Å)	d₃{ \(1 \overline{1 } 01\) } (Å)	α₁₂ (°)	α₂₃ (°)	α₁₃ (°)
Measured	3.811	4.357	3.804	116.12	63.90	52.22
Laves	3.615	4.094	3.615	116.20	63.80	52.40

Fig. 13 Tensile flow curves of CLF-1 steel and CLF-P steel at room temperature and 923 K

Fig. 14 Comparison of calculated and experimental values of CLF-P steel in N + T and TMTT70 conditions at 25 °C and 650 °C

Fig. 15 Schematic diagram of the microstructural features evolution upon thermodynamic design and TMT

References 38

[1]	Y. Wu, Z. Chen, L. Hu, M. Jin, Y. Li, J. Jiang, J. Yu, C. Alejaldre, E. Stevens, K. Kim, D. Maisonnier, A. Kalashnikov, K. Tobita, D. Jackson, D. Perrault, Nat. Energy 11, 1 (2016) DOI
[2]	Z.X. Xia, C. Zhang, H. Lan, Z.G. Yang, P.H. Wang, J.M. Chen, Z.Y. Xu, X.W. Li, S. Liu, Mater. Sci. Eng. A 657, 528 (2010)
[3]	J. Chen, Y. Liu, Y. Xiao, Y. Liu, C. Liu, H. Li, Acta Metall. Sin. -Engl. Lett. 706, 31 (2018)
[4]	J. Moon, T.H. Lee, S.D. Kim, C.H. Lee, J.H. Jang, J.H. Shin, J.W. Lee, B.H. Lee, D.W. Suh, Mater. Charact. 9, 170 (2020)
[5]	J.G. Chen, C.X. Liu, C. Wei, Y.C. Liu, H.J. Li, Acta Metall. Sin. -Engl. Lett. 1151, 32 (2019)
[6]	L. Tan, T.S. Byun, Y. Katoh, L.L. Snead, Acta Mater. 11, 71 (2014)
[7]	X.F. Guo, J.M. Gong, Y. Jiang, D.S. Rong, Mater. Sci. Eng. A 199, 564 (2013)
[8]	C.G. Panait, A. Zielinska-Lipiec, T. Koziel, A. Czyrska-Filemonowicz, A.F. Gourgues-Lorenzon, W. Bendick, Mater. Sci. Eng. A 4062, 527 (2010)
[9]	L. Tan, L.L. Snead, Y. Katoh, J. Nucl. Mater. 42, 478 (2016)
[10]	S.Z. Li, Z. Eliniyaz, F. Sun, Y.Z. Shen, L.T. Zhang, A.D. Shan, Mater. Sci. Eng. A 882, 559 (2013)
[11]	S.Z. Li, Z. Eliniyaz, L.T. Zhang, F. Sun, Y.Z. Shen, A.D. Shan, Mater. Charact. 144, 73 (2012)
[12]	R.Y. Zhou, L.H. Zhu, Y.P. Huang, Mater. Charact. 18, 190 (2022)
[13]	W. Wang, S.J. Liu, G. Xu, B.R. Zhang, Q.Y. Huang, Nucl. Eng. Technol. 518, 48 (2016)
[14]	K.C. Sahoo, J. Vanaja, P. Parameswaran, V.D. Vijayanand, K. Laha, Mater. Sci. Eng. A 54, 686 (2017)
[15]	Z.F. Peng, Y.Y. Ren, Acta Metall. Sin. 472, 37 (2001)
[16]	L. Cipolla, H.K. Danielsen, D. Venditti, P.E. Di Nunzio, J. Hald, M.A.J. Somers, Acta Mater. 669, 58 (2010)
[17]	P. Prakash, J. Vanaja, N. Srinivasan, P. Parameswaran, G. Rao, K. Laha, Mater. Sci. Eng. A 171, 724 (2018)
[18]	M. Nohrer, W. Mayer, S. Primig, S. Zamberger, E. Kozeschnik, H. Leitner, Metall. Mater. Trans. A Phy. Metall. Mater. Sci. 4210, 45 (2014)
[19]	R. Ravikirana, S. Mythili, S. Raju, T. Saroja, T. Jayakumar, E.R. kumar, Mater. Sci. Technol. 448, 31 (2015)
[20]	P.A. Kumar, J. Vanaja, G.V.P. Reddy, G. Rao, Mater. Sci. Eng. A 15, 843 (2022)
[21]	Y. Gao, Z.M. Wang, Y.C. Liu, W.C. Li, C.X. Liu, H.J. Li, Metals 12, 8 (2018) DOI URL
[22]	T. Ungar, A. Borbely, Appl. Phys. Lett. 3173, 69 (1996)
[23]	F. HajyAkbary, J. Sietsma, A.J. Bottger, M.J. Santofimia, Mater. Sci. Eng. A 208, 639 (2015)
[24]	T. Ungar, G. Tichy, Phys. Status Solidi A Appl. Mat. 425, 171 (1999)
[25]	L.Y. Zhang, L.M. Yu, Y.C. Liu, C.X. Liu, H.J. Li, J.F. Wu, Mater. Sci. Eng. A 66, 695 (2017)
[26]	S. Zhu, M. Yang, X.L. Song, S. Tang, Z.D. Xiang, Mater. Charact. 60, 98 (2014)
[27]	G. Dimmler, P. Weinert, E. Kozeschnik, H. Cerjak, Mater. Charact. 341, 51 (2003)
[28]	A.N. Christensen, R. Hmlinen, U. Turpeinen, A.F. Andresen, S.J. Cyvin, Acta Chem. Scand. 89-90, 32a (1978)
[29]	A.L. Bowman, G.P. Arnold, E.K. Storms, N.G. Nereson, Acta Crystallogr. 3102, 28 (2010)
[30]	P.Y. Yan, L.M. Yu, Y.C. Liu, C.X. Liu, L.J. Huijun, J.F. Wu, J. Alloys Compd. 368, 739 (2018)
[31]	H. Chilukuru, K. Durst, S. Wadekar, M. Schwienheer, A. Scholz, C. Berger, K.H. Mayer, W. Blum, Mater. Sci. Eng. A 81, 510-511 (2009)
[32]	L. Tan, J.T. Busby, P.J. Maziasz, Y. Yamamoto, J. Nucl. Mater. 713, 441 (2013)
[33]	M. Taneike, F. Abe, K. Sawada, Nature 294, 424 (2003)
[34]	A. Kostka, K.G. Tak, R.J. Hellmig, Y. Estrin, G. Eggeler, Acta Mater. 539, 55 (2007)
[35]	K.S. Cho, S.S. Park, D.H. Choi, H. Kwon, J. Alloys Compd. 314, 626 (2015)
[36]	G.E. Lucas, J. Nucl. Mater. 287, 206 (1993)
[37]	I.G. Taylor, Proc. R. Soc. A 362, 145 (1934)
[38]	J. Vivas, C. Capdevila, E. Altstadt, M. Houska, D. San-Martin, Scr. Mater. 14, 153 (2018)