Hot Deformation Behavior and Hardness of a CoCrFeMnNi High-Entropy Alloy with High Content of Carbon

doi:10.1007/s40195-019-00916-0

Abstract

Abstract:

A CoCrFeMnNi high-entropy alloy with a high content of carbon was synthesized, and its hot deformation behavior was studied at the temperatures 800-1000 °C at the strain rates ranging from 0.001 to 0.1 s^-1. As-prepared alloy is a face-centered cubic-structured solid solution, with a large amount of carbides residing at grain boundaries. True stress-strain curves were employed to develop the constitutive equation of apparent activation energy. The apparent activation energy (Q) was found to be 423 kJ mol^-1, indicating a dynamic flow softening behavior. The size of dynamic recrystallized (DRXed) grains increases with increasing the temperature or decreasing the strain rate. A processing map was sketched on the basis of the flow stress. The temperature range of 900-1000 °C and 10^-3-10^-2.6 s^-1 strain rate were found to be the optimum hot-forging parameter. With increasing temperature or decreasing strain rate, the volume fraction of fine carbides (≤?1 μm) increases. A lot of coarse carbides can be found in the matrix after deformation at 800 °C, which leads to a high hardness value of 345 HV. The carbides after deformation at 1000 °C are mainly nano-sized M₇C₃ and M₂₃C₆, which can promote the nucleation of DRX.

Key words: High-entropy alloy, Carbon Apparent activation energy, Processing map, Dynamic recrystallization

Yi-Tao Wang, Jian-Bo Li, Yun-Chang Xin, Xian-Hua Chen, Muhammad Rashad, Bin Liu, Yong Liu. Hot Deformation Behavior and Hardness of a CoCrFeMnNi High-Entropy Alloy with High Content of Carbon[J]. Acta Metallurgica Sinica (English Letters), 2019, 32(8): 932-943.

Figures/Tables 15

Fig. 1 Structure of the (CoCrFeMnNi)95C5 (at.%) alloy at the initial homogenized condition: a SEM-BSE image, b X-ray diffraction pattern

Fig. 2 Stress-strain curves at various deformation temperatures and strain rates of a 10-1 s-1, b 10-2 s-1, c 10-3 s-1

Fig. 3 Variation of activation energy (Q) with true strain

Fig. 4 Zener-Hollomon parameter of (CoCrFeMnNi)95C5 (at.%) HEA as a function of strain rate and temperature. The values on the contour lines are lnZ

Fig. 5 a Processing map at a true strain of 0.65, b optical micrograph showing the cracking at the edge of the specimen which was deformed at lnZ?=?53.19 (high Z, 800 °C/10-1 s-1)

Fig. 6 SEM micrographs of specimens deformed at a lnZ?=?53.19 (high Z, 800 °C/10-1 s-1), b lnZ?=?48.59 (high Z, 800 °C/10-3 s-1), c lnZ?=?44.48 (intermediate Z, 1000 °C/10-1 s-1), d lnZ?=?39.88 (low Z, 1000 °C/10-3 s-1). The volume fractions of coarse particles are a 12.14%, b 10.44%, c 6.48%, d 3.09%, while the volume fractions of fine particles are a 0%, b 4.12%, c 6.44%, d 7.14%, respectively

Fig. 7 XRD patterns of the (CoCrFeMnNi)95C5 (at.%) alloy in the different conditions of Z value. lnZ?=?48.59 (high Z, 800 °C/10-3 s-1) and lnZ?=?39.88 (low Z, 1000 °C/10-3 s-1)

Fig. 8 STEM image of (CoCrFeMnNi)95C5 (at.%) alloy deformed at lnZ?=?39.88 (low Z, 1000 °C/10-3 s-1) a, distributions of alloy constituents: b Cr, c Mn, d Fe, e Co, f Ni, g C

Fig. 9 EBSD inverse pole figure (IPF) maps and image quality (IQ) maps of the specimens hot-compressed at different conditions: a, b lnZ?=?53.19 (high Z, 800 °C/10-1 s-1); c, d lnZ?=?48.59 (high Z, 800 °C/10-3 s-1); e, f lnZ?=?39.88 (low Z, 1000 °C/10-3 s-1). The fractions of low-angle grain boundaries of a, b, c are 21, 13, 5%, respectively

Fig. 10 TEM bright-field images and the selected area electron diffraction patterns (SAEDs) of (CoCrFeMnNi)95C5 (at.%) alloys in lnZ?=?48.59 (high Z, 800 °C/10-3 s-1) a, aM23C7 carbides; b-d lnZ?=?39.88 (low Z, 1000 °C/10-3 s-1), b the mixture of M23C6 and M7C3 carbides, c irregular dislocation cells around the carbides, d DRX grain in the vicinity of carbide particles

Fig. 11 Hardness of deformed HEAs tested at the room temperature depending on different strain rates a, b various Zener-Hollomon parameters

Table 1 Summary of hardness of CoCrFeNi-based alloys

Alloy	Microhardness (HV)
AlCoCrFeNi (SPS) [37]	625
CoCrFeNiMn (SPS) [38]	646
CoCrFeMnNi (AM) [35]	170
Al_0.5CoCrCuFeNi (AM) [36]	208
(CoCrFeMnNi)₉₈C₂ (at.%) (AM) [35]	240
(CoCrFeMnNi)₉₅C₅ (at.%) (AM) [this work]	345

Table 2 Activation energy (Q) of alloys based on CoCrFeMnNi

Alloy	Activation energy (kJ/mol)
CoCrFeMnNi [40]	350
(CoCrFeMnNi)₉₉C₁ (at.%) [31]	385.43
(CoCrFeMnNi)₉₅C₅ (at.%) [this work]	423

Fig. 12 Comparison between the experimental and calculated values of (CoCrFeMnNi)95C5 (at.%) alloy hardness at different Z values

Table 3 Hardness parameters of the (CoCrFeMnNi)95C5 (at.%) alloy at different Z conditions

Zener-Hollomon parameter (lnZ)	V_fcc (%)	HV_CoCrFeMnNi (HV) [35]	G (GPa) [50]	b [50]	f (Fine carbides) (%)	d (nm)	V_cc (Coarse carbides) (%)	HV_cc (Coarse carbides) [35]
48.59	82.68	160	80	0.254	4.12	250	10.44	900
39.88	89.74				7.14	150	3.09

References

[1]	K. Fukaura, Y. Yokoyama, D. Yokoi, N. Tsujii, K. Ono, Metall.Mater. Trans. A 35, 1289 (2004)
[2]	I. Picas, N. Cuadrado, D. Casellas, A. Goez, L. Llanes, in Fatigue 2010, ed. by P. Lukas(Elsevier Science Bv, Amsterdam, 2010), p.1777
[3]	J.W. Yeh, S.K. Chen, S.J. Lin, J.Y. Gan, T.S. Chin, T.T. Shun,C.H. Tsau, S.Y. Chang, Adv. Eng. Mater. 6, 299(2004)
[4]	C.J. Tong, Y.L. Chen, J.W. Yeh, S.J. Lin, S.K. Chen, T.T. Shun,C.H. Tsau, S.Y. Chang, Metall. Mater. Trans. A 36, 881 (2005)
[5]	J.W. Yeh, S.Y. Chang, Y.D. Hong, S.K. Chen, S.J. Lin, Mater.Chem. Phys. 103, 41(2007)
[6]	A. Li, X. Zhang, Acta Metall.Sin. (Engl. Lett.) 22, 219(2009)
[7]	X. Yang, X. Wang, X. Ling, D. Wang, Results Phys. 7, 1412(2017)
[8]	B. Gludovatz, A. Hohenwarter, D. Catoor, E.H. Chang, E.P. George, R.O. Ritchie, Science 345, 1153 (2014)
[9]	H. Shahmir, T. Mousavi, J. He, Z. Lu, M. Kawasaki, T.G. Langdon,Mater. Sci. Eng. A 705, 411 (2017)
[10]	X.L. Shang, Z.J. Wang, Q.F. Wu, J.C. Wang, J.J. Li, J.K. Yu, Acta Metall.Sin. (Engl. Lett.) 32, 41(2019)
[11]	Y. Lu, H. Huang, X. Gao, C. Ren, J. Gao, H. Zhang, S. Zheng,Q. Jin, Y. Zhao, C. Lu, T. Wang, T. Li, J. Mater. Sci. Technol. 35,369(2019)
[12]	B. Zhang, Y. Zhang, S. Guo, J. Mater. Sci. 53, 14729(2018)
[13]	W. Li, P.K. Liaw, Y. Gao, Intermetallics 99, 69 (2018)
[14]	Y.Z. Tian, S.J. Sun, H.R. Lin, Z.F. Zhang, J. Mater. Sci. Technol.35, 334(2019)
[15]	S.G. Ma, Y. Zhang, Mater. Sci. Eng. A 532, 480 (2012)
[16]	C.Y. Hsu, J.W. Yeh, S.K. Chen, T.T. Shun, Metall. Mater. Trans.A 35, 1465 (2004)
[17]	A. Zaddach, R. Scattergood, C. Koch, Mater. Sci. Eng. A 636, 373(2015)
[18]	H. Zuhailawati, T.C. Geok, P. Basu, Mater. Des. 31, 2211(2010)
[19]	S. Kang, Y.S. Jung, J.H. Jun, Y.K. Lee, Mater. Sci. Eng. A 527,745 (2010)
[20]	S. Fang, W. Chen, Z. Fu, Mater. Des. 54, 973(2014)
[21]	J.M. Zhu, H.M. Fu, H.F. Zhang, A.M. Wang, H. Li, Z.Q. Hu, J.Alloys Compd. 509, 3476(2011)
[22]	T.D. Huang, L. Jiang, C.L. Zhang, H. Jiang, Y.P. Lu, T.J. Li, Sci.China Technol. Sci. 61, 117(2018)
[23]	Z. Wu, C.M. Parish, H. Bei, J. Alloys Compd. 647, 815(2015)
[24]	J.Y. He, H. Wang, H.L. Huang, X.D. Xu, M.W. Chen, Y. Wu, X.J. Liu,T.G. Nieh, K. An, Z.P. Lu, Acta Mater. 102, 187(2016)
[25]	L.B. Chen, R. Wei, K. Tang, J. Zhang, F. Jiang, L. He, J. Sun,Mater. Sci. Eng. A 716, 150 (2018)
[26]	S. Orhan, A.O. Er, N. Camu?cu, E. Aslan, NDT E Int. 40, 121(2007)
[27]	N. Camu?cu, E. Aslan, J. Mater. Process. Technol. 170, 121(2005)
[28]	E.O. Ezugwu, Z.M. Wang, A.R. Machado, J. Mater. Process.Technol. 86, 1(1999)
[29]	X. Qin, D. Huang, X. Yan, X. Zhang, M. Qi, S. Yue, J. Alloys Compd. 770, 507(2019)
[30]	M. Saadati, R.A. Khosroshahi, G. Ebrahimi, M. Jahazi, Mater.Charact. 131, 234(2017)
[31]	J. Li, B. Gao, S. Tang, B. Liu, Y. Liu, Y. Wang, J. Wang, J. Alloys Compd. 747, 571(2018)
[32]	C. Zener, J.H. Hollomon, J. Appl. Phys. 15, 22(1944)
[33]	N.R. Jaladurgam, A.K. Kanjarla, Mater. Sci. Eng. A 712, 240 (2018)
[34]	F. Kong, Y. Chen, D. Zhang, S. Zhang, Mater. Sci. Eng. A 539,107 (2012)
[35]	N.D. Stepanov, N.Y. Yurchenko, M.A. Tikhonovsky, G.A. Salishchev,J. Alloys Compd. 687, 59(2016)
[36]	C.C. Tung, J.W. Yeh, T.T. Shun, S.K. Chen, Y.S. Huang, H.C. Chen, Mater. Lett. 61, 1(2007)
[37]	W. Ji, Z. Fu, W. Wang, H. Wang, J. Zhang, Y. Wang, F. Zhang, J.Alloys Compd. 589, 61(2014)
[38]	W. Ji, W. Wang, H. Wang, J. Zhang, Y. Wang, F. Zhang, Z. Fu,Intermetallics 56, 24 (2015)
[39]	S. Liu, Q. Pan, H. Li, Z. Huang, K. Li, X. He, X. Li, J. Mater. Sci.54, 1(2019)
[40]	N. Stepanov, M. Tikhonovsky, N. Yurchenko, D. Zyabkin, M. Klimova,S. Zherebtsov, A. Efimov, G. Salishchev, Intermetallics 59,8 (2015)
[41]	G. Qin, R. Chen, H. Zheng, H. Fang, L. Wang, Y. Su, J. Guo, H. Fu, J. Mater. Sci. Technol. 35, 578(2019)
[42]	Z. Wang, Q. Fang, J. Li, B. Liu, Y. Liu, J. Mater. Sci. Technol. 34,349(2018)
[43]	K. Evans, Treatise on Materials Science & Technology (Elsevier,Amsterdam, 1974), p. 113
[44]	B. Liu, J. Wang, Y. Liu, Q. Fang, Y. Wu, S. Chen, C.T. Liu, Intermetallics 75, 25 (2016)
[45]	S. Chen, D. Fu, H. Luo, Y. Wang, J. Teng, H. Zhang, Vacuum 149,297 (2018)
[46]	R.R. Eleti, T. Bhattacharjee, L. Zhao, P.P. Bhattacharjee, N. Tsuji,Mater. Chem. Phys. 210, 176(2018)
[47]	K.Y. Tsai, M.H. Tsai, J.W. Yeh, Acta Mater. 61, 4887(2013)
[48]	S. Jiang, Y. Zhang, S. Wang, C. Zhao, J. Mater. Sci. 52, 3199(2017)
[49]	T.Y. Kwak, W.J. Kim, J. Mater. Sci. Technol. 35, 181(2019)
[50]	G. Laplanche, P. Gadaud, O. Horst, F. Otto, G. Eggeler, E. George,J. Alloys Compd. 623, 348(2015)
[51]	Z. Wang, I. Baker, W. Guo, J.D. Poplawsky, Acta Mater. 126, 346(2017)
[52]	S. Zhang, W. Zeng, X. Gao, D. Zhou, Y. Lai, J. Alloys Compd.684, 201(2016)