Ultrahard BCC-AlCoCrFeNi bulk nanocrystalline high-entropy alloy formed by nanoscale diffusion-induced phase transition

doi:10.1016/j.jmst.2021.11.025

Abstract

Abstract:

In the current work, the BCC-AlCoCrFeNi bulk nanocrystalline high-entropy alloy (nc-HEA) with ultra-high hardness was formed by nanoscale diffusion-induced phase transition in a nanocomposite. First, a dual-phase Al/CoCrFeNi nanocrystalline high-entropy alloy composite (nc-HEAC) was prepared by a laser source inert gas condensation equipment (laser-IGC). The as-prepared nc-HEAC is composed of well-mixed FCC-Al and FCC-CoCrFeNi nanocrystals. Then, the heat treatment was used to trigger the interdiffusion between Al and CoCrFeNi nanocrystals and form an FCC-AlCoCrFeNi phase. With the increase of the annealing temperature, element diffusion intensifies, and the AlCoCrFeNi phase undergoes a phase transition from FCC to BCC structure. Finally, the BCC-AlCoCrFeNi bulk nc-HEA with high Al content (up to 50 at.%) was obtained for the first time. Excitingly, the nc-HEAC (Al-40%) sample exhibits an unprecedented ultra-high hardness of 1124 HV after annealing at 500 °C for 1 h. We present a systematic investigation of the relationship between the microstructure evolution and mechanical properties during annealing, and the corresponding micro-mechanisms in different annealing stages are revealed. The enhanced nanoscale thermal diffusion-induced phase transition process dominates the mechanical performance evolution of the nc-HEACs, which opens a new pathway for the design of high-performance nanocrystalline alloy materials.

Key words: High-entropy alloy, Nanocrystalline, Composites, Diffusion-induced phase transition, Mechanical, Inert gas condensation

Junjie Wang, Zongde Kou, Shu Fu, Shangshu Wu, Sinan Liu, Mengyang Yan, Zhiqiang Ren, Di Wang, Zesheng You, Si Lan, Horst Hahn, Xun-Li Wang, Tao Feng. Ultrahard BCC-AlCoCrFeNi bulk nanocrystalline high-entropy alloy formed by nanoscale diffusion-induced phase transition[J]. J. Mater. Sci. Technol., 2022, 115: 29-39.

Figures/Tables 12

Fig. 1. Schematic diagram of the preparation process of Al/CoCrFeNi nc-HEAC.

Table 1. Actual composition (at.%) of designed Al/CoCrFeNi nc-HEACs.

Sample	Al	Cr	Fe	Co	Ni
Al-30%	31.31	18.22	17.68	15.84	17.04
Al-40%	39.99	13.76	15.44	15.73	14.93
Al-50%	51.33	12.00	12.52	12.28	11.88

Fig. 2. Microstructure of the as-prepared 40%-Al/CoCrFeNi nc-HEAC: (a) Bright-field TEM images, the EDS analyses of (area a1) CoCrFeNi HEA nanoparticle and (area a2) irregularly Al; (b, c) HRTEM images of the CoCrFeNi HEA and the Al grain taken along [011] axes; (d) HAADF-STEM image and corresponding EDS mappings taken from the nc-HEAC; (e) Compositional profile within the HEA grain highlighted in (d) marked with the white line.

Fig. 3. (a) Vickers hardness variations of laser-IGC Al/CoCrFeNi nc-HEAC samples with different Al content after isochronous (for 1 h) heat treatment. (b) The microhardness of the nc-HEACs and other AlCoCrFeNi HEAs with different Al content. Data reported in other alloys prepared by different methods are presented for comparison.

Fig. 4. In situ synchrotron XRD patterns of the Al-40% nc-HEAC at: (a) 25-1050 °C, (c) 400-500 °C. (b) The phase fraction of FCC-Al at 25-370 °C, (d) The phase fraction of BCC and FCC at 370-800 °C.

Fig. 5. TEM images of the Al-40% nc-HEAC sample after annealing at 300 °C for 1 h. (a) Bright-field TEM image showing the nanocrystalline morphology, (inset) XRD of Al-40% nc-HEAC at room temperature and annealed at 300 °C for 1 h. (b) HRTEM image of HEA particles, (inset) fast Fourier transformation (FFT) pattern collected from the grain interior. (c) STEM image, and (area c1 and c2) the EDS analyses of the edge and center regions of HEA grain. (d) The corresponding STEM-EDS maps of the pink rectangle area in (c). (e) Compositional profiles within the HEA grain highlighted in (d) marked with the white line.

Table 2. A summary of EDS results showing the structure and chemical compositions (at.%) of the phases formed in the Al-40% nc-HEAC sample at room temperature (RT) and after annealing at 300, 425 and 500 °C.

Area	Phase	Crystal structure	Al	Cr	Fe	Co	Ni
a1(Fig. 2)	CoCrFeNi	FCC	0.77	21.56	25.54	26.96	24.39
a2(Fig. 2)	Al	FCC	95.44	0	1.16	1.18	2.22
(c1)(Fig. 5)	Al,Cr,Fe, Co,Ni	FCC	16.77	19.62	22.59	20.11	20.91
c2(Fig. 5)	Al,Cr,Fe, Co,Ni	FCC	2.83	18.01	26.61	28.28	24.27
b1(Fig. 7)	Al,Ni-rich phase	B2	24.75	13.59	21.50	15.87	24.29
b7(Fig. 7)	Al,Cr,Fe, Co,Ni	FCC	16.74	22.64	22.78	20.21	17.63
b1(Fig. 8)	Al,Ni-rich phase	B2	31.32	10.80	11.72	18.69	27.47
b2(Fig. 8)	Fe,Cr-rich phase	BCC	12.06	28.49	28.57	19.07	11.82

Fig. 6. HRTEM images of the Al-40% nc-HEAC sample after annealing at 300 °C for 1 h. (a) HRTEM image, (inset) its corresponding FFT pattern, (a1-a3) HRTEM images of the pink rectangle regions of HEA grain taken along [011] axes in (a). (b) Lattice constants of the edge and center regions of HEA grains. (c-e) Intensity profiles along line 1 in (a1), line 2 in (a2) and line 3 in (a3), showing the interplanar spacings of (100), respectively.

Fig. 7. TEM images of the Al-40% nc-HEAC sample after annealing at 425 °C. (a) Bright-field TEM image, (b) HRTEM image, (b1-b3) the corresponding FFT patterns of BCC phase collected from the grain interior, (b4-b7) the corresponding FFT patterns of FCC phase collected from the grain interior.

Fig. 8. TEM images and corresponding FFT patterns of the Al-40% nc-HEAC sample after annealing at 500 °C for 1 h. (a) Bright-field TEM image showing the polycrystalline morphology. (b) HRTEM image of the disordered BCC and ordered BCC(B2) phase, (b1, b2) the corresponding FFT patterns collected from the grain interior and EDS chemical analysis. (c) Bright-field TEM image. (d) The corresponding STEM-EDS maps of the pink rectangle area in (c).

Fig. 9. Bright-field TEM images of the Al-40% nc-HEAC samples after 1 h isochronous heat treatment at (a) 600 °C, (b) 700 °C, (c) 800 °C, (d) 1000 °C.

Fig. 10. Microstructure of the as-cast Al40Co15Cr15Fe15Ni15 HEA: (a) EBSD inverse pole figur (IPF) image, (b) EBSD phase image. The BCC phase (red) are 100%. (c) SEM-EDS, (d) XRD.

References 53

[1]	J.C. Rao, H.Y. Diao, V. Ocelík, D. Vainchtein, C. Zhang, C. Kuo, Z. Tang, W. Guo, J.D. Poplawsky, Y. Zhou, P.K. Liaw, J.T.M. De Hosson, Acta Mater. 131 (2017) 206-220. DOI URL
[2]	W.R. Wang, W.L. Wang, S.C. Wang, Y.C. Tsai, C.H. Lai, J.W. Yeh, Intermetallics 26 (2012) 44-51. DOI URL
[3]	J. Joseph, P. Hodgson, T. Jarvis, X. Wu, N. Stanford, D.M. Fabijanic, Mater. Sci. Eng. A 733 (2018) 59-70. DOI URL
[4]	T. Butler, M. Weaver, Metals 6 (2016) 222. DOI URL
[5]	Y.F. Kao, T.J. Chen, S.K. Chen, J.W. Yeh, J. Alloy. Compd. 488 (2009) 57-64. DOI URL
[6]	M. Li, J. Gazquez, A. Borisevich, R. Mishra, K.M. Flores, Intermetallics 95 (2018) 110-118. DOI URL
[7]	W.R. Wang, W.L. Wang, J.W. Yeh, J. Alloy. Compd. 589 (2014) 143-152. DOI URL
[8]	R.S. Ganji, P. Sai Karthik, K. Bhanu Sankara Rao, K.V. Rajulapati, Acta Mater. 125 (2017) 58-68. DOI URL
[9]	V. Shivam, J. Basu, Y. Shadangi, M.K. Singh, N.K. Mukhopadhyay, J. Alloy. Compd. 757 (2018) 87-97. DOI URL
[10]	M. Vaidya, A. Prasad, A. Parakh, B.S. Murty, Mater. Des. 126 (2017) 37-46. DOI URL
[11]	S. Mohanty, T.N. Maity, S. Mukhopadhyay, S. Sarkar, N.P. Gurao, S. Bhowmick, K. Biswas, Mater. Sci. Eng. A 679 (2017) 299-313. DOI URL
[12]	A.S.M. Ang, C.C. Berndt, M.L. Sesso, A. Anupam, S. Praveen, R.S. Kottada, B.S. Murty, Metall. Mater. Trans. A 46 (2014) 791-800. DOI URL
[13]	A. Zhang, J. Han, J. Meng, B. Su, P. Li, Mater. Lett. 181 (2016) 82-85. DOI URL
[14]	J. Wang, S. Wu, S. Fu, S. Liu, M. Yan, Q. Lai, S. Lan, H. Hahn, T. Feng, Scr. Mater. 187 (2020) 335-339. DOI URL
[15]	A. Munitz, S. Salhov, S. Hayun, N. Frage, J. Alloy. Compd. 683 (2016) 221-230. DOI URL
[16]	T. Yang, S. Xia, S. Liu, C. Wang, S. Liu, Y. Zhang, J. Xue, S. Yan, Y. Wang, Mater. Sci. Eng. A 648 (2015) 15-22. DOI URL
[17]	C. Li, J.C. Li, M. Zhao, Q. Jiang, J. Alloy. Compd. 504 (2010) S515-S518. DOI URL
[18]	J.W. Yeh, S.K. Chen, S.J. Lin, J.Y. Gan, S.Y. Chang, Adv. Eng. Mater. 6 (2004) 299-303. DOI URL
[19]	Y. Wang, S. Ma, X. Chen, J. Shi, Y. Zhang, J. Qiao, Acta Metall. Sin. 26 (2013) 277-284. DOI URL
[20]	Q.H. Tang, Y. Huang, Y.Y. Huang, X.Z. Liao, T.G. Langdon, P.Q. Dai, Mater. Lett. 151 (2015) 126-129. DOI URL
[21]	P.F. Yu, H. Cheng, L.J. Zhang, H. Zhang, Q. Jing, M.Z. Ma, P.K. Liaw, G. Li, R.P. Liu, Mater. Sci. Eng. A 655 (2016) 283-291. DOI URL
[22]	M. Komarasamy, T. Wang, K. Liu, L. Reza-Nieto, R.S. Mishra, Scr. Mater. 162 (2019) 38-43. DOI URL
[23]	Y.C. Huang, C.S. Tsao, C. Lin, Y.C. Lai, S.K. Wu, C.H. Chen, Mater. Sci. Eng. A 769 (2020) 138526. DOI URL
[24]	T.S. Reddy, I.S. Wani, T. Bhattacharjee, S.R. Reddy, R. Saha, P.P. Bhattacharjee, Intermetallics 91 (2017) 150-157. DOI URL
[25]	C.W. Tsai, M.H. Tsai, J.W. Yeh, C.C. Yang, J. Alloy. Compd. 490 (2010) 160-165. DOI URL
[26]	J. Joseph, N. Stanford, P. Hodgson, D.M. Fabijanic, J. Alloy. Compd. 726 (2017) 885-895. DOI URL
[27]	R. Wang, K. Zhang, C. Davies, X. Wu, J. Alloy. Compd. 694 (2017) 971-981. DOI URL
[28]	I. Kunce, M. Polanski, K. Karczewski, T. Plocinski, K.J. Kurzydlowski, J. Alloy. Compd. 648 (2015) 751-758. DOI URL
[29]	P.D. Niu, R.D. Li, T.C. Yuan, S.Y. Zhu, C. Chen, M.B. Wang, L. Huang, Inter-metallics 104 (2019) 24-32.
[30]	F. Ye, Z. Jiao, S. Yan, L. Guo, L. Feng, J. Yu, Vacuum 174 (2020) 109178. DOI URL
[31]	Y. Liu, J. Chen, Z. Li, X. Wang, X. Fan, J. Liu, J. Alloy. Compd. 780 (2019) 558-564. DOI URL
[32]	X.B. Feng, W. Fu, J.Y. Zhang, J.T. Zhao, J. Li, K. Wu, G. Liu, J. Sun, Scr. Mater. 139 (2017) 71-76. DOI URL
[33]	Y.P. Cai, G.J. Wang, Y.J. Ma, Z.H. Cao, X.K. Meng, Scr. Mater. 162 (2019) 281-285. DOI URL
[34]	D. Zhao, T. Yamaguchi, J. Shu, T. Tokunaga, T. Danjo, Appl. Surf. Sci. 517 (2020) 145980. DOI URL
[35]	T. Yang, Y. Tong, Z.B. Jiao, J. Wei, J.X. Cai, X.D. Han, D. Chen, A. Hu, J.J. Kai, K. Lu, Y. Liu, C.T. Liu, Science 362 (2018) 933-937. DOI PMID
[36]	S. Jiang, H. Wang, Y. Wu, X. Liu, H. Chen, M. Yao, B. Gault, D. Ponge, D. Raabe, A. Hirata, M. Chen, Y. Wang, Z. Lu, Nature 544 (2017) 460-464. DOI URL
[37]	L. Fan, T. Yang, Y. Zhao, J. Luan, G. Zhou, H. Wang, Z. Jiao, C.T. Liu, Nat. Com-mun. 11 (2020) 6240.
[38]	H. Shiratori, T. Fujieda, K. Yamanaka, Y. Koizumi, K. Kuwabara, T. Kato, A. Chiba, Mater. Sci. Eng. A 656 (2016) 39-46. DOI URL
[39]	C. Yang, J. Lin, J. Zeng, S. Qu, X. Li, W. Zhang, D. Zhang, Adv. Eng. Mater. 18 (2016) 348-353. DOI URL
[40]	J. Hu, Y.N. Shi, X. Sauvage, G. Sha, K. Lu, Science 355 (2017) 1292. DOI PMID
[41]	Y.M. Wang, S. Cheng, Q.M. Wei, E. Ma, T.G. Nieh, A. Hamza, Scr. Mater. 51 (2004) 1023-1028. DOI URL
[42]	X. Huang, N. Hansen, N. Tsuji, Science 312 (2006) 249-251. DOI URL
[43]	T.J. Rupert, J.R. Trelewicz, C.A. Schuh, J. Mater. Res. 27(2012)1285-1294. DOI URL
[44]	C.H. Chen, Scr. Mater. 56 (2007) 713-716. DOI URL
[45]	X. Yang, P. Dong, Z. Yan, B. Cheng, X. Zhai, H. Chen, H. Zhang, W. Wang, J. Alloy. Compd. 836 (2020) 155411. DOI URL
[46]	Z. Tan, L. Wang, Y. Xue, P. Zhang, T. Cao, X. Cheng, Mater. Des. 109 (2016) 219-226. DOI URL
[47]	Z. Yuan, W. Tian, F. Li, Q. Fu, Y. Hu, X. Wang, J. Alloy. Compd. 806 (2019) 901-908. DOI URL
[48]	V. Shivam, Y. Shadangi, J. Basu, N.K. Mukhopadhyay, J. Alloy. Compd. 832 (2020) 154826. DOI URL
[49]	K. Lu, L. Lu, S. Suresh, Science 324 (2009) 349-352. DOI PMID
[50]	Ł. Rogal, D. Kalita, A. Tarasek, P. Bobrowski, F. Czerwinski, J. Alloy. Compd. 708 (2017) 344-352. DOI URL
[51]	G.M. Karthik, S. Panikar, G.D.J. Ram, R.S. Kottada, Mater. Sci. Eng. A 679 (2017) 193-203. DOI URL
[52]	T. Lu, W. Chen, Z. Li, T. He, B. Li, R. Li, Z. Fu, S. Scudino, J. Alloy. Compd. 801 (2019) 473-477. DOI URL
[53]	T. Lu, S. Scudino, W. Chen, P. Wang, D. Li, M. Mao, L. Kang, Y. Liu, Z. Fu, Mater. Sci. Eng. A 726 (2018) 126-136. DOI URL