Intermetallic Compounds in HEAs systems could give an extreme strength and corrosion resistance which attract enormous attention to the application. The Fe and Ni are added to the alloy system of CuTiZr ternary phase based on Cu2TiZr phase. The alloy is designed as CuFeTiZrNix (x= 0.1, 0.3, 0.5, 0.8, and 1.0 in molar ratio). The five kinds of alloys were investigated to the effect of Nickel content on the microstructure, hardness and electrochemical corrosion properties of the alloys annealed at 900°C for 2 hours.
In this study, the arc melting process is used to prepare the Cu-Fe-Ti-Zr-Ni alloys. The microstructure and composition were investigated by FE-SEM/EDS and X-Ray Diffractometer (XRD). The results show that the alloys are in dendritic structures with the Intermetallic phases. At Ni0.1 and Ni0.3 alloys, the dendrite tends to form the B2_BCC phase and Cu2TiZr Laves_C14 phase. However, the Fe2Zr Laves_C14 phase formed in the interdendrite region. Meanwhile, at Ni0.5 alloy, (Cu, Ni)-rich FCC phase appeared and B2_BCC phase in the dendrite region and still Fe2Zr Laves_C14 formed in the interdendrite region. At Ni0.8 and Ni1.0, the phases in the dendrite region still remain (Cu, Ni)-rich FCC and B2_BCC followed by Cu51Zr14 IMC phase formed and the Fe2Zr Laves_C14 phase formed in interdendrite region.
Further investigation, the mechanical hardness test and the electrochemical corrosion test of CuFeTiZrNix High Entropy Alloys system were revealed in this study. The hardness of the CuFeTiZrNix alloys was gradually decreased. However, it didn’t show many different results because the Laves phases existed in the systems. The corrosion resistance of the CuFeTiZrNix alloys by potentiodynamic polarization in 3.5wt% NaCl solution show better corrosion resistance and by the immersion test, the addition of Nickel content retarded the corrosion rate significantly.

Intermetallic Compounds in HEAs systems could give an extreme strength and corrosion resistance which attract enormous attention to the application. The Fe and Ni are added to the alloy system of CuTiZr ternary phase based on Cu2TiZr phase. The alloy is designed as CuFeTiZrNix (x= 0.1, 0.3, 0.5, 0.8, and 1.0 in molar ratio). The five kinds of alloys were investigated to the effect of Nickel content on the microstructure, hardness and electrochemical corrosion properties of the alloys annealed at 900°C for 2 hours.
In this study, the arc melting process is used to prepare the Cu-Fe-Ti-Zr-Ni alloys. The microstructure and composition were investigated by FE-SEM/EDS and X-Ray Diffractometer (XRD). The results show that the alloys are in dendritic structures with the Intermetallic phases. At Ni0.1 and Ni0.3 alloys, the dendrite tends to form the B2_BCC phase and Cu2TiZr Laves_C14 phase. However, the Fe2Zr Laves_C14 phase formed in the interdendrite region. Meanwhile, at Ni0.5 alloy, (Cu, Ni)-rich FCC phase appeared and B2_BCC phase in the dendrite region and still Fe2Zr Laves_C14 formed in the interdendrite region. At Ni0.8 and Ni1.0, the phases in the dendrite region still remain (Cu, Ni)-rich FCC and B2_BCC followed by Cu51Zr14 IMC phase formed and the Fe2Zr Laves_C14 phase formed in interdendrite region.
Further investigation, the mechanical hardness test and the electrochemical corrosion test of CuFeTiZrNix High Entropy Alloys system were revealed in this study. The hardness of the CuFeTiZrNix alloys was gradually decreased. However, it didn’t show many different results because the Laves phases existed in the systems. The corrosion resistance of the CuFeTiZrNix alloys by potentiodynamic polarization in 3.5wt% NaCl solution show better corrosion resistance and by the immersion test, the addition of Nickel content retarded the corrosion rate significantly.

[1] K.B. Zhang, Z.Y. Fu, J.Y. Zhang, W.M. Wang, H. Wang, Y.C. Wang, Q.J. Zhang, J. Shi, Microstructure and mechanical properties of CoCrFeNiTiAlx high-entropy alloys, Mat. Sci. Eng. a-Struct. 508 (2009) 214-219.
[2] J.W. Yeh, Alloy design strategies and future trends in high-entropy alloys, JOM-US 65 (2013) 1759-1771.
[3] J.W. Yeh, Y.L. Chen, S.J. Lin, S.K. Chen, High-entropy alloys–a new era of exploitation, Materials Science Forum, Trans Tech Publ, 2007, pp. 1-9.
[4] S. Sheikh, H.H. Mao, S. Guo, Predicting solid solubility in CoCrFeNiMx (M=4d transition metal) high-entropy alloys, J. Appl. Phys. 121 (2017).
[5] D.J. Fisher, High-entropy alloys-Microstructures and properties, foundations of materials science and engineering 86 (2015) I.
[6] C.Y. Hsu, T.S. Sheu, J.W. Yeh, S.K. Chen, Effect of iron content on wear behavior of AlCoCrFexMo0.5Ni high-entropy alloys, Wear 268 (2010) 653-659.
[7] J.W. Yeh, Recent progress in high-entropy alloys, Ann. Chim-Sci. Mat. 31 (2006) 633-648.
[8] M.-H. Tsai, Three strategies for the design of advanced high-entropy alloys, Entropy-Switz 18 (2016) 252.
[9] C. Ng, S. Guo, J.H. Luan, S.Q. Shi, C.T. Liu, Entropy-driven phase stability and slow diffusion kinetics in an Al0.5CoCrCuFeNi high entropy alloy, Intermetallics 31 (2012) 165-172.
[10] M.H. Tsai, K.C. Chang, J.H. Li, R.C. Tsai, A.H. Cheng, A second criterion for sigma phase formation in high-entropy alloys, Mater. Res. Lett. 4 (2016) 90-95.
[11] C.C. Tung, J.W. Yeh, T.T. Shun, S.K. Chen, Y.S. Huang, H.C. Chen, On the elemental effect of AlCoCrCuFeNi high-entropy alloy system, Mater. Lett. 61 (2007) 1-5.
[12] M.R. Chen, S.J. Lin, J.W. Yeh, S.K. Chen, Y.S. Huang, C.P. Tu, Microstructure and properties of Al0.5CoCrCuFeNiTix (x=0-2.0) high-entropy alloys, Mater. Trans. 47 (2006) 1395-1401.
[13] Y. Ye, Q. Wang, J. Lu, C. Liu, Y. Yang, High-entropy alloy: challenges and prospects, Materials Today 19 (2016) 349-362.
[14] M.H. Tsai, A.C. Fan, H.A. Wang, Effect of atomic size difference on the type of major intermetallic phase in arc-melted CoCrFeNiX high-entropy alloys, J. Alloy Compd. 695 (2017) 1479-1487.
[15] M.H. Tsai, K.Y. Tsai, C.W. Tsai, C. Lee, C.C. Juan, J.W. Yeh, Criterion for sigma phase formation in Cr- and V-containing high-entropy alloys, Mater. Res. Lett. 1 (2013) 207-212.
[16] N. Yurchenko, N. Stepanov, G. Salishchev, Laves-phase formation criterion for high-entropy alloys, Mater. Sci. Tech-Lond. 33 (2017) 17-22.
[17] Z. Zhu, K. Ma, Q. Wang, C. Shek, Compositional dependence of phase formation and mechanical properties in three CoCrFeNi-(Mn/Al/Cu) high entropy alloys, Intermetallics 79 (2016) 1-11.
[18] O. Myslyvchenko, O. Makarenko, M. Krapivka, A. Degula, Effect of nickel on the structure and phase composition of the VCrMnFeCoNix high-entropy alloy, Journal of Superhard Materials 37 (2015) 182-188.
[19] C.Y. Hsu, W.R. Wang, W.Y. Tang, S.K. Chen, J.W. Yeh, Microstructure and mechanical properties of new AlCoxCrFeMo0.5Ni high‐entropy alloys, Adv. Eng. Mater. 12 (2010) 44-49.
[20] D. Olson, Prediction of austenitic weld metal microstructure and properties, Welding journal 64 (1985) 281s-295s.
[21] B. Cantor, Multicomponent and high entropy alloys, Entropy-Switz 16 (2014) 4749-4768.
[22] Z.W. Zhang, C.T. Liu, M.K. Miller, X.L. Wang, Y.R. Wen, T. Fujita, A. Hirata, M.W. Chen, G. Chen, B.A. Chin, A nanoscale co-precipitation approach for property enhancement of Fe-base alloys, SCI. REP-UK. 3 (2013).
[23] B. Cantor, I.T.H. Chang, P. Knight, A.J.B. Vincent, Microstructural development in equiatomic multicomponent alloys, Mat. Sci. Eng. a-Struct. 375 (2004) 213-218.
[24] B. Cantor, K.B. Kim, P.J. Warren, Novel multicomponent amorphous alloys, Mater. Sci. Forum 386-3 (2002) 27-31.
[25] J. Dabrowa, G. Cieslak, M. Stygar, K. Mroczka, K. Berent, T. Kulik, M. Danielewski, Influence of Cu content on high temperature oxidation behavior of AlCoCrCuxFeNi high entropy alloys (x=0; 0.5; 1), Intermetallics 84 (2017) 52-61.
[26] M.H. Tsai, J.W. Yeh, High-entropy alloys: a critical review, Mater. Res. Lett. 2 (2014) 107-123.
[27] S. Guo, C.T. Liu, Phase stability in high entropy alloys: Formation of solid-solution phase or amorphous phase, Prog. Nat. Sci-Mater. 21 (2011) 433-446.
[28] J.W. Yeh, S.K. Chen, J.Y. Gan, S.J. Lin, T.S. Chin, T.T. Shun, C.H. Tsau, S.Y. Chang, Formation of simple crystal structures in Cu-Co-Ni-Cr-Al-Fe-Ti-V alloys with multiprincipal metallic elements, Metall. Mater. Trans. A 35a (2004) 2533-2536.
[29] X. Yang, Y. Zhang, Prediction of high-entropy stabilized solid-solution in multi-component alloys, Mater. Chem. Phys. 132 (2012) 233-238.
[30] A. Takeuchi, A. Inoue, Quantitative evaluation of critical cooling rate for metallic glasses, Mat. Sci. Eng. a-Struct. 304 (2001) 446-451.
[31] J.W. Yeh, S.K. Chen, S.J. Lin, J.Y. Gan, T.S. Chin, T.T. Shun, C.H. Tsau, S.Y. Chang, Nanostructured high-entropy alloys with multiple principal elements: Novel alloy design concepts and outcomes, Adv. Eng. Mater. 6 (2004) 299-303.
[32] A. Takeuchi, A. Inoue, Classification of bulk metallic glasses by atomic size difference, heat of mixing and period of constituent elements and its application to characterization of the main alloying element, Mater. Trans. 46 (2005) 2817-2829.
[33] Y. Zhang, Y.J. Zhou, J.P. Lin, G.L. Chen, P.K. Liaw, Solid‐solution phase formation rules for multi‐component alloys, Adv. Eng. Mater. 10 (2008) 534-538.
[34] S. Guo, Q. Hu, C. Ng, C.T. Liu, More than entropy in high-entropy alloys: Forming solid solutions or amorphous phase, Intermetallics 41 (2013) 96-103.
[35] Y. Zhang, J.W. Yeh, J.F. Sun, J.P. Lin, K.F. Yao, High-entropy alloys, Adv. Mater. Sci. Eng. (2015).
[36] H.F. Sheng, M. Gong, L.M. Peng, Microstructural characterization and mechanical properties of an Al0.5CoCrFeCuNi high-entropy alloy in as-cast and heat-treated/quenched conditions, Mat. Sci. Eng. a-Struct. 567 (2013) 14-20.
[37] J.Y. He, W.H. Liu, H. Wang, Y. Wu, X.J. Liu, T.G. Nieh, Z.P. Lu, Effects of Al addition on structural evolution and tensile properties of the FeCoNiCrMn high-entropy alloy system, Acta Mater. 62 (2014) 105-113.
[38] J.H. Zhu, P.K. Liaw, C.T. Liu, Effect of electron concentration on the phase stability of NbCr2-based Laves phase alloys, Mat. Sci. Eng. a-Struct. 240 (1997) 260-264.
[39] S. Guo, C. Ng, J. Lu, C.T. Liu, Effect of valence electron concentration on stability of fcc or bcc phase in high entropy alloys, J. Appl. Phys. 109 (2011).
[40] C.J. Tong, M.R. Chen, S.K. Chen, J.W. Yeh, T.T. Shun, S.J. Lin, S.Y. Chang, Mechanical performance of the AlxCoCrCuFeNi high-entropy alloy system with multiprincipal elements, Metall. Mater. Trans. A 36a (2005) 1263-1271.
[41] C.J. Tong, Y.L. Chen, S.K. Chen, J.W. Yeh, T.T. Shun, C.H. Tsau, S.J. Lin, S.Y. Chang, Microstructure characterization of AlxCoCrCuFeNi high-entropy alloy system with multiprincipal elements, Metall. Mater. Trans. A 36a (2005) 881-893.
[42] A.M. Li, X.Y. Zhang, Thermodynamic analysis of the simple microstructure of AlCrFeNiCu high-entropy alloy with multi-principal elements, Acta Metall. Sin-Engl. 22 (2009) 219-224.
[43] O.N. Senkov, G.B. Wilks, D.B. Miracle, C.P. Chuang, P.K. Liaw, Refractory high-entropy alloys, Intermetallics 18 (2010) 1758-1765.
[44] M.F. del Grosso, G. Bozzolo, H.O. Mosca, Determination of the transition to the high entropy regime for alloys of refractory elements, J. Alloy Compd. 534 (2012) 25-31.
[45] M.S. Lucas, G.B. Wilks, L. Mauger, J.A. Munoz, O.N. Senkov, E. Michel, J. Horwath, S.L. Semiatin, M.B. Stone, D.L. Abernathy, E. Karapetrova, Absence of long-range chemical ordering in equimolar FeCoCrNi, Appl. Phys. Lett. 100 (2012).
[46] C.Y. Hsu, J.W. Yeh, S.K. Chen, T.T. Shun, Wear resistance and high-temperature compression strength of Fcc CuCoNiCrAl0.5Fe alloy with boron addition, Metall. Mater. Trans. A 35a (2004) 1465-1469.
[47] K.B. Zhang, Z.Y. Fu, Effects of annealing treatment on phase composition and microstructure of CoCrFeNiTiAlx high-entropy alloys, Intermetallics 22 (2012) 24-32.
[48] F. Otto, Y. Yang, H. Bei, E.P. George, Relative effects of enthalpy and entropy on the phase stability of equiatomic high-entropy alloys, Acta Mater. 61 (2013) 2628-2638.
[49] D.B. Miracle, O.N. Senkov, A critical review of high entropy alloys and related concepts, Acta Mater. 122 (2017) 448-511.
[50] K.H. Cheng, C.H. Lai, S.J. Lin, J.W. Yeh, Recent progress in multi-element alloy and nitride coatings sputtered from high-entropy alloy targets, Ann. Chim-Sci. Mat. 31 (2006) 723-736.
[51] K.Y. Tsai, M.H. Tsai, J.W. Yeh, Sluggish diffusion in Co-Cr-Fe-Mn-Ni high-entropy alloys, Acta Mater. 61 (2013) 4887-4897.
[52] R. Akid, Corrosion of engineering materials, Handbook of Advanced Materials (2004) 487.
[53] G.F. Mars, Corrosion Engineering, 3rd, New York: Mc Graw-Hill Book Company, 2005.
[54] D.G. Enos, L.L. Scribner, The potentiodynamic polarization scan, Solartron Instruments, Hampshire, UK, Technical Report 33 (1997).
[55] A. G102-89, Standard practice for calculation of corrosion rates and related information from electrochemical measurements, Google Scholar (1999).
[56] Y. Shi, B. Yang, X. Xie, J. Brechtl, K.A. Dahmen, P.K. Liaw, Corrosion of Al xCoCrFeNi high-entropy alloys: Al-content and potential scan-rate dependent pitting behavior, Corrosion Science 119 (2017) 33-45.
[57] Y. Tang, Y. Zuo, J. Wang, X. Zhao, B. Niu, B. Lin, The metastable pitting potential and its relation to the pitting potential for four materials in chloride solutions, Corrosion Science 80 (2014) 111-119.
[58] R. Ovarfort, Critical pitting temperature measurements of stainless steels with an improved electrochemical method, Corrosion Science 29 (1989) 987-993.
[59] U.K. Mudali, B. Rai, Corrosion Science and Technology: Mechanism, Mitigation and Monitoring, (2008).
[60] Y. Zhang, T.T. Zuo, Z. Tang, M.C. Gao, K.A. Dahmen, P.K. Liaw, Z.P. Lu, Microstructures and properties of high-entropy alloys, Progress in Materials Science 61 (2014) 1-93.
[61] Y. Zhang, Z. Lu, S. Ma, P. Liaw, Z. Tang, Y. Cheng, M. Gao, Guidelines in predicting phase formation of high-entropy alloys, MRS Communications 4 (2014) 57-62.
[62] H. Jiang, K. Han, D. Qiao, Y. Lu, Z. Cao, T. Li, Effects of Ta addition on the microstructures and mechanical properties of CoCrFeNi high entropy alloy, Mater. Chem. Phys. 210 (2018) 43-48.
[63] W. Liu, J. He, H. Huang, H. Wang, Z. Lu, C. Liu, Effects of Nb additions on the microstructure and mechanical property of CoCrFeNi high-entropy alloys, Intermetallics 60 (2015) 1-8.
[64] G. Salishchev, M. Tikhonovsky, D. Shaysultanov, N. Stepanov, A. Kuznetsov, I. Kolodiy, A. Tortika, O. Senkov, Effect of Mn and V on structure and mechanical properties of high-entropy alloys based on CoCrFeNi system, J. Alloy Compd. 591 (2014) 11-21.
[65] Z. Wang, S. Guo, C.T. Liu, Phase selection in high-entropy alloys: from nonequilibrium to equilibrium, Jom-Us 66 (2014) 1966-1972.
[66] A. Standard, E92,“, Standard Test Method for Vickers Hardness of Metallic Materials, ASTM International, West Conshohocken, PA (2003).
[67] A. Standard, Standard practice for laboratory immersion corrosion testing of metals, American Society for Testing and Materials G31-72 (2004).
[68] W. Liu, T. Yang, C. Liu, Precipitation hardening in CoCrFeNi-based high entropy alloys, Mater. Chem. Phys. 210 (2018) 2-11.
[69] H. Bo, L. Duarte, W. Zhu, L. Liu, H. Liu, Z. Jin, C. Leinenbach, Experimental study and thermodynamic assessment of the Cu–Fe–Ti system, Calphad 40 (2013) 24-33.
[70] U.E. Klotz, C. Liu, P.J. Uggowitzer, J.F. Löffler, Experimental investigation of the Cu–Ti–Zr system at 800 C, Intermetallics 15 (2007) 1666-1671.
[71] F.R. De Boer, W. Mattens, R. Boom, A. Miedema, A. Niessen, Cohesion in metals, (1988).
[72] Y. Dong, Y. Lu, J. Kong, J. Zhang, T. Li, Microstructure and mechanical properties of multi-component AlCrFeNiMox high-entropy alloys, J. Alloy Compd. 573 (2013) 96-101.
[73] A. Kündig, M. Ohnuma, D. Ping, T. Ohkubo, K. Hono, In situ formed two-phase metallic glass with surface fractal microstructure, Acta Mater. 52 (2004) 2441-2448.
[74] G.N. Hermana, Prediction of the metallic glass formation regions for the Cu-Ti-Zr ternary system by the Calculation of Phase Diagram (CALPHAD) Method, 2017.
[75] K. Gunawardana, S.R. Wilson, M.I. Mendelev, X. Song, Theoretical calculation of the melting curve of Cu-Zr binary alloys, Physical Review E 90 (2014) 052403.
[76] M.C. Troparevsky, J.R. Morris, P.R. Kent, A.R. Lupini, G.M. Stocks, Criteria for predicting the formation of single-phase high-entropy alloys, Physical Review X 5 (2015) 011041.
[77] 謝政穎, CoCrFeNixTi0. 3 高熵合金微結構與性質研究, 逢甲大學材料科學與工程學系學位論文 (2015) 1-205.
[78] Y. Dong, Y.P. Lu, J.J. Zhang, T.J. Li, Microstructure and properties of multi-component AlxCoCrFeNiTi0. 5 high-entropy alloys, Materials Science Forum, Trans. Tech. Publ., (2013) 775-780.
[79] J. Kunze, V. Maurice, L.H. Klein, H.-H. Strehblow, P. Marcus, In situ STM study of the effect of chlorides on the initial stages of anodic oxidation of Cu (111) in alkaline solutions, Electrochimica Acta 48 (2003) 1157-1167.
[80] Y. Chen, U. Hong, H. Shih, J. Yeh, T. Duval, Electrochemical kinetics of the high entropy alloys in aqueous environments—a comparison with type 304 stainless steel, Corrosion Science 47 (2005) 2679-2699.
[81] N.S. Azarian, H.M. Ghasemi, M.R. Monshi, Synergistic erosion and corrosion behavior of AA5052 aluminum alloy in 3.5 wt% NaCl solution under various impingement angles, Journal of Bio-and Tribo-Corrosion 1 (2015) 10.
[82] Y.-J. Hsu, W.-C. Chiang, J.-K. Wu, Corrosion behavior of FeCoNiCrCux high-entropy alloys in 3.5% sodium chloride solution, Mater. Chem. Phys. 92 (2005) 112-117.
[83] 陳彥辰, CuZrTiFeCrx高熵合金之顯微結構、硬度與腐蝕之研究, 國立臺灣科技大學材料科學與工程學系學位論文 (2018) 1-75.