臺灣博碩士論文加值系統

本研究中添加稀土元素La進CoCrNi中熵合金，從微結構及機械性質兩個面向去探討La添加帶來的影響，並從塊材與薄膜去分別作討論。CoCrNiLa合金塊材是以電弧熔煉製備，再經過均質化、熱軋及再結晶處理，得到成分為(CoCrNi)100-xLax (x = 0, 0.10, 0.24, 0.32, 0.48) 的中熵合金塊材；CoCrNiLa合金薄膜則是以磁控濺鍍系統將(CoCrNi)100-xLax膜鍍在單晶(111)的矽基板上，透過調控La靶材的功率 (0–60 W) 來獲得不同La含量的(CoCrNi)100-xLax (x = 0, 1.6, 3.1, 4.8, 6.7, 9.0) 中熵合金薄膜。塊材方面， La ≤ 0.24 at.%時為FCC相，在La添加量達0.32 at.%以上時除了FCC相以外會有HCP相的LaNi5析出物出現。微量La添加時會有晶粒細化與晶格扭曲的效果，但在析出物出現後即減弱，此趨勢與母相中的La含量相符。機械性質在微量La添加會有提升的效果，並在x = 0.24時達最佳值，硬度、降伏強度與極限強度分別為235.5 HV、608 MPa及1110 MPa。薄膜方面，結構一開始呈現單一FCC相，隨著La含量增加出現了HCP相的LaNi5析出物與HCP的CoCrNi相，最終變為非晶相。由(111)繞射峰推估晶粒尺寸，晶粒尺寸將隨著La增加而從24.80 nm下降至1.39 nm，TEM可看到在x = 0, 1.6, 3.1時為純柱狀晶結構，其寬度隨著La含量增加而降低；x = 4.8時則呈現柱狀晶與等軸晶共存，柱狀晶的寬度也是比x = 3.1的更小，而等軸晶則是晶粒尺寸約100至200 nm；x = 6.7時為微量奈米晶分佈在非晶的母相中；x = 9.0時則轉變成完全非晶。奈米壓痕結果指出硬度值及楊氏模數隨著La含量增加而增加，於x = 3.1時達到最大值9.66 GPa及199.50 GPa，在更高La含量時則兩者皆下降。

In this study, different amounts of La were added to CoCrNi medium entropy (MEAs) and CoCrNi medium entropy alloy films (MEAFs) in order to investigate the effect of La on the microstructure and mechanical behaviors of the CoCrNi MEAs and the MEAFs. For the CoCrNi MEAs, the structures of La-0, La-0.1 and La-0.2 were FCC solid solutions, while LaNi5 HCP precipitates formed in the FCC matrix for La-0.3 and La-0.5. The presence of La in FCC matrix not only enhanced the lattice distortion but also reduced the grain size of the matrix. However, in the presence of LaNi5 precipitates resulted in decreased hardness and tensile strength in La-0.3 and La-0.5. The optimum mechanical properties with hardness, yield strength and ultimate tensile strength of 235.3 HV, 608 MPa and 1110 MPa were obtained with small amounts of La addition in La-0.2. For the CoCrNi MEAFs, the structures retained single FCC phase in La0 and La1.6. HCP LaNi5 phase was found in La3.1 and La4.8, and HCP CoCrNi phase was shown in La4.8 in addition to FCC phase. The structure of La6.7 transformed to mainly amorphous structure with small amounts of FCC nanocrystals embedded in the amorphous matrix. Eventually, La9.0 became totally amorphous. La0, La1.6 and La3.1 showed columnar grain structure, and the grain refinement effect was observed with La addition. Both columnar grains and equiaxed grains coexisted in La4.8. With excessive La addition, the structure transformed to amorphous structure. Both hardness and Young’s modulus increased with increasing La content. The maximum hardness and Young’s modulus of 9.66 GPa and 199.50 GPa were achieved in La3.1, while the mechanical properties declined with further La addition.

口試委員會審定書 #
誌謝 i
中文摘要 iii
ABSTRACT iv
CONTENTS v
LIST OF FIGURES viii
LIST OF TABLES xii
Chapter 1 Introduction 1
Chapter 2 Literature Review 3
2.1 Medium Entropy Alloys (MEAs) 3
2.1.1 Definition 3
2.1.2 Four Core Effects 3
2.1.3 Vacuum Arc Melting 7
2.1.4 Microstructure and Mechanical Properties of MEAs 7
2.2 Medium Entropy Alloy Films (MEAFs) 10
2.2.1 Magnetron Sputtering Deposition 10
2.2.2 Microstructure and Mechanical Properties of MEAFs 11
2.3 CoCrNi MEAs 13
2.3.1 CoCrNi MEAs 13
2.3.2 Effects of Alloying Elements 16
2.3.3 CoCrNi MEAFs 17
2.4 Rare Earth Element Addition 20
2.4.1 Y Addition 20
2.4.2 Nd Addition 20
2.4.3 La Addition 21
2.5 Strengthening Mechanism 22
2.5.1 Grain Refinement Strengthening 22
2.5.2 Solid Solution Strengthening 23
2.5.3 Precipitation Strengthening 24
Chapter 3 Experimental Procedures 26
3.1 Experimental Flow 26
3.2 Material Preparation 28
3.2.1 (CoCrNi)100-xLax MEAs 28
3.2.2 (CoCrNi)100-xLax MEAFs 29
3.3 Analytical Techniques 30
3.3.1 Electron Probe X-ray Microanalyzer (EPMA) 30
3.3.2 X-ray Diffraction (XRD) 30
3.3.3 Scanning Electron Microscope (SEM) 31
3.3.4 Electron Backscatter Diffraction (EBSD) 31
3.3.5 Energy-Dispersive X-ray spectroscopy (EDS) 31
3.3.6 Transmission Electron Microscope (TEM) 32
3.3.7 Uniaxial Tension Test 33
3.3.8 Vickers Hardness Test 34
3.3.9 Nanoindentation 34
Chapter 4 Results and Discussion 35
4.1 (CoCrNi)100-xLax MEAs 35
4.1.1 Chemical Compositions 35
4.1.2 XRD Results 38
4.1.3 Microstructure 40
4.1.4 Mechanical Properties 46
4.2 (CoCrNi)100-xLax MEAFs 52
4.2.1 Chemical Compositions 52
4.2.2 XRD Results 53
4.2.3 Microstructure 55
4.2.4 Mechanical Properties 59
Chapter 5 Conclusions 62
5.1 (CoCrNi)100-xLax MEAs 62
5.2 (CoCrNi)100-xLax MEAFs 63
REFERENCES 64

[1]J. W. Yeh, S. K. Chen, S. J. Lin, J. Y. Gan, T. S. Chin, T. T. Shun, C. H. Tsau and S. Y. Chang, Nanostructured high-entropy alloys with multiple principal elements: Novel alloy design concepts and outcomes, Adv. Eng. Mater. 6(5) (2004) 299–303.
[2]B. Cantor, I. T. H. Chang, P. Knight and A. J. B. Vincent, Microstructural development in equiatomic multicomponent alloys, Mater. Sci. Eng. A 375–377 (2004) 213–218.
[3]Y. F. Ye, Q. Wang, J. Lu, C. T. Liu and Y. Yang, High-entropy alloy: challenges and prospects, Mater. Today 19(6) (2016) 349–362.
[4]Y. J. Zhou, Y. Zhang, Y. L. Wang and G. L. Chen, Solid solution alloys of AlCoCrFeNiTix with excellent room-temperature mechanical properties, Appl. Phys. Lett. 90(18) (2007) 181904.
[5]Y. J. Zhou, Y. Zhang, T. N. Kim and G. L. Chen, Microstructure characterizations and strengthening mechanism of multi-principal component AlCoCrFeNiTi0.5 solid solution alloy with excellent mechanical properties, Mater. Lett. 62(17–18) (2008) 2673–2676.
[6]J. M. Wu, S. J. Lin, J. W. Yeh, S. K. Chen, Y. S. Huang and H. C. Chen, Adhesive wear behavior of AlxCoCrCuFeNi high-entropy alloys as a function of aluminum content, Wear 261(5–6) (2006) 513–519.
[7]M. H. Chuang, M. H. Tsai, W. R. Wang, S. J. Lin and J. W. Yeh, Microstructure and wear behavior of AlxCo1.5CrFeNi1.5Tiy high-entropy alloys, Acta Mater. 59(16) (2011) 6308–6317.
[8]Y. J. Hsu, W. C. Chiang and J. K. Wu, Corrosion behavior of FeCoNiCrCux high-entropy alloys in 3.5% sodium chloride solution, Mater. Chem. Phys. 92(1) (2005) 112–117.
[9]C. P. Lee, Y. Y. Chen, C. Y. Hsu, J. W. Yeh and H. C. Shih, The effect of Boron on the corrosion resistance of the high entropy alloys Al0.5CoCrCuFeNiBx, J. Electrochem. Soc. 154(8) (2007) C424–C430.
[10]D. H. Xiao, P. F. Zhou, W. Q. Wu, H. Y. Diao, M. C. Gao, M. Song and P. K. Liaw, Microstructure, mechanical and corrosion behaviors of AlCoCuFeNi-(Cr,Ti) high entropy alloys, Mater. Des. 116 (2017) 438–447.
[11]S. T. Chen, W. Y. Tang, Y. F. Kuo, S. Y. Chen, C. H. Tsau, T. T. Shun and J. W. Yeh, Microstructure and properties of age-hardenable AlxCrFe1.5MnNi0.5 alloys, Mater. Sci. Eng. A 527(21–22) (2010) 5818–5825.
[12]J. Chen, X. Zhou, W. Wang, B. Liu, Y. Lv, W. Yang, D. Xu and Y. Liu, A review on fundamental of high entropy alloys with promising high–temperature properties, J. Alloys Compd. 760 (2018) 15–30.
[13]H. Zhang, Y. Z. He, Y. Pan and S. Guo, Thermally stable laser cladded CoCrCuFeNi high-entropy alloy coating with low stacking fault energy, J. Alloys Compd. 600 (2014) 210–214.
[14]X. B. Feng, H. K. Yang, R. Fan, W. Q. Zhang, F. L. Meng, B. Gan and Y. Lu, Heavily twinned CoCrNi medium-entropy alloy with superior strength and crack resistance, Mater. Sci. Eng. A 788 (2020) 139591.
[15]J. P. Liu, J. X. Chen, T. W. Liu, C. Li, Y. Chen and L. H. Dai, Superior strength-ductility CoCrNi medium-entropy alloy wire, Scr. Mater. 181 (2020) 19–24.
[16]H. Q. Xu, Z. Y. Li, W. Zhou, L. H. Ma, M. D. Zhang and G. Li, Aluminum and titanium alloyed non-equiatomic Co–Fe–Ni medium-entropy alloy with ultra high strength and hardness, Mater. Sci. Eng. A 817 (2021) 141297.
[17]G. Laplanche, A. Kostka, C. Reinhart, J. Hunfeld, G. Eggeler and E. P. George, Reasons for the superior mechanical properties of medium-entropy CrCoNi compared to high-entropy CrMnFeCoNi, Acta Mater. 128 (2017) 292–303.
[18]A. S. Tirunilai, T. Hanemann, C. Reinhart, V. Tschan, K. P. Weiss, G. Laplanche, J. Freudenberger, M. Heilmaier and A. Kauffmann, Comparison of cryogenic deformation of the concentrated solid solutions CoCrFeMnNi, CoCrNi and CoNi, Mater. Sci. Eng. A 783 (2020) 139290.
[19]B. Gludovatz, A. Hohenwarter, K. V. Thurston, H. Bei, Z. Wu, E. P. George and R. O. Ritchie, Exceptional damage-tolerance of a medium-entropy alloy CrCoNi at cryogenic temperatures, Nat. Commun. 7 (2016) 10602.
[20]Z. Wu, H. Bei, G. M. Pharr and E. P. George, Temperature dependence of the mechanical properties of equiatomic solid solution alloys with face-centered cubic crystal structures, Acta Mater. 81 (2014) 428–441.
[21]N. Chawake, J. Zálešák, C. Gammer, R. Franz, M. J. Cordill, J. T. Kim and J. Eckert, Microstructural characterization of medium entropy alloy thin films, Scr. Mater. 177 (2020) 22–26.
[22]N. Wang, Q. P. Cao, X. D. Wang, D. X. Zhang and J. Z. Jiang, Tuning microstructure and enhancing mechanical properties of Co-Ni-V-Al medium entropy alloy thin films via deposition power, J. Alloys Compd. 875 (2021) 160003.
[23]F. Cao, P. Munroe, Z. Zhou and Z. Xie, Medium entropy alloy CoCrNi coatings: Enhancing hardness and damage-tolerance through a nanotwinned structuring, Surf. Coat. Technol. 335 (2018) 257–264.
[24]M. P. Agustianingrum, S. Yoshida, N. Tsuji and N. Park, Effect of aluminum addition on solid solution strengthening in CoCrNi medium-entropy alloy, J. Alloys Compd. 781 (2019) 866–872.
[25]D. Lee, H. U. Jeong, K. H. Lee, J. B. Jeon and N. Park, Precipitation and grain-boundary strengthening of Al-added CoCrNi medium-entropy alloys, Mater. Lett. 250 (2019) 127–130.
[26]W. Lu, X. Luo, Y. Yang, J. Zhang and B. Huang, Effects of Al addition on structural evolution and mechanical properties of the CrCoNi medium-entropy alloy, Mater. Chem. Phys. 238 (2019) 121841.
[27]D. Lee, M. P. Agustianingrum, N. Park and N. Tsuji, Synergistic effect by Al addition in improving mechanical performance of CoCrNi medium-entropy alloy, J. Alloys Compd. 800 (2019) 372–378.
[28]R. Chang, W. Fang, H. Yu, X. Bai, X. Zhang, B. Liu and F. Yin, Heterogeneous banded precipitation of (CoCrNi)93Mo7 medium entropy alloys towards strength–ductility synergy utilizing compositional inhomogeneity, Scr. Mater. 172 (2019) 144–148.
[29]N. Li, J. Gu, B. Gan, Q. Qiao, S. Ni and M. Song, Effects of Mo-doping on the microstructure and mechanical properties of CoCrNi medium entropy alloy, J. Mater. Res. 35(20) (2020) 2726–2736.
[30]Z. Wu, W. Guo, K. Jin, J. D. Poplawsky, Y. Gao and H. Bei, Enhanced strength and ductility of a tungsten-doped CoCrNi medium-entropy alloy, J. Mater. Res. 33(19) (2018) 3301–3309.
[31]R. Chang, W. Fang, X. Bai, C. Xia, X. Zhang, H. Yu, B. Liu and F. Yin, Effects of tungsten additions on the microstructure and mechanical properties of CoCrNi medium entropy alloys, J. Alloys Compd. 790 (2019) 732–743.
[32]W. Qu, Y. Hou, H. Ren, M. Zhang and Y. Ji, Grain refinement of the CrMnFeCoNi high entropy alloy cast ingots by adding lanthanum, Metall. Mater. Trans. B 52(3) (2021) 1194–1199.
[33]D. Yao, F. Qiu, Q. Jiang, Y. Li and L. Arnberg, Effect of lanthanum on grain refinement of casting Aluminum-Copper alloy, Int. J. Metalcast. 7(1) (2015) 49–54.
[34]G. Y. Lin, K. Li, D. Feng, Y. P. Feng, W. Y. Song and M. Q. Xiao, Effects of La–Ce addition on microstructure and mechanical properties of Al–18Si–4Cu–0.5Mg alloy, Trans. Nonferrous Met. Soc. China 29(8) (2019) 1592–1600.
[35]Q. J. Zheng, L. L. Zhang, H. X. Jiang, J. Z. Zhao and J. He, Effect mechanisms of micro-alloying element La on microstructure and mechanical properties of hypoeutectic Al-Si alloys, J. Mater. Sci. Technol. 47 (2020) 142–151.
[36]J. W. Yeh, Recent progress in high-entropy alloys, Ann. Chim.-Sci. Mat. 31(6) (2006) 633–648.
[37]J. W. Yeh, Alloy design strategies and future trends in high-entropy alloys, JOM 65(12) (2013) 1759–1771.
[38]J. W. Yeh, Physical metallurgy of high-entropy alloys, JOM 67(10) (2015) 2254–2261.
[39]Y. Zhang, Y. J. Zhou, J. P. Lin, G. L. Chen and P. K. Liaw, Solid-solution phase formation rules for multi-component alloys, Adv. Eng. Mater. 10(6) (2008) 534–538.
[40]M. C. Gao, P. K. Liao, J. W. Yeh and Y. Zhang, High-entropy alloys: Fundamentals and applications, Springer International Publishing: Cham, Switzerland, 2016.
[41]M. H. Tsai and J. W. Yeh, High-entropy alloys: A critical review, Mater. Res. Lett. 2(3) (2014) 107–123.
[42]K. Y. Tsai, M. H. Tsai and J. W. Yeh, Sluggish diffusion in Co–Cr–Fe–Mn–Ni high-entropy alloys, Acta Mater. 61(13) (2013) 4887–4897.
[43]T. T. Shun, C. H. Hung and C. F. Lee, Formation of ordered/disordered nanoparticles in FCC high entropy alloys, J. Alloys Compd. 493(1–2) (2010) 105–109.
[44]C. J. Tong, Y. L. Chen, J. W. Yeh, S. J. Lin, S. K. Chen, T. T. Shun, C. H. Tsau and S. Y. Chang, Microstructure characterization of AlxCoCrCuFeNi high-entropy alloy system with multiprincipal elements, Metall. Mater. Trans. A 36 (2005) 881–893.
[45]M. H. Tsai, H. Yuan, G. Cheng, W. Xu, K. Y. Tsai, C. W. Tsai, W. W. Jian, C. C. Juan, W. J. Shen, M. H. Chuang, J. W. Yeh and Y. T. Zhu, Morphology, structure and composition of precipitates in Al0.3CoCrCu0.5FeNi high-entropy alloy, Intermetallics 32 (2013) 329–336.
[46]J. W. Yeh, S. J. Lin, T. S. Chin, J. Y. Gan, S. K. Chen, T. T. Shun, C. H. Tsau and S. Y. Chou, Formation of simple crystal structures in Cu-Co-Ni-Cr-Al-Fe-Ti-V alloys with multiprincipal metallic elements, Metall. Mater. Trans. A 35(8) (2004) 2533–2536.
[47]Q. He and Y. Yang, On lattice distortion in high entropy alloys, Front. Mater. 5 (2018).
[48]Z. Wang, Q. Fang, J. Li, B. Liu and Y. Liu, Effect of lattice distortion on solid solution strengthening of BCC high-entropy alloys, J. Mater. Sci. Technol. 34(2) (2018) 349–354.
[49]Y. Zhang, X. Yang and P. K. Liaw, Alloy design and properties optimization of high-entropy alloys, JOM 64(7) (2012) 830–838.
[50]J. Chen, P. Niu, Y. Liu, Y. Lu, X. Wang, Y. Peng and J. Liu, Effect of Zr content on microstructure and mechanical properties of AlCoCrFeNi high entropy alloy, Mater. Des. 94 (2016) 39–44.
[51]M. H. Tsai, Physical properties of high entropy alloys, Entropy 15(12) (2013) 5338–5345.
[52]S. Ranganathan, Alloyed pleasures: Multimetallic cocktails, Curr. Sci. 85(10) (2003) 1404–1406.
[53]O. N. Senkov, G. B. Wilks, D. B. Miracle, C. P. Chuang and P. K. Liaw, Refractory high-entropy alloys, Intermetallics 18(9) (2010) 1758–1765.
[54]O. N. Senkov, G. B. Wilks, J. M. Scott and D. B. Miracle, Mechanical properties of Nb25Mo25Ta25W25 and V20Nb20Mo20Ta20W20 refractory high entropy alloys, Intermetallics 19(5) (2011) 698–706.
[55]S. Yoshida, T. Bhattacharjee, Y. Bai and N. Tsuji, Friction stress and Hall-Petch relationship in CoCrNi equi-atomic medium entropy alloy processed by severe plastic deformation and subsequent annealing, Scr. Mater. 134 (2017) 33–36.
[56]H. W. Deng, Z. M. Xie, B. L. Zhao, Y. K. Wang, M. M. Wang, J. F. Yang, T. Zhang, Y. Xiong, X. P. Wang, Q. F. Fang and C. S. Liu, Tailoring mechanical properties of a CoCrNi medium-entropy alloy by controlling nanotwin-HCP lamellae and annealing twins, Mater. Sci. Eng. A 744 (2019) 241–246.
[57]J. Q. Zhao, H. Tian, Z. Wang, X. J. Wang and J. W. Qiao, FCC-to-HCP phase transformation in CoCrNix medium-entropy alloys, Acta Metall. Sin. (Engl. Lett.) 33(8) (2020) 1151–1158.
[58]S. Praveen, J. W. Bae, P. Asghari-Rad, J. M. Park and H. S. Kim, Ultra-high tensile strength nanocrystalline CoCrNi equi-atomic medium entropy alloy processed by high-pressure torsion, Mater. Sci. Eng. A 735 (2018) 394–397.
[59]S. Praveen, J. W. Bae, P. Asghari-Rad, J. M. Park and H. S. Kim, Annealing-induced hardening in high-pressure torsion processed CoCrNi medium entropy alloy, Mater. Sci. Eng. A 734 (2018) 338–340.
[60]I. Moravcik, V. Hornik, P. Minárik, L. Li, I. Dlouhy, M. Janovska, D. Raabe and Z. Li, Interstitial doping enhances the strength-ductility synergy in a CoCrNi medium entropy alloy, Mater. Sci. Eng. A 781 (2020) 139242.
[61]I. Moravcik, H. Hadraba, L. Li, I. Dlouhy, D. Raabe and Z. Li, Yield strength increase of a CoCrNi medium entropy alloy by interstitial nitrogen doping at maintained ductility, Scr. Mater. 178 (2020) 391–397.
[62]N. An, Y. Sun, Y. Wu, J. Tian, Z. Li, Q. Li, J. Chen and X. Hui, High temperature strengthening via nanoscale precipitation in wrought CoCrNi-based medium-entropy alloys, Mater. Sci. Eng. A 798 (2020) 140213.
[63]Y. Zhang, T. T. Zuo, Z. Tang, M. C. Gao, K. A. Dahmen, P. K. Liaw and Z. P. Lu, Microstructures and properties of high-entropy alloys, Prog. Mater. Sci. 61 (2014) 1–93.
[64]H. Yao, J. W. Qiao, M. Gao, J. Hawk, S. G. Ma and H. Zhou, MoNbTaV medium-entropy alloy, Entropy 18(5) (2016) 189.
[65]A. Fu, B. Liu, W. Lu, B. Liu, J. Li, Q. Fang, Z. Li and Y. Liu, A novel supersaturated medium entropy alloy with superior tensile properties and corrosion resistance, Scr. Mater. 186 (2020) 381–386.
[66]P. J. Kelly and R. D. Arnell, Magnetron sputtering: a review of recent developments and applications, Vacuum 56(3) (2000) 159–172.
[67]X. H. Yan, J. S. Li, W. R. Zhang and Y. Zhang, A brief review of high-entropy films, Mater. Chem. Phys. 210 (2018) 12–19.
[68]A. Baptista, F. Silva, J. Porteiro, J. Míguez and G. Pinto, Sputtering physical vapour deposition (PVD) coatings: A critical review on process improvement and market trend demands, Coatings 8(11) (2018) 402.
[69]N. L. Okamoto, S. Fujimoto, Y. Kambara, M. Kawamura, Z. M. Chen, H. Matsunoshita, K. Tanaka, H. Inui and E. P. George, Size effect, critical resolved shear stress, stacking fault energy, and solid solution strengthening in the CrMnFeCoNi high-entropy alloy, Sci. Rep. 6 (2016) 35863.
[70]Z. Wu, H. Bei, F. Otto, G. M. Pharr and E. P. George, Recovery, recrystallization, grain growth and phase stability of a family of FCC-structured multi-component equiatomic solid solution alloys, Intermetallics 46 (2014) 131–140.
[71]P. E. Waudby, Rare earth additions to steel, Int. Met. Rev. 23(1) (1978) 74–98.
[72]M. M. Song, B. Song, W. B. Xin, G. L. Sun, G. Y. Song and C. L. Hu, Effects of rare earth addition on microstructure of C–Mn steel, Ironmak. Steelmak. 42(8) (2015) 594–599.
[73]L. J. Zhang, M. D. Zhang, Z. Zhou, J. T. Fan, P. Cui, P. F. Yu, Q. Jing, M. Z. Ma, P. K. Liaw, G. Li and R. P. Liu, Effects of rare-earth element, Y, additions on the microstructure and mechanical properties of CoCrFeNi high entropy alloy, Mater. Sci. Eng. A 725 (2018) 437–446.
[74]G. R. Li, M. Liu, H. M. Wang, D. Zhang, F. Tang, C. W. Wang, Y. T. Zhao, G. Chen and X. Z. Kai, Effect of the rare earth element yttrium on the structure and properties of boron-containing high-entropy alloy, JOM 72(6) (2020) 2332–2339.
[75]C. Wang, T. H. Li, Y. C. Liao, C. L. Li, J. S. C. Jang and C. H. Hsueh, Hardness and strength enhancements of CoCrFeMnNi high-entropy alloy with Nd doping, Mater. Sci. Eng. A 764 (2019) 138192.
[76]R. O. Scattergood and D. J. Bacon, The Orowan mechanism in anisotropic crystals, Philos. Mag. 31(1) (1975) 179–198.
[77]P. Rodriguez, Sixty years of dislocations, Bulletin of Materials Science 19(6) (1996) 857–872.
[78]E. O. Hall, The deformation and ageing of mild steel: III Discussion of results, Proc. Phys. Soc. B 64(9) (1951) 747–752.
[79]N. J. Petch, The cleavage strength of polycrystals, J. Iron Steel Inst. 174 (1953) 25–28.
[80]N. Hansen, Hall–Petch relation and boundary strengthening, Scr. Mater. 51(8) (2004) 801–806.
[81]C. E. Carlton and P. J. Ferreira, What is behind the inverse Hall–Petch effect in nanocrystalline materials?, Acta Mater. 55(11) (2007) 3749–3756.
[82]R. W. Armstrong, 60 years of Hall-Petch: Past to present nano-scale connections, Mater. Trans. 55(1) (2014) 2–12.
[83]E. O. Hall, Yield point phenomena in metals and alloys, Plenum Press, New York, 1970.
[84]Y. Li, A. J. Bushby and D. J. Dunstan, The Hall-Petch effect as a manifestation of the general size effect, Proc. R. Soc. A Math. Phys. Eng. Sci. 472(2190) (2016) 20150890.
[85]J. D. Eshelby, F. C. Frank and F. R. N. Nabarro, XLI. The equilibrium of linear arrays of dislocations, Lond.Edinb.Dubl.Phil.Mag. 42(327) (1951) 351–364.
[86]T. G. Nieh and J. Wadsworth, Hall-Petch relation in nanocrystalline solids, Scr. Metall. Mater. 25(4) (1991) 955–958.
[87]J. Wei, S. Jiang, Z. Chen and C. Liu, Increasing strength and ductility of a Mg–9Al alloy by dynamic precipitation assisted grain refinement during multi-directional forging, Mater. Sci. Eng. A 780 (2020) 139192.
[88]X. J. Guan, F. Shi, H. M. Ji and X. W. Li, A possibility to synchronously improve the high-temperature strength and ductility in face-centered cubic metals through grain boundary engineering, Scr. Mater. 187 (2020) 216–220.
[89]S. Tanigawa and M. Doyama, Hume-Rothery's 15% rule and the pseudo-alloy-atom model, Phys. Lett. A 43(1) (1973) 17–18.
[90]W. L. Chiou and S. Riegelman, Pharmaceutical applications of solid dispersion systems, J. Pharm. Sci. 60(9) (1971) 1281–1302.
[91]R. E. Smallman and A. H. W. Ngan, Physical metallurgy and advanced materials engineering, 7th ed., Butterworth-Heinemann2007.
[92]T. Gladman, Precipitation hardening in metals, Mater. Sci. Technol. 15(1) (2013) 30–36.
[93]A. I. Takeuchi, A., 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(12) (2005) 2817–2829.
[94]D. B. Miracle and O. N. Senkov, A critical review of high entropy alloys and related concepts, Acta Mater. 122 (2017) 448–511.
[95]U. M. R. Seelam and C. Suryanarayana, Metallography of sputter-deposited SS304+Al coatings, Metallogr., Microstruct., Anal. 2(5) (2013) 287–298.
[96]Y. C. Hsu, C. L. Li and C. H. Hsueh, Modifications of microstructures and mechanical properties of CoCrFeMnNi high entropy alloy films by adding Ti element, Surf. Coat. Technol. 399 (2020) 126149.
[97]S. Guo and C. T. Liu, Phase stability in high entropy alloys: Formation of solid-solution phase or amorphous phase, Prog. Nat. Sci.: Mater. Int. 21(6) (2011) 433–446.
[98]Y. Zhang, Z. P. Lu, S. G. Ma, P. K. Liaw, Z. Tang, Y. Q. Cheng and M. C. Gao, Guidelines in predicting phase formation of high-entropy alloys, MRS Commun. 4(2) (2014) 57–62.
[99]A. J. Zaddach, C. Niu, C. C. Koch and D. L. Irving, Mechanical properties and stacking fault energies of NiFeCrCoMn high-entropy alloy, JOM 65(12) (2013) 1780–1789.
[100]G. Laplanche, P. Gadaud, C. Bärsch, K. Demtröder, C. Reinhart, J. Schreuer and E. P. George, Elastic moduli and thermal expansion coefficients of medium-entropy subsystems of the CrMnFeCoNi high-entropy alloy, J. Alloys Compd. 746 (2018) 244–255.
[101]Y. C. Hsu, C. L. Li and C. H. Hsueh, Effects of Al addition on microstructures and mechanical properties of CoCrFeMnNiAlx high entropy alloy films, Entropy 22(1) (2019) 2.
[102]J. Schiotz and K. W. Jacobsen, A maximum in the strength of nanocrystalline copper, Science 301(5638) (2003) 1357–1359.
[103]J. Hu, Y. N. Shi, X. Sauvage, G. Sha and K. Lu, Grain boundary stability governs hardening and softening in extremely fine nanograined metals, Science 355(6331) (2017) 1292–1296.
[104]X. Gu, H. Luan, X. Yang, X. Wang, K. Fang, J. Li, Y. Jia, K. Yao, Z. Zhang and N. Chen, Formation and properties of amorphous multi-component (CrFeMoNbZr)Ox Thin Films, Metals 10(5) (2020) 599.