Mechanical properties and microstructural evolution of heterogeneous nanostructured refractory medium/highentropy alloys

Metals are the most widely applied materials as structural parts in daily life. Metals with high strength and ductility, especially in extreme thermo-mechanical service environment, have been pursued for a long time. Refractory medium/high-entropy alloys (RM/HEAs) could maintain the notable strength, even at elevated temperatures. Thus, the RM/HEAs have recently attracted extensive attention as promising candidates in structural material applications. Furthermore, uniformly reducing the grain size to nanoscale is able to further strengthen the RM/HEAs. However, it always results in the mechanical instability and strain localization, due to the severe inhibition of the homogenous plasticity controlled by dislocation multiplications and motions, leading to the catastrophic brittleness and deterioration of wear resistance. Fortunately, such issue can be apparently alleviated by developing heterogeneous nanostructures, including gradient nanostructure (GNS) or / and amorphous-crystalline nanostructure. In a heterogeneous nanostructured alloy, homogeneous plastic deformation can be effectively harvested through the cooperation of strain/stress distribution of the various domains. It thus effectively inhibits the strain localization, suppresses the mechanical instability, and delays the microcrack initiation and propagation, for which the strength-ductility synergy can be achieved, and the wear performance can be improved.

Recent years, increasing research works have been devoted to developing heterogeneous nanostructured RM/HEAs. However, the relevant works are still at an initial stage. Far less efforts have been taken to clarify the underlying mechanisms, including heterogeneous nanostructure formation mechanism, deformation mechanism in plastic deformations and wears, etc. Uncovering the underlying mechanisms is a very critical prerequisite to get deep insights into the design of materials with strength-ductility synergy, which promote developing RM/HEAs with superior mechanical performance.

Therefore, in this work, two strategies of laser surface remelting and elevated temperature sliding are proposed to develop heterogeneous nanostructured RM/HEAs which include the gradient nanostructured TiZrHfTaNb RHEA, the amorphous-crystalline plus gradient nanostructured TiZrHfTaNb0.2 RHEA, and amorphous-crystalline plus gradient nanostructured TaMoNb MEA film. The underlying microstructural evolution upon the laser surface treatment and sliding wears are systematically examined for clarifying the corresponding microstructure-property relationship. Three parts are included to elaborate these two strategies carried out on three kinds of RM/HEAs.

In the first part, a novel laser surface treatment technique is carried out to successfully fabricate a ~ 100 μm-thick GNS layer on a promising TiZrHfTaNb RHEA. Microstructural characterizations in various depths of the GNS layer reveal that the laser-treated phase decomposition-mediated gradient grain size refinement mechanism dominated the formation of the GNS layer. Consequently, the facile laser surface remelting-induced GNS TiZrHfTaNb RHEA shows a significantly enhanced wear performance comparing with the as-cast counterpart, with the wear rate decreasing by an order of magnitude.

In the second part, the glass-forming ability of TiZrHfTaNb0.2 HEA is effectively enhanced by decreasing Nb elemental content, leading to fabricating a ~ 5 μm-thick amorphous-nanocrystalline layer on the ~ 100 μm-thick GNS surface by the laser surface remelting. The specific amorphous-nanocrystalline layer shows an ultrahigh yield strength of ~ 6.0 GPa with a compressive strain of ~ 25% during the localized micropillar compression tests. The atomic observations reveal that cooperative co-deformation mechanisms including the well-retained dislocation activities in nanograins but crystallization in amorphous GBs, which subsequently lead to the grain coarsening via GB-mediated plasticity.

In the third part, a strategy is proposed to achieve superior wear resistance via the in-situ forming amorphous-crystalline nanocomposite layer and GNS during wear at an elevated temperature. This strategy is realized in a magnetron-sputtered RMEA TaMoNb film upon sliding wear at 300 ℃. The detailed cross-sectional wear-induced microstructures are analyzed to uncover the wear mechanism, which reveals that a dense 300 nm-thick nanocomposite layer comprising equiaxed nanograins of only ~ 6 nm embedded in the amorphous oxide matrix covers on the 600 nm-thick plastic deformation region with gradient nanostructure. Consequently, the TaMoNb film shows a remarkably low wear rate upon wear at 300 ℃, less than 25% of those at RT and 400 ℃. Such superior wear resistance should be attributed to the particular wear-induced microstructure at 300 ℃ which has high strength and large homogeneous deformation.

This thesis presents an original study of structure-property relationship of heterogeneous nanostructured RM/HEAs, which is expected to contribute the in-depth comprehension of the underlying grain refinement, deformation, strengthening and wear mechanisms of the studied RM/HEAs. It will make contributions to both the scientific study and the commercial application of RM/HEAs. The originality and significance of this thesis can be identified by (i) developing a novel laser surface treatment technique for fabricate a GNS layer on a TiZrHfTaNbx RHEA; (ii) revealing the grain refinement mechanism during the laser surface treatment; (iii) verifying the improvements of the laser-treated induced GNS layer on the mechanical properties and revealing the strengthening mechanisms involved; (iv) proposing a strategy to achieve exceptional wear performance via in situ forming the amorphous-crystalline nanocomposite layer and GNS during wear at an elevated temperature; (v) revealing the formation mechanisms of sliding wear induced amorphous-crystalline nanocomposite layer and GNS and revealing the wear mechanisms involved.

[1] Alvi, S., Jarzabek, D., gilzad kohan, M., Hedman, D., Jenczyk, P., Natile, M., Vomiero, A., Akhtar, F., 2020. Synthesis and Mechanical Characterization of a CuMoTaWV High-Entropy Film by Magnetron Sputtering. ACS Appl. Mater. Int. 12, 21070-21079.
[2] An, X.H., Wu, S.D., Wang, Z.G., Zhang, Z.F., 2019. Significance of stacking fault energy in bulk nanostructured materials: Insights from Cu and its binary alloys as model systems. Prog. Mater. Sci. 101, 1-45.
[3] An, Z., Mao, S., Liu, Y., Zhou, H., Zhai, Y., Tian, Z., Liu, C., Zhang, Z., Han, X., 2021. Hierarchical grain size and nanotwin gradient microstructure for improved mechanical properties of a non-equiatomic CoCrFeMnNi high-entropy alloy. J. Mater. Sci. Technol. 92, 195-207.
[4] Archard, J.F., 1953. Contact and Rubbing of Flat Surfaces. J. Appl. Phys. 24, 981-988.
[5] Argibay, N., Furnish, T.A., Boyce, B.L., Clark, B.G., Chandross, M., 2016. Stress-dependent grain size evolution of nanocrystalline Ni-W and its impact on friction behavior. Scripta Mater. 123, 26-29.
[6] Argon, A., 2008. Strengthening Mechanisms in Crystal Plasticity.
[7] Balluffi, R., Ruoff, A., 1963. On Strain‐Enhanced Diffusion in Metals. I. Point Defect Models. J. Appl. Phys. 34, 1634-1647.
[8] Blau, P., Julian, P., 2010. Elevated-temperature tribology of metallic materials. Tribol. Int. 43, 1203-1208.
[9] Braic, V., Balaceanu, M., Braic, M., Vladescu, A., Panseri, S., Russo, A., 2012. Characterization of multi-principal-element (TiZrNbHfTa)N and (TiZrNbHfTa)C coatings for biomedical applications. J. Mech.Behav. Biomed. Mater. 10, 197-205.
[10] Cantor, B., Chang, I., Knight, P., Vincent, A.J.B., 2004. Microstructural development in equiatomic multicomponent alloys. Mater. Sci. Eng. A 375-377, 213-218.
[11] Cao, P., 2020. The Strongest Size in Gradient Nanograined Metals. Nano Lett. 2, 1440-1446.
[12] Carney, C., Dogan, O., Jablonksi, P., Hawk, J., Alman, D., 2015. Design of Refractory High-Entropy Alloys. JOM 67.
[13] Cavaliere, P., 2015. Mechanical Properties of Nanocrystalline Materials, pp. 3-16.
[14] Chen, G., Qiao, J.W., Jiao, Z.M., Zhao, D., Zhang, T.W., Ma, S.G., Wang, Z.H., 2019a. Strength-ductility synergy of Al0.1CoCrFeNi high-entropy alloys with gradient hierarchical structures. Scripta Mater. 167, 95-100.
[15] Chen, H., Cui, H.-Z., Jiang, D., Song, X., Zhang, L., Ma, G., Gao, X., Niu, H., Zhao, X., Li, J., Zhang, C., Wang, R., Sun, X., 2021. Formation and Beneficial Effects of the Amorphous/Nanocrystalline Phase in Laser Remelted (FeCoCrNi)75Nb10B8Si7 High-Entropy Alloy Coatings Fabricated by Plasma Cladding. J. Alloys Compd. 899, 163277.
[16] Chen, H., Kauffmann, A., Gorr, B., Schliephake, D., Seemüller, C., Wagner, J.N., Christ, H.J., Heilmaier, M., 2015. Microstructure and mechanical properties at elevated temperatures of a new Al-containing refractory high-entropy alloy Nb-Mo-Cr-Ti-Al. J. Alloys Compd. 661.
[17] Chen, M.-R., Lin, S.-J., Yeh, J.-W., Chuang, M.-H., Lee, P.-H., Huang, Y.-S., 2006. Effect of vanadium addition on the microstructure, hardness, and wear resistance of Al 0.5 CoCrCuFeNi high-entropy alloy. Metall. Mater. Trans. A 37, 1363-1369.
[18] Chen, S., Tseng, K.-K., Tong, Y., Li, W., Tsai, C.-W., Yeh, J.-W., Liaw, P.K., 2019b. Grain growth and Hall-Petch relationship in a refractory HfNbTaZrTi high-entropy alloy. J. Alloys Compd. 795, 19-26.
[19] Chen, X., Han, Z., Li, X., Lu, K., 2016. Lowering coefficient of friction in Cu alloys with stable gradient nanostructures. Sci. Adv. 2, e1601942.
[20] Chen, X., Han, Z., Lu, K., 2014. Wear mechanism transition dominated by subsurface recrystallization structure in Cu–Al alloys. Wear 320, 41–50.
[21] Chen, X., Han, Z., Lu, K., 2018. Friction and Wear Reduction in Copper with a Gradient Nano-grained Surface Layer. ACS Appl. Mater. Inter. 10, 13829-13838.
[22] Cheng, Z., Wang, S., Wu, G., Gao, J., Yang, X., Wu, H., 2022. Tribological properties of high-entropy alloys: A review. Int. J. Miner. Metall. Mater. 29, 389-403.
[23] Cheng, Z., Yang, L., Huang, Z., Wan, T., Zhu, M., Ren, F., 2021. Achieving low wear in a μ-phase reinforced high-entropy alloy and associated subsurface microstructure evolution. Wear 474-475, 203755.
[24] Cheng, Z., Zhou, H., Lu, Q., Gao, H., Lu, L., 2018a. Extra strengthening and work hardening in gradient nanotwinned metals. Science 362, eaau1925.
[25] Cheng, Z., Zhou, H., Lu, Q., Gao, H., Lu, L., 2018b. Extra strengthening and work hardening in gradient nanotwinned metals. Science 362, eaau1925.
[26] Coury, F.G., Kaufman, M., Clarke, A., 2019. Solid-solution strengthening in refractory high entropy alloys. Acta Mater. 175.
[27] Curry, J., Babuska, T., Furnish, T., lu, P., Adams, D., Kustas, A., Nation, B., Dugger, M., Chandross, M., Clark, B., Boyce, B., Schuh, C., Argibay, N., 2018. Achieving Ultralow Wear with Stable Nanocrystalline Metals. Adv. Mater. 30, 1802026.
[28] Das, G., 1972. A new structure of sputtered tantalum. Thin Solid Films 12, 305-311.
[29] Deng, G., Tieu, K., Lan, X., Su, L., Wang, L., Zhu, Q., Zhu, H., 2019. Effects of normal load and velocity on the dry sliding tribological behaviour of CoCrFeNiMo0.2 high entropy alloy. Tribol. Int. 144, 106116.
[30] Diao, H.Y., Feng, R., Dahmen, K.A., Liaw, P.K., 2017. Fundamental deformation behavior in high-entropy alloys: An overview. Curr. Opin. Solid State Mater. Sci. 21, 252-266.
[31] Dirras, G., Lilensten, L., Djemia, P., Laurent-Brocq, M., Tingaud, D., Couzinie, J.-P., Perrière, L., Chauveau, T., Guillot, I., 2016. Elastic and plastic properties of as-cast equimolar TiHfZrTaNb high-entropy alloy. Mater. Sci. Eng. A 654, 30-38.
[32] Divinski, S., Pokoev, A., Neelamegan, E., Paul, A., 2018. A Mystery of "Sluggish Diffusion" in High-Entropy Alloys: The Truth or a Myth? Diffusion Foundations 17, 69-104.
[33] Dobbelstein, H., Thiele, M., Gurevich, E., George, E., Ostendorf, A., 2016. Direct Metal Deposition of Refractory High Entropy Alloy MoNbTaW. Physics Procedia 83, 624-633.
[34] Du, L.M., Lan, L.W., Zhu, S., Yang, H.J., Shi, X.H., Liaw, P.K., Qiao, J.W., 2018. Effects of temperature on the tribological behavior of Al0.25CoCrFeNi high-entropy alloy. J. Mater. Sci. Technol. 35.
[35] Erdemir, A., 2005. A crystal chemical approach to the formulation of self-lubricating nanocomposite coatings. Surf. Coat. Tech. 200, 1792-1796.
[36] Erdemir, A., 2012. A crystal-chemical approach to lubrication by solid oxides. Tribol. Lett. 8, 97-102.
[37] Fang, Q., Liu, F., Feng, H., Liaw, P., Jia, L., 2020a. Microstructure evolution and deformation mechanism of amorphous/crystalline high-entropy-alloy composites. J. Mater. Sci. Technol. 54.
[38] Fang, Q., Liu, F., Feng, H., Liaw, P., Jia, L., 2020b. Microstructure evolution and deformation mechanism of amorphous/crystalline high-entropy-alloy composites. J. Mater. Sci. Technol. 54, 14-19.
[39] Fang, S., Wang, C., Li, C.-L., Luan, J.-H., Jiao, Z.-B., Liu, C.-T., Hsueh, C.-H., 2020c. Microstructures and mechanical properties of CoCrFeMnNiV high entropy alloy films. J. Alloys Compd. 820, 153388.
[40] Fang, T., Li, W., Tao, N., Lu, K., 2011. Revealing Extraordinary Intrinsic Tensile Plasticity in Gradient Nano-Grained Copper. Science 331, 1587-1590.
[41] Fang, T.H., Tao, N., Lu, K., 2014. Tension-induced softening and hardening in gradient nanograined surface layer in copper. Scripta Mater. 77, 17–20.
[42] Farhat, Z., Ding, Y., Northwood, D., Alpas, A.T., 1996. Effect of grain size on friction and wear of nanocrystalline aluminum. Mater. Sci. Eng. A 206, 302-313.
[43] Farkas, D., van swygenhoven, H., Derlet, P., 2002. Intergranular fracture in nanocrystalline metals. Phys. Rev. B 66, 060101.
[44] Feng, X., Zhang, J., Wang, Y., Hou, Z.Q., Wu, K., Liu, G., Sun, J., 2017a. Size effects on the mechanical properties of nanocrystalline NbMoTaW refractory high entropy alloy thin films. Int. J. Plast. 95.
[45] Feng, X.B., Fu, W., Zhang, J.Y., Zhao, J.T., Li, J., Wu, K., Liu, G., Sun, J., 2017b. Effects of nanotwins on the mechanical properties of Al x CoCrFeNi high entropy alloy thin films. Scripta Mater. 139, 71-76.
[46] Fu, H., Zhou, X., Wu, B., Qian, L., Yang, X.-S., 2021. Atomic-scale dissecting the formation mechanism of gradient nanostructured layer on Mg alloy processed by a novel high-speed machining technique. J. Mater. Sci. Technol. 82, 227-238.
[47] Fu, Z., Chen, W., Wen, H., Zhang, D., Chen, Z., Zheng, B., Zhou, Y., Lavernia, E., 2016. Microstructure and strengthening mechanisms in an FCC structured single-phase nanocrystalline Co25Ni25Fe25Al7.5Cu17.5 high-entropy alloy. Acta Mater. 107, 59-71.
[48] Gaertner, D., Kottke, J., Chumlyakov, Y., Hergemöller, F., Wilde, G., Divinski, S., 2020. Tracer diffusion in single crystalline CoCrFeNi and CoCrFeMnNi high-entropy alloys: Kinetic hints towards a low-temperature phase instability of the solid-solution? Scripta Mater. 187, 57-62.
[49] Glienke, M., Vaidya, M., Gururaj, K., Daum, L., Tas, B., Rogal, Ł., K G, P., Wilde, G., Divinski, S., 2020. Grain boundary diffusion in CoCrFeMnNi high entropy alloy: Kinetic hints towards a phase decomposition. Acta Mater. 195.
[50] Gludovatz, B., Hohenwarter, A., Catoor, D., Chang, E.H., George, E.P., Ritchie, R.O., 2014. A fracture-resistant high-entropy alloy for cryogenic applications. Science 345, 1153.
[51] Gubicza, J., Heczel, A., Kawasaki, M., Han, J.-K., Zhao, Y., Xue, Y., Huang, S., Lábár, J., 2019a. Evolution of microstructure and hardness in Hf25Nb25Ti25Zr25 high-entropy alloy during high-pressure torsion. J. Alloys Compd. 788.
[52] Gubicza, J., Hung, P.T., Kawasaki, M., Han, J.-K., Zhao, Y., Xue, Y., Lábár, J.L., 2019b. Influence of severe plastic deformation on the microstructure and hardness of a CoCrFeNi high-entropy alloy: A comparison with CoCrFeNiMn. Mater. Charact. 154, 304-314.
[53] Guo, N.N., Wang, L., Luo, L., Chen, R., su, Y., Guo, J.J., Fu, H.Z., 2015. Hot deformation characteristics and dynamic recrystallization of the MoNbHfZrTi refractory high-entropy alloy. Mater. Sci. Eng. A 651.
[54] Guo, W., Liu, B., Liu, Y., Li, T., Fu, A., Fang, Q., Nie, Y., 2019. Microstructures and mechanical properties of ductile NbTaTiV refractory high entropy alloy prepared by powder metallurgy. J. Alloys Compd. 776, 428-436.
[55] H. Okamoto, P.R.S., L. Kacprzak, 1990. Binary Alloy Phase Diagrams.
[56] Hall, E.O., 1951. The Deformation and Ageing of Mild Steel: III Discussion of Results. Proceedings of the Physical Society. Section B 64, 747-753.
[57] He, J.Y., Liu, W.H., Wang, H., wu, Y., Liu, X.J., Nieh, T.G., Lu, Z.P., 2014. Effects of Al addition on structural evolution and tensile properties of the FeCoNiCrMn high-entropy alloy system. Acta Mater. 62, 105–113.
[58] Hebert, R., Perepezko, J., Rösner, H., Wilde, G., 2016. Deformation-driven catalysis of nanocrystallization in amorphous Al alloys. Beilstein J. Nanotechnol. 7, 1428-1433.
[59] Hoogeveen, R., Moske, M., Geisler, H., Samwer, K., 1996. Texture and phase transformation of sputter-deposited metastable Ta films and TaCu multilayers. Thin Solid Films 275, 203-206.
[60] Hou, Z., Zhang, P., Wu, K., Wang, Y., Liu, G., Zhang, G., Sun, J., 2019. Size dependent phase transformation and mechanical behaviors in nanocrystalline Ta thin films. Int. J. Refract. Met. 82, 7-14.
[61] Hsu, C.-Y., Sheu, T.-S., Yeh, J.-W., Lee, P.-H., 2010. Effect of iron content on wear behavior of AlCoCrFe x Mo 0.5Ni high-entropy alloys. Wear 268, 653-659.
[62] Huang, C., Zhang, Y., Shen, J., Vilar, R., 2011. Thermal stability and oxidation resistance of laser clad TiVCrAlSi high entropy alloy coatings on Ti-6A1-4V alloy. Surf. Coat. Tech. 206, 1389–1395.
[63] Huang, H., Wu, Y., He, J., Wang, H., Liu, X., An, K., Wu, W., Lu, Z., 2017. Phase-Transformation Ductilization of Brittle High-Entropy Alloys via Metastability Engineering. Adv. Mater. 29, 1701678.
[64] Huang, H.W., Wang, Z.B., Lu, J., Lu, K., 2015. Fatigue behaviors of AISI 316L stainless steel with a gradient nanostructured surface layer. Acta Mater. 87.
[65] Huang, X., Hansen, N., Tsuji, N., 2006. Hardening by Annealing and Softening by Deformation in Nanostructured Metals. Science 312, 249-251.
[66] Jang, D., Greer, J., 2010. Transition From a Strong-Yet-Brittle to a Stronger-and-Ductile State by Size Reduction of Metallic Glasses. Nat. Mater. 9, 215-219.
[67] Jang, D., Greer, J.R., 2011. Size-induced weakening and grain boundary-assisted deformation in 60 nm grained Ni nanopillars. Scripta Mater. 64, 77-80.
[68] Jeong, D., Gonzalez, F., Palumbo, G., Aust, K., Erb, U., 2001. The effect of grain size on the wear properties of electrodeposited nanocrystalline nickel coatings. Scripta Mater. 44, 493-499.
[69] Jiang, L., Bai, Z., Powers, M., Fan, Y., Zhang, W., George, E., Misra, A., 2022. Deformation mechanisms in crystalline-amorphous high-entropy composite multilayers. Mater. Sci. Eng. A, 143144.
[70] Jiang, S., Mao, Z., Zhang, Y., Li, H., 2017. Mechanisms of nanocrystallization and amorphization of NiTiNb shape memory alloy subjected to severe plastic deformation. Procedia Engineering 207, 1493-1498.
[71] Jiang, W., Atzmon, M., 2003. The effect of compression and tension on shear-band structure and nanocrystallization in amorphous Al90Fe5Gd5: A high-resolution transmission electron microscopy study. Acta Mater. 51, 4095-4105.
[72] Joseph, J., Haghdadi, N., Shamlaye, K., Hodgson, P., Barnett, M., Fabijanic, D., 2019. The sliding wear behaviour of CoCrFeMnNi and AlxCoCrFeNi high entropy alloys at elevated temperatures. Wear.
[73] Juan, C.-C., Tseng, K.-K., Hsu, W.-L., Tsai, M., Tsai, C.-W., Lin, C.-M., Lee, P.-H., Lin, S.-J., Yeh, J.-W., 2016. Solution strengthening of ductile refractory HfMoxNbTaTiZr high-entropy alloys. Mater. Lett. 175.
[74] Kang, B., Lee, J., Ryu, H.J., Hong, S., 2017. Ultra-high strength WNbMoTaV high-entropy alloys with fine grain structure fabricated by powder metallurgical process. Mater. Sci. Eng. A 712.
[75] Katnagallu, S., Wu, G., Singh, S.P., Nandam, S., Xia, W., Stephenson, L., Gleiter, H., Schwaiger, R., Hahn, H., Herbig, M., Raabe, D., Gault, B., Balachandran, S., 2020. Nanoglass–nanocrystal composite – a novel material class for enhanced strength –plasticity synergy. Small 2020, 2004400.
[76] Kim, J., Choi, Y., Suresh, S., Argon, A., 2002. Nanocrystallization During Nanoindentation of a Bulk Amorphous Metal Alloy at Room Temperature. Science 295, 654-657.
[77] Koch, C.C., Morris, D.G., Lu, K., Inoue, A., 2013. Ductility of Nanostructured Materials. MRS Bulletin 24, 54-58.
[78] Lee, S.-W., Huh, M., Chae, S., Lee, J.-C., 2006. Mechanism of the deformation-induced nanocrystallization in a Cu-based bulk amorphous alloy under uniaxial compression. Scripta Mater. 54, 1439-1444.
[79] Li, W.L., Tao, N., Lu, K., 2008. Fabrication of a gradient nano-micro-structured surface layer on bulk copper by means of a surface mechanical grinding treatment. Scripta Mater. 59, 546-549.
[80] Li, X., Jin, Z., Xin, Z., Lu, K., 2020a. Constrained minimal-interface structures in polycrystalline copper with extremely fine grains. Science 370, 831-836.
[81] Li, X., Lu, L., Li, J., Zhang, X., Gao, H., 2020b. Mechanical properties and deformation mechanisms of gradient nanostructured metals and alloys. Nat. Rev. Mater. 5, 706-723.
[82] Li, X.Y., Jin, Z.H., Zhou, X., Lu, K., 2020c. Constrained minimal-interface structures in polycrystalline copper with extremely fine grains. Science 370, 831-836.
[83] Li, Z., K G, P., Deng, Y., Raabe, D., Tasan, C., 2016. Metastable high-entropy dual-phase alloys overcome the strength–ductility trade-off. Nature 534, 227-230.
[84] Liang, D., Zhao, C., Zhu, W., Wei, P., Jiang, F., Ren, F., 2020. Significantly Enhanced Wear Resistance of an Ultrafine-Grained CrFeNi Medium-Entropy Alloy at Elevated Temperatures. Metall. Mater. Trans. A 51, 2834-2850.
[85] Lilensten, L., Couzinie, J.-P., Bourgon, J., Perrière, L., Dirras, G., Prima, F., Guillot, I., 2016. Design and tensile properties of a bcc Ti-rich high-entropy alloy with transformation-induced plasticity. Mater. Res. Lett. 5, 1-7.
[86] Lilensten, L., Couzinie, J.-P., Perrière, L., Hocini, A., Keller, C., Dirras, G., Guillot, I., 2017. Study of a bcc multi-principal element alloy: Tensile and simple shear properties and underlying deformation mechanisms. Acta Mater. 142.
[87] Liu, C., Li, Z., Lu, W., Bao, Y., Xia, W., Wu, X., Zhao, H., Gault, B., Liu, C., Herbig, M., Fischer, A., Dehm, G., Wu, G., Raabe, D., 2021. Reactive wear protection through strong and deformable oxide nanocomposite surfaces. Nat. Commun. 12, 5518.
[88] Liu, C., Liu, Y., Wang, Q., Liu, X., Bao, Y., Wu, G., Lu, J., 2020. Nano-Dual-Phase Metallic Glass Film Enhances Strength and Ductility of a Gradient Nanograined Magnesium Alloy. Adv. Sci. 7, 2001480.
[89] Liu, Q., Wang, G., Sui, X., Liu, Y., Li, X., Yang, J., 2019. Microstructure and mechanical properties of ultra-fine grained MoNbTaTiV refractory high-entropy alloy fabricated by spark plasma sintering. J. Mater. Sci. Technol. 35, 2600-2607.
[90] Liu, X., Lei, W., Ma, L., Liu, J., Cui, J., 2016a. Effect of Boron on the Microstructure, Phase Assemblage and Wear Properties of Al0.5CoCrCuFeNi High-Entropy Alloy. Rare Metal Mater. Eng. 45, 2201-2207.
[91] Liu, Y., Ma, S., Zhang, C., Zhang, T., Yang, H., Wang, Z., Qiao, J., 2016b. Tribological Properties of AlCrCuFeNi2 High-Entropy Alloy in Different Conditions. Metall. Mater. Trans. 47.
[92] Lu, J.Z., Luo, K., Zhang, Y., Sun, G., Gu, Y., Zhou, J., Ren, X.D., Zhang, X.-C., Zhang, L.F., Chen, K.M., Cui, C., Jiang, Y., 2010. Grain refinement mechanism of multiple laser shock processing impacts on ANSI 304 stainless steel. Acta Mater. 58, 5354-5362.
[93] Lu, K., 2014. Making strong nanomaterials ductile with gradients. Science 345, 1455-1456.
[94] Lu, K., 2016. Stabilizing nanostructures in metals using grain and twin boundary architectures. Nat. Rev. Mater. 1, 16019.
[95] Lu, Q., Shen, Y., Chen, X., Qian, L., Lu, K., 2004. Ultrahigh Strength and High Electrical Conductivity in Copper. Science 304, 422-426.
[96] Lu, Z.P., Wang, H., Chen, M.W., Baker, I., Yeh, J.-W., Liu, C., Nieh, T.G., 2015. An assessment on the future development of high-entropy alloys: Summary from a recent workshop. Intermetallics 66.
[97] Luo, J., Sun, W., Duan, R., Yang, W., Chan, K.C., Ren, F., Yang, X.-S., 2022. Laser surface treatment-introduced gradient nanostructured TiZrHfTaNb refractory high-entropy alloy with significantly enhanced wear resistance. J. Mater. Sci. Technol. 110, 43-56.
[98] Ma, E., Wu, X., 2019. Tailoring heterogeneities in high-entropy alloys to promote strength–ductility synergy. Nat. Commun. 10, 10.
[99] Ma, E., Zhu, T., 2017. Towards strength–ductility synergy through the design of heterogeneous nanostructures in metals. Mater. Today 20.
[100] Ma, G.Z., Song, K., Sun, B., Yan, Z.J., Kühn, U., Ding, C., Eckert, J., 2013. Effect of cold-rolling on the crystallization behavior of a CuZr-based bulk metallic glass. J. Mater. Sci. 48, 6825-6832.
[101] Ma, L., Wang, L., Zhang, T., Inoue, A., 2002. Bulk Glass Formation of Ti–Zr–Hf–Cu–M (M=Fe, Co, Ni) Alloys. Mater. Tran. 43, 277.
[102] Maier-Kiener, V., Schuh, B., George, E., Clemens, H., Hohenwarter, A., 2017. Nanoindentation testing as a powerful screening tool for assessing phase stability of nanocrystalline high-entropy alloys. Mater. Design 115, 479-485.
[103] Maiti, S., Steurer, W., 2015. Structural-disorder and its effect on the mechanical properties in single-phase TaNbHfZr high-entropy alloys. Acta Mater. 106.
[104] Mao, X., Sun, J., Feng, Y., Zhou, X., Zhao, X., 2019. High-temperature wear properties of gradient microstructure induced by ultrasonic impact treatment. Mater. Lett. 246.
[105] Mathiou, C., Poulia, A., Georgatis, E., Karantzalis, A.E., 2018. Microstructural features and dry - Sliding wear response of MoTaNbZrTi high entropy alloy. Mater. Chem. Phy. 210, 126-135.
[106] Ming, K., Gu, C., Su, Q., Xie, D., Wu, Y., Wang, Y., Shao, L., Nastasi, M., Wang, J., 2020. Strength and plasticity of amorphous ceramics with self-patterned nano-heterogeneities. Int. J. Plast. 134, 102837.
[107] Miracle, D., Senkov, O., 2016. A critical review of high entropy alloys and related concepts. Acta Mater. 122, 448-511.
[108] Murty, B.S., Yeh, J.-W., Ranganathan, S., 2014. High-Entropy Alloys, pp. 13-35.
[109] Nagarjuna, C., You, H.-J., Ahn, S., Song, J.-W., Jeong, K.-Y., Madavali, B., Song, G., Na, Y.-S., Won, J.W., Kim, H.-S., Hong, S.-J., 2021. Worn surface and subsurface layer structure formation behavior on wear mechanism of CoCrFeMnNi high entropy alloy in different sliding conditions. Appl. Surf. Sci. 549, 149202.
[110] Okamoto, H., 2010. Diagrams for Binary Alloys. ASM International, Materials Park, OH.
[111] Okamoto, N., Kashioka, D., Hirato, T., Inui, H., 2013. Specimen- and Grain-Size Dependence of Compression Deformation Behavior in Nanocrystalline Copper. Int. J. Plast. 56, 171-183.
[112] Otto, F., Dlouhy, A., Somsen, C., Bei, H., Eggeler, G., George, E., 2013. The influences of temperature and microstructure on the tensile properties of a CoCrFeMnNi high-entropy alloy. Acta Mater. 61, 5743-5755.
[113] Owen, L., Jones, N., 2018. Lattice distortions in high-entropy alloys. J. Mater. Res. 33, 2954-2969.
[114] Owen, L., Pickering, E., Playford, H., Stone, H., Tucker, M., Jones, N., 2017. An assessment of the lattice strain in the CrMnFeCoNi high-entropy alloy. Acta Mater. 122, 11-18.
[115] P. Villars, A.P., H. Okamoto, 1995. Handbook of Ternary Alloy Phase Diagrams ASM International, Materials Park, OH.
[116] Padmanabhan, K.A., Dinda, G., Hahn, H., Gleiter, H., 2007. Inverse Hall-Petch Effect and Grain Boundary Sliding Controlled Flow in Nanocrystalline Materials. Mater. Sci. Eng. A 452, 462-468.
[117] Pan, Q., Lu, L., 2022. Synthesis and deformation mechanics of gradient nanostructured materials. National Science Open 1, 20220010.
[118] Petch, N., 1953. The Cleavage Strength Of Polycrystals. J. Iron Steel Inst. Lond. 173, 25.
[119] Pickering, E., Jones, N., 2016. High-Entropy Alloys: A Critical Assessment of Their Founding Principles and Future Prospects. Int. Mater. Rev. 61.
[120] Pole, M., Sadeghilaridjani, M., Shittu, J., Ayyagari, A., Mukherjee, S., 2020. High temperature wear behavior of refractory high entropy alloys based on 4-5-6 elemental palette. J. Alloys Compd. 843, 156004.
[121] Popescu, A., Brânzoi, F., Constantin, I., Anastasescu, M., Burada, M., Mitrică, D., Anasiei, I., Olaru, M.-T., Constantin, V., 2021. Electrodeposition, Characterization, and Corrosion Behavior of CoCrFeMnNi High-Entropy Alloy Thin Films. Coatings 11, 1367.
[122] Poulia, A., Georgatis, E., Lekatou, A., Karantzalis, A., 2016. Microstructure and wear behavior of a refractory high entropy alloy. Int. J. Refract. Met. 57.
[123] Poulia, A., Georgatis, E., Lekatou, A., Karantzalis, A., 2017. Dry-Sliding Wear Response of MoTaWNbV High Entropy Alloy. Adv. Eng. Mater. 19, 1600535.
[124] Prasad, S.V., Battaile, C.C., Kotula, P.G., 2011. Friction transitions in nanocrystalline nickel. Scripta Mater. 64, 729-732.
[125] Ranganathan, S., 2003. Alloyed pleasures: Multimetallic cocktails. Current Science 85, 1025.
[126] Ren, F., Arshad, S., Bellon, P., Averback, R.S., Pouryazdan, M., Hahn, H., 2014. Sliding wear-induced chemical nanolayering in Cu–Ag, and its implications for high wear resistance. Acta Mater. 72, 148-158.
[127] Ribis, J., de Carlan, Y., 2012. Interfacial strained structure and orientation relationships of the nanosized oxide particles deduced from elasticity-driven morphology in oxide dispersion strengthened materials. Acta Mater. 60, 238-252.
[128] Rupert, T., Gianola, D., Gan, Y., Hemker, K., 2009. Experimental Observations of Stress-Driven Grain Boundary Migration. Science 326, 1686-1690.
[129] Rupert, T., Schuh, C., 2010. Sliding Wear of Nanocrystalline Ni-W: Structural Evolution and the Apparent Breakdown of Archard Scaling. Acta Mater. 58, 4137-4148.
[130] Rynio, C., Hattendorf, H., Klöwer, J., Eggeler, G., 2014. The evolution of tribolayers during high temperature sliding wear. Wear 315, 1-10.
[131] Sadeghilaridjani, M., Pole, M., Jha, S., Muskeri, S., Ghodki, N., Mukherjee, S., 2021. Deformation and tribological behavior of ductile refractory high-entropy alloys. Wear 478-479, 203916.
[132] Saeidi, K., Gao, X., Zhong, Y., Shen, Z.J., 2015. Hardened austenite steel with columnar sub-grain structure formed by laser melting. Mater. Sci. Eng. A 625, 221-229.
[133] Sakaki, K., Kawase, T., Hirato, M., Mizuno, M., Araki, H., Shirai, Y., Nagumo, M., 2006. The effect of hydrogen on vacancy generation in iron by plastic deformation. Scripta Mater. 55, 1031-1034.
[134] Sathiyamoorthi, P., Bae, J.W., Asghari-Rad, P., Park, J.M., Kim, H., 2018. Ultra-high tensile strength nanocrystalline CoCrNi equi-atomic medium entropy alloy processed by high-pressure torsion. Mater. Sci. Eng. A.
[135] Schuh, B., Völker, B., Todt, J., Schell, N., Perrière, L., Li, J., Couzinie, J.-P., Hohenwarter, A., 2017. Thermodynamic instability of a nanocrystalline, single-phase TiZrNbHfTa alloy and its impact on the mechanical properties. Acta Mater. 142, 201-212.
[136] Schuh, C., Lund, A., 2003. Atomistic basis for the plastic yield criterion of metallic glass. Nat. Mater. 2, 449-452.
[137] Senkov, O., Isheim, D., Seidman, D., Pilchak, A., 2016. Development of a Refractory High Entropy Superalloy. Entropy 18, 102.
[138] Senkov, O., Jensen, J., Pilchak, A.L., Miracle, D., Fraser, H.L., 2017. Compositional variation effects on the microstructure and properties of a refractory high-entropy superalloy AlMo 0.5 NbTa 0.5 TiZr. Mater. Design 139.
[139] Senkov, O., Miracle, D., Chaput, K., Couzinie, J.-P., 2018a. Development and exploration of refractory high entropy alloys—A review. J. Mater. Res. 33, 1-37.
[140] Senkov, O., Pilchak, A., Semiatin, S., 2018b. Effect of Cold Deformation and Annealing on the Microstructure and Tensile Properties of a HfNbTaTiZr Refractory High Entropy Alloy. Metall. Mater. Trans. A 49.
[141] Senkov, O., Senkova, S., Dimiduk, D., Woodward, C., Miracle, D., 2012. Oxidation behavior of a refractory NbCrMo0.5Ta0.5TiZr alloy. J. Mater. Sci. 47, 6522-6534.
[142] Senkov, O., Wilks, G., Miracle, D., Chuang, C., Liaw, P., 2010. Refractory high-entropy alloys. Intermetallics 18, 1758-1765.
[143] Senkov, O., Woodward, C., 2011. Microstructure and properties of a refractory NbCrMo0.5Ta0.5TiZr alloy. Mater. Sci. Eng. A 529, 311-320.
[144] Senkov, O.N., Semiatin, S.L., 2015. Microstructure and properties of a refractory high-entropy alloy after cold working. J. Alloys Compd. 649, 1110-1123.
[145] Senkov, O.N., Wilks, G.B., Scott, J.M., Miracle, D.B., 2011. Mechanical properties of Nb25Mo25Ta25W25 and V20Nb20Mo20Ta20W20 refractory high entropy alloys. Intermetallics 19, 698-706.
[146] Senkov, O.N., Woodward, C., Miracle, D.B., 2014. Microstructure and Properties of Aluminum-Containing Refractory High-Entropy Alloys. JOM 66, 2030-2042.
[147] Serdiuk, I., Sobol’, O., Grigoriev, S., Beresnev, V., Pogrebnjak, A., Kolesnikov, D., Nyemchenko, U., 2014. Tribological Characteristics of (TiZrHfVNbTa)N Coatings Applied Using the Vacuum Arc Deposition Method. J. Frict. Wear 35.
[148] Shahmir, H., He, J., Lu, Z., Kawasaki, M., Langdon, T., 2016. Effect of annealing on mechanical properties of a nanocrystalline CoCrFeNiMn high-entropy alloy processed by high-pressure torsion. Mater. Sci. Eng. A 676.
[149] Shahmir, H., Nili-Ahmadabadi, M., Shafiee, A., Andrzejczuk, M., Lewandowska, M., Langdon, T.G., 2018a. Effect of Ti on phase stability and strengthening mechanisms of a nanocrystalline CoCrFeMnNi high-entropy alloy. Mater. Sci. Eng. A 725, 196-206.
[150] Shahmir, H., Nili-Ahmadabadi, M., Shafiee, A., Langdon, T.G., 2018b. Effect of a minor titanium addition on the superplastic properties of a CoCrFeNiMn high-entropy alloy processed by high-pressure torsion. Mater. Sci. Eng. A 718, 468-476.
[151] Sheikh, S., Shafeie, S., Hu, Q., Ahlström, J., Persson, C., Veselý, J., Zýka, J., Klement, U., Guo, S., 2016. Alloy design for intrinsically ductile refractory high-entropy alloys. J. Appl. Phys. 120, 164902.
[152] Song, S.H., Chen, X.M., Weng, L.Q., 2011. Solute diffusion during high-temperature plastic deformation in alloys. Mater. Sci. Eng. A 528, 7196-7199.
[153] Spaepen, F., 1977. A Microscopic Mechanism for Steady State Inhomogeneous Flow in Metallic Glasses. Acta Metall. 25, 407-415.
[154] Stepanov, N., Yurchenko, N., Panina, E., Tikhonovsky, M., Zherebtsov, S., 2017. Precipitation-strengthened refractory Al0.5CrNbTi2V0.5 high entropy alloy. Mater. Lett. 188, 162-164.
[155] Stott, F.H., 2002. High-temperature sliding wear of metals. Tribol. Int. 35, 489–495.
[156] Tabor, D., 1951. The Hardness of Metals. Journal of the Institue of Metals 79, 67-76.
[157] Takeuchi, A., Chen, N., Wada, T., Yokoyama, Y., Kato, H., Inoue, A., Yeh, J.W., 2011. Pd20Pt20Cu20Ni20P20 high-entropy alloy as a bulk metallic glass in the centimeter. Intermetallics 19, 1546-1554.
[158] Talachi, A., Eizadjou, M., Manesh, H., Janghorban, K., 2011. Wear characteristics of severely deformed aluminum sheets by accumulative roll bonding (ARB) process. Mater. Charact. 62, 12-21.
[159] Tao, N., Wang, Z.B., Tong, W.P., Sui, M., Lu, J., Lu, K., 2002. An investigation of surface nanocrystallization mechanism in Fe induced by surface mechanical attrition treatment. Acta Mater. 50, 4603-4616.
[160] Tiwari, G., Mehrotra, R., 2008. Diffusion and Melting. Defect Diffus. Forum 279, 23-37.
[161] Tong, C.-J., Chen, M.-R., Yeh, J.-W., Lin, S.-J., Lee, P.-H., Shun, T.-T., Chang, S.-Y., 2005a. Mechanical performance of the AlXCoCrCuFeNi high-entropy alloy system with multiprincipal elements. Metall. Mater. Trans. A 36, 1263-1271.
[162] Tong, C.-J., Chen, Y.-L., Yeh, J.-W., Lin, S.-J., Lee, P.-H., Shun, T.-T., Tsau, C.-H., Chang, S.-Y., 2005b. Microstructure characterization of AlXCoCrCuFeNi high-entropy alloy system with multiprincipal elements. Metall. Mater. Trans. A 36, 881-893.
[163] Tong, Z., Liu, H., Jiao, J., Zhou, W., Yang, Y., Ren, X., 2020a. Improving the strength and ductility of laser directed energy deposited CrMnFeCoNi high-entropy alloy by laser shock peening. Addit. Manuf. 35, 101417.
[164] Tong, Z., Liu, H., Jiao, J., Zhou, W., Yang, Y., Ren, X., 2020b. Microstructure, microhardness and residual stress of laser additive manufactured CoCrFeMnNi high-entropy alloy subjected to laser shock peening. J. Mater. Process. Tech. 285, 116806.
[165] Tsai, C., Tsai, M., Yeh, J.-W., 2013. Sluggish diffusion in Co–Cr–Fe–Mn–Ni high-entropy alloys. Acta Mater. 61, 4887–4897.
[166] Tsai, M.-H., Yeh, J.-W., 2014. High-Entropy Alloys: A Critical Review. Mater. Res. Lett. 2, 107-123.
[167] Tsai, M.T., Huang, J.C., Tsai, W.Y., Chou, T.H., Chen, C.-F., Li, T.H., Jang, J.S.C., 2018. Effects of ultrasonic surface mechanical attrition treatment on microstructures and mechanical properties of high entropy alloys. Intermetallics 93, 113-121.
[168] Tu, C.-H., Wu, S.-K., Lin, C., 2020. A study on severely cold-rolled and intermediate temperature aged HfNbTiZr refractory high-entropy alloy. Intermetallics 126, 106935.
[169] Vaidya, M., Sen, S., Zhang, X., Frommeyer, L., Rogal, Ł., Sankaran, S., Grabowski, B., Wilde, G., Divinski, S., 2020. Phenomenon of ultra-fast tracer diffusion of Co in HCP high entropy alloys. Acta Mater. 196.
[170] Valiev, R., 2004. Nanostructuring of metals by severe plastic deformation for advanced properties. Nat. Mater. 3, 511-516.
[171] Valiev, R., Estrin, Y., Horita, Z., Langdon, T.G., Zehetbauer, M.J., Zhu, Y., 2015. Fundamentals of Superior Properties in Bulk NanoSPD Materials. Mater. Res. Lett. 4, 1-21.
[172] Verma, A., Abhyankar, A.C., Mohape, M.R., Gowtam, D.S., Deshmukh, V.P., Shanmugasundaram, T., 2019. High temperature wear in CoCrFeNiCux high entropy alloys: The role of Cu. Scripta Mater. 161, 28-31.
[173] Viat, A., Guillonneau, G., Fouvry, S., Kermouche, G., Sao Joao, S., Wehrs, J., Michler, J., Henne, J.-F., 2017. Brittle to ductile transition of tribomaterial in relation to wear response at high temperatures. Wear 392-393.
[174] Wang, L., Zhang, Y., Zeng, Z., Zhou, H., He, J., Liu, P., Chen, M., Han, J., Srolovitz, D.J., Teng, J., Guo, Y., Yang, G., Kong, D., Ma, E., Hu, Y., Yin, B., Huang, X., Zhang, Z., Zhu, T., Han, X., 2022. Tracking the sliding of grain boundaries at the atomic scale. Science 375, 1261-1265.
[175] Wang, M., Tasan, C., Ponge, D., Kostka, A., Raabe, D., 2014. Smaller is less stable: Size effects on twinning vs. transformation of reverted austenite in TRIP-maraging steels. Acta Mater. 79, 268–281.
[176] Wang, P., Han, Z., Lu, K., 2018. Enhanced tribological performance of a gradient nanostructured interstitial-free steel. Wear 402.
[177] Wang, Y., Chen, M., Zhou, F., Ma, E., 2002. High tensile ductility in a nanostructured metal. Nature 419, 912-915.
[178] Wang, Y., Li, J., Hamza, A., Barbee, T., 2007. Ductile crystalline-amorphous nanolaminates. Proc. Natl. Acad. Sci. U. S. A. 104, 11155–11160.
[179] Wang, Y., Liao, X., Zhao, Y., Lavernia, E., Ringer, S., Horita, Z., Langdon, T.G., Zhu, Y., 2010. The role of stacking faults and twin boundaries in grain refinement of a Cu–Zn alloy processed by high-pressure torsion. Mater. Sci. Eng. A 527, 4959-4966.
[180] Wang, Z., Wang, C., Zhao, Y., Hsu, Y.-C., Li, C.-L., Kai, J.-J., Liu, C.-T., Hsueh, C.-H., 2020. High hardness and fatigue resistance of CoCrFeMnNi high entropy alloy films with ultrahigh-density nanotwins. Int. J. Plast. 131, 102726.
[181] Wang, Z.X., Li, F.Y., Pan, M.X., Zhao, D.Q., 2005. Effects of high pressure on the nucleation of Cu60Zr20Hf10Ti10 bulk metallic glass. J. Alloys Compd. 388, 262-265.
[182] Waseem, O., Lee, J., Lee, H., Ryu, H.J., 2017. Supplementary Information: The effect of Ti on the sintering and mechanical properties of high-entropy alloy TixWTaVCr fabricated via spark plasma sintering for fusion plasma-facing materials.
[183] Wei, B., Wu, W., Xie, D., Nastasi, M., Wang, J., 2021. Strength, plasticity, thermal stability and strain rate sensitivity of nanograined nickel with amorphous ceramic grain boundaries. Acta Mater. 212, 116918.
[184] Wohlbier, T., 2021. Metallic Glasses and Their Composites.
[185] Wu, B., Fu, H., Zhou, X., Qian, L., Luo, J., Zhu, J., Lee, W., Yang, X., 2021a. Severe plastic deformation-produced gradient nanostructured copper with a strengthening-softening transition. Mater. Sci. Eng. A 819, 141495.
[186] Wu, G., Balachandran, S., Gault, B., Xia, W., Liu, C., Rao, Z., Wei, Y., Liu, S., Lu, J., Herbig, M., Lu, W., Dehm, G., Li, Z., Raabe, D., 2020a. Crystal-Glass High-Entropy Nanocomposites with Near Theoretical Compressive Strength and Large Deformability. Adv. Mater. 32, 2002619.
[187] Wu, G., Chan, K.-C., Zhu, L., Sun, L., Lu, J., 2017. Dual-phase nanostructuring as a route to high-strength magnesium alloys. Nature 546, 80-83.
[188] Wu, G., Liu, C., Brognara, A., Ghidelli, M., Bao, Y., Liu, S., Wu, X., Xia, W., Zhao, H., Rao, J., Ponge, D., Devulapalli, V., Lu, W., Dehm, G., Raabe, D., Li, Z., 2021b. Symbiotic crystal-glass alloys via dynamic chemical partitioning. Mater. Today, 6-14.
[189] Wu, G., Liu, C., Sun, L., Wang, Q., Sun, B., Han, B., Kai, J.-J., Luan, J., Chain, T., Liu, Cao, K., Cheng, L., Lu, J., 2019. Hierarchical nanostructured aluminum alloy with ultrahigh strength and large plasticity. Nat. Commun. 10, 5099.
[190] Wu, G., Sun, L., Zhu, L., Liu, C., Wang, Q., Bao, Y., Lu, J., 2020b. Near-ideal strength and large compressive deformability of a nano-dual-phase glass-crystal alloy in sub-micron. Scripta Mater. 188, 290-295.
[191] Wu, W., Ni, S., Liu, Y., Song, M., 2016a. Effects of cold rolling and subsequent annealing on the microstructure of a HfNbTaTiZr high-entropy alloy. J. Mater. Res. 31, 3815-3823.
[192] Wu, X., Yang, M., Yuan, F., Chen, L., Zhu, Y., 2016b. Combining Gradient Structure and TRIP Effect to Produce Austenite Stainless Steel with High Strength and Ductility. Acta Mater. 112, 337-346.
[193] Wu, X., Yang, M., Yuan, F., Wu, G., Wei, Y., Huang, X., Zhu, Y., 2015. Heterogeneous lamella structure unites ultrafine-grain strength with coarse-grain ductility. Proc. Natl. Acad. Sci. U. S. A. 112, 1517193112.
[194] Wu, Y., Cai, Y., Wang, T., Shi, J.J., Zhu, J., Wang, Y., Hui, X.D., 2014. A Refractory Hf25Nb25Ti25Zr25 High-Entropy Alloy with Excellent Structural Stability and Tensile Properties. Mater. Lett. 130, 277.
[195] Xin, Z., Li, X., Lu, K., 2018. Enhanced thermal stability of nanograined metals below a critical grain size. Science 360, 526-530.
[196] Xin, Z., Li, X., Lu, K., 2019. Size Dependence of Grain Boundary Migration in Metals under Mechanical Loading. Phys. Rev. Lett. 122, 126101.
[197] Xu, W., Liu, X.C., Li, X.Y., Lu, K., 2019. Deformation induced grain boundary segregation in nanolaminated Al-Cu alloy. Acta Mater. 182.
[198] Yang, C., Aoyagi, K., Bian, H., Chiba, A., 2019. Microstructure evolution and mechanical property of a precipitation-strengthened refractory high-entropy alloy HfNbTaTiZr. Mater. Lett. 254.
[199] Yang, L., Cheng, Z., Zhu, W., Zhao, C., Ren, F., 2021. Significant reduction in friction and wear of a high-entropy alloy via the formation of self-organized nanolayered structure. J. Mater. Sci. Technol. 73, 1-8.
[200] Yang, L., Zhao, C., Zhu, W., Cheng, Z., Wei, P., Ren, F., 2020. Microstructure, Mechanical Properties, and Sliding Wear Behavior of Oxide-Dispersion-Strengthened FeMnNi Alloy Fabricated by Spark Plasma Sintering. Metall. Mater. Trans. A 51, 2796-2810.
[201] Yao, Y., Li, X., Wang, Y., Zhao, W., Li, G., Liu, R., 2014. Microstructural evolution and mechanical properties of Ti-Zr beta titanium alloy after laser surface remelting. J. Alloys Compd. 583, 43-47.
[202] Yavari, A.R., Botta, W., Rodrigues, C., Cardoso, C., Valiev, R., 2002. Nanostructured bulk Al90Fe5Nd5 prepared by cold consolidation of gas atomised powder using severe plastic deformation. Scripta Mater. 46, 711-716.
[203] Ye, Y., Wang, Q., Lu, J., Liu, C.T., Yang, Y., 2015. High-entropy alloy: challenges and prospects. Mater. Today 19, S1369702115004010.
[204] Ye, Y.X., Liu, C.Z., Wang, H., Nieh, T.G., 2018. Friction and wear behavior of a single-phase equiatomic TiZrHfNb high-entropy alloy studied using a nanoscratch technique. Acta Mater. 147, 78-89.
[205] Yeh, J.-W., 2006. Recent progress in high-entropy alloys. Eur. J. Control 31, 633-648.
[206] Yeh, J.-W., Chen, S.K., Lin, S.-J., Gan, J.-Y., Chin, T.-S., Shun, T., Tsau, C.H., Chang, S.Y., 2004. Nanostructured High‐Entropy Alloys with Multiple Principal Elements: Novel Alloy Design Concepts and Outcomes. Adv. Eng. Mater. 6, 299-303.
[207] Yin, C.-h., Liang, Y.-l., Liang, Y., Li, W., Yang, M., 2019. Formation of a self-lubricating layer by oxidation and solid-state amorphization of nano-lamellar microstructures during dry sliding wear tests. Acta Mater. 166, 208-220.
[208] Yu, P.F., Cheng, H., Zhang, L.J., Zhang, H., Jing, Q., Ma, M.Z., Liaw, P.K., Li, G., Liu, R.P., 2016. Effects of high pressure torsion on microstructures and properties of an Al0.1CoCrFeNi high-entropy alloy. Mater. Sci. Eng. A 655, 283-291.
[209] Yurchenko, N., Stepanov, N., Zherebtsov, S., Tikhonovsky, M., Salishchev, G., 2017. Structure and mechanical properties of B2 ordered refractory AlNbTiVZr x (x = 0–1.5) high-entropy alloys. Mater. Sci. Eng. A 704.
[210] Zhang, J., Gadelmeier, C., Sen, S., Wang, R., Zhang, X., Zhong, Y., Glatzel, U., Grabowski, B., Wilde, G., Divinski, S., 2022. Zr diffusion in BCC refractory high entropy alloys: A case of ’non-sluggish’ diffusion behavior. Acta Mater. 233, 117970.
[211] Zhang, J.Y., Cui, J.C., Liu, G., Sun, J., 2013. Deformation crossover in nanocrystalline Zr micropillars: The strongest external size. Scripta Mater. 68, 639-642.
[212] Zhang, L., Yu, G., Li, S., He, X., Xie, X., Xia, C., Ning, W., Zheng, C., 2019a. The effect of laser surface melting on grain refinement of phase separated Cu-Cr alloy. Opt. Laser Technol. 119, 105577.
[213] Zhang, T., Fan, Q., Ma, X., Wang, W., Wang, K., Shen, P., Yang, J., Wang, L., 2019b. Effect of Laser Remelting on Microstructural Evolution and Mechanical Properties of Ti-35Nb-2Ta-3Zr Alloy. Mater. Lett. 253.
[214] Zhang, Y., Greer, A., 2006. Thickness of shear bands in metallic glasses. Appl. Phys. Lett. 89, 071907-071907.
[215] Zhao, H., You, Z., Tao, N., Lu, L., 2021. Anisotropic strengthening of nanotwin bundles in heterogeneous nanostructured Cu: Effect of deformation compatibility. Acta Mater. 210, 116830.
[216] Zhou, X., Li, X.Y., Lu, K., 2018. Enhanced thermal stability of nanograined metals below a critical grain size. Science 360, 526.
[217] Zhou, Y., Zhang, Y., Wang, Y., Chen, G., 2007. Solid solution alloys of AlCoCrFeNiTix with excellent room-temperature mechanical properties. Appl. Phys. Lett. 90, 181904-181904.
[218] Zhu, W., Zhao, C., Zhang, Y., Kwok, C.T., Luan, J., Jiao, Z., Ren, F., 2020. Achieving exceptional wear resistance in a compositionally complex alloy via tuning the interfacial structure and chemistry. Acta Mater. 188, 697-710.
[219] Zhu, Y., Ameyama, K., Anderson, P., Beyerlein, I., Gao, H., Kim, H., Lavernia, E., Mathaudhu, S., Mughrabi, H., Tsuji, N., Zhang, X., Wu, X., Gilgenbach, C., Ritchie, R., 2021. Heterostructured materials: Superior properties from hetero-zone interaction. Mater. Res. Lett. 9, 1-31.
[220] Zou, Y., Ma, H., Spolenak, R., 2015. Ultrastrong ductile and stable high-entropy alloys at small scales. Nat. Commun. 6, 7748.
[221] Zou, Y., Maiti, S., Steurer, W., Spolenak, R., 2014. Size-dependent plasticity in an Nb25Mo25Ta25W25 refractory high-entropy alloy. Acta Mater. 65, 85–97.