Influence of Si addition on the microstructure, mechanical and wear properties of as-cast Al_0.43CoCrFeNi_2.1 high-entropy alloys and performance enhancement by cold rolling and annealing

Abstract

A series of as-cast Si_xAl_0.43CoCrFeNi_2.1 (x = 0, 0.1, 0.2, and 0.3) high-entropy alloys (HEAs) was successfully fabricated by vacuum-assisted melting. The phase constituents, microstructural features, and mechanical properties (including hardness, tensile behavior, and wear behavior) of alloys with various Si contents were evaluated. The results revealed that the addition of Si promoted the precipitation of a body-centered cubic 1 (BCC1) phase enriched in Al, Ni, and Si with a B2-ordered structure. Furthermore, the secondary BCC2 phase was enriched with Cr, Fe, and Si precipitates within the BCC1 matrix. Ultimately, a multiphase face-centered cubic (FCC)/(BCC1/BCC2) structure was formed. The microstructural evolution driven by Si addition significantly enhanced the mechanical properties of the Si_xAl_0.43CoCrFeNi_2.1 HEAs. As the Si content increased, the microhardness and tensile strength improved by approximately 42% and 55%, reaching 2.359 GPa and 785 MPa, respectively. The quantitative evaluation of the various strengthening mechanisms indicated that the intrinsic hardness of the FCC matrix and hardening due to BCC1/BCC2 precipitation dominated the overall microhardness. The comparison of the energy barriers indicates that BCC2 primarily strengthens the alloy through a shear mechanism rather than an Orowan bypass mechanism. Furthermore, with increasing Si content, reduced friction and wear, together with smoother worn surfaces, reflect a greatly enhanced wear resistance. After the optimal cold-rolling and 1 h annealing at 800°C, the Si_0.3Al_0.43CoCrFeNi_2.1 alloy showed 56% and 62% increases in microhardness and tensile strength, respectively, compared to the as-cast state, reaching 3.68 GPa and 1270 MPa. The enhanced mechanical properties are attributed to the synergistic effects of residual strain hardening by FCC ordering and L1₂/BCC precipitation strengthening.

Keywords

as-cast high-entropy alloys / microstructure / mechanical properties / wear resistance / cold-rolling and annealing / strengthening mechanisms

References

[1] Wang YP, Li BS, Ren MX, Yang C, Fu HZ. Microstructure and compressive properties of AlCrFeCoNi high entropy alloy. Mater. Sci. Eng. A. 2008, 491(1–2): 154

[2] E. Strumza and S. Hayun, Comprehensive study of phase transitions in equiatomic AlCoCrFeNi high-entropy alloy, J. Alloy. Compd., 856(2021), art. No. 158220.

[3] Guo YX, Shang XJ, Liu QB. Microstructure and properties of in situ TiN reinforced laser cladding CoCr₂FeNiTi_x high-entropy alloy composite coatings. Surf. Coat. Technol.. 2018, 344: 353

[4] Z.P. Sun, X.Z. Li, and Z.M. Wang, Microstructure and mechanical properties of low activation Fe–Ti–Cr–V–W multi-principal element alloys, J. Nucl. Mater., 533(2020), art. No. 152078.

[5] Dong Y, Lu YP, Kong JR, Zhang JJ, Li TJ. Microstructure and mechanical properties of multi-component AlCrFeNiMo_x high-entropy alloys. J. Alloy. Compd.. 2013, 573: 96

[6] Gao XZ, Lu YP, Zhang B, et al. . Microstructural origins of high strength and high ductility in an AlCoCrFeNi_2.1 eutectic high-entropy alloy. Acta Mater.. 2017, 141: 59

[7] Li MF, Henein H, Zhou CG, Liu J. Towards high-entropy alloys with high-temperature corrosion resistance and structural stability. J. Mater. Sci. Technol.. 2024, 174: 133

[8] S. Sharma, S.P. Dwivedi, K.A. Mohammed, et al., Investigation of surface hardness, thermostability, tribo-corrosion, and microstructural morphological properties of microwave-synthesized high entropy alloy FeCoNiMnCu coating claddings on steel, Sci. Rep., 14(2024), No. 1, art. No. 5160.

[9] Y.T. Zhang, M.W. Liu, J.Y. Sun, et al., Excellent thermal stability and mechanical properties of bulk nanostructured FeCoNiCu high entropy alloy, Mater. Sci. Eng. A, 835(2022), art. No. 142670.

[10] Xiao M, Nai SF, Nan S, et al. . Preparation, mechanical properties and wear resistance of dual-sized TiC particles reinforced high-entropy alloy cermet coating. J. Mater. Res. Technol.. 2024, 28: 97

[11] Cheng Z, Wang SZ, Wu GL, Gao JH, Yang XS, Wu HH. Tribological properties of high-entropy alloys: A review. Int. J. Miner. Metall. Mater.. 2022, 29(3): 389

[12] Lu YP, Dong Y, Jiang H, et al. . Promising properties and future trend of eutectic high entropy alloys. Scripta Mater.. 2020, 187: 202

[13] Y.C. Hsu, C.L. Li, and C.H. Hsueh, Effects of Al addition on microstructures and mechanical properties of CoCrFeMnNiAl_x high entropy alloy films, Entropy, 22(2019), No. 1, art. No. 2.

[14] H. Liu, J. Liu, X. Li, P.J. Chen, H.F. Yang, and J.B. Hao, Effect of heat treatment on phase stability and wear behavior of laser clad AlCoCrFeNiTi_0.8 high-entropy alloy coatings, Surf. Coat. Technol., 392(2020), art. No. 125758.

[15] Z. Li, K.T. Mei, J.W. Dong, Y. Yang, J.Q. Sun, and Z. Luo, An investigation on the wear and corrosion resistance of AlCoCrFeNi high-entropy alloy coatings enhanced by Ti and Si, Surf. Coat. Technol., 487(2024), art. No. 130949.

[16] Yang X, Chen DZ, Feng L, Qin G, Wu SP, Chen RR. Enhancing the mechanical properties of casting eutectic high-entropy alloys via W addition. Int. J. Miner. Metall. Mater.. 2024, 31(6): 1364

[17] Xiao N, Guan X, Wang D, et al. . Impact of W alloying on microstructure, mechanical property and corrosion resistance of face-centered cubic high entropy alloys: A review. Int. J. Miner. Metall. Mater.. 2023, 30(9): 1667

[18] Lu YP, Gao XZ, Jiang L, et al. . Directly cast bulk eutectic and near-eutectic high entropy alloys with balanced strength and ductility in a wide temperature range. Acta Mater.. 2017, 124: 143

[19] Y.P. Lu, Y. Dong, S. Guo, et al., A promising new class of high-temperature alloys: Eutectic high-entropy alloys, Sci. Rep., 4(2014), art. No. 6200.

[20] Ye XC, Wang T, Xu ZY, et al. . Effect of Ti content on microstructure and mechanical properties of CuCoFeNi high-entropy alloys. Int. J. Miner. Metall. Mater.. 2020, 27(10): 1326

[21] Wang WR, Wang WL, Yeh JW. Phases, microstructure and mechanical properties of Al_xCoCrFeNi high-entropy alloys at elevated temperatures. J. Alloy. Compd.. 2014, 589: 143

[22] S.L. He, F.Y. Zhang, H.S. Jin, F. Wang, L.Q. Wang, and F.X. Yin, Microstructure, mechanical and corrosion properties of carbon-supersaturated Al_0.5CoCrFeNi high-entropy alloy films, J. Alloy. Compd., 1036(2025), art. No. 182118.

[23] Li YT, Chen XM, Zeng XK, Liu M, Jiang X, Leng YX. Hard yet tough and self-lubricating (CuNiTiNbCr)C_x high-entropy nanocomposite films: Effects of carbon content on structure and properties. J. Mater. Sci. Technol.. 2024, 173: 20

[24] Chen WQ, Li B, Yang H, Xu L, Ye XC, Fang D. Effect of B content on microstructure and mechanical properties of (Co₃₀Cr₂₅Fe₄₀Ni₅)_100−xB_x high-entropy alloys. J. Mater. Res.. 2023, 38(12): 3187

[25] Y.H. Jia, Z.J. Wang, Q.F. Wu, et al., Boron microalloying for high-temperature eutectic high-entropy alloys, Acta Mater., 262(2024), art. No. 119427.

[26] X.D. Wang, T.X. Li, D.F. Xu, et al., Enabling high strength yet ductility in a refractory high-entropy alloy through oxygen-nitrogen synergistic effect, Acta Mater., 296(2025), art. No. 121229.

[27] Xue WD, Yang XM, Ye XX, et al. . Effects of silicon carbide on the corrosion of metallic materials in molten LiF-NaF-KF salt. Corros. Sci.. 2018, 143: 157

[28] Stepanov ND, Yurchenko NY, Tikhonovsky MA, Salishchev GA. Effect of carbon content and annealing on structure and hardness of the CoCrFeNiMn-based high entropy alloys. J. Alloy. Compd.. 2016, 687: 59

[29] J. Zhou, T.H. Jiang, H.C. Liao, H. Chen, J.W. Zheng, and W.J. Zhu, Effect of carbon alloying on microstructure and mechanical behaviors of Fe₃₅Ni₃₅Cr₂₀Mn₁₀ multi-component alloy, Mater. Charact., 188(2022), art. No. 111934.

[30] Seol JB, Bae JW, Li ZM, et al. . Boron doped ultrastrong and ductile high-entropy alloys. Acta Mater.. 2018, 151: 366

[31] P.P. Cui, W. Li, P. Liu, et al., Effects of nitrogen content on microstructures and mechanical properties of (AlCrTiZrHf)N high-entropy alloy nitride films, J. Alloys Compd., 834(2020), art. No. 155063.

[32] Y.L. Guo, J.Y. He, Z.M. Li, L.N. Jia, X.X. Wu, and C.M. Liu, Strengthening and dynamic recrystallization mediated by Si-alloying in a refractory high entropy alloy, Mater. Sci. Eng. A, 832(2022), art. No. 142480.

[33] Rahman A, Jacucci G. Relative stability of f.c.c. and b.c.c. structures for model systems at high temperatures. Il Nuovo Cimento D. 1984, 4(4): 357

[34] Zhang C, Wu GF, Dai PQ. Phase transformation and aging behavior of Al_0.5CoCrFeNiSi_0.2 high-entropy alloy. J. Mater. Eng. Perform.. 2015, 24(5): 1918

[35] Choudhuri D, Alam T, Borkar T, et al. . Formation of a Huesler-like L2₁ phase in a CoCrCuFeNiAlTi high-entropy alloy. Scripta Mater.. 2015, 100: 36

[36] HajyAkbary F, Sietsma J, Böttger AJ, Santofimia MJ. An improved X-ray diffraction analysis method to characterize dislocation density in lath martensitic structures. Mater. Sci. Eng. A. 2015, 639: 208

[37] Tan XD, Xu YB, Yang XL, Wu D. Microstructure–properties relationship in a one-step quenched and partitioned steel. Mater. Sci. Eng. A. 2014, 589: 101

[38] Yasuda HY, Shigeno K, Nagase T. Dynamic strain aging of Al_0.3CoCrFeNi high entropy alloy single crystals. Scripta Mater.. 2015, 108: 80

[39] Lu ZP, Lei ZF, Huang HL, et al. . Deformation behavior and toughening of high-entropy alloys. Acta Metall. Sin.. 2018, 54(11): 1553

[40] Chen J, Zhang WN, Liu ZY, Wang GD. The role of retained austenite on the mechanical properties of a low carbon 3Mn–1.5Ni steel. Metall. Mater. Trans. A. 2017, 48(12): 5849

[41] Gwalani B, Soni V, Lee M, Mantri SA, Ren Y, Banerjee R. Optimizing the coupled effects of Hall–Petch and precipitation strengthening in a Al_0.3CoCrFeNi high entropy alloy. Mater. Des.. 2017, 121: 254

[42] Güemes RS, Bellón B, Esteban-Manzanares G, Segurado J, Capolungo L, LLorca J. Multiscale modelling of precipitation hardening in Al–Cu alloys: Dislocation dynamics simulations and experimental validation. Acta Mater.. 2020, 188: 475

[43] Ma KK, Wen HM, Hu T, et al. . Schoenung, Mechanical behavior and strengthening mechanisms in ultrafine grain precipitation-strengthened aluminum alloy. Acta Mater.. 2014, 62: 141

[44] Wen HM, Topping TD, Isheim D, Seidman DN, Lavernia EJ. Strengthening mechanisms in a high-strength bulk nanostructured Cu–Zn–Al alloy processed via cryomilling and spark plasma sintering. Acta Mater.. 2013, 61(8): 2769

[45] Hao JM, Ma Y, Wang Q, et al. . Formation of cuboidal B2 nanoprecipitates and microstructural evolution in the body-centered-cubic Al_0.7NiCoFe_1.5Cr_1.5 high-entropy alloy. J. Alloy. Compd.. 2019, 780: 408

[46] Sass V, Glatzel U, Feller-Kniepmeier M. Anisotropic creep properties of the nickel-base superalloy CMSX-4. Acta Mater.. 1996, 44(5): 1967

[47] Y.J. Guo, C.G. Li, M. Zeng, J.Q. Wang, P.R. Deng, and Y. Wang, In-situ TiC reinforced CoCrCuFeNiSi_0.2 high-entropy alloy coatings designed for enhanced wear performance by laser cladding, Mater. Chem. Phys., 242(2020), art. No. 122522.

[48] D.S. Yang, J. Cheng, Z.M. Tang, et al., Friction and wear properties of D-Gun sprayed CrFeNiAl_0.3Ti_0.3–Ag–SrSO₄ high entropy alloy matrix self-lubricating coating at elevated temperature, Tribol. Int., 200(2024), art. No. 110151.

[49] M. Chen, Z.S. Xu, B. Xue, Y. Liu, and W.D. Ma, Friction and wear performance of a NiAl-8wt% serpentine-2wt%TiC composite at high temperatures, Mater. Res. Express, 5(2018), No. 9, art. No. 096521.

[50] H. Liu, S.F. Sun, T. Zhang, G.Z. Zhang, H.F. Yang, and J.B. Hao, Effect of Si addition on microstructure and wear behavior of AlCoCrFeNi high-entropy alloy coatings prepared by laser cladding, Surf. Coat. Technol., 405(2021), art. No. 126522.

[51] J. Zhou, H.C. Liao, H.M. Chen, D. Feng, and W.J. Zhu, Effect of cold rolling on microstructure and mechanical behavior of Fe₃₅Ni₃₅Cr₂₀Mn₁₀ high-entropy alloy, Mater. Charact., 218(2024), art. No. 114503.

[52] Wang L, Huang YD, Liu SH, et al. . Microstructure, mechanical property and strengthening mechanism analysis of drop-cast and thermo-mechanically processed Co_31.5Fe_18.5Ni_31.5Al_18.5 eutectic high-entropy alloy. J. Mater. Sci. Technol.. 2026, 244: 261

RIGHTS & PERMISSIONS

University of Science and Technology Beijing