Eutectic alloys are a class of multi-phase materials named for their formation through eutectic reactions during solidification. They have a long history as the most widely used casting alloys. High-entropy alloys (HEAs), on the other hand, are a novel class of multi-principal element alloys that have rapidly developed since their conceptualization in 2004. Combining the advantages of eutectic alloys and HEAs, eutectic high-entropy alloys (EHEAs) were first proposed in 2014. Over a decade, EHEAs have been systematically investigated by focusing on alloy design, microstructure/performance optimization, large-scale fabrication, and potential applications. Their unique microstructures and excellent comprehensive properties have made EHEAs promising materials across various domains, garnering significant attention in recent years. By revisiting the advances in composition design, manufacturing, and applications of EHEAs over the past decade, this review offered insights into future trends and developments in this rapidly evolving field.
Keywords：eutectic high-entropy alloy;
composition design;
microstructure control;
material manufacturing;
application
WANG Zhijun, BAI Xiaoyu, WANG Jianbin, JIANG Hui, JIAO Wenna, LI Tianxin, LU Yiping. Revisiting the Development of Eutectic High-Entropy Alloys over the Past Decade (2014-2024): Design, Manufacturing, and Applications[J]. Acta Metallurgica Sinica, 2025, 61(1): 1-11 DOI:10.11900/0412.1961.2024.00250
Fig.1
Strategies to design eutectic high-entropy alloys (EHEAs)
(a) calculated pseudo-binary-phase diagram for FeCoNiCrNb x alloys[22] (b1-b4) microstructures of (CoCrFeNi)Mx EHEAs obtained by the simple mixing method[23] (c) empirical design criteria for EHEAs based on the relationship between valence electron concentration (VEC) and atomic size difference (δr)[25] (d) empirical design criteria for EHEAs based on the relationship between mixed enthalpy of solid solution (ΔH) and VEC of solid solution (VECss) (IMC—intermetallic compound)[26]
Fig.2
Schematic diagram of designing EHEAs with machine learning[27] (xi is the ith input parameter, y is the output parameter. The f1(x) and f2(x) are the internal layer functions in an artificial neural network model)
Fig.4
Microstructures of EHEAs tailored by various processing methods
(a) BSE image, EBSD phase, and Inverse pole figures (IPFs) of the directionally solidified Al19Fe20Co20Ni41 EHEA, showing a herringbone-like eutectic microstructure (BEC—branched eutectic colonies, AEC—aligned eutectic colonies)[48]
(b) EBSD IPF map of as-printed AlCoCrFeNi2.1 EHEA, showing ultrafine nanolamellar eutectic colonies with different crystallographic orientations (Inset shows the EBSD phase map)[50]
(c) EBSD phase map of the anomalous eutectic structure in remelted additive manufactured Ni32Co30Cr10Fe10Al18 EHEA[51]
(d) EBSD phase map of equiaxed ultrafine-grained structure in the 90% cold-rolled AlCoCrFeNi2.1 EHEA after isothermal annealing[53]
(e) SEM image and EBSD phase map of the AlCoCrFeNi2.1 EHEA cold-rolled by 84%-86% followed by non-isothermally annealing, showing heterogeneous duplex microstructure consisting of lamellar and ultrafine-grained structure[52]
(f) IPFs of the phase-selectively recrystallized Ni30Co30Cr10Fe10Al18W2 EHEA, showing the microstructure with a fully recrystallized fcc phase embedded in the skeleton of a B2 phase[54]
Fig.5
Mechanical properties of EHEAs with different microstructures
(a) directionally solidified Al19Fe20Co20Ni41 EHEA with herringbone-like microstructure (Inset shows the strain-hardening rate curves. MDIH and MBIH refer to multi-slip dislocation-induced hardening and microband-induced hardening, respectively; εU—uniform strain; σy—yield strength of Al19Fe20Co20Ni41 EHEA; σUTS—ultimate tensile strength of Al19Fe20Co20Ni41 EHEA)[48]
(b) as-printed and annealed AlCoCrFeNi2.1 EHEA with ultrafine nanolamellar structure (Inset shows the schematic of a dogbone-shaped specimen under tensile loading. σu—ultimate tensile strength of AlCoCrFeNi2.1 EHEA; σ0.2—yield strength of AlCoCrFeNi2.1 EHEA)[50]
(c) additive manufactured Ni32Co30Cr10Fe10Al18 EHEA with anomalous eutectic structure[51]
(e) heterogeneous-grained AlCoCrFeNi2.1 EHEA (Inset shows the loading-unloading-reloading behavior of the DPHL700 and the as-cast EHEA, DPHL—dual-phase heterogeneous lamella, UFG EHEA—ultrafine-grain EHEA, CH EHEA—complex and hierarchical EHEA)[52]
High-entropy alloys (HEAs) can have either high strength or high ductility, and a simultaneous achievement of both still constitutes a tough challenge. The inferior castability and compositional segregation of HEAs are also obstacles for their technological applications. To tackle these problems, here we proposed a novel strategy to design HEAs using the eutectic alloy concept, i.e. to achieve a microstructure composed of alternating soft fcc and hard bcc phases. As a manifestation of this concept, an AlCoCrFeNi2.1 (atomic portion) eutectic high-entropy alloy (EHEA) was designed. The as-cast EHEA possessed a fine lamellar fcc/B2 microstructure, and showed an unprecedented combination of high tensile ductility and high fracture strength at room temperature. The excellent mechanical properties could be kept up to 700 degrees C. This new alloy design strategy can be readily adapted to large-scale industrial production of HEAs with simultaneous high fracture strength and high ductility.
GaoX Z, LuY P, ZhangB, et al.
Microstructural origins of high strength and high ductility in an AlCoCrFeNi2.1 eutectic high-entropy alloy
<p>A series of CoCrFeNbxNi (x values in molar ratio, x = 0, 0.25, 0.45, 0.5, 0.75, 1.0 and 1.2) high entropy alloys (HEAs) was prepared to investigate the alloying effect of Nb on the microstructures and mechanical properties. The results indicate that the prepared CoCrFeNbxNi (x > 0) HEAs consist of a simple FCC solid solution phase and a Laves phase. The microstructures of the alloys change from an initial single-phase FCC solid solution structure (x = 0) to a hypoeutectic microstructure (x = 0.25), then to a full eutectic microstructure (x = 0.45) and finally to a hypereutectic microstructure (0.5 < x < 1.2). The compressive test results show that the Nb0.45 (x = 0.45) alloy with a full eutectic microstructure possesses the highest compressive fracture strength of 2558 MPa and a fracture strain of 27.9%. The CoCrFeNi alloy exhibits an excellent compressive ductility, which can reach 50% height reduction without fracture. The Nb0.25 alloy with a hypoeutectic structure exhibits a larger plastic strain of 34.8%. With the increase of Nb content, increased hard/brittle Laves phase leads to a decrease of the plasticity and increases of the Vickers hardness and the wear resistance. The wear mass loss, width and depth of wear scar of the Nb1.2 (x = 1.2) alloy with a hypereutectic structure are the lowest among all alloy systems, indicating that the wear resistance of the Nb1.2 alloy is the best one.</p>
JinX, LiangY X, BiJ, et al.
Enhanced strength and ductility of Al0.9CoCrNi2.1 eutectic high entropy alloy by thermomechanical processing
Unique strength-ductility balance of AlCoCrFeNi2.1 eutectic high entropy alloy with ultra-fine duplex microstructure prepared by selective laser melting
Remelting induced fully-equiaxed microstructures with anomalous eutectics in the additive manufactured Ni32Co30Cr10Fe10Al18 eutectic high-entropy alloy
Realizing improved strength-ductility synergy in eutectic alloys acting as in situ composite materials remains a challenge in conventional eutectic systems, which is why eutectic high-entropy alloys (EHEAs), a newly-emerging multi-principal-element eutectic category, may offer wider in situ composite possibilities. Here, we use an AlCoCrFeNi EHEA to engineer an ultrafine-grained duplex microstructure that deliberately inherits its composite lamellar nature by tailored thermo-mechanical processing to achieve property combinations which are not accessible to previously-reported reinforcement methodologies. The as-prepared samples exhibit hierarchically-structural heterogeneity due to phase decomposition, and the improved mechanical response during deformation is attributed to both a two-hierarchical constraint effect and a self-generated microcrack-arresting mechanism. This work provides a pathway for strengthening eutectic alloys and widens the design toolbox for high-performance materials based upon EHEAs.
WaniI S, BhattacharjeeT, SheikhS, et al.
Tailoring nanostructures and mechanical properties of AlCoCrFeNi2.1 eutectic high entropy alloy using thermo-mechanical processing
3D printing of high-strength alloys enables efficient manufacturing of complex metallic components. Yet, the as-built parts are often characterized by unsatisfied ductility due to micro-defects, requiring additional heat treatment to optimize the structure before in-site applications. The post heat-processing, however, often changes the shape of the printed parts, deteriorating the quality of the printed components. In addition, many printed large-scale alloy parts with complex shapes are difficult to be processed by hot isostatic pressing. This requires that the alloys can be printed with good strength and ductility without the necessity of additional thermal processing. Here, we show that excellent ductility and ultrahigh strength can be achieved in a eutectic high-entropy alloy (EHEA) by large-volume 3D printing. The as-printed EHEA has a tensile yield strength of 1040 MPa, and a total elongation of 24%, as well as superior corrosion resistance in seawater environment. The excellent combination of properties outperforms that of all other existing metallic materials. Note that these astonishing properties are from specimens directly after 3D printing without any subsequent heat treatment and hot isostatic pressing. The exceptional mechanical properties are mainly ascribed to the fine lamella spacing in the composite structure consisting of face-centered cubic matrix and B2 precipitates, which renders high resistance for dislocation movement and extends work hardening capability. The EHEA printed in large volume without post processing thus shows high applicability for mass-production at an industrial scale.
ReddyS R, YoshidaS, SunkariU, et al.
Engineering heterogeneous microstructure by severe warm-rolling for enhancing strength-ductility synergy in eutectic high entropy alloys
In-situ synthesis of nano-lamellar Ni1.5CrCoFe0.5Mo0.1Nb x eutectic high-entropy alloy coatings by laser cladding:Alloy design and microstructure evolution
An eutectic high-entropy alloy consisting Al, Co, Cr, Fe and Ni elements was prepared by vacuum directional solidification technology. The alloy exhibits excellent comprehensive mechanical performance during tension at temperature range of 600-700 °C. The microstructure reveals the intersection of twin-twin is the prevailing deformation mechanism and the twins play a dual role in strengthening and toughening the alloy in the thermomechanical process. The deformation twin variants I and Π were formed by the edge dislocation 112ˉ and the mixed dislocation 211ˉ on the {111} crystal planes, respectively. Besides, the dislocation jogs and kinks caused by twin intersection on the slip planes can strengthen the alloy, which may contribute to the high strength (the tensile strengths at the 600° and 700° tensile tests are respectively780 MPa and 630 MPa.). Moreover, the coherent twin boundary migration has the function of coordinating deformation and contributes to the high ductility of the alloy.
LiY, ShiP J, WangM Y, et al.
Unveiling microstructural origins of the balanced strength-ductility combination in eutectic high-entropy alloys at cryogenic temperatures
Y-Hf Co-doped AlCoCrFeNi2.1 eutectic high-entropy alloy with excellent oxidation and spallation resistance under thermal cycling conditions at 1100 oC and 1200 oC
Gas tungsten arc welding of as-cast AlCoCrFeNi2.1 eutectic high entropy alloy
[J]. Mater. Des., 2022, 223: 111176
LiP, SunH T, DongH G, et al.
Microstructural evolution, bonding mechanism and mechanical properties of AlCoCrFeNi2.1 eutectic high entropy alloy joint fabricated via diffusion bonding
... [22,23,25,26]Strategies to design eutectic high-entropy alloys (EHEAs)
(a) calculated pseudo-binary-phase diagram for FeCoNiCrNb x alloys[22] (b1-b4) microstructures of (CoCrFeNi)Mx EHEAs obtained by the simple mixing method[23] (c) empirical design criteria for EHEAs based on the relationship between valence electron concentration (VEC) and atomic size difference (δr)[25] (d) empirical design criteria for EHEAs based on the relationship between mixed enthalpy of solid solution (ΔH) and VEC of solid solution (VECss) (IMC—intermetallic compound)[26] ...
... (a) calculated pseudo-binary-phase diagram for FeCoNiCrNb x alloys[22] (b1-b4) microstructures of (CoCrFeNi)Mx EHEAs obtained by the simple mixing method[23] (c) empirical design criteria for EHEAs based on the relationship between valence electron concentration (VEC) and atomic size difference (δr)[25] (d) empirical design criteria for EHEAs based on the relationship between mixed enthalpy of solid solution (ΔH) and VEC of solid solution (VECss) (IMC—intermetallic compound)[26] ...
A new strategy to design eutectic high-entropy alloys using simple mixture method
... ,23,25,26]Strategies to design eutectic high-entropy alloys (EHEAs)
(a) calculated pseudo-binary-phase diagram for FeCoNiCrNb x alloys[22] (b1-b4) microstructures of (CoCrFeNi)Mx EHEAs obtained by the simple mixing method[23] (c) empirical design criteria for EHEAs based on the relationship between valence electron concentration (VEC) and atomic size difference (δr)[25] (d) empirical design criteria for EHEAs based on the relationship between mixed enthalpy of solid solution (ΔH) and VEC of solid solution (VECss) (IMC—intermetallic compound)[26] ...
... (a) calculated pseudo-binary-phase diagram for FeCoNiCrNb x alloys[22] (b1-b4) microstructures of (CoCrFeNi)Mx EHEAs obtained by the simple mixing method[23] (c) empirical design criteria for EHEAs based on the relationship between valence electron concentration (VEC) and atomic size difference (δr)[25] (d) empirical design criteria for EHEAs based on the relationship between mixed enthalpy of solid solution (ΔH) and VEC of solid solution (VECss) (IMC—intermetallic compound)[26] ...
A new strategy to design eutectic high-entropy alloys using mixing enthalpy
... ,25,26]Strategies to design eutectic high-entropy alloys (EHEAs)
(a) calculated pseudo-binary-phase diagram for FeCoNiCrNb x alloys[22] (b1-b4) microstructures of (CoCrFeNi)Mx EHEAs obtained by the simple mixing method[23] (c) empirical design criteria for EHEAs based on the relationship between valence electron concentration (VEC) and atomic size difference (δr)[25] (d) empirical design criteria for EHEAs based on the relationship between mixed enthalpy of solid solution (ΔH) and VEC of solid solution (VECss) (IMC—intermetallic compound)[26] ...
... (a) calculated pseudo-binary-phase diagram for FeCoNiCrNb x alloys[22] (b1-b4) microstructures of (CoCrFeNi)Mx EHEAs obtained by the simple mixing method[23] (c) empirical design criteria for EHEAs based on the relationship between valence electron concentration (VEC) and atomic size difference (δr)[25] (d) empirical design criteria for EHEAs based on the relationship between mixed enthalpy of solid solution (ΔH) and VEC of solid solution (VECss) (IMC—intermetallic compound)[26] ...
A new pseudo binary strategy to design eutectic high entropy alloys using mixing enthalpy and valence electron concentration
(a) calculated pseudo-binary-phase diagram for FeCoNiCrNb x alloys[22] (b1-b4) microstructures of (CoCrFeNi)Mx EHEAs obtained by the simple mixing method[23] (c) empirical design criteria for EHEAs based on the relationship between valence electron concentration (VEC) and atomic size difference (δr)[25] (d) empirical design criteria for EHEAs based on the relationship between mixed enthalpy of solid solution (ΔH) and VEC of solid solution (VECss) (IMC—intermetallic compound)[26] ...
... (a) calculated pseudo-binary-phase diagram for FeCoNiCrNb x alloys[22] (b1-b4) microstructures of (CoCrFeNi)Mx EHEAs obtained by the simple mixing method[23] (c) empirical design criteria for EHEAs based on the relationship between valence electron concentration (VEC) and atomic size difference (δr)[25] (d) empirical design criteria for EHEAs based on the relationship between mixed enthalpy of solid solution (ΔH) and VEC of solid solution (VECss) (IMC—intermetallic compound)[26] ...
... [27]Schematic diagram of designing EHEAs with machine learning<sup>[<xref ref-type="bibr" rid="R27">27</xref>]</sup> (<i>x<sub>i</sub></i> is the <i>i</i>th input parameter, <i>y</i> is the output parameter. The <i>f</i><sub>1</sub>(<i>x</i>) and <i>f</i><sub>2</sub>(<i>x</i>) are the internal layer functions in an artificial neural network model)Fig.2
... [27] (xi is the ith input parameter, y is the output parameter. The f1(x) and f2(x) are the internal layer functions in an artificial neural network model)Fig.2
... [48,50~54]Mechanical properties of EHEAs with different microstructures
(a) directionally solidified Al19Fe20Co20Ni41 EHEA with herringbone-like microstructure (Inset shows the strain-hardening rate curves. MDIH and MBIH refer to multi-slip dislocation-induced hardening and microband-induced hardening, respectively; εU—uniform strain; σy—yield strength of Al19Fe20Co20Ni41 EHEA; σUTS—ultimate tensile strength of Al19Fe20Co20Ni41 EHEA)[48] ...
... (a) directionally solidified Al19Fe20Co20Ni41 EHEA with herringbone-like microstructure (Inset shows the strain-hardening rate curves. MDIH and MBIH refer to multi-slip dislocation-induced hardening and microband-induced hardening, respectively; εU—uniform strain; σy—yield strength of Al19Fe20Co20Ni41 EHEA; σUTS—ultimate tensile strength of Al19Fe20Co20Ni41 EHEA)[48] ...
Unique strength-ductility balance of AlCoCrFeNi2.1 eutectic high entropy alloy with ultra-fine duplex microstructure prepared by selective laser melting
... ,50~54]Microstructures of EHEAs tailored by various processing methods
(a) BSE image, EBSD phase, and Inverse pole figures (IPFs) of the directionally solidified Al19Fe20Co20Ni41 EHEA, showing a herringbone-like eutectic microstructure (BEC—branched eutectic colonies, AEC—aligned eutectic colonies)[48] ...
... (b) EBSD IPF map of as-printed AlCoCrFeNi2.1 EHEA, showing ultrafine nanolamellar eutectic colonies with different crystallographic orientations (Inset shows the EBSD phase map)[50] ...
... 基于凝固组织调控的fcc/B2共晶高熵合金性能优化策略已经得到广泛的探索.最初报道的AlCoCrFeNi2.1共晶高熵合金以真空感应熔炼和浇铸的方式制造，抗拉强度接近1000 MPa，延伸率大于25%[13].真空电弧熔炼与铜模铸造技术能够实现更高的熔体纯净度和冷却速率，有效细化了共晶片层，可以提升AlCoCrFeNi2.1合金抗拉强度至1200 MPa[14].通过定向凝固调控共晶形貌可进一步提升共晶高熵合金的力学性能.研究[45]表明，随着抽拉速率的增加，AlCoCrFeNi2.1合金微观组织由层状共晶向胞状共晶转变，在60 μm/s的抽拉速率下局部出现枝-共晶凝固组织，其沿定向凝固方向的拉伸塑性增至37%.Shi等[48]增加抽拉速率至250 μm/s，制备出的“鱼骨状”共晶组织能够有效促进微裂纹的均匀形核，结合fcc相优异的裂纹钝化能力，有助于避免裂纹的灾难性扩展，从而使Al19Fe20Co20Ni41合金塑性提升了3倍，如图5a[48]所示.具有不同微观组织的共晶高熵合金的力学性能<sup>[<xref ref-type="bibr" rid="R48">48</xref>,<xref ref-type="bibr" rid="R50">50</xref>~<xref ref-type="bibr" rid="R54">54</xref>]</sup>Mechanical properties of EHEAs with different microstructures
(a) directionally solidified Al19Fe20Co20Ni41 EHEA with herringbone-like microstructure (Inset shows the strain-hardening rate curves. MDIH and MBIH refer to multi-slip dislocation-induced hardening and microband-induced hardening, respectively; εU—uniform strain; σy—yield strength of Al19Fe20Co20Ni41 EHEA; σUTS—ultimate tensile strength of Al19Fe20Co20Ni41 EHEA)[48] ...
... (b) as-printed and annealed AlCoCrFeNi2.1 EHEA with ultrafine nanolamellar structure (Inset shows the schematic of a dogbone-shaped specimen under tensile loading. σu—ultimate tensile strength of AlCoCrFeNi2.1 EHEA; σ0.2—yield strength of AlCoCrFeNi2.1 EHEA)[50] ...
Remelting induced fully-equiaxed microstructures with anomalous eutectics in the additive manufactured Ni32Co30Cr10Fe10Al18 eutectic high-entropy alloy
... (e) SEM image and EBSD phase map of the AlCoCrFeNi2.1 EHEA cold-rolled by 84%-86% followed by non-isothermally annealing, showing heterogeneous duplex microstructure consisting of lamellar and ultrafine-grained structure[52] ...
... (e) heterogeneous-grained AlCoCrFeNi2.1 EHEA (Inset shows the loading-unloading-reloading behavior of the DPHL700 and the as-cast EHEA, DPHL—dual-phase heterogeneous lamella, UFG EHEA—ultrafine-grain EHEA, CH EHEA—complex and hierarchical EHEA)[52] ...
... ~54]Microstructures of EHEAs tailored by various processing methods
(a) BSE image, EBSD phase, and Inverse pole figures (IPFs) of the directionally solidified Al19Fe20Co20Ni41 EHEA, showing a herringbone-like eutectic microstructure (BEC—branched eutectic colonies, AEC—aligned eutectic colonies)[48] ...
... (f) IPFs of the phase-selectively recrystallized Ni30Co30Cr10Fe10Al18W2 EHEA, showing the microstructure with a fully recrystallized fcc phase embedded in the skeleton of a B2 phase[54] ...
... 基于凝固组织调控的fcc/B2共晶高熵合金性能优化策略已经得到广泛的探索.最初报道的AlCoCrFeNi2.1共晶高熵合金以真空感应熔炼和浇铸的方式制造，抗拉强度接近1000 MPa，延伸率大于25%[13].真空电弧熔炼与铜模铸造技术能够实现更高的熔体纯净度和冷却速率，有效细化了共晶片层，可以提升AlCoCrFeNi2.1合金抗拉强度至1200 MPa[14].通过定向凝固调控共晶形貌可进一步提升共晶高熵合金的力学性能.研究[45]表明，随着抽拉速率的增加，AlCoCrFeNi2.1合金微观组织由层状共晶向胞状共晶转变，在60 μm/s的抽拉速率下局部出现枝-共晶凝固组织，其沿定向凝固方向的拉伸塑性增至37%.Shi等[48]增加抽拉速率至250 μm/s，制备出的“鱼骨状”共晶组织能够有效促进微裂纹的均匀形核，结合fcc相优异的裂纹钝化能力，有助于避免裂纹的灾难性扩展，从而使Al19Fe20Co20Ni41合金塑性提升了3倍，如图5a[48]所示.具有不同微观组织的共晶高熵合金的力学性能<sup>[<xref ref-type="bibr" rid="R48">48</xref>,<xref ref-type="bibr" rid="R50">50</xref>~<xref ref-type="bibr" rid="R54">54</xref>]</sup>Mechanical properties of EHEAs with different microstructures
(a) directionally solidified Al19Fe20Co20Ni41 EHEA with herringbone-like microstructure (Inset shows the strain-hardening rate curves. MDIH and MBIH refer to multi-slip dislocation-induced hardening and microband-induced hardening, respectively; εU—uniform strain; σy—yield strength of Al19Fe20Co20Ni41 EHEA; σUTS—ultimate tensile strength of Al19Fe20Co20Ni41 EHEA)[48] ...
In-situ synthesis of nano-lamellar Ni1.5CrCoFe0.5Mo0.1Nb x eutectic high-entropy alloy coatings by laser cladding:Alloy design and microstructure evolution
Y-Hf Co-doped AlCoCrFeNi2.1 eutectic high-entropy alloy with excellent oxidation and spallation resistance under thermal cycling conditions at 1100 oC and 1200 oC
Gas tungsten arc welding of as-cast AlCoCrFeNi2.1 eutectic high entropy alloy
0
2022
Microstructural evolution, bonding mechanism and mechanical properties of AlCoCrFeNi2.1 eutectic high entropy alloy joint fabricated via diffusion bonding
图1
