Next Article in Journal
A Hybrid Design of Experiment Approach in Analyzing the Electrical Discharge Machining Influence on Stir Cast Al7075/B4C Metal Matrix Composites
Previous Article in Journal
Pilot Tests of Pre-Reduction in Chromium Raw Materials from Donskoy Ore Mining and Processing Plant and Melting of High-Carbon Ferrochromium
 
 
Search for Articles:
Title / Keyword
Author / Affiliation / Email
Journal
Article Type
 
 
Advanced Search
 
Section
Special Issue
Volume
Issue
Number
Page
 
Journals
Metals
Volume 14
Issue 2
10.3390/met14020204
metals-logo
Submit to this Journal Review for this Journal Propose a Special Issue
► Article Menu

Article Menu

share Share announcement Help format_quote Cite question_answer Discuss in SciProfiles
first_page
settings
Order Article Reprints
Font Type:
Arial Georgia Verdana
Font Size:
Aa Aa Aa
Line Spacing:
Column Width:
Background:
Article

High-Temperature Thermal Stability of Hot Isostatic Pressed Co25.1Cr18.8Fe23.3Ni22.6Ta8.5Al1.7 (at%) Eutectic High-Entropy Alloy

by
Dongyue Li
1,*,
Chengshuang Wu
1,
Lu Xie
1,
Yong Zhang
2,* and
Wenrui Wang
1,*
1
School of Mechanical Engineering, University of Science and Technology Beijing, Beijing 100083, China
2
Beijing Advanced Innovation Center of Materials Genome Engineering, State Key Laboratory for Advanced Metals and Materials, University of Science and Technology Beijing, Beijing 100083, China
*
Authors to whom correspondence should be addressed.
Metals 2024, 14(2), 204; https://doi.org/10.3390/met14020204
Submission received: 9 January 2024 / Revised: 4 February 2024 / Accepted: 5 February 2024 / Published: 7 February 2024
(This article belongs to the Section Entropic Alloys and Meta-Metals)
Browse Figures
Versions Notes

Abstract

:
An eutectic high-entropy alloy (EHEA) consisting mainly of a face-centered cubic (FCC) phase and a C14 Laves phase with the compositions of Co25.1Cr18.8Fe23.3Ni22.6Ta8.5Al1.7 (at%) was successfully prepared by hot isostatic pressing. The present EHEA exhibits a skeleton-type Laves phase structure, deviating from typical EHEA structures. After a series of annealing treatments at 1000 °C for different durations (ranging from 0 to 150 h), the Co3Ta phase precipitated after annealing. The mechanical properties measured at 850 °C showed a tensile strength of 441 MPa and an elongation of 3.3%. The results of the high-temperature tests showed that the mechanical properties of this alloy did not change significantly before and after annealing, and its microstructure showed a high degree of stability, which suggests that the material has some potential for use in high-temperature environments.

1. Introduction

High-temperature alloys are now an essential component for the hot-end parts of aerospace engines, having been designed to suit the demanding material requirements of contemporary engines. Currently, almost fifty percent of high-temperature alloys are employed in modern aerospace engines. The four hot-end components of combustion chambers, guiding vanes, turbine blades, and turbine disks are the primary applications for high-temperature alloys. Other applications include casings, rings, afterburners, and tail nozzles. Numerous academics have valued the development of novel high-temperature alloys as well as the enhancement of the performance of existing high-temperature alloys.
According to the Carnot cycle, a heat engine’s efficiency is positively connected with its working temperature; the higher the temperature, the more efficient the heat engine. Raising the operating temperature lowers fuel consumption, emissions, and operational costs in the nuclear, coal, and oil power generation industries. Raising the operating temperature of jet engines will result in better performance, including more payload, faster lift, and longer range. Therefore, all types of heat engines (such as internal combustion engines and gas turbines) must raise their operating temperature as much as possible in order to enhance the energy utilization rate. Nickel-based high-temperature alloys are currently the most often utilized type of high-temperature alloys. High-temperature alloys based on nickel have an initial melting point of about 1300 °C and a maximum applicable temperature of 1277 °C. The following are the primary reinforcing phases found in alloys based on nickel: When the temperature rises above 800 °C, the primary reinforcing phase (γ′) in alloys based on nickel begins to dissolve, resulting in a significant reduction in the mechanical properties of nickel-based high-temperature alloys. Studying novel high-temperature alloys with superior mechanical qualities in temperatures above 800 °C is therefore extremely important.
Typically, alloys consist of a single primary element with trace amounts of additional elements added to modify their microstructure and improve their properties. The notions of “high-entropy alloys” and “multi-major alloys,” which Cantor [1] and Yeh [2] introduced in 2004, disrupted the conventional alloy design paradigm and revolutionized the alloy design process. The notions of “high-entropy alloys” and “multi-master alloys”, which Cantor and Yeh introduced in 2004, disrupted conventional alloy design ideas and advanced alloy design techniques. The advent of high-entropy alloys offers a fresh approach to resolving conventional alloy issues. It has four major effects: high entropy effect in thermodynamics, hysteresis diffusion in dynamics, lattice distortion effect, and cocktail effect in performance [3,4,5]. The components of new alloys get increasingly complex because of the variety of random combinations that exist between the elements. The advent of high-entropy alloys widens the field of study on novel metal materials and breaks the constraints of element kinds and ratios in conventional alloys [6,7,8,9,10].
The characteristics of high-entropy alloys are frequently intimately linked to their phase structure, and biphasic alloys can achieve exceptional mechanical qualities by making use of the intricate phase-strengthening effect. During solidification, biphasic high-entropy alloys immediately generate in-situ composites with both soft and hard phases. The combination of high strength and high plasticity, along with outstanding thermal stability at high temperatures, can be realized by the utilization of interfacial strengthening. Different eutectic high entropy alloys with both soft and hard phases have been devised in order to achieve the balance between the strength and flexibility of high entropy alloys, in addition to the introduction of the second phase through precipitation strengthening. Eutectic alloys are renowned for having a wide range of superior qualities, including balanced mechanical properties and outstanding casting flowability. Thus, the idea of eutectic high-entropy alloys arose to enhance the flowability and castability of high-entropy alloys by fusing the benefits of eutectic points and high-entropy alloys. In actuality, eutectic high-entropy alloys have good castability and exceptional mechanical properties and solve the casting segregation issue of high-entropy alloys. The design principles of eutectic and high-entropy alloys are combined in eutectic high-entropy alloys [11]. Since the AlCoCrFeNi2.1 eutectic high-entropy alloy was successfully conceived and manufactured by Lu et al., it has drawn the interest and investigation of numerous academics [12,13]. Because of its distinct composition and microstructure, EHEA is anticipated to be able to balance the alloy’s strength and plasticity [14]. EHEA benefits from a distinct microstructure and composition that should provide a good balance between the alloy’s strength and malleability. In order to achieve a balance between strength and plasticity, the design technique for EHEA involves creating an alloy with both hard and soft phases and using interfacial reinforcement to get strength from the hard phase and plasticity from the soft phase [15]. The EHEA thus formed is expected to obtain excellent high-temperature properties, providing strong support for the application of EHEA in high-temperature environments [16,17,18].
The eutectic product in EHEA may be the Laves phase; as-cast EHEA, including the Laves phase, has been demonstrated to show brittleness with high strength and limited flexibility [19,20]. In compression trials below 800 °C, EHEA containing a substantial quantity of Laves phase only exhibits plasticity at the material’s edge; the material as a whole remains brittle [16,21]. It is anticipated that more microstructure alteration will balance the strength and plasticity [21].
Face-centered cubic (soft) and Laves (hard) phases are both present in CoCrFeNiTa-based EHEA, and it is anticipated that these phases will have superior qualities at high temperatures [22,23,24,25]. Eutectic reactions yield the Laves phase and the FCC phase [26]. The FCC phase can give the material room to accumulate dislocations during deformation and maintain its plasticity [22,23,24]. The FCC phase loses strength at high temperatures; thus, strengthening it while maintaining its flexibility is necessary to enhance its functionality even more. It is demonstrated that, at normal temperatures, the nanoscale L12 phase that precipitates in the FCC phase can simultaneously increase its strength and flexibility [27,28,29]. Additionally, the production of a high-density nano-L12 phase is promoted by the addition of a modest amount of Al (1.7 at%) to Co27Cr21Fe18Ni24Ta10 EHEA [25]. The findings demonstrate that the L12 phase is stable at high temperatures and has the potential to cause strain hardening in the material [25]. Nevertheless, in the as-cast form, Co27Cr21Fe18Ni24Ta10 EHEA displays a characteristic eutectic laminar lamellar structure, with a lengthy, striated Laves phase that causes early cracking during compression, resulting in brittle fracture, according to practical tests [25]. Since the extended Laves phase is thought to be harmful to EHEA’s high-temperature mechanical properties, its structure, morphology, and distribution should be controlled. During compression testing, it has been discovered that the Laves phase is more resistant to crack initiation and extension when its structure shifts from a long strip to an equiaxial structure [25,30]. As a result, it is anticipated that changing the Laves phase’s shape will significantly enhance performance.
Different preparation and processing methods can directly affect the microstructure and properties of EHEA. A wide range of scholars have intensively studied AlCoCrFeNi2.1 EHEAs to understand the effect of processing on the microstructure and properties of high-entropy alloys. EHEAs can be easily prepared on a large scale by conventional melting and casting processes, with a fairly homogeneous and reproducible layered structure and excellent mechanical properties [31,32]. Directed solidification can further tune the microstructure and properties of cast EHEAs, thus making EHEAs suitable for application as high-strength large castings [33,34]. The main advantage of EHEAs stems from the remarkable tunability of their microstructure and properties through thermomechanical processing. Reddy et al. [35] developed a novel hybrid processing route for EHEA, combining low-temperature rolling and room-temperature rolling to tune the microstructure. The result is a bi-heterostructure nanostructured EHEA with an unprecedented increase in strength and mechanical properties comparable to those of martensitic aged steels. The intriguing microstructure and attractive mechanical properties have inspired others to investigate the preparation of EHEA. The microstructure and properties of EHEA fabricated by additive manufacturing (AM) is an area of considerable interest [36]. The study by Ren et al. [37] is particularly notable in this regard. Printed EHEA prepared by laser powder bed fusion (L-PBF) processing successfully achieved a nano lamellar structure. The heterogeneous structure provides better strength-ductility synergy than cast EHEA. Different annealing treatments can further improve the strength properties of the printed EHEA.
Compared to the casting method, powder metallurgy is a more efficient way of preparation for modifying the shape, size, and distribution of the alloy’s second phase. It is discovered that AlxCoCrFeNi high-entropy alloys made by mechanical alloying are thermodynamically stable to 800 °C and that the five-member HEA has a comparatively smaller grain growth factor than the four-member CoCrFeNi alloy [38]. Liu and colleagues utilized hot extrusion to produce a fine equiaxial microstructure that improved the strength and ductility of pre-alloyed powders of CoCrFeNi-based high-entropy alloys [39]. In order to demonstrate the impact of various microstructures on high-temperature mechanical properties, we used powder metallurgy to create EHEA with diffusely dispersed secondary phases, adhering to the previously mentioned microstructure design methodologies.
In this work, tensile fracture experiments were conducted at 850 °C and the microstructures of non-equimolar EHEA with nominal compositions of Co25.1Cr18.8Fe23.3-Ni22.6Ta8.5Al1.7 (at%) were examined for samples with varying annealing periods at 1000 °C. The “Simple hybrid method” was created to prepare the EHEAs from binary phase diagrams based on M-Ta (where M = Co, Cr, Fe, and Ni) [31].

2. Materials and Methods

A few of the reported EHEA are included in Table 1. As-cast microstructures of all of them have two phases. These EHEAs can be thought of as being composed of elements from two different groups, A and B, based on the enthalpy of mixing between the constituent elements. The enthalpy of mixing between the elements in group A is almost negligible, and their atomic radii and chemical activity are comparable. As a result, they easily form basic solid solutions and are fully soluble. The elements of group B, on the other hand, mix easily to produce ordered solid solutions or intermetallic compounds because they have very negative enthalpies of mixing.
The phase diagrams of multi-primary element alloys are very complex, making it impossible to find eutectic spots in EHEA precisely. In the as-cast state, CoCrFeNi alloys form a basic FCC solid solution structure. The eutectic reactions between the Co, Cr, Fe, and Ni elements and the Ta element have a significantly negative enthalpy of mixing. Rich (Ni, Co, Cr, Fe) solid solution phases with Ta elements are present in the eutectic compositions Ni86.3Ta13.7, Co92Ta8, Cr87Ta13, and Fe92.5Ta7.5. By summing the binary eutectic compositions based on the summing of all the individual binary eutectic compositions, an attempt has been made in this study to create the pseudo-binary eutectic composition (CoCrFeNi)Mx (M = Ta). Calculated based on a molar ratio of 1:1 for each eutectic component:
(1/4) Ni86.3 Ta13.7 + (1/4) Co92 Ta8 + (1/4) Cr87 Ta13 + (1/4) Fe92.5 Ta7.5 = Co23 Cr21.8 Fe23.1 Ni21.6 Ta10.5
By manipulating the resulting composition, adding a small amount of Al (1.7 at%) to the non-equimolar ratio of Co23Cr21.8Fe23.1Ni22.6Ta10.5 EHEA can promote the formation of high-density L12 ordered nanoprecipitates. The thermodynamic stability of coherently organized L12 analytes makes them a useful source of strain hardening to withstand softening at high temperatures [25]. The proportion of each component was suitably regulated based on the elemental distribution states in each phase, and the final proportion of each component was found to be Co25.1Cr18.8Fe23.3Ni22.6Ta8.5-Al1.7 (at%).
The monomers of each element were weighed proportionately, and the mass ratio between the elements was determined using the molar ratio. EHEA ingots are obtained through vacuum induction melting and remelted three times to ensure that the element distribution is sufficiently uniform. The ingots were then processed through a gas atomization process while being shielded by argon to create EHEA powder. After sieving, powder with a 50–100 μm particle size is used for hot isostatic pressing. The oxygen content was determined using a Leco O/N analyzer (LECO TCH 600, LECO Corporation Inc., St. Joseph, MI, USA). The atomized powder was encapsulated in a 316L stainless steel can measuring 50 mm (diameter) × 120 mm (height). Steel can be degassed and vacuum sealed. For 60 min, the tanks are heated to 1150 °C in order to perform hot isostatic pressing. It was then kept at that temperature and pressure for 120 min after being pushed to 120 MPa. The final blanks were allowed to cool in the air. The sample after hot isostatic pressing and the sample with the steel can removed are shown in Figure 1. Annealing with different holding times at 1000 °C, with argon gas protection for 0–150 h, and ice water quenching thereafter.
The blank can be regarded as isotropic as the heated isostatic pressure is about equal in all directions. A tensile specimen measuring 5 mm in length, 1.5 mm in width, and 1 mm in thickness was cut from the blank. The samples were heated for ten minutes to 850 °C at a rate of 1 °C/s. Then, using an electronic LE5150 universal testing machine (ELE International, Milton Keynes, UK) with a heating oven and a strain rate of 10−3/s, uniaxial tensile tests were performed at 850 °C. A video tensiometer from LVE (Versalis, San Donato Milanese, Italy) was used to measure the strain rate. During the tensile operation, the displacement was measured using an LVE video extensometer. At least three samples were tested under each condition.
X-ray diffraction (XRD) analysis of the samples was performed at room temperature using an X-ray device, ISODEBYEFLEX 3003 (GE Inspection Technologies GmbH, Alemanha, Germany), with Cu Kα1 radiation running at 40 keV and 30 mA. The scanning range is from 10° to 90° with a scanning step of 0.033°.
A Quanta FEG 250 scanning electron microscope (SEM) (FEI, Lausanne, Switzerland) was used to examine the microstructure and fracture morphology of the tensile pattern of EHEA samples that were hot isostatically pressed and subsequently annealed.

3. Results and Discussion

The element fractions, as determined by SEM surface examination, are shown in Table 2. Figure 2 shows the XRD pattern of the extruded and subsequently annealed EHEA bulk sample. The main diffraction peaks can be identified with the FCC phase and the Laves phase (structural type of MgZn2, space group 194). The annealed EHEA samples’ XRD spectra do not show the superlattice reflections of the L12 phase because of their tiny size. Notably, the positions of the Laves phase’s primary diffraction peaks remain unaltered, suggesting that the annealing procedure has no discernible impact on the phase’s lattice characteristics. Other smaller diffraction peaks appear in the annealed EHEA, which can be recognized as Co3Ta phases (around 35 and 58 degrees, structure type Ni3Sn, space group 194 [42]. The EHEA annealed for 100 h shows two peaks at 41 degrees, and it can be seen that the peaks at around 41 degrees are shifted for different annealing times, indicating that heat treatment and quenching altered the facet spacing and that the high cooling rate led to lattice distortion [43]. After 100 h of annealing, the Co3Ta diffraction peaks emerged in the EHEA sample, and the positions and intensities of the other prominent peaks remained largely unchanged. The sample that underwent 150 h of annealing showed a decrease in the intensity of the Co3Ta phase peaks in the XRD spectra. This suggests that the Co3Ta phase precipitated and remelted as the annealing time increased. The results indicate that the EHEA changes from the FCC + Laves phase to the FCC + Laves + Co3Ta phase under prolonged annealing at 1000 °C (about 100 h). Meanwhile, the Laves phase’s diffraction peaks essentially stopped changing, indicating that the microstructure had stabilized.
The unannealed sample’s energy spectrum scanning results are shown in Figure 3, which also shows the elemental distribution. It can be seen that the Laves phase is rich in Ta and Co, and the FCC phase is rich in Fe, Co, Cr, and Ni. This is consistent with the reported element distribution results of CoCrFeNiTa0.4 containing the Laves phase and FCC phase [13]. A cross-sectional view of the particles is provided by the backscattered electron (BSE) picture, which displays a skeleton-like eutectic structure (see Figure 4). It is completely different from the lamellar organization of traditional EHEA [13]. We checked the porosity by looking at the cross-sections of the samples. No pores were found in the BSE images (both low and high magnification), and all the samples were almost completely dense. This shows that hot isostatic pressing can effectively densify the powder because the difference between hot isostatic pressing and traditional powder metallurgy preparation process is that the pressure applied during hot isostatic pressing is greater, and the heat and pressure holding time is longer (2 h), and pressure comes from multiple directions (including above, below and side), which helps reduce the porosity of the alloy. The brightly imaged rod-like structures were determined to be the Laves phase by SEM-BSE chemical analysis, while the darker portions are associated with the FCC phase. The EHEA microstructure is uniformly distributed, as shown by the BSE map, which is especially noteworthy in the Laves phase. The Laves phase highlights its thermodynamic stability during high-temperature annealing by significantly coarsening to around 5 μm and then stabilizing with increasing annealing time. The EBSD phase composition map of EHEA is shown in Figure 5, where it is evident that the Laves phase in the 50-h annealed EHEA expands and coarsens, resulting in increased connectivity. The Co3Ta phase is visible and scattered throughout the Laves phase in the 100-h annealed EHEA. Grain coarsening and growth are suggested by longer annealing times, which also result in less discernible grain boundaries. The engineering stress-strain curves for the extruded and then-annealed EHEA evaluated at 850 °C are shown in Figure 6. And the macrostructure of the original tensile specimen before and after fracture is shown in Figure 6. It can be seen that brittle fractures occurred in all specimens. As the annealing time increases, the tensile strength of EHEA first decreases and then increases, reaching the highest value at 100 h (the tensile strength reaches 441 MPa). This is consistent with the change of the Co3Ta phase in the XRD diffraction pattern (Figure 2). In the sample annealed for 50 h, no Co3Ta phase diffraction peak appears, but the intensity of the Laves phase peak becomes stronger. At the same time, the grains are coarsened (Figure 5), and the slip surface is reduced, preventing dislocations from accumulating. In the sample annealed for 100 h, a nanoscale Co3Ta phase precipitated on the surface of the Laves phase (Figure 5), which played a pinning role during the dislocation slip process and thus improved the performance of the EHEA. After annealing for 150 h, the Co3Ta phase melted back, and its content decreased (Figure 2), resulting in a decrease in the pinning effect and, thus, a decrease in tensile strength. The elongation at the break of the alloy in the four states is less than 10%, which may be related to the processing method. The Laves phase is coarse and has strong connectivity, which is inconsistent with the fine grains and structures that can be obtained by powder metallurgy [39]. It may be that the pressure and temperature maintained for too long during the powder densification process cause the Laves phase to aggregate and grow, resulting in enhanced connectivity. Clearly, this connection differs from that of traditional high-temperature alloys and other high-entropy alloys, which exhibit a strength-ductility tradeoff [32]. The fracture scan shown in Figure 7 shows fewer ductile pits and more brittle dissociation surfaces, which is a typical brittle fracture. This can be attributed to the fact that the pressure and temperature maintained for a long time during hot isostatic pressing caused the rapid aggregation and growth of Laves phases, and the increase in size enhanced the connectivity between Laves phases, resulting in the formation of a skeleton structure that is not conducive to tensile ductility (Figure 4).
Figure 8 shows the room temperature hardness values of the alloy as extruded and subsequently annealed. It can be seen from the figure that as the annealing time increases, the alloy hardness first decreases and then becomes stable. During the annealing process, the internal stress generated by hot isostatic pressing is released, resulting in a significant reduction in the alloy hardness. The alloy completes recrystallization in the initial stage of annealing, and then as the annealing time increases, its microstructure tends to be stable, the grain growth is slow, and the hardness no longer changes [38].

4. Conclusions

We prepared EHEA highly stable at high temperatures and obtained EHEA with a skeleton-type Laves phase. The main conclusions are as follows:
(1)
The morphology, size, and distribution of the second phase of the eutectic high-entropy alloy were changed by hot isostatic pressing of pre-alloyed powders, and a uniformly distributed eutectic skeleton-type organization of the Laves phase and the FCC phase was obtained.
(2)
The eutectic high-entropy alloy demonstrated tensile mechanical properties reaching 412 MPa at 850 °C, showcasing its high-temperature strength.
(3)
Its excellent thermal stability can be seen from the mechanical property test and microstructure after annealing. Annealing causes the nano-Co3Ta phase to precipitate on the surface of the Laves phase, which enhances the performance of EHEA through pinning.
(4)
After annealing, the hardness first decreases and then tends to stabilize with the extension of the annealing time, indicating that it has stability at high temperatures of 1000 °C.

Author Contributions

D.L. conceived and designed the study. C.W. conducted the experiments and analyzed the data. W.W. contributed to data analysis and interpretation. D.L. wrote and revised the manuscript. Y.Z. and L.X. provided critical feedback and revisions to the manuscript. All authors have read and agreed to the published version of the manuscript.

Funding

This research was funded by the National Natural Science Foundation of China, grant number 52101189; National Key R&D Program of China (Grant No. 2020YFA0405700); Chinese Postdoctoral Science Foundation, grant number 2020M680343; and the Fundamental Research Funds for the Central Universities, grant number FRF-TP-20-050A1.

Data Availability Statement

The original contributions presented in the study are included in the article material, further inquiries can be directed to the corresponding authors.

Conflicts of Interest

The authors declare no conflict of interest.

References

  1. Cantor, B.; Chang, I.T.H.; Knight, P.; Vincent, A.J.B. Microstructural development in equiatomic multicomponent alloys. Mater. Sci. Eng. A 2004, 375–377, 213–218. [Google Scholar] [CrossRef]
  2. Yeh, J.W.; Chen, S.K.; Lin, S.J.; Gan, J.Y.; Chin, T.S.; Shun, T.T.; Tsau, C.H.; Chang, S.Y. Nanostructured High-Entropy Alloys with Multiple Principal Elements: Novel Alloy Design Concepts and Outcomes. Adv. Eng. Mater. 2004, 6, 299–303. [Google Scholar] [CrossRef]
  3. Li, W.; Xie, D.; Li, D.; Zhang, Y.; Gao, Y.; Liaw, P.K. Mechanical behavior of high-entropy alloys. Prog. Mater. Sci. 2021, 118, 100777. [Google Scholar] [CrossRef]
  4. Tsai, K.Y.; Tsai, M.H.; Yeh, J.W. Sluggish diffusion in Co–Cr–Fe–Mn–Ni high-entropy alloys. Acta Mater. 2013, 61, 4887–4897. [Google Scholar] [CrossRef]
  5. Lu, Y.; Dong, Y.; Jiang, H.; Wang, Z.; Cao, Z.; Guo, S.; Wang, T.; Li, T.; Liaw, P. Promising properties and future trend of eutectic high entropy alloys. Scr. Mater. 2020, 187, 202–209. [Google Scholar] [CrossRef]
  6. Chen, S.; Aitken, Z.H.; Pattamatta, S.; Wu, Z.; Yu, Z.; Srolovitz, D.J.; Liaw, P.K.; Zhang, Y.W. Simultaneously enhancing the ultimate strength and ductility of high-entropy alloys via short-range ordering. Nat. Commun. 2021, 12, 4953. [Google Scholar] [CrossRef] [PubMed]
  7. Lee, C.; Maresca, F.; Feng, R.; Chou, Y.; Ungar, T.; Widom, M.; An, K.; Poplawsky, J.D.; Chou, Y.C.; Liaw, P.K.; et al. Strength can be controlled by edge dislocations in refractory high-entropy alloys. Nat. Commun. 2021, 12, 5474. [Google Scholar] [CrossRef]
  8. Yang, T.; Zhao, Y.L.; Tong, Y.; Jiao, Z.B.; Wei, J.; Cai, J.X.; Han, X.D.; Chen, D.; Hu, A.; Kai, J.J.; et al. Multicomponent intermetallic nanoparticles and superb mechanical behaviors of complex alloys. Science 2018, 362, 933–937. [Google Scholar] [CrossRef]
  9. Pan, Q.; Zhang, L.; Feng, R.; Lu, Q.; An, K.; Chuang, A.C.; Poplawsky, J.D.; Liaw, P.K.; Lu, L. Gradient cell–structured high-entropy alloy with exceptional strength and ductility. Science 2021, 374, 984–989. [Google Scholar] [CrossRef]
  10. Ding, Q.; Zhang, Y.; Chen, X.; Fu, X.; Chen, D.; Chen, S.; Gu, L.; Wei, F.; Bei, H.; Gao, Y.; et al. Tuning element distribution, structure and properties by composition in high-entropy alloys. Nature 2019, 574, 223–227. [Google Scholar] [CrossRef]
  11. Lu, Y.; Gao, X.; Jiang, L.; Chen, Z.; Wang, T.; Jie, J.; Kang, H.; Zhang, Y.; Guo, S.; Ruan, H. Directly cast bulk eutectic and near-eutectic high entropy alloys with balanced strength and ductility in a wide temperature range. Acta Mater. 2017, 124, 143–150. [Google Scholar] [CrossRef]
  12. Lu, Y.; Wu, X.; Fu, Z.; Yang, Q.; Zhang, Y.; Liu, Q.; Li, T.; Tian, Y.; Tan, H.; Li, Z.; et al. Ductile and ultrahigh-strength eutectic high-entropy alloys by large-volume 3d printing. J. Mater. Sci. Technol. 2022, 126, 15–21. [Google Scholar] [CrossRef]
  13. Lu, Y.; Jiang, H.; Guo, S.; Wang, T.; Cao, Z.; Li, T. A new strategy to design eutectic high-entropy alloys using mixing enthalpy. Intermetallics 2017, 91, 124–128. [Google Scholar] [CrossRef]
  14. Wang, M.; Lu, Y.; Lan, J.; Wang, T.; Zhang, C.; Cao, Z.; Li, T.; Liaw, P. Lightweight, ultrastrong and high thermal-stable eutectic high-entropy alloys for elevated-temperature applications. Acta Mater. 2023, 248, 118806. [Google Scholar] [CrossRef]
  15. Liu, Q.; Liu, X.; Fan, X.; Li, R.; Tong, X.; Yu, P.; Li, G. Designing novel AlCoCrNi eutectic high entropy alloys. J. Alloys Compd. 2022, 904, 163775. [Google Scholar] [CrossRef]
  16. Ye, X.; Cheng, Z.; Liu, C.; Wu, X.; Yu, L.; Liu, M.; Fang, D.; Zhao, G.; Li, B. The microstructure and properties of Fe55Cr15Ni(30−x)Nbx eutectic high-entropy alloys. Mater. Sci. Eng. A 2022, 841, 143026. [Google Scholar] [CrossRef]
  17. Jiao, W.; Miao, J.; Lu, Y.; Chen, X.; Ren, Z.; Yin, G.; Li, T. Designing CoCrFeNi-M (M = Nb, Ta, Zr, and Hf) eutectic high-entropy alloys via a modified simple mixture method. J. Alloys Compd. 2023, 941, 168975. [Google Scholar] [CrossRef]
  18. Zhang, Y.; Wang, X.; Li, J.; Huang, Y.; Lu, Y.; Sun, X. Deformation mechanism during high-temperature tensile test in an eutectic high-entropy alloy AlCoCrFeNi2.1. Mater. Sci. Eng. A 2018, 724, 148–155. [Google Scholar] [CrossRef]
  19. Guénolé, J.; Mouhib, F.; Huber, L.; Grabowski, B.; Korte-Kerzel, S. Basal slip in Laves phases: The synchroshear dislocation. Scr. Mater. 2019, 166, 134–138. [Google Scholar] [CrossRef]
  20. Ding, Z.Y.; He, Q.F.; Wang, Q.; Yang, Y. Superb strength and high plasticity in laves phase rich eutectic medium-entropy-alloy nanocomposites. Int. J. Plast. 2018, 106, 57–72. [Google Scholar] [CrossRef]
  21. Jiang, H.; Qiao, D.; Lu, Y.; Ren, Z.; Cao, Z.; Wang, T.; Li, T. Direct solidification of bulk ultrafine-microstructure eutectic high-entropy alloys with outstanding thermal stability. Scr. Mater. 2019, 165, 145–149. [Google Scholar] [CrossRef]
  22. Ai, C.; He, F.; Guo, M.; Wang, Z.; Yuan, Z.; Guo, Y.; Liu, Y.; Liu, L. Alloy design, micromechanical and macromechanical properties of CoCrFeNiTax eutectic high entropy alloys. J. Alloys Compd. 2018, 735, 2653–2662. [Google Scholar] [CrossRef]
  23. Huo, W.; Zhou, H.; Fang, F.; Zhou, X.; Xie, Z.; Jiang, J. Microstructure and properties of novel CoCrFeNiTax eutectic high-entropy alloys. J. Alloys Compd. 2018, 735, 897–904. [Google Scholar] [CrossRef]
  24. Jiang, H.; Han, K.; Qiao, D.; Lu, Y.; Cao, Z.; Li, T. Effects of Ta addition on the microstructures and mechanical properties of CoCrFeNi high entropy alloy. Mater. Chem. Phys. 2018, 210, 43–48. [Google Scholar] [CrossRef]
  25. Han, L.; Xu, X.; Wang, L.; Pyczak, F.; Zhou, R.; Liu, Y. A eutectic high-entropy alloy with good high-temperature strength-plasticity balance. Mater. Res. Lett. 2019, 7, 460–466. [Google Scholar] [CrossRef]
  26. He, F.; Wang, Z.; Cheng, P.; Wang, Q.; Li, J.; Dang, Y.; Wang, J.; Liu, C. Designing eutectic high entropy alloys of CoCrFeNiNbx. J. Alloys Compd. 2016, 656, 284–289. [Google Scholar] [CrossRef]
  27. Wang, L.; Wu, X.; Su, H.; Deng, B.; Liu, G.; Han, Z.; Su, Y.; Huang, Y.; Zhang, Y.; Shen, J.; et al. Microstructure and mechanical property of novel L12 nanoparticles-strengthened CoFeNi-based medium entropy alloys. Mater. Sci. Eng. A 2022, 840, 142917. [Google Scholar] [CrossRef]
  28. Zhao, Y.L.; Yang, T.; Tong, Y.; Wang, J.; Luan, J.; Jiao, Z.; Chen, D.; Yang, Y.; Hu, A.; Liu, C.; et al. Heterogeneous precipitation behavior and stacking-fault-mediated deformation in a CoCrNi-based medium-entropy alloy. Acta Mater. 2017, 138, 72–82. [Google Scholar] [CrossRef]
  29. Du, C.; Hu, L.; Pan, Q.; Chen, K.; Zhou, P.; Wang, G. Effect of Cu on the strengthening and embrittling of an FeCoNiCr-xCu HEA. Mater. Sci. Eng. A 2022, 832, 142413. [Google Scholar] [CrossRef]
  30. Sui, S.; Tan, H.; Chen, J.; Zhong, C.; Li, Z.; Fan, W.; Gasser, A.; Huang, W. The influence of Laves phases on the room temperature tensile properties of Inconel 718 fabricated by powder feeding laser additive manufacturing. Acta Mater. 2019, 164, 413–427. [Google Scholar] [CrossRef]
  31. Jiang, H.; Han, K.; Gao, X.; Lu, Y.; Cao, Z.; Gao, M.; Hawk, J.; Li, T. A new strategy to design eutectic high-entropy alloys using simple mixture method. Mater. Des. 2018, 142, 101–105. [Google Scholar] [CrossRef]
  32. Daoud, H.M.; Manzoni, A.M.; Wanderka, N.; Glatzel, U. High-Temperature Tensile Strength of Al10Co25Cr8Fe15Ni36Ti6 Compositionally Complex Alloy (High-Entropy Alloy). JOM 2015, 67, 2271–2277. [Google Scholar] [CrossRef]
  33. Zheng, H.; Chen, R.; Qin, G.; Li, X.; Su, Y.Q.; Ding, H.; Guo, J.; Fu, H. Phase separation of AlCoCrFeNi2.1 eutectic high-entropy alloy during directional solidification and their effect on tensile properties. Intermetallics 2019, 113, 106569. [Google Scholar] [CrossRef]
  34. Wang, L.; Yao, C.; Shen, J.; Zhang, Y.; Wang, T.; Ge, Y.; Gao, L.; Zhang, G. Microstructures and room temperature tensile properties of as-cast and directionally solidified AlCoCrFeNi2.1 eutectic high-entropy alloy. Intermetallics 2020, 118, 106681. [Google Scholar] [CrossRef]
  35. Reddy, S.R.; Yoshida, S.; Bhattacharjee, T.; Sake, N.; Lozinko, A.; Guo, S.; Bhattacharjee, P.P.; Tsuji, N. Nanostructuring with Structural-Compositional Dual Heterogeneities Enhances Strength-Ductility Synergy in Eutectic High Entropy Alloy. Sci. Rep. 2019, 9, 11505. [Google Scholar] [CrossRef]
  36. Zhu, Y.; Zhou, S.; Xiong, Z.; Liang, Y.; Xue, Y.; Wang, L. Enabling stronger eutectic high-entropy alloys with larger ductility by 3D printed directional lamellae. Addit. Manuf. 2021, 39, 101901. [Google Scholar] [CrossRef]
  37. Ren, J.; Zhang, Y.; Zhao, D.; Chen, Y.; Guan, S.; Liu, Y.; Liu, L.; Peng, S.; Kong, F.; Poplawsky, J.; et al. Strong yet ductile nanolamellar high-entropy alloys by additive manufacturing. Nature 2022, 608, 62–68. [Google Scholar] [CrossRef] [PubMed]
  38. Garlapati, M.M.; Vaidya, M.; Karati, A.; Mishra, S.; Bhattacharya, R.; Murty, B.S. Influence of Al content on thermal stability of nanocrystalline AlxCoCrFeNi high entropy alloys at low and intermediate temperatures. Adv. Powder Technol. 2020, 31, 1985–1993. [Google Scholar] [CrossRef]
  39. Liu, B.; Wang, J.; Liu, Y.; Fang, Q.; Wu, Y.; Chen, S.; Liu, C. Microstructure and mechanical properties of equimolar FeCoCrNi high entropy alloy prepared via powder extrusion. Intermetallics 2016, 75, 25–30. [Google Scholar] [CrossRef]
  40. Wang, M.; Lu, Y.; Wang, T.; Zhang, C.; Cao, Z.; Li, T.; Liaw, P. A novel bulk eutectic high-entropy alloy with outstanding as-cast specific yield strengths at elevated temperatures. Scr. Mater. 2021, 204, 114132. [Google Scholar] [CrossRef]
  41. Lin, X.; Wang, M.; Ren, G.; Qiao, D.; Lu, Y.; Wang, T.; Li, T. Microstructure evolution and mechanical properties of CrFeNixV0.64Ta0.36 eutectic high-entropy alloys. Mater. Charact. 2021, 181, 111449. [Google Scholar] [CrossRef]
  42. He, X.; Kong, L.; Liu, B. Stability of the Metastable Phases in the Co-Ta System Studied by ab initio and Thermodynamic Calculations Together with Ion-Beam-Mixing Experiment. J. Phys. Soc. Jpn. 2005, 74, 2501–2505. [Google Scholar] [CrossRef]
  43. Zhou, P.F.; Xiao, D.H.; Yuan, T.C. Microstructure, Mechanical and Corrosion Properties of AlCoCrFeNi High-Entropy Alloy Prepared by Spark Plasma Sintering. Acta Metall. Sin. 2020, 33, 937–946. [Google Scholar] [CrossRef]
Metals 14 00204 g001
Figure 1. (a) samples obtained by hot isostatic pressing; (b) sample after removing steel can.
Figure 1. (a) samples obtained by hot isostatic pressing; (b) sample after removing steel can.
Metals 14 00204 g001
Metals 14 00204 g002
Figure 2. XRD patterns of extruded and subsequently heat-treated specimens.
Figure 2. XRD patterns of extruded and subsequently heat-treated specimens.
Metals 14 00204 g002
Metals 14 00204 g003
Figure 3. SEM-EDS mapping of the alloy in the extruded state, (a) original morphology, (b) elemental distribution with colors.
Figure 3. SEM-EDS mapping of the alloy in the extruded state, (a) original morphology, (b) elemental distribution with colors.
Metals 14 00204 g003
Metals 14 00204 g004
Figure 4. Low magnification SEM (left) and high magnification BSE (right) backscattered electron images of extruded and 1000 °C annealed alloys where the annealing times are (a) 0 h; (b) 50 h; (c) 100 h; (d) 150 h, respectively.
Figure 4. Low magnification SEM (left) and high magnification BSE (right) backscattered electron images of extruded and 1000 °C annealed alloys where the annealing times are (a) 0 h; (b) 50 h; (c) 100 h; (d) 150 h, respectively.
Metals 14 00204 g004
Metals 14 00204 g005
Figure 5. EBSD scanning phase compositions of extruded and annealed alloys at 1000 °C; (a) extruded; (b) annealed 50 h; (c) annealed 100 h; (d) annealed 150 h.
Figure 5. EBSD scanning phase compositions of extruded and annealed alloys at 1000 °C; (a) extruded; (b) annealed 50 h; (c) annealed 100 h; (d) annealed 150 h.
Metals 14 00204 g005
Metals 14 00204 g006
Figure 6. Tensile properties of extruded and subsequently annealed alloys in tension at 850 °C.
Figure 6. Tensile properties of extruded and subsequently annealed alloys in tension at 850 °C.
Metals 14 00204 g006
Metals 14 00204 g007
Figure 7. Low magnification and corresponding high magnification scans of the fracture of tensile specimens with different annealing times, where the annealing times are (a) 0 h, (b) 50 h, (c) 100 h, and (d) 150 h, respectively.
Figure 7. Low magnification and corresponding high magnification scans of the fracture of tensile specimens with different annealing times, where the annealing times are (a) 0 h, (b) 50 h, (c) 100 h, and (d) 150 h, respectively.
Metals 14 00204 g007
Metals 14 00204 g008
Figure 8. Vickers hardness values of specimens with different annealing times.
Figure 8. Vickers hardness values of specimens with different annealing times.
Metals 14 00204 g008
Table 1. The phase composition for typical EHEAs (adapted from [12,13,40,41]).
Table 1. The phase composition for typical EHEAs (adapted from [12,13,40,41]).
EHEAsPhase1Phase2Ref.
AlCoCrFeNi2.1(Fe,Co,Co)-rich(Al,Ni)-rich[12]
CoCrFeNiTa0.4(Co,Cr,Fe,Ni)-rich(Ta,Co)-rich[13]
AlCr1.3TiNi2(Ni,Ti,Al)-rich(Cr,Ni)-rich[40]
CrFeNi1.85V0.64Ta0.36(Cr,Ni,V)-rich(Fe,Ta)-rich[41]
Table 2. The chemical composition (in at%) of the extruded EHEA samples was measured by SEM-EDS.
Table 2. The chemical composition (in at%) of the extruded EHEA samples was measured by SEM-EDS.
AlCrFeCoNiTa
Measured2.56 ± 0.218.94 ± 0.123.10 ± 0.324.59 ± 0.219.41 ± 0.311.40 ± 0.4
Designed1.7018.8023.3025.1022.608.50
Disclaimer/Publisher’s Note: The statements, opinions and data contained in all publications are solely those of the individual author(s) and contributor(s) and not of MDPI and/or the editor(s). MDPI and/or the editor(s) disclaim responsibility for any injury to people or property resulting from any ideas, methods, instructions or products referred to in the content.

Share and Cite

MDPI and ACS Style

Li, D.; Wu, C.; Xie, L.; Zhang, Y.; Wang, W. High-Temperature Thermal Stability of Hot Isostatic Pressed Co25.1Cr18.8Fe23.3Ni22.6Ta8.5Al1.7 (at%) Eutectic High-Entropy Alloy. Metals 2024, 14, 204. https://doi.org/10.3390/met14020204

AMA Style

Li D, Wu C, Xie L, Zhang Y, Wang W. High-Temperature Thermal Stability of Hot Isostatic Pressed Co25.1Cr18.8Fe23.3Ni22.6Ta8.5Al1.7 (at%) Eutectic High-Entropy Alloy. Metals. 2024; 14(2):204. https://doi.org/10.3390/met14020204

Chicago/Turabian Style

Li, Dongyue, Chengshuang Wu, Lu Xie, Yong Zhang, and Wenrui Wang. 2024. "High-Temperature Thermal Stability of Hot Isostatic Pressed Co25.1Cr18.8Fe23.3Ni22.6Ta8.5Al1.7 (at%) Eutectic High-Entropy Alloy" Metals 14, no. 2: 204. https://doi.org/10.3390/met14020204

APA Style

Li, D., Wu, C., Xie, L., Zhang, Y., & Wang, W. (2024). High-Temperature Thermal Stability of Hot Isostatic Pressed Co25.1Cr18.8Fe23.3Ni22.6Ta8.5Al1.7 (at%) Eutectic High-Entropy Alloy. Metals, 14(2), 204. https://doi.org/10.3390/met14020204

Note that from the first issue of 2016, this journal uses article numbers instead of page numbers. See further details here.

Article Metrics

Back to TopTop