Method for improving corrosion resistance of eutectic high-entropy alloy

Abstract

The application belongs to the technical field of alloy material preparation, and particularly relates to a method for improving corrosion resistance of eutectic high-entropy alloy. The method comprises the following steps: homogenization annealing treatment, quenching treatment, cold rolling treatment, low-temperature short-time annealing treatment and quenching treatment. Through the method, fine FCC phase rich in Cr element is precipitated in B2 lamella of the eutectic high-entropy alloy, and structural defects such as dislocation, subgrain boundary, small-angle and large-angle grain boundary and twin boundary are introduced into the alloy. The above-mentioned microstructure characteristics promote the nucleation and growth of corrosion-resistant passivation film on the surface of the eutectic high-entropy alloy, thereby improving the corrosion resistance of the eutectic high-entropy alloy in a corrosive medium. The method is simple and easy to implement, low in cost, and very suitable for industrialized production and application of high-performance eutectic high-entropy alloy.

Description

Technical Field

[0001] This invention belongs to the field of alloy material preparation technology, specifically relating to a method for improving the corrosion resistance of eutectic high-entropy alloys. Background Technology

[0002] Traditional metallic material composition design typically uses one or two alloying elements as the main components, while adding other trace elements to adjust the alloy's microstructure and properties. This approach concentrates the composition of traditional metallic materials primarily in the peripheral regions of the multi-element phase diagram, significantly limiting the range of possible compositional designs. To broaden the design space for metallic materials, researchers have proposed the concept of high-entropy alloys. Currently, high-entropy alloys generally refer to emerging alloy systems that use four or more alloying elements as main components. The compositional design concept of high-entropy alloys expands the design area of ​​alloy composition to the central region of the multi-element phase diagram, greatly broadening the range of alloy compositional designs. The unique compositional design concept of high-entropy alloys results in four major effects: the thermodynamic "high-entropy effect," the kinetic "hysteresis diffusion effect," the structural "lattice distortion effect," and the performance "cocktail effect." Benefiting from these effects, high-entropy alloys exhibit a series of properties superior to traditional materials, such as excellent low-temperature mechanical properties and resistance to high-temperature softening, good strength-ductility matching, corrosion resistance, wear resistance, and radiation resistance, making them potential candidates for novel structural materials. Currently, the most widely studied high-entropy alloy system is the single-phase solid solution high-entropy alloy. However, numerous studies have shown that single-phase FCC solid solution high-entropy alloys often exhibit high plasticity but insufficient strength, while single-phase BCC solid solution high-entropy alloys often possess high strength but poor plasticity. Furthermore, single-phase solid solution high-entropy alloys also suffer from poor casting fluidity and difficulty in feeding, leading to significant casting defects in large-volume ingots, further limiting the industrial application of high-entropy alloys.

[0003] To solve the above problems, researchers proposed the design concept of eutectic high-entropy alloys. Eutectic high-entropy alloys are high-entropy alloys obtained through eutectic reactions, and the alloys possess the characteristics of both high-entropy alloys and eutectic alloys. Research results show that eutectic high-entropy alloys have a series of advantages such as good casting fluidity, uniform composition and structure, and few casting defects. At the same time, eutectic high-entropy alloys have a unique two-phase lamellar structure and can be regarded as an in-situ self-generated composite material, which also endows them with excellent mechanical properties and broad application prospects. Currently, the most widely studied eutectic high-entropy alloy system is the AlCoCrFeNi alloy system, which has good strength-ductility matching ability at low, room, and high temperatures and exhibits good engineering application value. However, compared with traditional metal materials such as duplex stainless steel, the corrosion resistance of as-cast eutectic high-entropy alloys is still insufficient, making it difficult to meet the requirements for the corrosion resistance of metal materials in high-end industrial fields such as aerospace and automotive manufacturing, which greatly limits the engineering application and promotion of eutectic high-entropy alloys. Summary of the Invention

[0004] The purpose of the present invention is to provide a method for improving the corrosion resistance of eutectic high-entropy alloys. Through the method of the present invention, eutectic high-entropy alloys with excellent corrosion resistance can be prepared to meet the requirements for high-performance metal materials in high-end industrial fields such as aerospace and automotive manufacturing.

[0005] To achieve the above purpose, the present invention adopts the following technical solutions:

[0006] A method for improving the corrosion resistance of eutectic high-entropy alloys, comprising the following steps:

[0007] (1) Perform homogenization annealing treatment on the eutectic high-entropy alloy substrate;

[0008] (2) Perform quenching treatment on the eutectic high-entropy alloy after homogenization annealing treatment; [[ID=1九]]

[0009] (3) Perform cold rolling treatment on the eutectic high-entropy alloy after homogenization annealing and quenching treatment;

[0010] (四) Perform low-temperature short-time annealing treatment on the eutectic high-entropy alloy after cold rolling treatment;

[0011] (5) Perform quenching treatment on the eutectic high-entropy alloy after low-temperature short-time annealing treatment.

[0012] In the method for improving the corrosion resistance of eutectic high-entropy alloys, the eutectic high-entropy alloy substrate is composed of elements Al, Co, Cr, Fe, and Ni, and the alloy general formula is AlCo 1-x CrFe 1+x / 2 Ni 2.1+x / 2 , where 0 < x ≤ 1, and x is the molar ratio of the elements. [[ID=三十六]]

[0013] In the method for improving the corrosion resistance of eutectic high-entropy alloys, the preferred x value is 1.

[0014] In the method for improving the corrosion resistance of eutectic high-entropy alloys, in step (1), the homogenization annealing temperature is 1150~1250℃ and the homogenization annealing time is 12~36h.

[0015] In the method for improving the corrosion resistance of eutectic high-entropy alloys, in step (2), the quenching medium is water and the temperature is 10-30℃.

[0016] In the method for improving the corrosion resistance of eutectic high-entropy alloys, step (3) involves multi-pass cold rolling, with a total reduction of 70% to 90%.

[0017] In the method for improving the corrosion resistance of eutectic high-entropy alloys, in step (4), the low-temperature short-time annealing temperature is 700-1000℃ and the low-temperature short-time annealing time is 0.5-1.5h.

[0018] In the method for improving the corrosion resistance of eutectic high-entropy alloys, in step (5), the quenching medium is water and the temperature is 10-30℃.

[0019] The method for improving the corrosion resistance of eutectic high-entropy alloys, after the treatment in steps (1) to (5), fine FCC phases rich in Cr are precipitated in the B2 layer of the eutectic high-entropy alloy, and at the same time, structural defects such as dislocations, subgrain boundaries, small-angle and large-angle grain boundaries and twin boundaries are introduced into the alloy.

[0020] The method for improving the corrosion resistance of eutectic high-entropy alloys, after treatment in steps (1) to (5), results in a self-corrosion potential of the eutectic high-entropy alloy in a 3.5% sodium chloride aqueous solution of -0.25 to -0.16 V (vs SCE), and a corrosion current density of 6.0 × 10⁻⁶ V. -8 ~3×10 -7 A / cm 2 The pitting potential is 0.17–0.24 V (vs SCE), and the passivation current density is 1 × 10⁻⁶. -7 ~7×10 -7 A / cm 2 .

[0021] The present invention discloses a method for improving the corrosion resistance of eutectic high-entropy alloys. The design concept of this method is as follows:

[0022] AlCoCrFeNi eutectic high-entropy alloys consist of two phases: FCC and B2. The FCC phase is rich in CoCrFe, while the B2 phase is rich in NiAl. Studies (doi.org / 10.1007 / s11665-021-06563-w) show that the FCC phase, due to its high CoCrFe content, forms a dense passivation film with good protection rich in Cr2O3 on its surface. Conversely, the B2 phase, rich in NiAl, mainly forms a porous passivation film with poor protection rich in Al2O3. Therefore, in corrosive media, the eutectic high-entropy alloy primarily undergoes selective corrosion of the B2 phase. Current research also indicates that structural defects such as dislocations, subgrain boundaries, grain boundaries, and twin boundaries in the material can serve as nucleation sites for the passivation film, promoting rapid growth and repassivation capabilities. Constructing these structural defects in the material can effectively improve its corrosion resistance in corrosive media.

[0023] This invention utilizes controlled cold rolling and low-temperature short-time annealing processes to regulate the microstructure of eutectic high-entropy alloys. On one hand, it induces the precipitation of fine FCC phases rich in Cr in the B2 lamellars, promoting the formation of a protective passivation film on the B2 lamellar surface. On the other hand, it introduces structural defects such as dislocations, subgrain boundaries, small-angle and large-angle grain boundaries, and twin boundaries into the eutectic high-entropy alloy, providing diffusion channels for the outward diffusion of passivation film-forming elements and promoting the nucleation and growth of the corrosion-resistant passivation film on the alloy surface. By combining these microstructural characteristics, the corrosion resistance of the eutectic high-entropy alloy in corrosive media is improved.

[0024] The present invention discloses a method for improving the corrosion resistance of eutectic high-entropy alloys, which has the following characteristics:

[0025] 1. The method of this invention is simple, easy to implement, and low in cost. It only requires cold rolling and low-temperature short-time annealing to significantly improve the corrosion resistance of eutectic high-entropy alloys, facilitating large-scale industrial production and application. The eutectic high-entropy alloys prepared by this method can meet the urgent needs of aerospace, automotive manufacturing, and other fields for high-performance metallic materials.

[0026] 2. This invention can promote the application of eutectic high-entropy alloys in practical engineering fields, and has important academic value and social benefits. Attached Figure Description

[0027] Figure 1 AlCrFe2O3 prepared by the method of the present invention in Example 1 1.5 Ni 2.6 EBSD phase distribution diagram of eutectic high-entropy alloy (low-temperature short-time annealing temperature of 800℃);

[0028] Figure 2AlCrFe2O3 prepared by the method of the present invention in Example 1 1.5 Ni 2.6 Recrystallization distribution diagram of eutectic high-entropy alloy (low-temperature short-time annealing temperature of 800℃);

[0029] Figure 3 AlCrFe2O3 prepared by the method of the present invention in Example 1 1.5 Ni 2.6 EBSD IPF plot of eutectic high-entropy alloy (low-temperature short-time annealing temperature of 800℃);

[0030] Figure 4 AlCrFe2O3 prepared by the method of the present invention in Example 1 1.5 Ni 2.6 Grain boundary distribution diagram of eutectic high-entropy alloy (low-temperature short-time annealing temperature of 800℃);

[0031] Figure 5 AlCrFe2O3 prepared by the method of the present invention in Example 1 1.5 Ni 2.6 Potentiodynamic polarization curves of a eutectic high-entropy alloy (short-time annealing temperature of 800℃) in a 3.5wt% sodium chloride aqueous solution. In the figure, the horizontal axis logi represents the corrosion current density (A / cm). 2 The vertical axis E represents the self-corrosion potential (V vs. SCE).

[0032] Figure 6 Comparative Example 1: As-cast AlCrFe 1.5 Ni 2.6 EBSD phase distribution diagram of eutectic high-entropy alloy;

[0033] Figure 7 Comparative Example 1: As-cast AlCrFe 1.5 Ni 2.6 Grain boundary distribution diagram of eutectic high-entropy alloy;

[0034] Figure 8 Comparative Example 1: As-cast AlCrFe 1.5 Ni 2.6 Potentiodynamic polarization curves of eutectic high-entropy alloys in 3.5 wt% sodium chloride aqueous solution. In the figure, the horizontal axis logi represents the corrosion current density (A / cm). 2 The vertical axis E represents the self-corrosion potential (Vvs.SCE). Detailed Implementation

[0035] In its specific implementation, this invention proposes a method to improve the corrosion resistance of eutectic high-entropy alloys. The steps of this method are as follows: homogenization annealing → quenching → cold rolling → low-temperature short-time annealing → quenching. Through the treatment of this invention, fine FCC phases rich in Cr are precipitated in the B2 lamellars of the eutectic high-entropy alloy, while structural defects such as dislocations, subgrain boundaries, small-angle and large-angle grain boundaries, and twin boundaries are introduced into the alloy.

[0036] The invention will now be further described with reference to specific examples:

[0037] Example 1:

[0038] The chemical formula of the eutectic high-entropy alloy in this embodiment is AlCrFe. 1.5 Ni 2.6 The composition (at%) is Al 16.39%, Cr 16.39%, Fe 24.59%, and Ni 42.63%.

[0039] AlCrFe 1.5 Ni 2.6 The eutectic high-entropy alloy was homogenized and annealed at 1200℃ for 24 hours, followed by water quenching at 24℃. The homogenized and quenched eutectic high-entropy alloy was then subjected to multi-pass cold rolling, with a reduction of 10% per pass and a total reduction of 78%. The cold-rolled eutectic high-entropy alloy was then annealed at 800℃ for 1 hour, followed by water quenching at 26℃.

[0040] like Figure 1 As shown in the EBSD phase distribution diagram of the eutectic high-entropy alloy prepared in Example 1, it can be seen that AlCrFe 1.5 Ni 2.6 Fine FCC phases rich in Cr precipitated in the B2 lamellae of the eutectic high-entropy alloy; such as Figure 2 As shown in the recrystallization distribution diagram of the eutectic high-entropy alloy prepared in Example 1, partial recrystallization occurred in the prepared alloy. The alloy simultaneously contains deformed structures, substructures, and recrystallized structures, with area proportions of 55.5%, 10.6%, and 33.9%, respectively. The deformed and substructure structures generally contain a large number of dislocations and subgrain boundaries. Figure 3 As shown in the EBSD IPF image of the eutectic high-entropy alloy prepared in Example 1, it can be seen that the prepared alloy simultaneously contains ultrafine / nanocrystalline grains, micron-sized recrystallization, and lamellar coarse grains. Figure 4 As shown in the figure, the grain boundary distribution diagram of the eutectic high-entropy alloy prepared in Example 1 shows that there are a large number of small-angle and large-angle grain boundaries in the prepared alloy. At the same time, annealing twins are formed in the FCC layers, and the twin grain boundary ratio is 25.2%.

[0041] like Figure 5 As shown, the potentiodynamic polarization curve of the eutectic high-entropy alloy prepared in Example 1 in a 3.5 wt% sodium chloride aqueous solution is displayed. The self-corrosion potential of the alloy is -0.21 V (vs SCE), and the corrosion current density is 1.3 × 10⁻⁶. -7 A / cm 2 The pitting potential is 0.21V (vs SCE), and the passivation current density is 6.7×10⁻⁶. -7 A / cm 2 .

[0042] Comparative Example 1:

[0043] The chemical formula of this comparative eutectic high-entropy alloy is AlCrFe. 1.5 Ni 2.6 The composition (at%) is Al 16.39%, Cr 16.39%, Fe 24.59%, and Ni 42.63%. In this comparative example, the eutectic high-entropy alloy is in the as-cast state.

[0044] like Figure 6 As shown, Comparative Example 1: As-cast AlCrFe 1.5 Ni 2.6 The EBSD phase distribution diagram of the eutectic high-entropy alloy reveals that the as-cast AlCrFe 1.5 Ni 2.6 The eutectic high-entropy alloy has a simple lamellar microstructure, and the B2 lamellars do not contain fine FCC precipitates rich in Cr. For example... Figure 7 As shown, Comparative Example 1: As-cast AlCrFe 1.5 Ni 2.6 The grain boundary distribution diagram of the eutectic high-entropy alloy reveals that the as-cast AlCrFe 1.5 Ni 2.6 The content of structural defects such as grain boundaries and twin boundaries in the eutectic high-entropy alloy is lower than that in the alloy prepared by this invention.

[0045] like Figure 8 As shown, Comparative Example 1: As-cast AlCrFe 1.5 Ni 2.6 The potentiodynamic polarization curves of the eutectic high-entropy alloy in a 3.5 wt% sodium chloride aqueous solution are shown. The alloy's self-corrosion potential is -0.26 V (vs SCE), and the corrosion current density is 3.2 × 10⁻⁶. -7 A / cm 2 The pitting potential is 0.16V (vs SCE), and the passivation current density is 7.2×10⁻⁶. -7 A / cm 2 .

[0046] By comparing the AlCrFe prepared by the method of the present invention 1.5 Ni2.6 Eutectic high-entropy alloys and as-cast AlCrFe 1.5 Ni 2.6 Electrochemical parameters of the eutectic high-entropy alloy revealed that after cold rolling and low-temperature short-time annealing, the self-corrosion potential and pitting potential of the eutectic high-entropy alloy increased, while the corrosion current density and passivation current density decreased, indicating that the corrosion resistance of the eutectic high-entropy alloy prepared by the method of this invention was significantly improved. The above results demonstrate that the microstructure of the eutectic high-entropy alloy after cold rolling and low-temperature short-time annealing promotes the nucleation and growth of the corrosion-resistant passivation film on the surface of the eutectic high-entropy alloy, thereby improving its corrosion resistance in corrosive media. The method of this invention is simple, easy to implement, and low-cost, making it very suitable for the industrial production and application of high-performance eutectic high-entropy alloys.

[0047] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and are not intended to limit them. Although the invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features therein. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for improving the corrosion resistance of eutectic high-entropy alloys, characterized in that, Includes the following steps: (1) Homogenize the eutectic high-entropy alloy matrix by annealing; (2) Quenching treatment is performed on the eutectic high-entropy alloy after homogenization annealing; (3) The eutectic high-entropy alloy after homogenization annealing and quenching is subjected to cold rolling; (4) Perform low-temperature short-time annealing on the eutectic high-entropy alloy after cold rolling; (5) Quenching treatment is performed on the eutectic high-entropy alloy after low-temperature short-time annealing; The eutectic high-entropy alloy matrix is ​​composed of Al, Co, Cr, Fe, and Ni elements, and the general alloy formula is AlCo. 1-x CrFe 1+x / 2 Ni 2.1+x / 2 , where 0 < x ≤ 1, and x is the molar ratio of the elements; In step (3), the cold rolling process is a multi-pass cold rolling process, and the total reduction of the cold rolling process is 70%~90%; In step (4), the low-temperature short-time annealing temperature is 700~1000℃, and the low-temperature short-time annealing time is 0.5~1.5h; After the treatment in steps (1) to (5), fine FCC phases rich in Cr were precipitated in the B2 layer of the eutectic high entropy alloy. At the same time, structural defects such as dislocations, subgrain boundaries, small-angle and large-angle grain boundaries and twin boundaries were introduced into the alloy.

2. The method for improving the corrosion resistance of eutectic high-entropy alloys according to claim 1, characterized in that, The value of x is 1.

3. The method for improving the corrosion resistance of eutectic high-entropy alloys according to claim 1, characterized in that, In step (1), the homogenization annealing temperature is 1150~1250℃ and the homogenization annealing time is 12~36h.

4. The method for improving the corrosion resistance of eutectic high-entropy alloys according to claim 1, characterized in that, In step (2), the quenching medium is water, and the temperature is 10~30℃.

5. The method for improving the corrosion resistance of eutectic high-entropy alloys according to claim 1, characterized in that, In step (5), the quenching medium is water, and the temperature is 10~30℃.

6. The method for improving the corrosion resistance of eutectic high-entropy alloys according to any one of claims 1 to 5, characterized in that, After steps (1) to (5), the self-corrosion potential of the eutectic high-entropy alloy in a 3.5% sodium chloride aqueous solution is -0.25 to -0.16 V (vs SCE), and the corrosion current density is 6.0 × 10⁻⁶. -8 ~3×10 -7 A / cm 2 The pitting potential is 0.17~0.24V (vs SCE), and the passivation current density is 1×10⁻⁶. -7 ~7×10 -7 A / cm 2 .

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