Method for improving mechanical properties of eutectic high-entropy alloy

Abstract

This invention belongs to the field of alloy material preparation technology, specifically relating to a method for improving the mechanical properties of eutectic high-entropy alloys. The method comprises the following steps: homogenization annealing → quenching → cold rolling → low-temperature short-time annealing → quenching. This invention constructs a multi-layered heterogeneous lamellar structure in the eutectic high-entropy alloy through cold rolling and low-temperature short-time annealing, enhancing the strengthening and hardening effect of the eutectic high-entropy alloy during deformation, thereby improving its mechanical properties. This method is simple, easy to implement, and low-cost. The preparation process parameters can be flexibly selected according to the performance requirements of the service environment, making it highly suitable for the industrial production and application of high-performance eutectic high-entropy alloys.

Description

Technical Field

[0001] This invention belongs to the field of alloy material preparation technology, specifically relating to a method for improving the mechanical properties of eutectic high-entropy alloys. The method allows for flexible selection of preparation process parameters based on the performance requirements of the service environment, resulting in eutectic high-entropy alloys with excellent mechanical properties, which can be applied to key metal components in high-end industrial fields such as aerospace and automotive manufacturing. Background Technology

[0002] Eutectic high-entropy alloys are high-entropy alloys obtained through eutectic reactions, possessing characteristics of both high-entropy and eutectic alloys. The four major effects present in high-entropy alloys—high-entropy effect, lattice distortion effect, hysteresis diffusion effect, and cocktail effect—give them superior properties distinct from traditional alloys. Eutectic alloys, obtained through isothermal transformation processes, generally exhibit good fluidity, which helps reduce casting defects and dendrite segregation during the casting process, thus improving the alloy's casting performance. Furthermore, eutectic alloys have a regularly arranged layered or rod-like structure, which can be considered an in-situ self-generated composite material. Therefore, the mechanical properties of the material can be coordinated and improved by controlling the phase composition of the two phases in the eutectic alloy. In addition, the eutectic structure may also endow the material with special optical effects, electromagnetic effects, magnetoelectric effects, and other superimposed effects. These characteristics make eutectic high-entropy alloys widely valuable for research and application in materials science, energy, and metallurgy. Since the concept of eutectic high-entropy alloys was proposed, a large number of eutectic high-entropy alloy systems have been developed. Among them, the most widely studied is the AlCoCrFeNi eutectic high-entropy alloy system. This system exhibits good strength-plasticity matching ability under wide temperature range conditions. At the same time, its corrosion resistance in seawater is comparable to that of some stainless steels and far exceeds that of copper alloys. Therefore, it is expected to replace copper alloys in ship structural components, such as propellers, pumps and valves, condensers, and key metal structural materials for seawater piping systems.

[0003] While AlCoCrFeNi-based eutectic high-entropy alloys possess the advantage of strong and ductile properties, their mechanical properties still fall short compared to ultra-high-strength steels such as martensitic steel and transformation-induced plasticity steel. This makes it difficult to meet the performance requirements of metallic materials in high-end industrial fields such as aerospace and automotive manufacturing, significantly limiting the engineering application and promotion of eutectic high-entropy alloys. Therefore, developing a method to improve the mechanical properties of eutectic high-entropy alloys can further expand their application in practical engineering fields, possessing significant academic value and social benefits. Summary of the Invention

[0004] The purpose of this invention is to provide a method for improving the mechanical properties of eutectic high-entropy alloys. This method can produce eutectic high-entropy alloys with excellent mechanical properties, which are suitable for use as structural materials for key metal components in high-end industrial fields such as aerospace and automobile manufacturing.

[0005] To achieve the above objectives, the present invention adopts the following technical solution:

[0006] A method for improving the mechanical properties of eutectic high-entropy alloys includes the following steps:

[0007] (1) Homogenize the eutectic high-entropy alloy matrix by annealing;

[0008] (2) Quenching the eutectic high-entropy alloy after homogenization annealing;

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

[0010] (4) The eutectic high-entropy alloy after cold rolling is subjected to low-temperature short-time annealing;

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

[0012] The method for improving the mechanical properties of eutectic high-entropy alloys, wherein the eutectic high-entropy alloy matrix is ​​composed of Al, Co, Cr, Fe and Ni elements, and the alloy formula is AlCo. 1-x CrFe 1+x / 2 Ni 2.1+x / 2 Where 0 < x ≤ 1, x is the molar ratio of the elements, and the preferred value of x is 1.

[0013] In the method for improving the mechanical properties of eutectic high-entropy alloys, in step (1), the homogenization annealing temperature is 1150-1250℃ and the homogenization annealing time is 12-36h.

[0014] In the method for improving the mechanical properties of eutectic high-entropy alloys, in step (2), the quenching medium is water and the temperature is 10-30℃.

[0015] In the method for improving the mechanical properties of eutectic high-entropy alloys, step (3) involves multi-pass cold rolling, with a total reduction of 70% to 90%, preferably 5% to 10% per pass.

[0016] In the method for improving the mechanical properties of eutectic high-entropy alloys, in step (4), the low-temperature short-time annealing temperature is 600-1000℃ and the low-temperature short-time annealing time is 0.5-1.5h.

[0017] In the method for improving the mechanical properties of eutectic high-entropy alloys, in step (5), the quenching medium is water and the temperature is 10-30℃.

[0018] The method for improving the mechanical properties of eutectic high-entropy alloys, after processing in steps (1) to (5), results in a multi-layered heterogeneous lamellar structure in the eutectic high-entropy alloy. The main characteristics of this multi-layered heterogeneous lamellar structure are: fine B2 precipitates are precipitated in the FCC lamellars of the treated eutectic high-entropy alloy, and fine FCC precipitates are precipitated in the B2 lamellars, thus constituting heterogeneity in the size and spatial distribution of the two phases; the treated eutectic high-entropy alloy undergoes selective recrystallization of the FCC phase, resulting in the simultaneous presence of ultrafine / nanocrystalline, micron-level recrystallization, and lamellar coarse grains in the alloy, thus constituting heterogeneity in the size of the grains at multiple scales; at the same time, a certain proportion of twins exists in the treated eutectic high-entropy alloy, with the preferred twin grain boundary ratio being 20% ​​to 30%.

[0019] The method for improving the mechanical properties of eutectic high-entropy alloys, after processing in steps (1) to (5), results in a room temperature tensile yield strength of 600 to 1300 MPa, a tensile strength of 1050 to 1750 MPa, and a fracture elongation of 6% to 25% for the eutectic high-entropy alloys.

[0020] This invention discloses a method for improving the mechanical properties of eutectic high-entropy alloys. The design concept of this method is as follows:

[0021] The excellent strength-ductility matching ability of eutectic high-entropy alloys is fundamentally due to the fact that this alloy system is an in-situ self-generated composite material. Compared with traditional homogeneous structural materials, eutectic high-entropy alloys exhibit non-uniform distribution characteristics in their internal spatial composition, structure, and properties. In the field of materials science, this type of metallic material with "soft" and "hard" structural units is called "heterogeneous metallic material." The inspiration for heterogeneous structure design originates from natural biological materials, such as seashells and abalone shells. These types of biological materials generally possess excellent strength-ductility matching capabilities, mainly because these materials have complex multiphase, multiscale, and multi-level structural features.

[0022] This invention, by controlling the composition and processing technology of high-entropy alloys, can introduce a large number of heterogeneous interface structures similar to those in biological materials. During deformation, the presence of numerous heterogeneous interfaces induces a large number of geometrically necessary dislocations to coordinate the strain gradients on both sides of the heterogeneous structure interfaces, generating a heterogeneous deformation-induced strengthening and hardening mechanism. This significantly improves the work-hardening ability of the alloy, ultimately achieving an excellent balance between strength and plasticity. Therefore, constructing multi-scale, multi-level heterogeneous structures in high-entropy alloys through microstructural design is an important approach to obtaining superior mechanical properties.

[0023] Previous research (doi.org / 10.1038 / s41467-019-08460-2) has found that fully recrystallized AlCoCrFeNi can be achieved through cold rolling and non-isothermal annealing. 2.1 Introducing heterogeneity, with coupling of two-phase size and spatial distribution, into eutectic high-entropy alloys yields high-strength and high-ductility dual-phase heterogeneous lamellar high-entropy alloys. Another study (doi.org / 10.1016 / j.actamat.2018.12.012) indicates that by adjusting the cold rolling and isothermal annealing processes, in Al... 0.1 In high-entropy CoCrFeNi alloys, a grain heterogeneous structure including deformed grains and recrystallized grains can be constructed, which simultaneously improves the strength and plasticity of the alloy.

[0024] If a multi-level heterogeneous lamellar structure can be constructed in a eutectic high-entropy alloy by adjusting the preparation process—that is, the heterogeneity of the superposition of the two-phase size and spatial distribution heterogeneity formed by phase decomposition and the recrystallization of the multi-scale grain size heterogeneity—it will effectively enhance the strengthening and hardening effect of the eutectic high-entropy alloy during deformation, thereby significantly improving the mechanical properties of the eutectic high-entropy alloy. Therefore, the method of this invention selects to control the microstructure of the eutectic high-entropy alloy by controlling the preparation process parameters, including the total cold rolling reduction, the low-temperature short-time annealing temperature, and the low-temperature short-time annealing time, etc., to construct a multi-level heterogeneous structure in the alloy and achieve the improvement of the alloy's mechanical properties.

[0025] This invention discloses a method for improving the mechanical properties of eutectic high-entropy alloys, which has the following characteristics:

[0026] 1. The method of the present invention can flexibly select the preparation process parameters according to the different requirements of the service environment for material performance. The eutectic high entropy alloy prepared by the method of the present invention can meet the urgent needs of aerospace, automobile manufacturing, energy and petrochemical fields for high-performance metal materials.

[0027] 2. The method of the present invention is simple, easy to implement, and low in cost. It only requires cold rolling and low-temperature short-time annealing to achieve a significant improvement in the performance of eutectic high-entropy alloys, which is convenient for large-scale industrial production and application. Attached Figure Description

[0028] 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℃);

[0029] Figure 2 AlCrFe2O3 prepared by the method of the present invention in Example 1 1.5 Ni 2.6Recrystallization distribution diagram of eutectic high-entropy alloy (low-temperature short-time annealing temperature of 800℃);

[0030] 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℃);

[0031] 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℃);

[0032] Figure 5 AlCrFe2O3 prepared by the method of the present invention in Example 1 1.5 Ni 2.6 Engineering stress-strain curves of eutectic high-entropy alloy (low-temperature short-time annealing temperature of 800℃); in the figure, the horizontal axis Strain represents strain (%) and the vertical axis Stress represents stress (MPa);

[0033] Figure 6 AlCrFe2 prepared using the method of the present invention in Example 2 1.5 Ni 2.6 EBSD phase distribution diagram of eutectic high-entropy alloy (low-temperature short-time annealing temperature of 900℃);

[0034] Figure 7 AlCrFe2 prepared using the method of the present invention in Example 2 1.5 Ni 2.6 Recrystallization distribution diagram of eutectic high-entropy alloy (low-temperature short-time annealing temperature of 900℃);

[0035] Figure 8 AlCrFe2 prepared using the method of the present invention in Example 2 1.5 Ni 2.6 EBSD IPF plot of eutectic high-entropy alloy (low-temperature short-time annealing temperature of 900℃);

[0036] Figure 9 AlCrFe2 prepared using the method of the present invention in Example 2 1.5 Ni 2.6 Grain boundary distribution diagram of eutectic high-entropy alloy (low-temperature short-time annealing temperature of 900℃);

[0037] Figure 10 AlCrFe2 prepared using the method of the present invention in Example 2 1.5 Ni 2.6Engineering stress-strain curves of eutectic high-entropy alloy (low-temperature short-time annealing temperature of 900℃); in the figure, the horizontal axis Strain represents strain (%) and the vertical axis Stress represents stress (MPa).

[0038] Figure 11 Comparative Example 1: As-cast AlCrFe 1.5 Ni 2.6 EBSD phase distribution diagram of eutectic high-entropy alloy;

[0039] Figure 12 Comparative Example 1: As-cast AlCrFe 1.5 Ni 2.6 Engineering stress-strain curves of eutectic high-entropy alloys; in the figure, the horizontal axis Strain represents strain (%) and the vertical axis Stress represents stress (MPa). Detailed Implementation

[0040] The invention will be further illustrated below with specific examples:

[0041] Example 1:

[0042] 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%.

[0043] 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℃.

[0044] 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 B2 phases exist within the FCC lamellae of the eutectic high-entropy alloy, while fine FCC phases exist within the B2 lamellae, indicating that the alloy preparation exhibits heterogeneity in both phase size and spatial distribution; for example... Figure 2 As shown in the recrystallization distribution diagram of the eutectic high-entropy alloy prepared in Example 1, it can be observed that the alloy simultaneously contains deformation structure, substructure structure, and recrystallization structure, with the area proportions of each structure being 55.5%, 10.6%, and 33.9%, respectively. 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, micron-level recrystallization, and lamellar coarse grains, that is, the alloy exhibits heterogeneity in multi-scale grain size. Figure 4 As shown in the grain boundary distribution diagram of the eutectic high-entropy alloy prepared in Example 1, it can be found that annealed twins were formed in the FCC layers of the alloy, and the twin grain boundary ratio was 25.2%.

[0045] like Figure 5 As shown, the engineering stress-strain curve of the eutectic high-entropy alloy prepared in Example 1 is shown. The room temperature tensile yield strength of the prepared alloy is 985 MPa, the tensile strength is 1405 MPa, and the elongation at break is 18%.

[0046] Example 2:

[0047] 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%.

[0048] 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 20℃. The homogenized and quenched eutectic high-entropy alloy was then subjected to multi-pass cold rolling, with a reduction of 8% per pass and a total reduction of 75%. The cold-rolled eutectic high-entropy alloy was then annealed at 900℃ for 1 hour, followed by water quenching at 24℃.

[0049] like Figure 6 As shown in the EBSD phase distribution diagram of the eutectic high-entropy alloy prepared in Example 2, it can be seen that the eutectic high-entropy alloy prepared in Example 2 also exhibits heterogeneity in the size and spatial distribution of the two phases; as Figure 7 As shown in the recrystallization distribution diagram of the eutectic high-entropy alloy prepared in Example 2, it can be observed that the prepared alloy also simultaneously contains deformation structure, substructure structure, and recrystallization structure, with the area proportions of each structure being 19.5%, 40.8%, and 39.7%, respectively. Figure 8 As shown in the EBSD IPF image of the eutectic high-entropy alloy prepared in Example 2, it can be seen that the alloy prepared in Example 2 also contains ultrafine / nanocrystalline, micron-recrystallized, and lamellar coarse grains, that is, the alloy prepared in Example 2 also forms heterogeneity of multi-scale grain size. Figure 9As shown in the grain boundary distribution diagram of the eutectic high-entropy alloy prepared in Example 2, it can be found that annealed twins are formed in the FCC layers, and the proportion of twin grain boundaries is 21.4%.

[0050] like Figure 10 As shown, the engineering stress-strain curve of the eutectic high-entropy alloy prepared in Example 2 is shown. The room temperature tensile yield strength of this alloy is 757 MPa, the tensile strength is 1162 MPa, and the elongation at break is 18.5%.

[0051] Comparative Example 1:

[0052] 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%. This comparative alloy has a cast structure.

[0053] like Figure 11 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 Eutectic high-entropy alloys have a simple lamellar structure, with no fine precipitates in each lamellar.

[0054] like Figure 12 As shown, Comparative Example 1: As-cast AlCrFe 1.5 Ni 2.6 The engineering stress-strain curve of the eutectic high-entropy alloy shows that the as-cast yield strength is 522 MPa, the tensile strength is 1028 MPa, and the elongation is 18.3%.

[0055] By comparing the AlCrFe prepared by the method of the present invention 1.5 Ni 2.6 Eutectic high-entropy alloys and as-cast AlCrFe 1.5 Ni 2.6 The mechanical properties of the eutectic high-entropy alloys show that the strength of the alloys prepared by the method of this invention is significantly improved, while the elongation at break remains essentially unchanged. This indicates that the method of this invention can significantly improve the mechanical properties of eutectic high-entropy alloys. Table 1 also lists AlCrFe alloys prepared in other embodiments of this invention. 1.5 Ni 2.6 The mechanical properties of eutectic high-entropy alloys can be observed by adjusting the preparation process parameters in the method of this invention to obtain eutectic high-entropy alloys with high strength or high plasticity.

[0056] Table 1. AlCrFe prepared in other embodiments of the present invention1.5 Ni 2.6 Mechanical properties of eutectic high-entropy alloys.

[0057]

[0058] The results show that this invention constructs a multi-layered heterogeneous lamellar structure in eutectic high-entropy alloys through cold rolling and low-temperature short-time annealing, enhancing the strengthening and hardening effect of the eutectic high-entropy alloy during deformation, thereby improving the mechanical properties of the eutectic high-entropy alloy. The method of this invention is simple, easy to implement, and low-cost. The preparation process parameters can be flexibly selected according to the performance requirements of the material in the service environment, making it very suitable for the industrial production and application of high-performance eutectic high-entropy alloys.

[0059] 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 mechanical properties 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; 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 600~1000℃, and the low-temperature short-time annealing time is 0.5~1.5h; The eutectic high-entropy alloy matrix is composed of Al, Co, Cr, Fe and Ni elements, and the general formula of the alloy is AlCo 1-x CrFe 1+x / 2 Ni 2.1+x / 2 wherein 0 < x < 1, x is the molar ratio of the elements.

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

3. The method for improving the mechanical properties 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 mechanical properties 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 mechanical properties 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 mechanical properties of eutectic high-entropy alloys according to any one of claims 1 to 5, characterized in that, After processing in steps (1) to (5), the microstructure of the eutectic high entropy alloy is a multi-level heterogeneous lamellar structure. The main characteristics of the multi-level heterogeneous lamellar structure are: fine B2 precipitates are precipitated in the FCC lamellars of the processed eutectic high entropy alloy, and fine FCC precipitates are precipitated in the B2 lamellars, thus forming heterogeneity in the size and spatial distribution of the two phases; the processed eutectic high entropy alloy undergoes selective recrystallization of the FCC phase, resulting in the simultaneous presence of ultrafine / nanocrystalline, micron recrystallization and lamellar coarse grains in the alloy, thus forming heterogeneity in the size of the grains at multiple scales; at the same time, a certain proportion of twins exist in the processed eutectic high entropy alloy.

7. The method for improving the mechanical properties of eutectic high-entropy alloys according to any one of claims 1 to 5, characterized in that, After processing in steps (1) to (5), the room temperature tensile yield strength of the eutectic high entropy alloy is 600~1300MPa, the tensile strength is 1050~1750MPa, and the elongation at break is 6%~25%.

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