High-entropy alloy with excellent creep performance and preparation method thereof

Abstract

The application relates to a high-entropy alloy with excellent creep performance and a preparation method thereof. a Co b Cr c Ni d Ta p Al q M n wherein 10<=a<=20, 20<=b<=25, 10<=c<=20, 25<=d<=35, 5<=p<=10, 0<=q<=8 and 0<=n<=5. The preparation method comprises the following steps: allocating raw materials according to designed components, then carrying out smelting under a protective atmosphere, and then carrying out solid solution water quenching treatment + hot rolling treatment and again solid solution treatment, and then quenching after heat preservation at 750 DEG C to 950 DEG C. The product is obtained by reasonably regulating and controlling components, heat deformation and heat treatment processes. The product has a service life of 1245h under high-temperature creep conditions of 750 DEG C / 350MPa, is far higher than similar products, has a tensile strength of greater than 1.5GPa at room temperature, breaks through the bottleneck that Laves eutectic high-entropy alloys have no tensile plasticity at room temperature, and has a wide engineering application prospect.

Description

Technical Field

[0001] This invention belongs to the field of high-entropy alloy materials technology, and specifically relates to a high-entropy alloy with excellent creep properties, its preparation method, and the preparation method thereof. Background Technology

[0002] High entropy alloys (HEAs) are solid solutions composed of five or more constituent elements in equiatomic or near-equiatomic ratios, with the atomic ratio of each main element ranging from 5% to 35%. Due to their high thermodynamic mixing entropy effect, severe crystallographic lattice distortion effect, kinetic hysteresis diffusion effect, and the "cocktail" effect in overall performance, HEAs are considered one of the most promising and competitive materials of the 21st century, boasting superior physical, chemical, and mechanical properties compared to traditional alloy materials, including outstanding mechanical properties, good corrosion resistance, excellent thermal stability, and remarkable soft magnetic properties.

[0003] However, practical engineering applications place higher demands on the strength and plasticity of structural materials. Single-phase FCC-structured HEA systems (such as Cantor alloys) exhibit good plasticity with elongation after fracture exceeding 50%, but their tensile strength is only around 500 MPa. Body-centered cubic (BCC) structured HEA systems (such as TiZrHfNb alloys) can achieve tensile strengths of around 800 MPa, but they do not exhibit significant room-temperature macroscopic plastic deformation. This inverse relationship between strength and plasticity severely restricts the large-scale application of HEAs as advanced structural materials in engineering. Therefore, how to maximize ultra-high tensile strength while ensuring plasticity applicable to practical engineering is currently a key research focus in the field of high-entropy alloys.

[0004] In recent years, eutectic high entropy alloys (EHEAs) have been extensively studied and developed rapidly. Compared with the above-mentioned HEAs, EHEAs have some new structural and performance characteristics, such as: (1) tightly packed multiphase ultrafine lamellar layers; (2) near-equilibrium microstructure with strong casting fluidity; (3) adjustable microstructure and high defect structure stability; (4) outstanding creep resistance and fracture strength, which can achieve good synergistic control of strength and plasticity. Taking FeCoCrNiTa-based EHEAs as an example, its microstructure consists of FCC soft phase and Laves hard phase, in which the Laves phase and FCC phase are eutectic reaction products: the FCC phase is relatively soft, which can provide a large space for dislocation accumulation; the Laves phase is hard and brittle, which, although providing high overall strength, is very easy to induce crack initiation and propagation, resulting in the overall brittle fracture of the EHEA. In general, its room temperature intrinsic brittleness limits the alloy's processing and deformation capabilities, while the high density cannot meet the demand for low cost. Therefore, obtaining new eutectic high-entropy alloy compositions through reasonable composition design methods and studying the optimization of the alloy's microstructure and properties has significant theoretical and practical value. Summary of the Invention

[0005] To address the shortcomings of existing technologies, the present invention aims to provide a high-entropy alloy with excellent creep properties and its preparation method. By rationally controlling the alloy composition and subsequent hot deformation and heat treatment processes, a synergistic strengthening effect of the Laves hard and brittle phase and the L12 nano-precipitate phase is introduced into the FCC-type HEA matrix, forming a positive synergy of soft and hard dual-phase structure, which effectively improves the room temperature tensile properties and high temperature creep properties of the material.

[0006] To achieve the above objectives, the present invention adopts the following technical solution:

[0007] This invention utilizes a soft-hard dual-phase structure to control the room-temperature tensile properties and high-temperature creep properties of the material. The alloy composition, expressed as atomic molar percentage, is: Fe a Co b Cr c Ni d Ta p Al q M n The M is one or more of rare earth elements (Ru and Re), B, C, Si, and P; wherein 10≤a≤20, 20≤b≤25, 10≤c≤20, 25≤d≤35, 5≤p≤10, 0≤q≤8, 0≤n≤5, and a+b+c+d+p+q+n=100.

[0008] Preferably, the alloy composition, expressed as atomic molar percentage, is: Fe a Co b Cr c Ni d Tap Al q M n The M is one or more of rare earth elements, B, C, Si, and P; wherein 16≤a≤20, 23≤b≤25, 16≤c≤20, 25≤d≤28, 5≤p≤8, 5≤q≤8, 0≤n≤1 and a+b+c+d+p+q+n=100, and the rare earth element is Ru and / or Re.

[0009] As a further preferred option, the alloy composition, expressed as atomic molar percentage, is: Fe a Co b Cr c Ni d Ta p Al q M n The M is one or more of rare earth elements, B, C, Si, and P; wherein 18≤a≤19, 24.5≤b≤25, 17.5≤c≤18.5, 25.5≤d≤26.5, 5.5≤p≤6.5, 5.5≤q≤6.5, 0.02≤n≤0.1 and a+b+c+d+p+q+n=100, and the rare earth element is Ru and / or Re.

[0010] The designed composition includes Fe. 18.95 Co 25 Cr 18 Ni 26 Ta6Al6B 0.05 Fe 19 Co 25 Cr 18 Ni 26 Ta6Al5Ru 1.5 Of the two schemes, Fe 18.95 Co 25 Cr 18 Ni 26 Ta6Al6B 0.05 This component, combined with the optimized process of this invention, results in a product whose performance far surpasses that of other technical solutions of this invention and existing similar products.

[0011] The present invention discloses a high-entropy alloy with excellent creep properties, which contains a soft matrix and a hard phase. The soft matrix includes at least one of FCC phase and L12 phase, preferably FCC phase and L12 phase, and the hard phase includes at least one of Laves phase, B2 phase, σ phase and η phase, preferably Laves phase.

[0012] Preferably, in this invention, the L12 coherent phase and the plastic face-centered cubic (FCC) solid solution are used as a soft matrix.

[0013] In this invention, the Laves hard phase is the reinforcing phase.

[0014] The Laves phase is preferably a C14 type (MgZn2 structure) Laves phase.

[0015] This invention utilizes a dual-phase structure of soft and hard materials to synergistically control the strength and plasticity of the material.

[0016] This invention provides a novel high-entropy alloy with excellent creep properties and its preparation method. Compared with the high-temperature alloy with the Chinese designation GH4169, it has superior creep properties and superior tensile strength and room temperature tensile plasticity compared with the as-cast Laves-type eutectic high-entropy alloy.

[0017] In the preferred scheme, M is one or more of the elements Ru, Re, B, etc.

[0018] This invention discloses a high-entropy alloy with excellent creep properties, comprising the following steps:

[0019] Step 1

[0020] Raw materials are formulated according to the composition design, and then smelted and cast to obtain the cast product;

[0021] Step Two

[0022] The obtained as-cast product is subjected to homogenization treatment at a temperature of 1200~1300℃, preferably 1240~1280℃, more preferably 1240~1260℃, and held at that temperature for 20~32 hours, preferably 24 hours.

[0023] Step 3

[0024] The homogenized high-entropy alloy ingot is placed in a heating furnace at 1000~1100℃ and held for 25~60 minutes, preferably 25~35 minutes, and more preferably 30 minutes, and then rolled. The rolling deformation is 35%~90%, preferably 40~80%, and more preferably 60%~75%; to obtain the hot-deformed high-entropy alloy.

[0025] Step Four

[0026] The hot-deformed high-entropy alloy is placed in a heating furnace at 1100~1250℃, preferably 1150~1200℃, and more preferably 1180~1200℃, and held for 20~32 hours, preferably 24 hours, before water quenching to obtain a high-entropy alloy with uniformly distributed spheroidized Laves phase; then placed in a heat treatment furnace at 750℃~950℃, preferably 800~900℃, and held for 16~48 hours, preferably 24 hours, before water quenching to obtain a high-entropy alloy material with nanoscale L12 coherent phase dispersion strengthening.

[0027] This invention discloses a high-entropy alloy with excellent creep properties and its preparation method, wherein the impurity content in the raw materials is less than 0.1%. This invention does not impose particularly strict requirements on the morphology of the raw materials; they can be granular or have other morphologies.

[0028] In industrial applications, the raw materials are melted multiple times (3-5 times) in an electric arc melting furnace under an argon protective atmosphere with oxygen absorption in titanium, according to the designed high-entropy alloy composition ratio, to obtain a master alloy ingot. Then, the master alloy ingot is remelted under an argon protective atmosphere, and the molten master alloy is cast into a water-cooled copper mold using the suction casting device of the electric arc furnace to obtain the initial cast high-entropy alloy ingot.

[0029] In a preferred embodiment, the homogenization process is followed by water quenching to room temperature, which preserves the microstructure at high temperatures.

[0030] In this invention, by homogenizing under the above conditions, microsegregation can be eliminated, Laves spheroidization can be fully achieved and continuous distribution can be reduced, thereby reducing crack propagation along continuously distributed Laves and ensuring mechanical properties.

[0031] In a preferred embodiment, the heat deformation treatment is followed by water quenching to room temperature, and the water quenching treatment can preserve the microstructure at high temperatures.

[0032] The inventors discovered that hot deformation treatment disperses the continuously distributed Laves reinforcing phase inside the alloy, inhibiting crack propagation along the continuously distributed Laves.

[0033] The inventors discovered that after heat treatment in step 1), the volume fraction of the spheroidized Laves phase did not change much, but its distribution became more uniform and dispersed. After step 2), a high-density, nanoscale L12 coherent dispersed strengthening phase was precipitated in the soft phase of the FCC matrix of the high-entropy alloy material.

[0034] The hot rolling deformation process parameters of the present invention have a significant impact on the microstructure of the final material. If the hot rolling deformation is too small, the uniform dispersion of Laves will not be obvious, while if the hot rolling deformation is too large, cracks may be generated, reducing mechanical properties.

[0035] The present invention also provides a high-entropy alloy material with excellent creep properties prepared by the above preparation method.

[0036] In the preferred embodiment, the high-entropy alloy material with excellent creep properties utilizes a soft (FCC+L12) and hard (Laves) dual-phase structure to synergistically control the high-temperature creep properties and room-temperature tensile properties of the material.

[0037] The preferred embodiment yields a nanoscale L12 coherent phase dispersion-strengthened high-entropy alloy material, which is a Laves-strengthened face-centered cubic high-entropy alloy material. Under creep conditions of 750℃ / 350MPa, its lifespan reaches 1245 hours, far exceeding that of the Chinese high-temperature alloy GH4169 (≥1000 hours). Its room-temperature tensile strength is as high as 1.5 GPa, while its elongation after fracture is 5-10%, which can be optimized to 9-10%. Compared with traditional cast Laves-type eutectic high-entropy alloys, the hot-deformed Laves-strengthened face-centered cubic high-entropy alloy exhibits higher strength while significantly improving its plasticity, and also possesses excellent high-temperature creep performance.

[0038] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and equivalent substitutions can be made without departing from the principle of the present invention, and the technical solutions obtained by these improvements and equivalent substitutions should also fall within the protection scope of the present invention.

[0039] Advantages of this invention:

[0040] 1. The face-centered cubic high-entropy alloy with synergistic reinforcement of Laves hard and brittle phase and L12 dispersed nano-precipitates provided by the present invention has excellent high-temperature creep performance and room-temperature tensile performance. Under the creep condition of 750℃ / 300MPa, its service life is far superior to that of the high-temperature alloy with Chinese grade GH4169, and it also has room-temperature tensile plasticity and can be processed.

[0041] 2. The series of face-centered cubic high-entropy alloys with synergistic reinforcement of Laves hard and brittle phase and L12 dispersed nano-precipitates provided by this invention have a wide composition range and broad preparation conditions. The size, volume fraction and distribution of Laves phase and L12 nano-precipitates can be adjusted by modifying both the alloy composition and the subsequent hot deformation and heat treatment processes, thereby achieving the control of the mechanical properties of the alloy.

[0042] 3. The high-entropy alloy with excellent creep properties and its preparation method provided by this invention are both prepared from common non-toxic metal raw materials. The production process is simple and the process time is short. Therefore, it has advantages in terms of safety and economy in engineering applications. Attached Figure Description

[0043] Figure 1 The Fe obtained in Example 1 and Comparative Example 1 of this invention 18.95 Co 25 Cr 18 Ni 26 Ta6Al6B 0.05 Physical image of high-entropy alloy ingots prepared by vacuum arc melting and corresponding SEM images of their microstructure;

[0044] Figure 2 Fe obtained in Example 1 of the present invention 18.95 Co 25 Cr 18 Ni 26 Ta6Al6B 0.05 Scanning electron micrographs of the high-entropy alloy, showing low-magnification microstructures in the solution-treated state, the hot-rolled and re-solution-treated aged state, and high-magnification microstructures after aging at 800℃ and 900℃.

[0045] Figure 3 The hot-rolled and solution-treated aged Fe obtained in Example 1 of this invention 18.95 Co 25 Cr 18 Ni 26 Ta6Al6B 0.05 Transmission electron micrographs of high-entropy alloys, and selected area electron diffraction spots of the Laves and L12 phases;

[0046] Figure 4 High-angle annular dark-field scanning transmission image and corresponding energy spectrum of the hot-rolled + resolution-aged sample obtained in Example 1 of this invention.

[0047] Figure 5 Comparison of room temperature tensile properties curves of alloys in Example 1 and Comparative Example 1 of this invention.

[0048] Figure 6 Comparison of high-temperature creep performance curves of alloys in Example 1 and Comparative Example 2 at 750℃ / 350MPa. Detailed Implementation

[0049] The following examples are provided in conjunction with the method of the present invention.

[0050] The present invention will now be described in detail with reference to specific embodiments and accompanying drawings. These embodiments are implemented based on the technical solutions of the present invention, and detailed implementation methods and specific operation processes are provided.

[0051] The face-centered cubic high-entropy alloys used in the following examples have the following composition: Fe a Co b Cr c Ni d Ta p Al q M n (The content of each element is in atomic molar ratio), where 10≤ a≤20, 20≤ b≤25, 10≤ c≤20, 25≤ d≤35, 5≤ p≤10, 0≤ q≤8, 0≤ n≤5, and a+b+c+d+p+q+n=100;

[0052] Example 1:

[0053] Fe 18.95 Co 25 Cr 18 Ni 26 Ta6Al6B 0.05 Face-centered cubic high-entropy alloys and their preparation methods are described below:

[0054] S1: Face-centered cubic high-entropy alloy ingots were prepared using vacuum arc melting technology;

[0055] S2: The face-centered cubic high-entropy alloy ingot obtained in step S1 is homogenized at 1250℃ for 24 hours and then wire-cut into alloy plates with a thickness of 4mm.

[0056] S3: The face-centered cubic high-entropy alloy plate obtained in step S2 is subjected to hot deformation treatment with a 70% rolling reduction after being held at 1100℃ for 30 minutes.

[0057] S4: The hot-deformed face-centered cubic high-entropy alloy obtained in step S3 is subjected to heat treatment process: held at 1250℃ for 24 hours and water quenched; held at 800℃ for 24 hours and water quenched to obtain a face-centered cubic high-entropy alloy with synergistic reinforcement of Laves hard and brittle phase and L12 dispersed nano precipitate phase, which gives the alloy good processing performance.

[0058] The face-centered cubic high-entropy alloy, which is synergistically reinforced by the Laves hard and brittle phase and the L12 dispersed nano-precipitates obtained in the above steps, was characterized by microstructure and tested for high-temperature creep properties and room-temperature tensile properties.

[0059] High-temperature creep testing of the alloy was conducted using an RDJ-30 mechanical creep testing machine. The test temperature range was 750-900℃, and the applied stress range was 170-400MPa. The specimens were standardized plate-shaped samples, with a test section length of 10mm and a width of 3mm. The resulting alloy, after heat treatment, achieved a high-temperature creep life of 1245 hours at 750℃ / 350MPa.

[0060] A room temperature uniaxial tensile test was performed on an Instron mechanical testing machine at a tensile strain rate of 10. -3 s -1 The sample was an I-shaped sample with a test section length of 3 mm and a width of 1.5 mm. During the test, the change in gauge length of the sample was measured using an AVE 2-model 2663-901 Instron video extensometer. The room temperature tensile strength of the alloy obtained after heat treatment was 1529 MPa, and the elongation at break was 9.5%.

[0061] Example 2:

[0062] The alloy's specific composition is Fe. 19Co 25 Cr 18 Ni 26 Ta6Al5Ru 1.5 All other preparation conditions were the same as in Example 1.

[0063] Finally, the material was found to have a high-temperature creep life of 47 h at 750℃ / 300MPa, a room temperature tensile strength of 1476MPa, and an elongation at break of 4.5%.

[0064] Example 3:

[0065] All other conditions were the same as in Example 1, except that the hot deformation reduction was 40%.

[0066] The final room temperature tensile mechanical properties of the material are: tensile strength of 1463 MPa and elongation at break of 4.4%.

[0067] Comparative Example 1:

[0068] Cast Fe without hot deformation and heat treatment processes 18.95 Co 25 Cr 18 Ni 26 Ta6Al6B 0.05 The room temperature tensile mechanical properties of the face-centered cubic high-entropy alloy are: tensile strength of 1149 MPa and elongation at break of 2.6%.

[0069] Comparative Example 2:

[0070] Calvin M. Stewart studied the creep properties of IN718 alloy (Chinese designation GH4169) at 750℃ / 350MPa, and the tested creep life was 42.7h.

Claims

1. A high-entropy alloy with excellent creep properties, characterized in that: The alloy composition, expressed as atomic molar percentage, is: Fe a Co b Cr c Ni d Ta p Al q M n M is one or more of Ru, Re, B, C, Si, and P; where 18≤a≤19, 24.5≤b≤25, 17.5≤c≤18.5, 25.5≤d≤26.5, 5.5≤p≤6.5, 5.5≤q≤6.5, 0.02≤n≤0.1 and a+b+c+d+p+q+n=100; It contains a soft matrix and a hard phase, wherein the soft matrix includes at least one of the FCC phase and the L12 phase, and the hard phase includes at least one of the Laves phase, the B2 phase, the σ phase, and the η phase.

2. The high-entropy alloy with excellent creep properties according to claim 1, characterized in that: The soft matrix is ​​a composite of FCC and L12 phases, and the hard phase is the Laves phase.

3. The high-entropy alloy with excellent creep properties according to claim 1, characterized in that: The hard phase is the reinforcing phase; the Laves phase is a C14 type Laves phase.

4. A method for preparing a high-entropy alloy with excellent creep properties as described in any one of claims 1-3, characterized in that... Includes the following steps: Step 1 Raw materials are formulated according to the composition design, and then smelted and cast to obtain the cast product; Step Two The obtained as-cast product is subjected to homogenization treatment at a temperature of 1200~1300℃ for 20~32 hours. Step 3 After homogenization, the high-entropy alloy ingot is placed in a heating furnace at 1000~1100℃ and held for 25~60 minutes, and then rolled with a rolling deformation of 35%~90% to obtain the hot-deformed high-entropy alloy. Step Four The hot-deformed high-entropy alloy was placed in a heating furnace at 1100~1250℃ and held for 20~32 hours, then quenched in water to obtain a high-entropy alloy with uniformly distributed spheroidized Laves phase; then placed in a heat treatment furnace at 750℃~950℃ and held for 16~48 hours, then quenched in water to obtain a high-entropy alloy material with nanoscale L12 coherent phase dispersion strengthening.

5. The method for preparing a high-entropy alloy with excellent creep properties according to claim 4, characterized in that: The impurity content in the raw materials is less than 0.1%.

6. The method for preparing a high-entropy alloy with excellent creep properties according to claim 4, characterized in that: In step two, the homogenization temperature is 1240~1280℃; In step three, the rolling deformation is 40-80%; In step four, the hot-deformed high-entropy alloy is placed in a heating furnace at 1150~1200°C and held for 20~32 hours, then quenched in water to obtain a high-entropy alloy with uniformly distributed spheroidized Laves phase; then it is placed in a heat treatment furnace at 800~900°C and held for 16~48 hours, then quenched in water to obtain a high-entropy alloy material with nanoscale L12 coherent phase dispersion strengthening.

7. The method for preparing a high-entropy alloy with excellent creep properties according to claim 4, characterized in that: According to the designed high-entropy alloy composition ratio, each raw material is melted 3 to 5 times in an electric arc melting furnace with an argon protective atmosphere to obtain a master alloy ingot. Then, the master alloy ingot is remelted under an argon protective atmosphere, and the molten master alloy is cast into a water-cooled copper mold using the suction casting device of the electric arc furnace to obtain the initial cast high-entropy alloy ingot.

8. The method for preparing a high-entropy alloy with excellent creep properties according to claim 4, characterized in that: The obtained nanoscale L12 coherent phase dispersion-strengthened high-entropy alloy material is a Laves-strengthened face-centered cubic high-entropy alloy material. Under creep conditions of 750℃ / 350MPa, its lifespan is greater than or equal to 1000h; its room temperature tensile strength is as high as 1.5GPa, while its elongation at break is 5~10%.

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