A seven-element equal-component high-entropy alloy and its preparation method

Abstract

The present invention belongs to the field of high entropy alloys and relates to a seven-element equal-component high entropy alloy and a preparation method thereof. The high entropy alloy is a eutectic high entropy alloy, and the phase of the high entropy alloy is a combination of a BCC phase and a B2 phase; the high entropy alloy includes seven metal elements, namely zirconium, titanium, hafnium, cobalt, nickel, copper, and niobium, and the seven metal elements are in an equimolar ratio. The new combination of the BCC phase and the B2 phase of the high entropy alloy gives the eutectic high entropy alloy excellent high-strength performance, especially the combined phase is conducive to stabilizing its excellent strength at high temperatures. Therefore, based on the eutectic microstructure characteristics of the high entropy alloy, it is more suitable for industrial processing and casting, and common casting defects (such as internal shrinkage, component segregation, etc.) can be prevented from occurring during the casting process, thereby reducing the preparation cost of processing in industrial applications.

Description

Technical Field

[0001] The present invention belongs to the field of high entropy alloy materials, and more specifically, relates to a seven-element equal-component high entropy alloy and a preparation method thereof. Background Art

[0002] The general design concept of traditional alloys is to use one or two primary elements as the main elements. That is, the matrix of the alloy is composed of one or two primary elements. Then, small amounts of other elements are added to the pure metal matrix to improve the overall structure and properties of the alloy, such as traditional alloys such as steel, aluminum alloys, and titanium alloys. However, based on the design concept of traditional alloys, a new type of multi-component alloy with high mixing entropy has been proposed. These alloys generally contain five or more primary elements in a near-equal composition. Subsequently, a large number of high-entropy alloys with properties different from traditional alloys have been designed and developed by researchers around the world, such as high strength, high hardness, corrosion resistance, thermal stability, and magnetic properties. Therefore, high-entropy alloys with multi-principal component characteristics have quickly become a research hotspot in the field of metal materials.

[0003] On the other hand, eutectic alloys, due to their good liquid fluidity and excellent castability, can prevent the occurrence of common casting defects (such as internal shrinkage and composition segregation) during the casting process. These casting defects are the main culprits that damage the mechanical properties of alloy materials and limit their application. In addition, eutectic alloys have a regularly arranged autogenous two-phase lamellar structure and are regarded as a native composite material, which has significant advantages in low-cost mass production and balanced strength / plasticity combination. In recent years, the rapid rise of multi-principal element high-entropy alloys based on new alloy design concepts has provided opportunities for the development and research of eutectic high-entropy alloys. Eutectic high-entropy alloys combine the advantages and benefits of high-entropy alloys and traditional eutectic alloys, showing good two-phase lamellar heterogeneous structure and rare castability, while also displaying superior mechanical properties compared to traditional alloys.

[0004] To date, there are still not many eutectic high-entropy alloy systems that have been developed. According to their phase composition, they are mainly concentrated in the face-centered cubic (FCC) phase / body-centered cubic (BCC) phase combination (such as the Al-Cr-Co-Ni system) and the FCC phase / intermetallic compound (IMCs) phase combination (such as the Co-Fe-Ni-Mo / V / W / Ta system). However, eutectic high-entropy components containing FCC phases generally have low strength and poor high-temperature mechanical properties, while eutectic high-entropy alloys containing IMCs phases have high strength but poor stability.

[0005] Therefore, the above problems have greatly limited the industrial application and development of eutectic high-entropy alloys. There is an urgent need to design, develop and research eutectic high-entropy alloy systems with new combination phases. A method that can optimize the strength and toughness of high-entropy alloys and significantly reduce the preparation cost is the key to expanding the application field of high-entropy alloys. Summary of the Invention

[0006] To address the aforementioned deficiencies or improvements in the prior art, the present invention provides a novel high-entropy alloy material and a method for preparing the same. This high-entropy alloy is composed of seven metallic elements (zirconium, titanium, hafnium, cobalt, nickel, copper, and niobium) in equal atomic percentages, forming a eutectic high-entropy alloy with a combination of BCC and B2 phases. This eutectic high-entropy alloy exhibits excellent high-strength properties, and the combination of BCC and B2 phases, in particular, helps stabilize the high-entropy alloy's excellent strength at high temperatures.

[0007] To achieve the above object, in a first aspect of the present invention, a seven-element equal-component high-entropy alloy is provided, wherein the high-entropy alloy is a eutectic high-entropy alloy, and the phase of the high-entropy alloy is a combination of a BCC phase and a B2 phase;

[0008] The high entropy alloy includes seven metal elements, namely zirconium, titanium, hafnium, cobalt, nickel, copper and niobium, and the seven metal elements are in an equal molar ratio.

[0009] As a preferred embodiment of the present invention, the BCC phase is rich in the metal element niobium, the B2 phase is rich in the metal elements hafnium and cobalt, and the metal elements titanium, zirconium, cobalt and nickel are uniformly distributed in the two phases.

[0010] In a second aspect of the present invention, a method for preparing a seven-element equal-component high-entropy alloy is provided, the method comprising:

[0011] (1) Weighing metal zirconium, metal titanium, metal hafnium, metal cobalt, metal nickel, metal copper, and metal niobium in equal molar ratios; placing the metal raw materials into a first water-cooled crucible pool in an electric arc furnace, and placing a titanium ingot into a second water-cooled crucible pool; evacuating the interior of the electric arc furnace, and filling the vacuumed electric arc furnace chamber with a protective gas;

[0012] (2) adjusting the tungsten electrode of the electric arc furnace to above the second water-cooled crucible, and repeatedly melting the titanium ingot until the residual oxygen in the electric arc furnace is eliminated;

[0013] (3) adjusting the tungsten electrode of the electric arc furnace to above the first water-cooled crucible, pre-melting the metal niobium and metal hafnium, and then smelting all the metal raw materials to melt the metal raw materials uniformly; repeating step (2) to obtain an alloy ingot;

[0014] (4) repositioning the tungsten electrode of the electric arc furnace above the first water-cooled crucible, and repeatedly smelting the alloy ingot to obtain an alloy mother ingot with uniform composition;

[0015] (5) The alloy mother ingot is moved into a suction casting crucible and melted; after melting, the alloy mother ingot is cooled to obtain the high entropy alloy material.

[0016] As a preference of the present invention, in step (1), the purity of the metal raw materials is greater than or equal to 99.9%.

[0017] As a preferred embodiment of the present invention, in the step (1), the weighed metal raw materials are placed in the first water-cooled crucible pool from top to bottom in order of their melting points from low to high.

[0018] As a preferred embodiment of the present invention, in step (1), the interior of the electric arc furnace is evacuated, and a protective gas is filled into the vacuumed electric arc furnace chamber, comprising:

[0019] The electric arc furnace is pre-evacuated to a vacuum degree of 0.8-1.5*10Pa and then backfilled with argon gas to 0.4 atmospheres for gas washing, and the gas washing cycle is repeated twice;

[0020] After the gas washing is completed, the vacuum degree is pre-evacuated to 0.8~1.5*10Pa and then the molecular pump power is turned on to evacuate the vacuum degree inside the arc furnace to 4.2~6.8*10 -4 Pa;

[0021] Argon is filled into the vacuumed arc furnace chamber to make the gas pressure in the arc furnace reach 0.4 atmospheres.

[0022] As a preferred embodiment of the present invention, in step (2), the titanium ingot is repeatedly smelted until residual oxygen in the electric arc furnace is eliminated, including: using a current of 200 to 350 A to smelt for 1 to 3 minutes, cooling; and repeatedly smelting the titanium ingot 4 to 6 times.

[0023] As a preferred embodiment of the present invention, in step (3), after the tungsten electrode of the electric arc furnace is adjusted to directly above the first crucible, the metal niobium and metal hafnium are pre-melted with a current of 200 to 350 A, and then all the metal raw materials are smelted with a current of 300 to 500 A. After smelting for 1 to 2 minutes, the metal raw materials are cooled; wherein the vertical distance between the tungsten electrode of the electric arc furnace and the first crucible is 8 to 15 mm.

[0024] As a preferred embodiment of the present invention, in the step (4), the metal raw material is repeatedly smelted, including: smelting the metal raw material with a current of 300 to 500 A for 1 to 5 minutes, cooling after smelting, and repeatedly smelting 4 to 7 times.

[0025] As a preferred embodiment of the present invention, in the step (5), the alloy ingot is suction-casted, comprising:

[0026] The tungsten electrode of the electric arc furnace is adjusted to 5-10 mm above the suction casting crucible. After the arc is successfully struck, the melting arc is increased to 250-400 A within 3 seconds, the alloy ingot is melted for 5-8 seconds, and then the melt is sucked into a water-cooled copper mold.

[0027] In general, the above technical solutions conceived by the present invention have the following technical advantages compared with the existing technology:

[0028] The high entropy alloy of the present invention is a seven-element equal-component ZrTiHfCoNiCuNb high entropy alloy, wherein the atomic ratios between the metal elements are equal and the alloy has a eutectic structure.

[0029] Compared with existing high-entropy alloys, eutectic high-entropy alloys have good liquid fluidity and excellent castability, avoiding the occurrence of casting defects during the casting process, and have a relatively uniform autogenous lamellar two-phase eutectic structure. It is a native composite metal material that can be mass-produced at low cost.

[0030] Compared to existing eutectic high-entropy alloys, the eutectic high-entropy alloy of the present invention has simple equal-component high-entropy characteristics and forms a combined phase of BCC phase and B2 phase, which can enhance the strength of the alloy. The ZrTiHfCoNiCuNb eutectic high-entropy alloy of the present invention is a eutectic high-entropy alloy with a relatively low melting point (~1356K). Since its combined phases BBC phase and B2 phase are both strengthening phases, the new combination of BCC phase and B2 phase may bring excellent high-strength performance to the eutectic high-entropy alloy. In particular, this combined phase is conducive to stabilizing its excellent strength at high temperatures.

[0031] However, the complexity and instability of most existing high-entropy alloys, as well as factors such as the imbalance between multiple components, atomic diffusion limitations, incompatibility of components, and phase transition dynamics, make it difficult to achieve eutectic high-entropy alloys with equal atomic ratios. In existing eutectic high-entropy alloys, due to the complexity of the structure of the high-entropy alloy itself and the high-entropy effect, the combination of these two phases has rarely been reported. In addition, the development of eutectic high-entropy alloys is still in its early stages, and the design, development, and research of this two-phase combination eutectic high-entropy alloy are not in-depth. However, when evaluating its mechanical properties, both the BCC phase and the B2 phase are strengthening phases and are conducive to maintaining strength stability at high temperatures. Therefore, compared to eutectic high-entropy alloy components with other phase combinations, the seven-element equal-component ZrTiHfCoNiCuNb high eutectic alloy of the present invention has outstanding mechanical strength and high-temperature stability.

[0032] Furthermore, the ZrTiHfCoNiCuNb high-entropy alloy provided by the present invention is proved to be a eutectic high-entropy alloy through microstructure analysis, phase analysis and retrieval, and combined with its melting characteristics. Specifically, by comparing the phases of X-ray diffraction peaks and combining the microstructure and elemental analysis by scanning electron microscopy, it was confirmed that its eutectic phases are BBC and B2, respectively, and in particular, it was confirmed that the Nb element plays an important role in the formation of this eutectic structure. According to the analysis results, the BCC phase is mainly composed of Nb elements, while the B2 phase is mainly composed of the other 6 elements. This may be due to the positive mixing enthalpy between Nb elements and Zr, Hf, Ti, and Cu. In the high-temperature liquid state, Nb is miscible with all elements. However, when the melt is cooled to the eutectic temperature, due to the combined influence of thermodynamic and kinetic factors, the liquid phase solidifies through eutectic solidification and simultaneously crystallizes two solid phases, namely the BCC phase mainly composed of Nb elements and the B2 phase composed of other elements, thereby forming a self-generated lamellar eutectic structure.

[0033] Therefore, the ZrTiHfCoNiCuNb high-entropy alloy of the present invention is more suitable for industrial processing and casting, and can prevent the occurrence of common casting defects (such as internal shrinkage and composition segregation) during the casting process, thereby reducing the production cost of processing in industrial applications. In addition, the eutectic high-entropy alloy is composed of dual strengthening phases BCC and B2, and its eutectic structure can prevent the occurrence of internal casting defects. It may have important application potential in metal structural materials and special alloy materials, such as industrial facilities and defense fields. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] Figure 1 This is the X-ray diffraction test pattern of the ZrTiHfCoNiCuNb high entropy alloy prepared in Example 1 of the present invention;

[0035] Figure 2 This is a SEM microstructure image of the ZrTiHfCoNiCuNb high entropy alloy prepared in Example 1 of the present invention at 500 times magnification; the scale is 50 μm;

[0036] Figure 3 This is a SEM microstructure image of the ZrTiHfCoNiCuNb high entropy alloy prepared in Example 1 of the present invention at 1000 times magnification; the scale is 40 μm;

[0037] Figure 4 This is a SEM microstructure image of the ZrTiHfCoNiCuNb high entropy alloy prepared in Example 1 of the present invention at 10,000 times magnification; the scale is 4 μm;

[0038] Figure 5This is a SEM microstructure image of the ZrTiHfCoNiCuNb high entropy alloy prepared in Example 1 of the present invention at a magnification of 15,000 times; the scale is 3 μm;

[0039] Figure 6 This is the EDS element distribution spectrum of the ZrTiHfCoNiCuNb high entropy alloy prepared in Example 1 of the present invention at 20,000 times magnification;

[0040] Figure 7 This is a DTA curve diagram of the ZrTiHfCoNiCuNb high entropy alloy prepared in Example 1 of the present invention. DETAILED DESCRIPTION

[0041] In order to make the objectives, technical solutions and advantages of the present invention more clearly understood, the present invention is further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely for the purpose of explaining the present invention and are not intended to limit the present invention. In addition, the technical features involved in the various embodiments of the present invention described below may be combined with each other as long as they do not conflict with each other.

[0042] In an embodiment of the present invention, a method for preparing a seven-element equal-component high-entropy alloy is as follows:

[0043] Step 1: Ingredients and sample preparation:

[0044] (1) Weigh the metal raw materials according to the molar ratio of equal proportion; before weighing the raw materials, first grind and polish off the oxide scale on the surface of the pure metal, then use anhydrous ethanol to ultrasonically clean for 5 minutes, repeat the cleaning twice to remove impurities on the metal surface, and after cleaning, place the raw materials under an electric hair dryer to dry.

[0045] The above metal raw materials are placed in the first water-cooled crucible pool in the electric arc furnace, and the titanium ingot is placed in the second water-cooled crucible pool. The copper block with the lower melting point is placed first in the lowest layer of the first crucible. Then, nickel blocks, cobalt blocks, titanium wire, and zirconium blocks are added in descending order of melting point. Finally, hafnium blocks and niobium blocks with the highest melting points are placed in the top layer.

[0046] First, start the mechanical pump to pre-evacuate the arc furnace. When the vacuum degree is 0.8~1.5*10Pa, refill with high-purity argon gas to raise the pressure in the furnace chamber to 0.5 atmospheres, then stop charging and cycle the gas washing twice. Then open the bypass valve again and use the mechanical pump to pre-evacuate the furnace chamber. When the vacuum degree is again 0.8~1.5*10Pa, turn on the molecular pump power and evacuate the furnace chamber to 4.2~6.8*10 -4 Pa.

[0047] Step 2: Alloy smelting:

[0048] Position the tungsten electrode of the electric arc furnace above the second crucible containing the titanium ingot. Then, melt the titanium ingot at a current of 200-350A for 1-3 minutes, then turn off the current and cool it down. Repeat this process 4-6 times to eliminate any residual oxygen in the furnace. Next, position the tungsten electrode of the electric arc furnace directly above the first crucible, at a vertical distance of 8-15mm from the first crucible. Turn on the power and pre-melt the Nb and Hf blocks (with the highest melting points) with a low current. Then, melt all the raw materials at 300-500A, adding electromagnetic stirring. Melt for 1-2 minutes, then turn off the current. Next, position the tungsten electrode of the electric arc furnace above the second water-cooled crucible containing the titanium ingot. Melt the titanium ingot again at a current of 200-350A for 1-3 minutes, then turn off the current and cool it down to eliminate any oxygen in the furnace after the initial melting. The electromagnetic stirring current is 2-4A, and the stirring current must be turned off 10 seconds before the end of each melting.

[0049] Adjust the tungsten electrode of the electric arc furnace to just above the first water-cooled crucible again, turn on the power, and melt the alloy ingot at 300-500A for 1-5 minutes. Add electromagnetic stirring, turn off the current after melting, and repeat the melting 4-7 times to obtain an alloy ingot with uniform composition.

[0050] Step 3: Place the alloy ingot into a suction casting crucible, adjust the tungsten electrode of the arc furnace to directly above the suction casting crucible, turn on the arc furnace power supply, and after successful arc ignition, increase the current of the melting arc to 250-400A within 3s. After the alloy ingot is melted, press the suction casting switch to quickly suck the melt into the copper mold to prepare a high entropy alloy material.

[0051] The specific embodiments are as follows;

[0052] Example 1: A seven-element equal-component ZrTiHfCoNiCuNb high-entropy alloy, wherein the molar atomic percentage of each element is Zr:Ti:Hf:Co:Ni:Cu:Nb=1:1:1:1:1:1:1:1.

[0053] The preparation method of the seven-element equal-component eutectic high-entropy alloy specifically includes the following steps:

[0054] Step 1: Ingredients and sample preparation:

[0055] According to the atomic composition ratio of the eutectic high-entropy alloy, pure metal zirconium block (Zr), titanium wire (Ti), hafnium block (Hf), cobalt block (Co), nickel block (Ni), copper block (Cu) and niobium block (Nb) were weighed as raw materials, and the molar percentage of each element was converted to Zr:Ti:Hf:Co:Ni:Cu:Nb=1:1:1:1:1:1:1 to make a sample ingot with a total weight of 50g.

[0056] The raw material pure metals used in the embodiments of the present invention are all high-purity metals with a purity greater than 99.9%. The oxide scale on the surface of the raw materials needs to be removed before mixing. The prepared raw materials are ultrasonically cleaned for 10 minutes using industrial anhydrous ethanol as a solvent, and then dried using an electric hair dryer after cleaning.

[0057] Step 2: Alloy smelting:

[0058] First, place the weighed copper block in the lowest layer of the first water-cooled copper crucible, then place the nickel block, cobalt block, titanium wire and zirconium block in order according to the melting point of the raw material metals, and finally place the hafnium block and niobium block with the highest melting point on the top layer. In addition, place a 40g titanium ingot in the second water-cooled crucible to remove residual oxygen during the smelting process.

[0059] Then, first pre-evacuate the arc furnace to 10Pa and then backfill with high-purity argon to 0.4 atmospheres, then evacuate again for gas washing, and cycle the gas washing twice. After the gas washing is completed, evacuate the vacuum to 10Pa again and turn on the molecular pump power to evacuate the vacuum inside the arc furnace to 5*10 -4 Subsequently, high-purity argon is filled into the vacuumed arc furnace chamber as a protective gas, so that the vacuum degree in the arc furnace reaches 0.4 atmospheres again.

[0060] Adjust the tungsten pole of the electric arc furnace to the top of the second crucible containing the titanium ingot, and then use a current of 300A to melt for 2 minutes, then turn off the current to cool, and repeat the melting of the titanium ingot 5 times to eliminate the residual oxygen in the electric arc furnace. Then adjust the tungsten pole of the electric arc furnace to the top of the first crucible, with a vertical distance of 10mm from the first crucible, turn on the power, first use a small current to pre-melt the Nb block and Hf block with the highest melting point, and then use 400A to melt all the raw materials, add electromagnetic stirring, and turn off the current after melting for 1.5 minutes. Then adjust the tungsten pole of the electric arc furnace to the top of the second water-cooled crucible containing the titanium ingot, and use a current of 300A to melt the titanium ingot for 2 minutes again, then turn off the current to cool, so as to eliminate the oxygen in the electric arc furnace again after the first melting of the raw materials.

[0061] The tungsten electrode of the electric arc furnace was readjusted to the top of the first water-cooled crucible, the power was turned on, and the alloy ingot was melted with a current of 450A for 3 minutes. Electromagnetic stirring was added, and the current was turned off after melting. The melting was repeated 6 times to obtain an alloy ingot with uniform composition.

[0062] Step 3: Place the alloy ingot into a suction casting crucible, adjust the tungsten electrode of the arc furnace to directly above the suction casting crucible, turn on the arc furnace power, and after successful arc ignition, increase the melting arc to 400A within 3 seconds. After the alloy ingot is melted, press the suction casting switch to quickly suck the melt into the copper mold to prepare the alloy material.

[0063] Test 1, based on the X-ray diffraction test and phase composition analysis of the seven-element equal-component ZrTiHfCoNiCuNb high-entropy alloy in Example 1:

[0064] The alloy rods were cut into thin slices using a diamond cutter. The surfaces of the slices were carefully polished with sandpaper and then cleaned with ultrasonic vibrations in anhydrous ethanol. Phase measurement and analysis were then performed using a German D2 PHASER diffractometer. The test parameters were: CuKα radiation, a step size of 0.02°, a rate of 5° / min, and a 2θ scanning angle of 20° to 100°.

[0065] like Figure 1 This is the X-ray diffraction pattern of the seven-element equal-component ZrTiHfCoNiCuNb high-entropy alloy. The results of phase library comparison show that the alloy is composed of a combination of BCC phase and B2 phase. The BCC phase is metallic Nb, while the B2 phase is rich in CoHf.

[0066] Test 2, based on the microstructural analysis of the seven-element equal-component ZrTiHfCoNiCuNb high-entropy alloy in Example 1:

[0067] A thin circular sample was cut from the alloy rod prepared by suction casting using a diamond cutting machine. The sample surface was carefully polished with sandpaper of different roughness and then mechanically polished. The micromorphology was observed using an Oxford TENSCAN MIRA3 scanning electron microscope equipped with EDS function.

[0068] like Figures 2 to 5 The following are BSE scanning microstructure diagrams of the seven-element equal-component ZrTiHfCoNiCuNb high-entropy alloy prepared in the embodiment at magnifications of 500 times, 1000 times, 10,000 times, and 15,000 times, respectively. It can be seen from the figure that the dendrite structure of the ZrTiHfCoNiCuNb high-entropy alloy is fine. This is because the cooling rate of the prepared sample is relatively fast. Only when the magnification is magnified to 10,000 times can the lamellar dual-phase eutectic structure be clearly observed. Combined with the XRD results, the two phases with different light and dark contrasts can be identified as BCC phase and B2 phase. Figure 6 By comparing the elemental diagram and XRD phase, it can be confirmed that Figure 4 and Figure 5 In the authigenic lamellar structure, the relatively dark lamellar area is the BCC phase, while the relatively bright lamellar area is the B2 phase.

[0069] like Figure 6This is an EDS plot of the elemental distribution of the seven-element, equal-composition ZrTiHfCoNiCuNb high-entropy alloy prepared in Example 1. It can be seen that the Ti, Co, Ni, and Hf elements are relatively evenly distributed in the two phases, while the Nb and Cu elements exhibit distinct inhomogeneities. This indicates that the two phases of the eutectic high-entropy alloy are Nb-rich and Nb-poor, respectively. The Nb-rich phase is also Cu-poor, but the distribution of Cu in the Nb-poor phase is relatively uniform. Combined with the physical phase comparison results of the PDF of the XRD spectrum, it can be determined that the Nb-rich phase in the EDS has a BCC structure, while the Nb-poor phase has a B2 structure.

[0070] Test 3, DTA measurement and melting characteristic analysis based on the seven-element equal-component ZrTiHfCoNiCuNb high-entropy alloy in Example 1:

[0071] A circular thin slice sample with a mass of approximately 35 mg was cut from the alloy rod prepared by suction casting using a diamond cutting machine. The slice was then polished with sandpaper and ultrasonically cleaned with anhydrous ethanol. The cleaned sample was dried and placed in a TA-Q600 DTA crucible to measure the melting behavior during the heating process. The heating rate was 40 K / min, and the temperature range was 25°C to 1200°C. During the measurement, an argon flow with a flow rate of 80 ml / min was used as the protective gas. The crucible was an alumina crucible with a capacity of 80 μl.

[0072] like Figure 7 This is a heat flow curve of the seven-element equal-component ZrTiHfCoNiCuNb high-entropy alloy bar during the heating process. As can be seen from the figure, the alloy has a clear eutectic melting peak, which spans the temperature range of 113K, and there is an inconspicuous shoulder peak on the left side of the melting peak, indicating that the alloy may deviate slightly from the eutectic point. The melting point (Tm) of this alloy is 1356K and the liquidus is 1469K.

[0073] Based on the above tests, it can be seen that the eutectic high-entropy alloy of the present invention has simple iso-component high-entropy characteristics and forms a combined phase of BCC and B2 phases. Therefore, the eutectic high-entropy alloy of the present invention relies on strengthening phases such as BCC and B2 phases, which can facilitate the maintenance of strength stability at high temperatures, making it more suitable for industrial processing and casting. During the casting process, it can prevent the occurrence of common casting defects (such as internal shrinkage and composition segregation), thereby reducing the processing and preparation costs in industrial applications.

[0074] It will be easily understood by those skilled in the art that the above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A seven-element equal-component high-entropy alloy, characterized in that: The high entropy alloy is a eutectic high entropy alloy, and the phase of the high entropy alloy is a combination of a BCC phase and a B2 phase; The high entropy alloy includes seven metal elements, namely zirconium, titanium, hafnium, cobalt, nickel, copper and niobium, and the seven metal elements are in an equal molar ratio.

2. The method for preparing a seven-element equal-component high-entropy alloy according to claim 1, wherein: The method comprises: (1) Weighing metal zirconium, metal titanium, metal hafnium, metal cobalt, metal nickel, metal copper, and metal niobium in equal molar ratios; placing the metal raw materials into a first water-cooled crucible pool in an electric arc furnace, and placing a titanium ingot into a second water-cooled crucible pool; evacuating the interior of the electric arc furnace, and filling the vacuumed electric arc furnace chamber with a protective gas; (2) adjusting the tungsten electrode of the electric arc furnace to above the second water-cooled crucible, and repeatedly melting the titanium ingot until the residual oxygen in the electric arc furnace is eliminated; (3) adjusting the tungsten electrode of the electric arc furnace to above the first water-cooled crucible, pre-melting the metal niobium and metal hafnium, and then smelting all the metal raw materials to melt the metal raw materials uniformly; repeating step (2) to obtain an alloy ingot; (4) repositioning the tungsten electrode of the electric arc furnace above the first water-cooled crucible, and repeatedly smelting the alloy ingot to obtain an alloy mother ingot with uniform composition; (5) The alloy mother ingot is moved into a suction casting crucible and melted; after melting, the alloy mother ingot is cooled to obtain the high entropy alloy material.

3. The method for preparing a seven-element equal-component high-entropy alloy according to claim 2, wherein: In step (1), the purity of the metal raw materials is greater than or equal to 99.9%.

4. The method for preparing a seven-element equal-component high-entropy alloy according to claim 2, wherein: In step (1), the weighed metal raw materials are placed in the first water-cooled crucible pool from top to bottom in order of their melting points from low to high.

5. The method for preparing a seven-element equal-component high-entropy alloy according to claim 2, wherein: In step (1), the interior of the electric arc furnace is evacuated, and a protective gas is filled into the evacuated electric arc furnace chamber, comprising: The arc furnace is pre-evacuated to a vacuum degree of (0.8-1.5)*10 Pa and then backfilled with high-purity argon gas to 0.4 atmospheres for gas washing, and the gas washing cycle is repeated twice; After the gas cleaning is completed, pre-evacuate the vacuum to (0.8~1.5)*10 Pa and then turn on the molecular pump power to evacuate the vacuum inside the arc furnace to (4.2~6.8)*10 -4 Pa; Argon is filled into the vacuumed arc furnace chamber to make the gas pressure in the arc furnace reach 0.4 atmospheres.

6. The method for preparing a seven-element equal-component high-entropy alloy according to claim 2, wherein: In step (2), the titanium ingot is repeatedly smelted until residual oxygen in the electric arc furnace is eliminated, including: using a current of 200 to 350 A for 1 to 3 minutes, cooling; and repeatedly smelting the titanium ingot 4 to 6 times.

7. The method for preparing a seven-element equal-component high-entropy alloy according to claim 2, wherein: In step (3), after adjusting the tungsten electrode of the electric arc furnace to directly above the first crucible, the metal niobium and metal hafnium are pre-melted with a current of 200 to 350 A, and then all the metal raw materials are smelted with a current of 300 to 500 A. After smelting for 1 to 2 minutes, the metal raw materials are cooled; wherein the vertical distance between the tungsten electrode of the electric arc furnace and the first crucible is 8 to 15 mm.

8. The method for preparing a seven-element equal-component high-entropy alloy according to claim 2, wherein: In step (4), the metal raw material is repeatedly smelted, comprising: The metal raw material is smelted for 1 to 5 minutes using a current of 300 to 500 A, cooled after smelting, and repeatedly smelted 4 to 7 times.

9. The method for preparing a seven-element equal-component high-entropy alloy according to claim 2, wherein: In step (5), the alloy ingot is suction-casted, comprising: The tungsten electrode of the electric arc furnace was adjusted to 5-10 mm above the suction casting crucible. After the arc was successfully struck, the melting arc was increased to 250-400 A within 3 seconds, the alloy ingot was melted for 5-8 seconds, and then the melt was sucked into a water-cooled copper mold for cooling.

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