A high-entropy alloy and a preparation method thereof

Abstract

This invention relates to a high-entropy alloy and its preparation method. The preparation method includes laying high-entropy metal raw materials in three layers—lower, middle, and upper—to obtain a composite block; and melting the composite block to obtain the high-entropy alloy. The high-entropy alloy raw materials are divided into high-melting-point metals with melting points ≥1600℃ and low-melting-point metals with melting points <1600℃. The lower and upper layers are composed of high-melting-point metals, and the middle layer is composed of low-melting-point metals. The high-entropy alloy preparation method provided by this invention can stably control the deviation of volatile components to ≤±1.0 at.%, reducing the burn-off rate of typical volatile metals such as Al and Mn by more than 70%, without the need to add an additional 3-5 wt.% of excess raw materials to compensate for losses, and eliminating impurity phases and microstructure segregation caused by excess elements.

Description

Technical Field

[0001] This invention relates to the field of high-entropy alloy technology, specifically to a high-entropy alloy and its preparation method. Background Technology

[0002] High-entropy alloys are a new type of material composed of five or more main elements, with each element having a single atom proportion of no less than 5%, hence the name multi-component alloys. Due to their multi-component nature, these alloys possess high mixing entropy, enabling them to form relatively stable single-phase super solid solutions. Non-consumable vacuum arc melting is the mainstream process for laboratory and small-batch preparation of high-entropy alloy ingots. It uses a tungsten inert gas (TIG) arc as the heat source to melt the raw material, and after multiple remelting cycles to eliminate component segregation, the ingot is obtained. During arc melting, the instantaneous temperature of the arc plasma zone can reach 5000-6000 K, while the saturated vapor pressure of volatile components such as Al, Mn, Zn, Mg, Sn, and rare earth elements increases sharply at high temperatures, making them highly susceptible to vaporization and loss. For example, the vapor pressure of Al at 2000 K can reach approximately 10... -1 The volatilization rate increases exponentially in the local high-temperature region (>3000K) of the arc plasma, which is on the order of Pa, resulting in a significant deviation between the final ingot composition and the nominal ratio.

[0003] Traditional mainstream charging and melting methods employ a mixed, flat-laying method for single-element raw materials, where all metal blocks are randomly mixed and laid at the bottom of the crucible, with volatile metals directly exposed to the arc bombardment area. During the initial melting stage, a large amount of vaporization and volatilization occurs, resulting in a final alloy composition deviation typically reaching ±2.5-3.5 at.%. The industry can only compensate for this loss by adding an excess of 3-5 wt.% of volatile metals, but this excessive addition induces macroscopic component segregation and the precipitation of impurity phases, significantly reducing the stability of the alloy's mechanical properties. If a unidirectional layered charging method is adopted, with a volatile metal bottom layer and a refractory metal top layer covering it, the upper refractory metal forms a single layer of shielding, which can slightly reduce volatilization during the initial melting. However, this method has the following problems: 1) After melting, the ingot needs to be flipped 4-6 times for homogenization. After flipping, the bottom volatile metal will be exposed on the top surface of the crucible, leading to concentrated burn-off during subsequent remelting; 2) The arc can penetrate the upper molten pool and directly heat the bottom volatile raw materials. Therefore, the composition deviation remains at ±2.0-3.0 at.%, and the material control accuracy cannot meet the requirements for the preparation of precision high-entropy alloys.

[0004] Existing technologies disclose several methods, such as CN116092604A and CN115821143A, which involve placing metal raw materials into the furnace melting tank in order of increasing melting point. However, adjusting the charging order does not create a physical shielding structure, and low-melting-point volatile elements remain directly exposed to the arc area, failing to fundamentally solve the burn-off problem. Other melting methods, such as CN122214640A, disclose a method to improve the uniformity of volatile element composition in the vacuum consumable arc remelting (VAR) process. This method employs a "micro-argon charging with small current for short-time arc initiation + fast argon charging with large current to establish a stable molten pool," improving the uniformity of volatile element composition in titanium alloy ingots. However, this technology targets the VAR process with consumable electrodes for titanium alloy ingot preparation, and its "small current arc initiation" aims to quickly establish a stable molten pool, rather than protecting volatile components.

[0005] Currently, it is generally believed that the loss of volatile elements in high-entropy alloy smelting can only be reduced by two methods: over-compensation of excessive feed and increasing argon pressure. There is a lack of a complete process solution that simultaneously solves the loss of volatile elements and component segregation from the perspective of "physical shielding of feed + step-low heat input preheating". Summary of the Invention

[0006] The purpose of this invention is to address the technical shortcomings of existing vacuum arc melting processes, such as severe burn-off of volatile metals, large ingot composition deviations, the need for excessive material addition for compensation, and secondary volatilization after multiple remelting. This invention utilizes two layers of high-melting-point refractory metals to completely encapsulate the volatile raw materials, forming a physical thermal insulation shield. Combined with a stepped current curve of low-current preheating and conduction heating during the initial melting process, and high-current stirring of the molten pool, this prevents the arc plasma from directly bombarding the volatile components, reducing the instantaneous vaporization rate. This allows the ingot composition deviation to be controlled within ±1.0 at.% without the need for excessive addition of volatile metals, while simultaneously ensuring elemental uniformity after multiple remelting cycles, resulting in a high-entropy alloy ingot with a single solid solution phase and no obvious oxide inclusions.

[0007] To achieve the above-mentioned technical objectives, the present invention provides a method for preparing a high-entropy alloy, comprising: High-entropy metal raw materials are laid in three layers: lower, middle and upper, to obtain a composite block. The composite block is melted to obtain a high-entropy alloy; The high-entropy alloy raw material is divided into high-melting-point metals with a melting point ≥1600℃ and low-melting-point metals with a melting point <1600℃. The lower layer and the upper layer are composed of high-melting-point metals, and the middle layer is composed of low-melting-point metals.

[0008] Furthermore, the thickness of the lower layer and the upper layer is 1 / 4 to 1 / 3 of the height of the composite block. It should be noted that the structure of the composite block can be cubic, cylindrical, or other shapes that can form a regular layered structure. Based on the shape of the crucible, the preferred structure of the composite block is a cylinder with a diameter of 5-15 mm.

[0009] Furthermore, the melting process employs non-consumable vacuum arc melting.

[0010] Furthermore, the non-consumable vacuum arc melting includes, The composite block is placed in a non-consumable vacuum arc furnace, and evacuated and filled with argon gas to an absolute pressure of 30-60 kPa. Then, an initial current of 60-150 A is maintained for 10-30 seconds to allow the lower layer to melt slightly and the middle layer to heat up and melt through heat conduction. After the molten pool is formed, the working current is increased to 200-400A and the liquid phase is maintained for 30-90s, and then cooled to obtain the initial molten alloy ingot; After flipping the initial melted alloy ingot, maintain it in the liquid phase for 30-60 seconds at the working current or at a current 1%-10% higher than the working current, and then continue to flip and remelt 4-8 times.

[0011] Furthermore, the vacuuming to a pressure ≤ 5 × 10⁻⁶ -3 Pa.

[0012] Furthermore, the process of vacuuming and argon filling is repeated 2-3 times. After the final argon filling, the high-purity Ti is melted by arc ignition and then aspirated for 1-2 minutes.

[0013] Furthermore, in the presence of the liquid phase, an electric arc electromagnetic stirring is used to promote its convection.

[0014] Furthermore, the purity of the high-entropy alloy raw material is ≥99.5%.

[0015] Furthermore, the compositional deviation of the low-melting-point metal is within ±2.0 at.%.

[0016] The present invention also provides a high-entropy alloy, which is obtained by the above-described preparation method.

[0017] Compared with the prior art, the beneficial effects of the present invention include: (1) The loss of volatile elements is greatly reduced and the accuracy of composition control is significantly improved: the composition deviation of traditional mixed flat loading is ±2.5-3.5 at.%, and the deviation of unidirectional layered loading is ±2.0-3.0 at.%, while the high-entropy alloy preparation method provided by the present invention can stably control the composition deviation of volatile components to ≤±2.0 at.%, and the loss rate of typical volatile metals such as Al and Mn is reduced by more than 70%, without the need to add 3-5 wt.% of excess raw materials to compensate for the loss, and eliminates the segregation of impurities and microstructure caused by excess elements.

[0018] (2) Excellent uniformity of structure: The high entropy alloy preparation method provided by the present invention has pre-alloyed the volatile metals after the initial melting of the fully encapsulated interlayer, and there are no exposed blocks of pure low-boiling-point metals after flipping.

[0019] (3) The process is highly versatile and the equipment modification cost is zero: The high-entropy alloy preparation method provided by this invention only requires adjusting the raw material loading arrangement and the melting current program. Conventional commercial non-consumable vacuum arc melting furnaces can be used directly without adding tooling or modifying the furnace structure, making it suitable for laboratory research and development and small-batch trial production scenarios.

[0020] (4) Wide range of applicable alloy systems: The high-entropy alloy preparation method provided by this invention can prepare refractory high-entropy alloys containing Al, Mn, Zn, Mg, and rare earth elements, as well as transition medium-entropy / high-entropy alloys. Typical systems include multi-element alloys such as MoNbTaWAl, TiZrVMn, CoCrFeNiZn, and MoNbTaCe.

[0021] The above description is merely an overview of the technical solution of the present invention. In order to better understand the technical means of the present invention and to implement it in accordance with the contents of the specification, and in order to make the above and other objects, features and advantages of the present invention more apparent and understandable, specific embodiments of the present invention are described below. Attached Figure Description

[0022] To more clearly illustrate the technical solution of the present invention, the accompanying drawings used in the present invention will be briefly described below. Obviously, the drawings described below are merely some embodiments of the present invention, and those skilled in the art can obtain other drawings based on these drawings without any creative effort.

[0023] Figure 1 A flowchart of the high-entropy alloy preparation method of the present invention is shown. Detailed Implementation

[0024] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be 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 illustrative and not intended to limit the invention.

[0025] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains; the terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the invention; the terms “comprising” and “having”, and any variations thereof, in the specification, claims, and foregoing description of the invention, are intended to cover non-exclusive inclusion.

[0026] In this document, the term "embodiment" means that a particular feature, structure, or characteristic described in connection with an embodiment may be included in at least one embodiment of the invention. The appearance of this phrase in various places throughout the specification does not necessarily refer to the same embodiment, nor is it a separate or alternative embodiment mutually exclusive with other embodiments. It will be explicitly and implicitly understood by those skilled in the art that the embodiments described herein can be combined with other embodiments.

[0027] During vacuum arc melting, the arc temperature can exceed 5000K. When high-boiling-point components such as W (boiling point 5555℃) and Mo (boiling point 4639℃) are still in solid state or have just melted, low-boiling-point components such as Al (boiling point 2467℃) and Mn (boiling point 2061℃) have already vaporized violently. Studies have shown that during the melting and preparation of refractory high-entropy alloys, it is very easy to cause the volatilization of low-melting-boiling substances, which in turn leads to the composition of the formed alloy deviating from the initial setting. To compensate for burn-off, existing technologies often require the excessive addition of 3%-10% of volatile elements. However, this "extensive compensation" has fundamental defects: (1) The amount of compensation is difficult to control precisely: the burn-off rate is affected by many factors such as melting current, melting time, crucible position, and number of times of turning, and the fluctuation between batches is large; (2) It is easy to introduce impurity phases: excessive addition changes the nominal composition and may exceed the single-phase solid solution zone, precipitating harmful second phases.

[0028] Furthermore, even with a unidirectional layered loading method that uses a volatile metal bottom layer and a refractory metal top layer, the composition deviation still remains within ±2.0-3.0 at.%, and the material control precision cannot meet the requirements for the preparation of precision high-entropy alloys.

[0029] Therefore, this invention is proposed.

[0030] A method for preparing a high-entropy alloy, comprising, High-entropy metal raw materials are laid in three layers: lower, middle and upper, to obtain a composite block. The composite block is melted to obtain a high-entropy alloy; The high-entropy alloy raw material is divided into high-melting-point metals with a melting point ≥1600℃ and low-melting-point metals with a melting point <1600℃. The lower layer and the upper layer are composed of high-melting-point metals, and the middle layer is composed of low-melting-point metals.

[0031] In some preferred embodiments, the purity of the high-entropy alloy raw material is ≥99.5%. In this invention, the type of high-melting-point metal is not strictly limited. Exemplarily, high-melting-point metals can be Mo, W, Ta, Nb, Ti, Cr, Zr, V, Ce, La, Y, etc., and low-melting-point metals can be Fe, Co, Ni, Mn, Al, Sn, Zn, Mg, etc. To satisfy the definition of a high-entropy alloy, the high-entropy metal raw material contains two or more high-melting-point metals and three or more low-melting-point metals.

[0032] This invention lays out high-entropy metal raw materials in three layers: a lower layer, a middle layer, and a top layer, forming a composite block similar to a sandwich structure. The upper and lower layers are refractory metals with melting points ≥1600℃, completely encapsulating the middle layer of low-melting-point, volatile metal raw materials. In the initial stage of smelting, the electric arc acts only on the top layer of refractory metal, while the middle layer slowly heats up through heat conduction from the solid metal, avoiding the instantaneous high temperatures caused by direct irradiation from the 5000K electric arc plasma. The refractory metal melts first to form a continuous liquid protective film, sealing off the volatile elements inside the molten pool and reducing the partial pressure of metal vapor on the surface of the molten pool, thus inhibiting vaporization reactions from a thermodynamic perspective.

[0033] In some preferred embodiments, the thickness of the lower layer and the upper layer is 1 / 4 to 1 / 3 of the height of the composite block.

[0034] In some preferred embodiments, the melting is performed using a non-consumable vacuum arc melting process.

[0035] This invention, through extensive practical application, employs a stepped current-assisted temperature control method. In the initial melting stage, a low-current, long-term preheating process is used to prevent the top refractory layer from being instantly broken down by a high current. After the middle layer of raw materials has synchronously heated and pre-alloyed through heat conduction, the high current is increased to form a stable molten pool, which is then mixed using electromagnetic stirring. The low-current preheating stage significantly shortens the time that volatile metals are directly exposed to high-temperature plasma, reducing the volatilization exposure time by more than 60% compared to traditional processes. After the initial melting of the composite block, the volatile components have already pre-alloyed with the refractory metal, and there are no purely volatile metal blocks. During the remelting process, there are no concentrated exposed low-boiling-point raw materials, and the multiple remelting processes do not result in localized concentrated volatilization, thus balancing compositional accuracy and microstructure uniformity.

[0036] In some preferred embodiments, the non-consumable vacuum arc melting includes, The composite block is placed in a non-consumable vacuum arc furnace, and evacuated and filled with argon gas to an absolute pressure of 30-60 kPa. Then, an initial current of 60-150 A is maintained for 10-30 seconds to allow the lower layer to melt slightly and the middle layer to heat up and melt through heat conduction. After the molten pool is formed, the working current is increased to 200-400A and the liquid phase is maintained for 30-90s, and then cooled to obtain the initial molten alloy ingot; After flipping the initial melted alloy ingot, maintain it in the liquid phase for 30-60 seconds at the working current or at a current 1%-10% higher than the working current, and then continue to flip and remelt 4-8 times.

[0037] In some preferred embodiments, the vacuuming to pressure ≤ 5 × 10⁻⁶ -3 Pa.

[0038] In some preferred embodiments, the vacuuming and argon filling processes are repeated 2-3 times, and after the final argon filling, the high-purity Ti is melted by arc ignition and then aspirated for 1-2 minutes.

[0039] In some preferred embodiments, when the liquid phase is present, electromagnetic stirring with an electric arc is used to promote convection.

[0040] The present invention will be further described in detail below through specific embodiments. It should be noted that the embodiments described below are exemplary and are only used to explain the present invention, and should not be construed as limiting the present invention. Where specific techniques or conditions are not specified in the embodiments, they shall be performed in accordance with the techniques or conditions described in the literature in the art or in accordance with the product instructions. Reagents or instruments used that do not specify the manufacturer are all conventional products that can be obtained commercially.

[0041] Example 1 A method for preparing a high-entropy alloy includes the following steps: S1, Ingredients With Al 0.5 Mn 0.5 CoCrNiW 0.5 Weigh out the following high-melting-point metals: W powder (99.9%, 10μm), Mo powder (99.9%, 10μm), and Cr powder (99.9%, 20μm), and the following low-melting-point metals: Al powder (99.9%, 20μm), Mn powder (99.9%, 20μm), Co powder (99.9%, 20μm), and Ni powder (99.9%, 20μm). Mix the W powder, Mo powder, and Cr powder to obtain a high-melting-point metal mixture, and mix the Al powder, Co powder, and Ni powder to obtain a low-melting-point metal mixture.

[0042] S2, Layered loading A portion of the high-melting-point metal mixture is spread evenly at the bottom of the crucible to form the lower layer. Then, a low-melting-point metal mixture is evenly spread on top of the lower layer, without touching the crucible wall or exceeding the boundary of the lower layer. The remaining high-melting-point metal mixture is spread evenly on top of the middle layer to form the upper layer that completely covers the middle layer, resulting in a cylindrical composite block with a diameter of 10 mm. The thickness of the lower and upper layers is 1 / 3 of the height of the composite block.

[0043] S3, Vacuuming and Gas Cleaning Transfer the crucible containing the composite block to a non-consumable vacuum arc melting furnace, and evacuate to a pressure ≤5×10⁻⁶. - 3 Pa, then fill with high-purity argon gas with a purity ≥99.999% to an absolute pressure of 45 kPa, repeat the vacuuming-argon filling process 3 times, and after the last argon filling, ignite an arc to melt a piece of high-purity Ti and absorb gas for 2 minutes.

[0044] S4, stepped current initial melting The initial current of 90A is maintained for 30 seconds, which allows the lower layer to melt slightly and the middle layer to heat up and melt through heat conduction, thus avoiding the instantaneous vaporization of volatile components caused by direct high current. After confirming that the material has been initially alloyed to form a molten pool, the working current is increased to 300A and maintained in the liquid phase for 60s. During this period, electromagnetic stirring with an electric arc is used to promote convection in the molten pool. Then, the material is cooled to obtain a pre-melted alloy ingot.

[0045] S5, Reflow and Remelting Homogenization The initial melted alloy ingot is flipped 180° and kept in the liquid phase for 45 seconds at a working current of 300A. During this period, electromagnetic stirring with an electric arc is used to promote convection in the molten pool. After cooling, it is remelted. This process of flipping and remelting is repeated 5 times to fully homogenize the alloy composition, ultimately yielding a high-entropy alloy ingot.

[0046] Example 2 A method for preparing a high-entropy alloy includes the following steps: S1, Ingredients With Al 0.5 MnCoCrNiW 0.5 Mo 0.5 Weigh out the following high-melting-point metals: W powder (99.9%, 10μm), Mo powder (99.9%, 10μm), and Cr powder (99.9%, 20μm), and the following low-melting-point metals: Al powder (99.9%, 20μm), Mn powder (99.9%, 20μm), Co powder (99.9%, 20μm), and Ni powder (99.9%, 20μm). Mix the W powder, Mo powder, and Cr powder to obtain a high-melting-point metal mixture, and mix the Al powder, Mn powder, Co powder, and Ni powder to obtain a low-melting-point metal mixture.

[0047] S2, Layered loading A portion of the high-melting-point metal mixture is spread evenly at the bottom of the crucible to form the lower layer. Then, a low-melting-point metal mixture is evenly spread on top of the lower layer, without touching the crucible wall or exceeding the boundary of the lower layer. The remaining high-melting-point metal mixture is spread evenly on top of the middle layer to form the upper layer that completely covers the middle layer, resulting in a cylindrical composite block with a diameter of 10 mm. The thickness of the lower and upper layers is 1 / 4 of the height of the composite block.

[0048] S3, Vacuuming and Gas Cleaning Transfer the crucible containing the composite block to a non-consumable vacuum arc melting furnace, and evacuate to a pressure ≤5×10⁻⁶. - 3 Pa, then fill with high-purity argon gas with a purity ≥99.999% to an absolute pressure of 45 kPa, repeat the vacuuming-argon filling process 3 times, and after the last argon filling, ignite an arc to melt a piece of high-purity Ti and absorb gas for 2 minutes.

[0049] S4, stepped current initial melting The initial current of 90A is maintained for 30 seconds, which allows the lower layer to melt slightly and the middle layer to heat up and melt through heat conduction, thus avoiding the instantaneous vaporization of volatile components caused by direct high current. After confirming that the material has been initially alloyed to form a molten pool, the working current is increased to 300A and maintained in the liquid phase for 60s. During this period, electromagnetic stirring with an electric arc is used to promote convection in the molten pool. Then, the material is cooled to obtain a pre-melted alloy ingot.

[0050] S5, Reflow and Remelting Homogenization The initial melted alloy ingot is flipped 180° and kept in the liquid phase for 45 seconds at a working current of 300A. During this period, electromagnetic stirring with an electric arc is used to promote convection in the molten pool. After cooling, it is remelted. This process of flipping and remelting is repeated 5 times to fully homogenize the alloy composition, ultimately yielding a high-entropy alloy ingot.

[0051] Example 3 Compared with Example 2, the difference is that in S4, the liquid phase is maintained at an initial current of 120A for 20s and at an operating current of 320A for 50s; in S5, the liquid phase is maintained at an operating current of 320A for 40s.

[0052] Comparative Example 1 A method for preparing a high-entropy alloy includes the following steps: T1, Ingredients With Al 0.5 MnCoCrNiW 0.5 Mo 0.5 Weigh out the high-melting-point metals: W powder (99.9%, 10μm), Mo powder (99.9%, 10μm), Cr powder (99.9%, 20μm), and the low-melting-point metals: Al powder (99.9%, 20μm), Mn powder (99.9%, 20μm), Co powder (99.9%, 20μm), and Ni powder (99.9%, 20μm); then mix them to obtain mixed metal powders.

[0053] T2, Vacuuming and Gas Cleaning The mixed metal powder was transferred into a crucible and then transferred to a non-consumable vacuum arc melting furnace, where a vacuum was drawn until the pressure was ≤5×10⁻⁶. -3Pa, then fill with high-purity argon gas with a purity ≥99.999% to an absolute pressure of 45 kPa, repeat the vacuuming-argon filling process 3 times, and after the last argon filling, ignite an arc to melt a piece of high-purity Ti and absorb gas for 2 minutes.

[0054] T3, stepped current initial melting The low-melting-point metal is melted by maintaining an initial current of 90A for 30 seconds. After confirming the formation of a molten pool, the working current is increased to 300A and maintained in the liquid phase for 60 seconds. During this period, electromagnetic stirring with an electric arc is used to promote convection in the molten pool. Subsequently, the molten alloy ingot is obtained by cooling.

[0055] T4, flipping and remelting for homogenization The initial melted alloy ingot is flipped 180° and kept in the liquid phase for 45 seconds at a working current of 300A. During this period, electromagnetic stirring with an electric arc is used to promote convection in the molten pool. After cooling, it is remelted. This process of flipping and remelting is repeated 5 times to fully homogenize the alloy composition, ultimately yielding a high-entropy alloy ingot.

[0056] Comparative Example 2 Compared with Example 2, the difference is that in step S2, the high melting point metal mixture is spread evenly on the bottom of the crucible to form a lower layer, and then the low melting point metal mixture is evenly spread on the lower layer.

[0057] Comparative Example 3 Compared with Example 2, the difference is that step S4 does not use a stepped current for initial melting, but directly maintains the liquid phase for 90s with a working current of 300A.

[0058] Table 1 shows the burn-off rates of Al and Mn and the compositional deviations of the ingots obtained in the examples and comparative examples.

[0059] Table 1. Al and Mn burn-off rates and compositional deviations

[0060] As shown in Table 1, Comparative Example 1 directly mixed all powders (including low-melting-point Al and Mn). When ignited by an electric arc, the arc directly acted on the Al / Mn powder exposed on the surface, causing it to vaporize instantly, resulting in the highest burn-off rate (Al 6.8%, Mn 8.0%). Comparative Example 2 consisted of a lower high-melting-point layer and a middle low-melting-point layer, without an upper covering layer. Although the low-melting-point layer was at the bottom, there was no covering layer on top. When the arc heated the lower high-melting-point metal, the heat radiated upwards, and the vapor generated by the heating of the middle Al / Mn layer could directly escape upwards into the vacuum chamber, resulting in the second highest burn-off rate (Al 5.1%, Mn 6.2%). Examples 1 and 2 completely encapsulated the low-melting-point metal mixture (Al, Mn) between two layers of high-melting-point metal. The mechanism of action lies in increasing the local vapor pressure: the upper high-melting-point metal acts like a "physical lid," trapping the vapor within the interlayer when the low-melting-point layer melts and vaporizes, rapidly increasing the partial pressure of Al / Mn in the sealed space, thereby inhibiting further vaporization and escape of the Al / Mn components in the liquid metal (thermodynamically, the evaporation rate drops sharply under saturated vapor pressure); and isolating direct arc impact: the arc first acts on the upper high-melting-point metal, avoiding direct cathode spot bombardment of the low-melting-point Al / Mn by the high-current arc, fundamentally eliminating liquid splashing and instantaneous overheating vaporization caused by arc force. Example 3 increased the initial melting current (120A) and operating current (320A) compared to Example 2, but the burn-off rate only increased slightly (Al 3.1%, Mn 3.5%), and the composition deviation was even better (1.3%). This indicates that, under the premise of an effective interlayer structure, the window for the stepped current is wider. A slightly larger current enhanced the electromagnetic stirring force, which promoted the dissolution of high-melting-point W / Mo. At the same time, because the physical constraints of the upper cover still existed, the vapor pressure suppression mechanism remained effective, preventing a rapid deterioration in burn-off.

[0061] Comparative Example 3: A high current of 300A was directly applied, resulting in extremely high local instantaneous temperatures (the center of the electric arc could reach several thousand degrees Celsius). The low-melting-point Al (melting temperature approximately 660℃) and Mn (approximately 1246℃) were subjected to strong thermal radiation and electron bombardment before the underlying high-melting-point metal had melted, resulting in severe overshoot boiling and the highest burn-off rate (Al 7.4%, Mn 9.0%).

[0062] The specific embodiments of the present invention described above do not constitute a limitation on the scope of protection of the present invention. Any other corresponding changes and modifications made in accordance with the technical concept of the present invention should be included within the scope of protection of the claims of the present invention.

Claims

1. A method for preparing a high-entropy alloy, characterized in that, include, High-entropy metal raw materials are laid in three layers: lower, middle and upper, to obtain a composite block. The composite block is melted to obtain a high-entropy alloy; The high-entropy alloy raw material is divided into high-melting-point metals with a melting point ≥1600℃ and low-melting-point metals with a melting point <1600℃. The lower layer and the upper layer are composed of high-melting-point metals, and the middle layer is composed of low-melting-point metals.

2. The method for preparing the high-entropy alloy according to claim 1, characterized in that, The thickness of the lower layer and the upper layer is 1 / 4 to 1 / 3 of the height of the composite block.

3. The method for preparing the high-entropy alloy according to claim 1, characterized in that, The melting process employs non-consumable vacuum arc melting.

4. The method for preparing the high-entropy alloy according to claim 3, characterized in that, The non-consumable vacuum arc melting includes, The composite block is placed in a non-consumable vacuum arc furnace, and evacuated and filled with argon gas to an absolute pressure of 30-60 kPa. Then, an initial current of 60-150 A is maintained for 10-30 seconds to allow the lower layer to melt slightly and the middle layer to heat up and melt through heat conduction. After the molten pool is formed, the working current is increased to 200-400A and the liquid phase is maintained for 30-90s, and then cooled to obtain the initial molten alloy ingot; After flipping the initial melted alloy ingot, maintain it in the liquid phase for 30-60 seconds at the working current or at a current 1%-10% higher than the working current, and then continue to flip and remelt 4-8 times.

5. The method for preparing the high-entropy alloy according to claim 4, characterized in that, The vacuuming process is completed to a pressure ≤ 5 × 10⁻⁶. -3 Pa.

6. The method for preparing the high-entropy alloy according to claim 4, characterized in that, The vacuuming and argon filling processes are repeated 2-3 times. After the final argon filling, the high-purity Ti is melted by arc ignition and then inhaled for 1-2 minutes.

7. The method for preparing the high-entropy alloy according to claim 4, characterized in that, In the presence of the liquid phase, electromagnetic stirring with an electric arc is used to promote convection.

8. The method for preparing a high-entropy alloy according to claim 1, characterized in that, The purity of the high-entropy alloy raw material is ≥99.5%.

9. The method for preparing a high-entropy alloy according to any one of claims 1-8, characterized in that, The compositional deviation of the low-melting-point metal is within ±2.0 at.%.

10. A high-entropy alloy, characterized in that, It is obtained by the preparation method according to any one of claims 1-9.

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