High-entropy alloy with flame retardant property and preparation method thereof

Abstract

The invention belongs to the field of metal combustion, and particularly relates to a high-entropy alloy with flame retardant property and a preparation method thereof. The general formula of the high-entropy alloy is A1-x / Bx, x is larger than 0 and smaller than or equal to 35 at%, A is a multi-principal-element alloy, B is at least one of Cr, Al and Si, the high-entropy alloy is of a simple cubic structure, and the oxygen pressure threshold value of the high-entropy alloy reaches up to 4.9 MPa. According to the invention, the alloying elements Al, Cr and Si added in the multi-principal element alloy are combined with reasonable processing means such as heat treatment and cold processing, and a heterostructure is constructed through 3D printing, so that the flame retardant property of the alloy can be further improved, and meanwhile, the high-temperature mechanical property of the alloy can also be greatly improved. The flame retardant property of the alloy is obviously higher than that of an existing high-entropy alloy system, and the alloy is expected to be applied to materials used under extreme working conditions such as high temperature, high pressure and oxygen enrichment.

Description

Technical Field

[0001] The present invention belongs to the field of metal combustion and material preparation thereof, and in particular relates to a high entropy alloy with flame retardant properties and a preparation method thereof. Background Art

[0002] High-entropy alloys (HEAs) are alloys containing three or more primary elements, with the atomic percentage of each element ranging from 5% to 35%. The emergence of HEAs transcends the traditional enthalpy-based design philosophy of alloys by innovatively incorporating the concept of configurational entropy, creating new opportunities for the development of new materials. In thermodynamics, according to the Gibbs free energy equation (ΔG = ΔHTΔS), at high temperatures, an increase in entropy effectively reduces the free energy of a system. Consequently, HEAs exhibit exceptionally high phase stability at high temperatures. Dynamically, the complex and diverse atomic environment within HEAs has been shown to effectively reduce the diffusion rate of each primary element within the system. At high temperatures, material deformation is primarily influenced by diffusion. HEAs, due to their unique high entropy effect and delayed diffusion, possess excellent high-temperature phase stability and mechanical properties. NbMoTaW HEAs, in particular, maintain a stable structure at 1400°C, exhibit excellent work-hardening capabilities at room temperature, and possess strengths exceeding 500 MPa at 1600°C. Therefore, these excellent characteristics of high entropy alloys make them likely to be widely used under high temperature conditions.

[0003] Metal materials exposed to high temperatures and oxygen-rich conditions are susceptible to a failure mode distinct from either melting or oxidative corrosion: metal combustion. The primary characteristics of metal combustion are a rapid rise in temperature, the generation of flames, and the accompanying intense heat release. Once combustion occurs, it typically lasts only a dozen seconds from start to finish. This failure mode can lead to rapid and catastrophic destruction of components, necessitating the urgent development of metal materials with superior flame-retardant properties. Summary of the Invention

[0004] The present invention discloses a high entropy alloy with flame retardant properties and a preparation method thereof, so as to solve any of the above and other potential problems of the prior art.

[0005] In order to solve the above technical problems, the technical solution of the present invention is: a high entropy alloy with flame retardant properties, the general formula of the high entropy alloy is A 1-x / B x , wherein 0<x≤35at%, A is a multi-principal alloy, B is at least one of Cr, Al, and Si, the high entropy alloy has a simple cubic structure, and its oxygen pressure threshold is as high as 4.9MPa.

[0006] Furthermore, the chemical formula of the multi-principal alloy is Fe a Co b Ni c , where 0<a≤35at%, 0<b≤35at%, 0<c≤35at%.

[0007] Furthermore, the chemical formula of the multi-principal alloy is Fe a Co b Ni c N y , wherein N is at least one of Cu, Ag, Au, and Pt, 0<a≤35at%, 0<b≤35at%, 0<c≤35at%, 0<y≤35at%.

[0008] Furthermore, the chemical formula of the multi-principal alloy is Nb e Mo f Ta g W h , where 0<e≤35at%, 0<f≤35at%, 0<g≤35at%, 0<h≤35at%.

[0009] Furthermore, the chemical formula of the multi-principal alloy is Nb e Mo f Ta g W h J p , wherein J is at least one of Cu, Ag, Au, Pt, and Sn, wherein 0<e≤35at%, 0<f≤35at%, 0<g≤35at%, 0<h≤35at%, 0<p≤10at%.

[0010] Furthermore, when x=30, the general formula of the high entropy alloy is (FeCoNi) 70 Cr 30 , and its oxygen pressure threshold is as high as 3.4MPa.

[0011] Furthermore, when x=5, the general formula of the high entropy alloy is (NbMoTaW) 95 The oxygen pressure threshold of Cr5 high entropy alloy reaches 0.37MPa.

[0012] Another object of the present invention is to provide a method for preparing the above-mentioned high entropy alloy, which specifically comprises the following steps:

[0013] S1) Weigh each raw material according to the designed ratio, pre-treat it and set it aside.

[0014] S2) Weighed raw materials are placed in a non-consumable vacuum arc furnace, and the raw materials are stacked in order of melting point, i.e., elements with high melting points are placed on the upper layer and elements with low melting points are placed on the lower layer;

[0015] S3) starting the equipment, first using a small electric arc to heat the upper layer element to red, then increasing the current to melt the upper layer high melting point element and then fuse it with the lower layer low melting point element to obtain an alloy ingot;

[0016] S4) remelting the obtained alloy ingot for a certain period of time, melting multiple times, and turning the alloy ingot over using a turning shovel after each melting, and then melting it again to obtain a master alloy;

[0017] S5) After the master alloy is fully and evenly melted, the alloy is suction-casted into a water-cooled copper mold using a vacuum suction casting device or a casting device to obtain a high-entropy alloy with flame retardant properties.

[0018] Furthermore, the pretreatment process of S1) is: using sandpaper and a grinding wheel to remove the oxide scale on the surface of the raw metal, and then using industrial ethanol to clean the raw material;

[0019] The purity of the raw metal is 99.9% or higher.

[0020] Furthermore, the specific process of S2) is as follows: first, the furnace chamber is vacuumed to 5×10 -3 Pa, and then filled with 0.05MPa high-purity argon gas, and then evacuated to 5×10 -3 Pa, and fill with high-purity argon gas to 0.05MPa.

[0021] A high-entropy alloy with flame-retardant properties is used in materials used under extreme working conditions such as high temperature, high pressure and oxygen enrichment.

[0022] The beneficial effect of the present invention is that: due to the adoption of the above-mentioned technical solution, the present invention can further improve the flame retardant properties of the alloy by combining the alloying elements Al, Cr, and Si added to the multi-principal alloy with reasonable heat treatment, cold working and other processing methods, as well as a method of constructing a heterogeneous structure through 3D printing, while also significantly improving the high-temperature mechanical properties of the alloy.

[0023] The multi-principal alloys used are FeCoNi and NbMoTaW high-entropy alloy materials, which are ordinary pure metal raw materials. They are also ordinary metal raw materials, cheap, and have the advantages of easy preparation, simple process, and safe use.

[0024] Compared with traditional alloys, the alloyed flame-retardant high-entropy alloy material provided by the present invention has the greatest feature of excellent flame retardancy. In addition, the high-temperature performance of the alloy can also be improved through appropriate processing methods and preparation techniques, making it very suitable for use in extreme conditions such as high temperature / high pressure / oxygen-rich conditions. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1This is an embodiment of the present invention (FeCoNi) 100-x Cr x This is the XRD pattern of a high entropy alloy.

[0026] Figure 2 This is an embodiment of the present invention (FeCoNi) 100-x Cr x It is the oxygen pressure threshold of high entropy alloy.

[0027] Figure 3 This is an embodiment of the present invention (FeCoNi) 70 Cr 30 Microstructure of the residual sample after high entropy alloy combustion. a)(FeCoNi) 70 Cr 30 Overall morphology of the high-entropy alloy, b) energy spectrum line scan from the melting zone to the matrix zone, c) transmission morphology of the heat-affected zone, d) energy spectrum surface scan of the heat-affected zone, Inset A1 is an enlarged view of the oxidation zone, and Inset A2 is an enlarged view of the oxidation zone-melting zone interface.

[0028] Figure 4 This is an embodiment of the present invention (FeCoNi) 95-x Cr5M x XRD patterns of (M=Al, Si)-based high-entropy alloys.

[0029] Figure 5 This is an embodiment of the present invention (FeCoNi) 100-x-y-z Cr x M y N z It is the oxygen pressure threshold of high entropy alloy (M=Al, Si, N=Cu, Ag, Au, Pt).

[0030] Figure 6 This is an embodiment of the present invention (NbMoTaW) 100-x-y-z Cr x M y It is the oxygen pressure threshold of high entropy alloy (M=Al, Si). DETAILED DESCRIPTION

[0031] The technical solution of the present invention is further described below with reference to specific implementation examples.

[0032] The present invention provides a high entropy alloy with flame retardant properties, the general formula of the high entropy alloy is A 1-x / B x , wherein 0<x≤35at%, A is a multi-principal alloy, B is at least one of Cr, Al, and Si, the high entropy alloy has a simple cubic structure, and its oxygen pressure threshold is as high as 4.9MPa.

[0033] Furthermore, the chemical formula of the multi-principal alloy is Fe a Co b Ni c , where 0<a≤35at%, 0<b≤35at%, 0<c≤35at%.

[0034] Furthermore, the chemical formula of the multi-principal alloy is Fe a Co b Ni c N y , wherein N is at least one of Cu, Ag, Au, and Pt, 0<a≤35at%, 0<b≤35at%, 0<c≤35at%, 0<y≤35at%.

[0035] Furthermore, the chemical formula of the multi-principal alloy is Nb e Mo f Ta g W h , where 0<e≤35at%, 0<f≤35at%, 0<g≤35at%, 0<h≤35at%.

[0036] Furthermore, the chemical formula of the multi-principal alloy is Nb e Mo f Ta g W h J p , wherein J is at least one of Cu, Ag, Au, Pt, and Sn, wherein 0<e≤35at%, 0<f≤35at%, 0<g≤35at%, 0<h≤35at%, 0<p≤10at%.

[0037] The present invention provides a method for preparing the above-mentioned high entropy alloy, which specifically comprises the following steps:

[0038] S1) Weigh each raw material according to the designed ratio, pre-treat it and set it aside.

[0039] S2) Weighed raw materials are placed in a non-consumable vacuum arc furnace, and the raw materials are stacked in order of melting point, i.e., elements with high melting points are placed on the upper layer and elements with low melting points are placed on the lower layer;

[0040] S3) starting the equipment, first using a small electric arc to heat the upper layer element to red, then increasing the current to melt the upper layer high melting point element and then fuse it with the lower layer low melting point element to obtain an alloy ingot;

[0041] S4) remelting the obtained alloy ingot for a certain period of time, melting multiple times, and turning the alloy ingot over using a turning shovel after each melting, and then melting it again to obtain a master alloy;

[0042] S5) After the master alloy is fully and evenly melted, the alloy is suction-casted into a water-cooled copper mold using a vacuum suction casting device or a casting device to obtain a high-entropy alloy with flame retardant properties.

[0043] Furthermore, the pretreatment process of S1) is: using sandpaper and a grinding wheel to remove the oxide scale on the surface of the raw metal, and then using industrial ethanol to clean the raw material;

[0044] The purity of the raw metal is 99.9% or higher.

[0045] Furthermore, the specific process of S2) is as follows: first, the furnace chamber is vacuumed to 5×10 -3 Pa, and then filled with 0.05MPa high-purity argon gas, and then evacuated to 5×10 -3 Pa, and fill with high-purity argon gas to 0.05MPa.

[0046] Example 1

[0047] (FeCoNi) 100-x Cr x Preparation and properties of high entropy alloys

[0048] 1. Composition design and preparation of high entropy alloys

[0049] (FeCoNi) 100-x Cr x The preparation process of high entropy alloy is as follows:

[0050] (1) Raw material preparation: The smelting raw materials used in the present invention are high-purity (≥99.9%) Fe, Co, Ni and Cr elements. The surface oxide scale of the raw materials is removed by means of a grinding wheel, etc. The metal after the oxide scale is placed in anhydrous ethanol and cleaned twice by ultrasonic oscillation. The raw materials are accurately weighed and proportioned according to the molar percentage, and the error is required to be controlled within ±0.002g. After the weighing is completed, the prepared raw materials are placed in anhydrous ethanol again and ultrasonically cleaned.

[0051] Table 1 (FeCoNi) 100-x Cr x Nominal composition of high entropy alloy (at.%)

[0052] alloy Fe Co Ni Cr FeCoNi 33.33 33.33 33.33 - <![CDATA[(FeCoNi) 95 Cr5]]> 31.67 31.67 31.67 5 <![CDATA[(FeCoNi) 85 Cr 15 ]]> 28.33 28.33 28.33 15 <![CDATA[(FeCoNi) 80 Cr 20 ]]> 26.67 26.67 26.67 20 <![CDATA[(FeCoNi) 75 Cr 25 ]]> 25 25 25 25 <![CDATA[(FeCoNi) 73 Cr 27 ]]> 24.33 24.33 24.33 27 <![CDATA[(FeCoNi) 70 Cr 30 ]]> 23.33 23.33 23.33 30 <![CDATA[(FeCoNi) 65 Cr 35 ]]> 21.67 21.67 21.67 35 <![CDATA[(FeCoNi) 55 Cr 45 ]]> 18.33 18.33 18.33 45

[0053] (2) Preparation of high entropy alloy: The present invention adopts WK-II type non-consumable high vacuum arc furnace to melt the alloy. Before melting, the weighed metal raw materials are placed in a water-cooled copper crucible melting pool. When placing, the metal with high melting point is placed on the top and the metal with low melting point is placed on the bottom of the crucible. This allows the metal with high melting point to melt first and also prevents the metal with low melting point from volatilizing or splashing due to excessive temperature. The furnace chamber is evacuated to 5×10 -3Pa, and then filled with 0.05MPa high-purity argon gas, and then evacuated to 5×10 -3 Pa, high-purity argon is filled to 0.05MPa to obtain a protective atmosphere. During smelting, the high-purity Ti ingot is first melted with an electric arc to absorb the free oxygen in the atmosphere in the furnace. During the first smelting, a small current should be used for smelting for a few seconds to melt the alloy slightly to prevent the raw materials from being blown away by directly opening a large current for melting. In order to ensure the uniform composition of the alloy ingot, the arc is maintained for 60-120 seconds after each alloy is melted. After the alloy ingot is cooled, it is turned over. This is repeated at least 4 times, and after smelting the alloy twice, it must be vacuumed and refilled with argon. After the master alloy is fully and evenly melted, open the furnace chamber and take out the alloy.

[0054] The refined alloy ingot was ground with a grinding wheel to remove the surface oxide scale, then placed in anhydrous ethanol and cleaned with ultrasonic vibration. The high entropy alloy was suction-casted into a water-cooled copper mold using a vacuum suction casting device to obtain a 10×10mm 2 High entropy alloy ingot samples. Finally, they are cut into round rod samples of the required size using wire electrospark cutting. The size of the samples is 3.5 × 50 mm. 2 .

[0055] 2. Structure and properties of high entropy alloys

[0056] 1) X-ray diffraction (XRD) test and phase analysis

[0057] 10×10×1mm was cut from the suction casting sample by wire cutting. 3 The square pieces were carefully ground using 240#, 400#, 1000#, and 2000# metallographic sandpaper in sequence. The phase composition of each sample was analyzed using an X-ray diffractometer with a scanning speed of 10° / min and a scanning angle 2θ ranging from 30° to 90°.

[0058] The XRD test results are as follows Figure 1 As shown in Figure 2, as the Cr content in the alloy increases, the alloy undergoes a transformation from the initial single FCC phase to an FCC+BCC dual phase. Specifically, when the Cr content is within 35 at.%, the alloy maintains an FCC single phase structure, while when the Cr content reaches 45%, an FCC+BCC dual phase structure emerges.

[0059] 2) Promote ignition and combustion experiments

[0060] The equipment used in the Promoted Ignition-Combustion (PIC) experiment is designed according to the American Society for Testing and Materials (ASTM) G124 standard. The high-pressure oxygen-enriched equipment includes a test chamber, a sample holder, a combustion medium, and a generator. The specific experimental steps are as follows:

[0061] ① Add igniter: Roll the igniter (such as magnesium strip) into a ring and put it on one end of the sample. The inner ring of the igniter must fit tightly with the sample, and the bottom surface of the igniter should be on the same plane as the bottom surface of the sample. At the same time, make one end of the magnesium strip closely contact with the resistance wire;

[0062] ②Install the sample: Fix the end of the sample without ignition agent on the sample clamp of the equipment;

[0063] ③ Vacuuming: After loading the sample in step ②, seal the reaction device, open the vacuum device, and extract the air in the reaction chamber;

[0064] ④ Filling with gas: Open the inflation device and fill with oxygen to the required oxygen pressure;

[0065] ⑤ Pressure regulation: Synchronously with step ④, the system automatically opens the pressure safety device and adjusts the oxygen pressure to the required level through the pressure automatic regulator. The pressure automatic regulator is designed to ensure stable pressure inside the reactor. During combustion, after the internal oxygen is consumed, the pressure automatic regulator automatically refills the reactor with oxygen to ensure stable reaction pressure. When the pressure exceeds the safety range of the equipment, the regulator automatically opens to regulate the pressure to avoid danger.

[0066] ⑥ Ignition: Ignite the ignition agent (such as magnesium strip) through the ignition device, and then ignite the sample. After the ignition agent is ignited, turn off the ignition device;

[0067] ⑦Observation and recording: The entire combustion process is recorded by a camera, and the pressure measuring device records the pressure changes in the system;

[0068] ⑧ Release gas: After observing the combustion reaction through the observation window, open the exhaust valve to discharge the gas in the reaction chamber. The end of combustion can be determined by the presence of luminous points and temperature measuring devices in the reaction chamber;

[0069] ⑨ Remove the sample: After the entire system cools to room temperature, remove the combustion products and unburned samples. By adjusting the oxygen pressure and analyzing the combustion process, the combustion performance of the high-entropy alloy can be studied.

[0070] Judging by oxygen pressure threshold (FeCoNi) 100-x Cr x The flame retardant properties of high entropy alloys. For flame retardant materials, the lowest combustion oxygen pressure is generally used as the oxygen pressure threshold. The ASTM G124 standard defines the lowest oxygen pressure as: the oxygen pressure when the burning length of the sample exceeds 30mm (1.2in.) in one or more tests under a specified oxygen concentration and fixed sample temperature. The experimental results are as follows Figure 2 As shown. It can be seen from the figure that (FeCoNi) 100-x Cr x High entropy alloys have excellent flame retardant properties, especially (FeCoNi) 70 Cr30 The oxygen pressure threshold of high entropy alloy reaches 3.4MPa, which exceeds the flame retardant performance of the commonly used Inconel 718 alloy (2.8MPa).

[0071] 3) Observation of the microstructure of the sample after combustion

[0072] Take (FeCoNi) 70 Cr 30 The residual samples after high entropy alloy combustion were hot mounted, ground and polished for scanning electron microscopy (SEM) and electron probe microscopy (EPMA) observations. Figure 3 (FeCoNi) 70 Cr 30 Microstructure of high entropy alloy after combustion. Figure 3 The results of a show that (FeCoNi) 70 Cr 30 The microstructure of high entropy alloy after combustion can be divided into four zones: oxidation zone, melting zone, heat affected zone (HAZ) and matrix zone. The oxidation zone is mainly composed of Cr-rich oxides, which are densely distributed and contain almost no pores ( Figure 3 A1 Figure); There is a continuous and dense Cr2O3 layer at the interface of the oxidation zone and the melting zone, which makes the interface of the oxidation zone and the melting zone well bonded ( Figure 3 Figure A2); The melting zone is rich in flame retardant elements such as Ni and Co ( Figure 3 b); Due to the high entropy effect, the heat affected zone still maintains the FCC single-phase structure, and the elements are evenly distributed (see Appendix Figure 3 c and 3d). These component distribution characteristics and structures can effectively hinder the diffusion of oxygen and inhibit the combustion reaction. This is (FeCoNi) 70 Cr 30 The main reason for the excellent flame retardant properties of high entropy alloys.

[0073] Example 2

[0074] (FeCoNi) 100-x-y Cr x M y Structure and properties of (M=Al, Si) high entropy alloys

[0075] In the high entropy alloy system provided by the present invention, the doping of other alloying elements will also significantly change the flame retardant properties of the high entropy alloy. Figure 4 The XRD patterns of high entropy alloys with different alloying elements added when the Cr content is 5 at.% are shown in Figure 1. 1, 2, and 3 correspond to (FeCoNi) 95 Cr5, (FeCoNi) 93 Cr5Al2、(FeCoNi) 93Cr5Si2 high entropy alloy. The horizontal axis is the 2θ angle, and the vertical axis is the diffraction intensity (arbitrary unit). Comparison (FeCoNi) 95 From the XRD pattern of Cr5 high entropy alloy, it can be found that the addition of 2at.% Al and Si does not change the single-phase FCC structure of the high entropy alloy. Figure 5 The flame retardant performance results of the high entropy alloy system are shown in Figure 1. As can be seen from the figure, the addition of different alloying elements can significantly change the flame retardant properties of the high entropy alloy. Compared with Al, the addition of Si can significantly improve the flame retardant properties of the high entropy alloy. From this experimental result, it can be concluded that the alloy provided by the present invention can also significantly improve the flame retardant properties of the high entropy alloy by adding replacement atoms.

[0076] Example 3

[0077] (NbMoTaW) 100-x-y Cr x M y Preparation and Properties of (M=Al, Si) High Entropy Alloys

[0078] 1. Composition design and preparation of high entropy alloys

[0079] (NbMoTaW) 100-x-y Cr x M y The preparation process of high entropy alloy is as follows:

[0080] (1) Raw material preparation: The smelting raw materials used in the present invention are high-purity (≥99.9%) Nb, Mo, Ta, W, Cr, Al and Si elements. The raw materials are subjected to surface oxide scale removal by means of a grinding wheel or pickling. The metals after oxide scale removal are placed in anhydrous ethanol and cleaned twice with ultrasonic oscillation. The metals are accurately weighed and proportioned according to the molar percentage, and the error is required to be controlled within ±0.002g. After weighing, the prepared raw materials are placed in anhydrous ethanol again and cleaned with ultrasonic oscillation.

[0081] Table 2 (NbMoTaW) 100-x-y Cr x M y Nominal composition of high entropy alloy (at.%)

[0082]

[0083]

[0084] (2) Preparation of high entropy alloy: The present invention adopts WK-II type non-consumable high vacuum arc furnace to melt the alloy. Before melting, the weighed metal raw materials are placed in a water-cooled copper crucible melting pool. When placing, the metal with high melting point is placed on the top and the metal with low melting point is placed on the bottom of the crucible. This allows the metal with high melting point to melt first and also prevents the metal with low melting point from volatilizing or splashing due to excessive temperature. The furnace chamber is evacuated to 5×10 -3 Pa, and then filled with 0.05MPa high-purity argon gas, and then evacuated to 5×10 -3 Pa, high-purity argon is filled to 0.05MPa to obtain a protective atmosphere. During smelting, the high-purity Ti ingot is first melted with an arc to absorb the free oxygen in the atmosphere in the furnace. During the first smelting, a small current should be used for a few seconds to melt the alloy slightly to prevent the raw materials from being blown away by directly melting with a large current. In order to ensure the uniform composition of the alloy ingot, after each alloy is melted, the arc is maintained for 120s, the melting current is 350-450A, and the ingot is turned over and tilted 45° before each smelting. This is repeated at least 6 times, and after melting the alloy twice, it must be vacuumed and refilled with argon. After the master alloy is fully and evenly melted, open the furnace chamber and take out the alloy.

[0085] The smelted alloy ingot was ground with a grinding wheel to remove the surface oxide scale, then placed in anhydrous ethanol and cleaned with ultrasonic oscillation. The high entropy alloy was cast into a water-cooled copper mold using a vacuum casting device to obtain a 15×10mm 2 High entropy alloy ingot sample. Finally, it is cut into round rod samples of required size by wire electrospark cutting. The size of the sample is 3 × 50 mm. 2 .

[0086] 2. Flame retardant properties of high entropy alloys

[0087] Tested by promoting ignition combustion experiment (NbMoTaW) 100-x-y Cr x M y Flame retardancy of high-entropy alloys. The equipment used in the promoted ignition-combustion (PIC) experiment was designed according to the American Society for Testing and Materials (ASTM) G124 standard. The high-pressure oxygen-enriched equipment includes a test chamber, a sample holder, a combustion medium, and a generator. The specific experimental steps are as follows:

[0088] ① Add igniter: Roll the igniter (such as magnesium strip) into a ring and put it on one end of the sample. The inner ring of the igniter must fit tightly with the sample, and the bottom surface of the igniter should be on the same plane as the bottom surface of the sample. At the same time, make one end of the magnesium strip closely contact with the resistance wire;

[0089] ②Install the sample: Fix the end of the sample without ignition agent on the sample clamp of the equipment;

[0090] ③ Vacuuming: After loading the sample in step ②, seal the reaction device, open the vacuum device, and extract the air in the reaction chamber;

[0091] ④ Filling with gas: Open the inflation device and fill with oxygen to the required oxygen pressure;

[0092] ⑤ Pressure regulation: Synchronously with step ④, the system automatically opens the pressure safety device and adjusts the oxygen pressure to the required level through the pressure automatic regulator. The pressure automatic regulator is designed to ensure stable pressure inside the reactor. During combustion, after the internal oxygen is consumed, the pressure automatic regulator automatically refills the reactor with oxygen to ensure stable reaction pressure. When the pressure exceeds the safety range of the equipment, the regulator automatically opens to regulate the pressure to avoid danger.

[0093] ⑥ Ignition: Ignite the ignition agent (such as magnesium strip) through the ignition device, and then ignite the sample. After the ignition agent is ignited, turn off the ignition device;

[0094] ⑦Observation and recording: The entire combustion process is recorded by a camera, and the pressure measuring device records the pressure changes in the system;

[0095] ⑧ Release gas: After observing the combustion reaction through the observation window, open the exhaust valve to discharge the gas in the reaction chamber. The end of combustion can be determined by the presence of luminous points and temperature measuring devices in the reaction chamber;

[0096] ⑨ Remove the sample: After the entire system cools to room temperature, remove the combustion products and unburned samples. By adjusting the oxygen pressure and analyzing the combustion process, the combustion performance of the high-entropy alloy can be studied.

[0097] Judging by oxygen pressure threshold (NbMoTaW) 100-x-y Cr x M y Flame retardant properties of high entropy alloys. For flame retardant materials, the lowest combustion oxygen pressure is generally used as the oxygen pressure threshold. The experimental results are as follows: Figure 6 As shown in the figure, compared with NbMoTaW high entropy alloy, (NbMoTaW) 100-x-y Cr x M y High entropy alloys have excellent flame retardant properties. It can be seen that the flame retardant properties of NbMoTaW series high entropy alloys can be effectively improved by alloying. Especially (NbMoTaW) 95 The oxygen pressure threshold of Cr5 high entropy alloy reaches 0.37MPa, which greatly improves the flame retardant properties of NbMoTaW high entropy alloy (0.1MPa).

[0098] Example 4

[0099] Table of some alloy compositions and properties studied in this invention.

[0100] The compositions and flame retardant performance parameters of FeCoNi and NbMoTaW high entropy alloys with various alloying ratios and enhanced flame retardancy prepared according to the methods of Examples 1, 2 and 3 are listed in Table 3.

[0101] Table 3 Composition, crystal structure and measured oxygen pressure threshold of some alloys studied in the present invention

[0102]

[0103]

[0104]

[0105] The invention innovates the alloying method in FeCoNi and NbMoTaW high entropy alloys, which significantly improves the flame retardancy of FeCoNi and NbMoTaW high entropy alloys. 95 The flame retardant performance of Si5 high entropy alloy reaches 4.9MPa, and it maintains a single-phase FCC structure. Its flame retardant performance is better than most common high-temperature alloys currently available, and its price is low, so it is expected to be used under extreme working conditions.

[0106] The above describes in detail a flame-retardant high-entropy alloy and its preparation method provided in the examples of this application. The description of the above examples is only intended to help understand the method and core concept of this application; at the same time, those skilled in the art will find that the specific implementation methods and application scopes may vary based on the concept of this application. In summary, the contents of this specification should not be construed as limiting this application.

[0107] For example, certain words are used in the specification and claims to refer to specific components. Those skilled in the art should understand that hardware manufacturers may use different nouns to refer to the same component. This specification and claims do not use differences in names as a way to distinguish components, but use differences in the functions of components as the criteria for distinction. For example, "including" and "comprising" mentioned throughout the specification and claims are open-ended terms, so they should be interpreted as "including / including but not limited to". "Approximately" means that within an acceptable error range, those skilled in the art can solve the technical problems within a certain error range and basically achieve the technical effects. The subsequent description in the specification is a preferred embodiment of the present application, but the description is for the purpose of illustrating the general principles of the present application, and is not used to limit the scope of the present application. The scope of protection of the present application shall be as defined in the attached claims.

[0108] It should also be noted that the terms "include," "comprises," or any other variations thereof are intended to encompass non-exclusive inclusion, such that a product or system comprising a series of elements includes not only those elements but also other elements not explicitly listed, or elements inherent to such product or system. In the absence of further limitations, an element defined by the phrase "comprises a..." does not exclude the presence of other identical elements in the product or system comprising the element.

[0109] It should be understood that the term "and / or" as used herein is merely a description of the relationship between associated objects, indicating that three possible relationships exist. For example, "A and / or B" can represent: A exists alone, A and B exist simultaneously, or B exists alone. Furthermore, the character " / " in this document generally indicates that the associated objects are in an "or" relationship.

[0110] The above description shows and describes several preferred embodiments of the present application. However, as previously mentioned, it should be understood that the present application is not limited to the form disclosed herein and should not be construed as excluding other embodiments. Instead, the present application can be used in various other combinations, modifications, and environments and can be modified within the scope of the application concept described herein through the above teachings or technology or knowledge in the relevant field. Modifications and variations made by those skilled in the art that do not depart from the spirit and scope of the present application should be protected by the claims appended hereto.

Claims

1. A high entropy alloy with flame retardant properties, characterized in that: The general formula of the high entropy alloy is A 1-x / B x , wherein 0<x≤35at%, A is a multi-principal alloy, B is at least one of Cr, Al, and Si, the high entropy alloy has a simple cubic structure, and its oxygen pressure threshold is as high as 4.9MPa.

2. The high entropy alloy according to claim 1, characterized in that The chemical formula of the multi-principal alloy is Fe a Co b Ni c , where 0<a≤35at%, 0<b≤35at%, 0<c≤35at%.

3. The high entropy alloy according to claim 1, characterized in that The chemical formula of the multi-principal alloy is Fe a Co b Ni c N y , wherein N is at least one of Cu, Ag, Au, and Pt, 0<a≤35at%, 0<b≤35at%, 0<c≤35at%, 0<y≤35at%.

4. The high entropy alloy according to claim 1, characterized in that The chemical formula of the multi-principal alloy is Nb e Mo f Ta g W h , where 0<e≤35at%, 0<f≤35at%, 0<g≤35at%, 0<h≤35at%.

5. The high entropy alloy according to claim 1, characterized in that The chemical formula of the multi-principal alloy is Nb e Mo f Ta g W h J p , wherein J is at least one of Cu, Ag, Au, Pt, and Sn, wherein 0<e≤35at%, 0<f≤35at%, 0<g≤35at%, 0<h≤35at%, 0<p≤10at%.

6. The high entropy alloy according to claim 2, characterized in that When x=30, the general formula of the high entropy alloy is (FeCoNi) 70 Cr 30 , and its oxygen pressure threshold is as high as 3.4MPa.

7. The high entropy alloy according to claim 4, characterized in that When x=5, the general formula of the high entropy alloy is (NbMoTaW) 95 The oxygen pressure threshold of Cr5 high entropy alloy reaches 0.37MPa.

8. A method for preparing a high entropy alloy according to any one of claims 1 to 7, characterized in that: The method specifically comprises the following steps: S1) weigh each raw material according to the designed ratio, carry out pretreatment, and set aside; S2) Weighed raw materials are placed in a non-consumable vacuum arc furnace, and the raw materials are stacked in order of melting point, i.e., elements with high melting points are placed on the upper layer and elements with low melting points are placed on the lower layer; S3) starting the equipment, first using a small electric arc to heat the upper layer element to red, then increasing the current to melt the upper layer high melting point element and then fuse it with the lower layer low melting point element to obtain an alloy ingot; S4) remelting the obtained alloy ingot for a certain period of time, melting multiple times, and turning the alloy ingot over using a turning shovel after each melting, and then melting it again to obtain a master alloy; S5) After the master alloy is fully and evenly melted, the alloy is suction-casted into a water-cooled copper mold using a vacuum suction casting device or a casting device to obtain a high-entropy alloy with flame retardant properties.

9. The method according to claim 8, characterized in that The pretreatment process of S1) is: using sandpaper and a grinder to remove the oxide scale on the surface of the raw metal, and then using industrial ethanol to clean the raw material; The purity of the raw metal is 99.9% or higher.

10. The method according to claim 8, characterized in that The specific process of S2) is as follows: first, vacuum the furnace chamber to 5×10 -3 Pa, and then filled with 0.05MPa high-purity argon gas, and then evacuated to 5×10 -3 Pa, and fill with high-purity argon gas to 0.05MPa.

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