High-hardness AlxCoCrFeNiNby high-entropy alloy, and preparation method and application thereof

Abstract

The application belongs to the technical field of metal materials, and particularly relates to a high-hardness AlxCoCrFeNiNby high-entropy alloy and a preparation method and application thereof. The high-entropy alloy is expressed as AlxCoCrFeNiNby, and the atomic percentage content of each element satisfies the conditions of Al: 0.07% to 19.35 at%, Co: 14.30% to 23.35 at%, Cr: 12.60% to 20.60 at%, Fe: 13.55% to 22.15 at%, Ni: 14.25% to 23.25 at%, and Nb: 0 to 44.00 at%; and further satisfies the following conditions: (1) the atomic ratio of Al:(CoCrFeNi):Nb is x:4:y; (2) 1<=x+y<=2; and (3) the sum of the atomic percentages of each element is 100. The Vickers hardness can reach 795 to 1080 HV, and the high-entropy alloy has the advantages of good high-temperature resistance and excellent wear resistance.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of metal materials, and particularly relates to a high-hardness AlxCoCrFeNiNby high-entropy alloy and a preparation method and application thereof. BACKGROUND

[0002] High-entropy alloys break the traditional metal material composed of one or two main elements, and the performance of the alloy is improved by adding other elements. The high-entropy alloy is usually composed of five or more elements in equal or near-equal molar ratio, and the proportion of each element is 5% to 35%. The high-entropy alloy has four special effects, i.e., high-entropy effect in thermodynamics, delayed diffusion effect in kinetics, lattice distortion effect in structure, and "cocktail effect" in performance. The high-entropy effect in thermodynamics makes the high-entropy alloy easy to form simple phase structures such as FCC, BCC, FCC+BCC mixed phase and HCP non-metallic intermetallic compound. The delayed diffusion effect in kinetics makes the high-entropy alloy better than the traditional metal in corrosion resistance and other properties. The lattice distortion effect in structure and the "cocktail effect" in performance make the high-entropy alloy improve in different properties to a certain extent. Therefore, the high-entropy alloy has good mechanical properties, wear resistance, corrosion resistance, high-temperature oxidation resistance and radiation resistance, which are generally better than the traditional metal materials. Vacuum induction melting is a common melting method for high-entropy alloys, which is easy to operate and has low cost. The metal elements of the high-entropy alloy are put into the crucible of the vacuum induction melting furnace from high to low according to a certain proportion, and the metal is melted by the eddy current in the electromagnetic induction to obtain high-entropy alloy ingot. A plurality of alloys can be melted at one time. In the process of melting and casting, the pores and gaps in the alloy during melting, as well as the dendrite growth and element segregation during solidification, will make the microstructure of the as-cast alloy uneven, which will affect the mechanical properties of the high-entropy alloy to a certain extent. At present, there are many studies on the processing of high-entropy alloys, mainly including rolling, heat treatment and welding processes, and there are few studies on high-temperature forging of high-entropy alloys.

[0003] Forging is a commonly used processing method, which is simple and greatly saves processing cost. After the ingot is forged, on the one hand, the defects of the cast alloy are improved, and the grains are obviously refined, which greatly improves the strength and plasticity of the alloy; on the other hand, the increase of the proportion of BCC phase in the alloy system after forging is also beneficial to the improvement of the strength of the alloy. However, forging of high-entropy alloy may cause cracks in the alloy. SUMMARY

[0004] In order to solve the problems in the prior art, that is, defects inevitably occur in the as-cast high-entropy alloy obtained by a conventional preparation method, and the defects and segregation can be reduced to a certain extent by using heat treatment alone, but the density cannot be improved, the high-temperature forging and heat treatment combined technical means are adopted in the application, so that the defects can be reduced, the segregation can be improved, the density can be improved, and the Vickers hardness of the AlxCoCrFeNiNby high-entropy alloy is greatly improved.

[0005] The technical scheme provided by the application is as follows:

[0006] A high-hardness AlxCoCrFeNiNby high-entropy alloy, which is expressed as AlxCoCrFeNiNby, and the atomic percentage content of each element satisfies the conditions that Al is 0.07% to 19.35 at%, Co is 14.30% to 23.35 at%, Cr is 12.60% to 20.60 at%, Fe is 13.55% to 22.15 at%, Ni is 14.25% to 23.25 at%, and Nb is 0 to 44.00 at%; and the following conditions are also satisfied: (1) the atomic ratio of Al:(CoCrFeNi):Nb is x:4:y; (2) 1<=x+y<=2; and (3) the sum of the atomic percentages of each element is 100.

[0007] The high-hardness AlxCoCrFeNiNby high-entropy alloy provided by the application has a Vickers hardness / HV of 795 to 1080, and has the advantages of high-temperature resistance and excellent wear resistance.

[0008] The reasons for selecting the main elements of the AlxCoCrFeNiNby high-entropy alloy in the application are as follows:

[0009] Al: Al is a typical main element that can form a high-entropy alloy, and the addition of Al can enhance the strength of the alloy and reduce the density of the alloy; Al is a common alloying element and is also easy to be oxidized to form an oxide film, but the atomic size of Al is larger than that of Co, Cr, Fe and Ni in the quaternary alloy CoCrFeNi, the mixing enthalpy is more negative, and the addition of Al elements can easily cause lattice distortion in the microstructure, promote the transformation of the high-entropy alloy from FCC to FCC+BCC and then to BCC structure, and thus the performance is improved to a certain extent;

[0010] Co: Co is a classic main element that is easy to form a high-entropy alloy, and is generally uniformly distributed in the alloy structure, and can also be mutually soluble with other elements;

[0011] Cr: Cr element is a typical main element that is easy to form high-entropy alloy, which improves the strength and hardness of the alloy, has little effect on the plasticity and toughness of the alloy, and improves the overall mechanical properties of the alloy. Cr element is infinitely soluble with Fe element, can inhibit the formation of brittle intermetallic compounds, and can be soluble with other elements, and tends to promote the formation of BCC phase;

[0012] Fe: Fe element is a main element, which is a classic main element that is easy to form high-entropy alloy, and can be soluble with other elements;

[0013] Ni: Ni element is a main element, which is a classic main element that is easy to form high-entropy alloy, tends to promote the formation of FCC phase, Ni element is infinitely soluble with Fe element, can inhibit the formation of brittle intermetallic compounds, and can be soluble with other elements;

[0014] Nb: Nb is a large atomic element, and has better oxidation resistance than Co, Cr and Ni. The addition of Nb changes the phase structure of the alloy, and the organization changes from hypoeutectic to hypereutectic. At the same time, the addition of Nb increases the lattice distortion of the alloy or precipitates a second phase in the matrix, and it is found that the precipitation of Laves phase can improve the strength and hardness of the alloy, so that the solid solution strengthening and precipitation hardening effect is obvious.

[0015] The application also provides a preparation method of the high-hardness AlxCoCrFeNiNby high-entropy alloy, comprising the following steps:

[0016] 1) The composition and content of the high-hardness AlxCoCrFeNiNby high-entropy alloy according to claim 1 are prepared by vacuum induction melting to obtain a cast high-entropy alloy;

[0017] 2) The cast high-entropy alloy is further subjected to high-temperature forging treatment;

[0018] 3) Finally, the high-entropy alloy after forging cooling is subjected to homogenization heat treatment to obtain the high-hardness AlxCoCrFeNiNby high-entropy alloy.

[0019] Based on the above technical scheme:

[0020] The cast ingot after melting is subjected to high-temperature forging to improve segregation and reduce defects;

[0021] The high-entropy alloy ingot after forging cooling is subjected to homogenization heat treatment, which can prevent the generation of cracks and eliminate internal stress on the basis of inheriting the advantages of high-temperature forging, and the size of the high-entropy alloy grains is refined after heat treatment.

[0022] Specifically, in step 1): at least 4-6 times of melting in the vacuum induction melting process, wherein, in the first melting, the current is controlled at 150-250 A to slowly melt the high-purity metal elements to prevent the volatilization of low-melting-point metals; in the remaining times of melting, the current is controlled at 250-300 A to effectively make the alloy melt to form a more uniform alloy ingot; after each melting, the ingot is turned over by 180 degrees before the next melting.

[0023] Specifically, the vacuum degree in the vacuum induction melting furnace is less than 5x10 -3 Pa, and the protective gas is high-purity argon with a purity of greater than 99.999%.

[0024] The vacuum induction melting method can specifically include the following steps:

[0025] (a) proportionally weighing the metal element raw materials, the purity of the metal raw materials being greater than 99.5%, processing the metal raw materials into precise spherical metal particles with a diameter of less than 5 mm, removing the oxide skin on the surface of the metal elements with SiC sandpaper, and then placing the metal elements in a pre-prepared mold in the vacuum induction melting furnace in the order of high melting point to low melting point;

[0026] (b) vacuumizing the vacuum induction melting furnace to greater than 5x10 -3 Pa, and filling the protective gas to less than 1.5x10 3 Pa, which is repeated 2-4 times, the protective gas being high-purity argon with a purity of greater than 99.999%, the flow rate of the argon being 3000 ml / min before 70% of the argon is introduced, and the flow rate of the remaining argon being 2000 ml / min;

[0027] (c) placing the high-purity metals in a mold of a predetermined size, melting the high-purity metals by using the vacuum induction melting process to obtain an alloy ingot, turning over the ingot by 180 degrees before melting again, which is repeated 4-6 times to make the alloy ingot melt more uniformly;

[0028] (d) after the vacuum induction melting is completed, cooling the high-entropy alloy ingot to room temperature, polishing the surface of the high-entropy alloy ingot to be smooth by using 180-2000# SiC sandpaper, placing the high-entropy alloy ingot in a methanol solution for ultrasonic cleaning to remove impurities on the surface, cleaning the high-entropy alloy ingot with anhydrous ethanol, and drying to obtain a high-entropy alloy ingot of a predetermined mold size. The obtained ingot is ultrasonically cleaned by placing the alloy ingot in a methanol solution for 5-15 min. The drying temperature is 30-100°C.

[0029] Further, in order to optimize the final forging size, in the vacuum melting process, the metal particles are placed in a mold of a predetermined size to prepare the high-entropy alloy ingot; the mold size is 300 mm in length, 200 mm in width, and 50-80 mm in height.

[0030] Specifically, in step 2), the high-temperature forging conditions are as follows: the furnace charging temperature is 600-700℃, the initial forging temperature is 1000-1250℃, the final forging temperature is 600-850℃, the forging ratio is 2-3.5, and the forging cooling mode is water cooling.

[0031] Specifically, in step 3), the high-temperature forging conditions are as follows:

[0032] The alloy is subjected to homogenization heat treatment at a heat treatment temperature of 600-800℃ for 2-4 hours under a protective gas condition, and then cooled to room temperature to obtain a high-hardness AlxCoCrFeNiNby high-entropy alloy in a heat-treated state.

[0033] The heating mode is as follows: before reaching half of the heat treatment temperature, the heating speed is 10-20℃ / min; and then, the heating speed is 20-30℃ / min.

[0034] Specifically, the protective gas for heat treatment is high-purity argon with a purity of greater than 99.999% and a vacuum degree of less than 10 -4 Pa.

[0035] The heat treatment can specifically include the following steps: placing the high-entropy alloy ingot cooled after the forging process into a quartz tube for homogenization heating under vacuum; characterized in that the heating speed is 10-30℃ / min, and a gradient heating method is adopted to avoid defects caused by rapid heating; before the heating temperature rises to half of the specified temperature, the heating speed is 10-20℃ / min, and after reaching half of the specified heating temperature, the heating speed is 20-30℃ / min; the homogenization heating specifically includes the following steps:

[0036] (a) cutting the high-entropy alloy ingot cooled after forging into block-shaped high-entropy alloy with a size of 200mm in length, 100mm in width, and 20-40mm in height using a wire cutting machine, so that the size of the high-entropy alloy can be placed in the quartz tube;

[0037] (b) introducing high-purity argon (purity greater than 99.999%) into the quartz tube to vacuumize, introducing argon to a vacuum degree of less than 10 -4 Pa, and the flow speed of the protective gas high-purity argon is fast first and then slow;

[0038] (c) heating the quartz tube for homogenization heat treatment at 600-800℃ for 2-4 hours, and cooling to room temperature to obtain a high-entropy alloy in a heat-treated state.

[0039] The application also provides the application of the high-hardness AlxCoCrFeNiNby high-entropy alloy described above, which is used for making cutting tool materials, die materials or bearing materials.

[0040] The high-hardness AlxCoCrFeNiNby high-entropy alloy provided by the application has high hardness, high-temperature resistance and excellent wear resistance, and can be used to make wear-resistant cutters, molds or bearing materials.

[0041] Compared with the prior art, the application has the following advantages:

[0042] 1) The high-entropy alloy is melted by vacuum induction melting technology to prevent the volatilization of low-melting-point metals, maximize the uniformity of alloy melting, and save costs;

[0043] 2) The cast ingot is subjected to high-temperature forging to improve segregation and reduce defects, enhance relevant performance, simplify the process flow, and maximize the reduction of production costs;

[0044] 3) After high-temperature forging, the uniform heat treatment is used to reduce the generation of forging cracks and improve the microstructure morphology after forging. BRIEF DESCRIPTION OF DRAWINGS

[0045] Figure 1 The XRD analysis diagram of the AlxCoCrFeNiNby high-entropy alloy prepared for Example 1 is shown in Figure 1. Figure 1 It can be obtained that the AlxCoCrFeNiNby high-entropy alloy obtained after high-temperature forging has a single-phase BCC structure;

[0046] Figure 2 The microstructure SEM diagram of the AlxCoCrFeNiNby high-entropy alloy prepared for Example 1 is shown in Figure 2. Figure 2 It can be obtained that the AlxCoCrFeNiNby high-entropy alloy obtained after high-temperature forging has a relatively perfect microstructure morphology diagram, and the dendrites in the microstructure diagram are obvious and have precipitates;

[0047] Figure 3 The XRD analysis diagram of the AlxCoCrFeNiNby high-entropy alloy prepared for Example 2 is shown in Figure 3. Figure 3 It can be obtained that the AlxCoCrFeNiNby high-entropy alloy obtained after high-temperature forging has obvious BCC phase structure and Laves phase distinction;

[0048] Figure 4 The microstructure SEM diagram of the AlxCoCrFeNiNby high-entropy alloy prepared for Example 2 is shown in Figure 4. Figure 4 It can be obtained that the AlxCoCrFeNiNby high-entropy alloy obtained after high-temperature forging has obvious BCC phase structure and Laves phase distinction in the microstructure. DETAILED DESCRIPTION

[0049] The principles and characteristics of the present application are described below, and the examples are used to explain the present application, but not to limit the scope of the present application.

[0050] Table 1 below is a comparison table of chemical compositions of embodiments of the present application

[0051] Table 2 below is a table of parameter values for vacuum melting of embodiments of the present application

[0052] Table 3 below is a table of parameter values for high-temperature forging of embodiments of the present application

[0053] Table 4 below is a table of parameter values for homogenization heat treatment of embodiments of the present application

[0054] Table 5 below is the Vickers hardness test results of embodiments of the present application

[0055] In the embodiments of the present application, the AlxCoCrFeNiNby high-entropy alloy is made of Al: 0.07% to 19.35 at%, Co: 14.30% to 23.35 at%, Cr: 12.60% to 20.60 at%, Fe: 13.55% to 22.15 at%, Ni: 14.25% to 23.25 at%, and Nb: 0 to 44.00 at%, and the composition of each element satisfies the following conditions: (1) the atomic ratio of Al:(CoCrFeNi):Nb is x:4:y; (2) 1≤x+y≤2; and (3) the sum of the atomic percentages of each element is 100.

[0056] The preparation steps of the embodiments of the present application are as follows: a cast high-entropy alloy is prepared by vacuum induction melting, the cast high-entropy alloy is then subjected to high-temperature forging treatment, and finally the high-entropy alloy after forging and cooling is subjected to homogenization heat treatment. The parameters of induction melting, high-temperature forging, and homogenization heat treatment are shown in the following tables.

[0057] Embodiment 1

[0058] A high-hardness AlxCoCrFeNiNby high-entropy alloy, and the specific implementation steps are as follows:

[0059] Step 1: Prepare a 1000g high-entropy alloy AlxCoCrFeNiNby ingot, accurately weigh the spherical metal particles according to the proportion, the purity of the metal raw material is greater than 99.5%, and the diameter of the metal particles is less than 5mm; the amount of metal raw material is shown in Table 1; the metal raw material is weighed on a balance with an error of 0.1g; the surface oxide is removed with fine SiC sandpaper, and then the metal raw material is placed in the pre-prepared mold in the vacuum induction melting furnace according to the order from high melting point to low melting point;

[0060] Step 2: The vacuum induction melting furnace is evacuated to greater than 5×10 -3 Pa, and the protective gas is filled to less than 1.5×10 3Pa, the process is repeated 3 times; the protective gas is high-purity argon (purity ≥ 99.999%), the flow rate of argon is fast first and then slow, the flow rate of argon before 70% of the vacuum induction furnace is 3000 ml / min, and the flow rate of subsequent argon is 2000 ml / min;

[0061] Step 3. High-purity metal is melted by vacuum induction melting process to obtain alloy ingot, and the ingot is flipped 180 degrees and then melted again. The process is repeated 4 times to make the ingot melt more uniformly. In the first melting, the current is controlled at 200A to slowly melt the high-purity metal to prevent low-melting-point metals from volatilizing. In the second to fifth melting, the current is controlled at 280A to effectively make the alloy melt uniformly to form a high-entropy alloy ingot with a size of 300mm×200mm×40mm.

[0062] Step 4. The high-entropy alloy ingot is cooled to room temperature, polished to a smooth surface with 1200# sandpaper, ultrasonically cleaned with a methanol solution to remove possible impurities on the surface, rinsed with 75% ethanol, and then blown dry. The blowing dry temperature is maintained at 50℃. After blowing dry, a molten bulk high-entropy alloy ingot is obtained.

[0063] Step 5. The bulk as-cast high-entropy alloy ingot with a size of 300mm×200mm×50mm is subjected to high-temperature forging treatment. The furnace temperature is 600℃, the initial forging temperature is 1000℃, the final forging temperature is 600℃, the forging ratio is 2:1, and the cooling method is water cooling.

[0064] Step 6. The high-entropy alloy ingot after forging and cooling is cut into a block with a size of 100mm×80mm×30mm, so that the size of the high-entropy alloy can be placed in a quartz tube.

[0065] Step 7. The quartz tube is connected to an argon gas vacuum pump to vacuumize the quartz tube to a vacuum degree greater than 10 -4 Pa, the process is repeated 3 times to ensure that there is no impurity gas in the vacuum furnace; the protective gas is high-purity argon (purity greater than 99.999%), the flow rate of argon is fast first and then slow, the flow rate of argon before 70% of the vacuum induction furnace is 3000 ml / min, and the flow rate of subsequent argon is 2000 ml / min;

[0066] Step 8. The quartz tube is heated, the heating speed is 15℃ / min before reaching 400℃, the heating speed is 25℃ / min between 400-800℃, and the high-entropy alloy is obtained by homogenizing heat treatment at 800℃ for 2 hours.

[0067] Step 9. The high-entropy alloy in a heat-treated state is cooled, and the cast ingot obtained after cooling is ultrasonically cleaned. The alloy ingot is placed in a methanol solution and ultrasonically cleaned for 15 min, then rinsed with a 75% ethanol solution, and finally a high-hardness AlxCoCrFeNiNby high-entropy alloy is obtained;

[0068] The detection results: the experimental results of Example 1 correspond to the Figure 1 and Figure 2 XRD detection angle range is 20-100 degrees, and the scanning speed is 4 degrees per minute. The polished sample is etched with aqua regia for about 20 s, and the microstructure morphology can be observed by scanning electron microscopy. The AlxCoCrFeNiNby high-entropy alloy has FCC and BCC phase structures, and according to the microstructure diagram, the microstructure is complete without obvious defects, which is better than the as-cast, and the dendritic structure and fine precipitated phase are generated.

[0069] Example 2

[0070] A high-hardness AlxCoCrFeNiNby high-entropy alloy, the specific implementation steps are as follows:

[0071] Step 1: Prepare a 1000g high-entropy alloy AlxCoCrFeNiNby ingot. The metal raw materials are weighed according to the proportion, and the purity of the metal raw materials is greater than 99.5%. The metal raw materials are processed into precise spherical metal particles, and the diameter of the metal particles is less than 5mm. The amount of metal raw materials is shown in Table 1. The metal raw materials are weighed on a balance with an error of 0.1g. The surface oxide is removed with fine SiC sandpaper, and then the metal raw materials are placed in the pre-prepared mold in the vacuum induction melting furnace according to the order of melting point from high to low;

[0072] Step 2. The vacuum induction melting furnace is evacuated to greater than 5x10 -3 Pa, and the protective gas is filled to less than 1.5x10 3 Pa. This process is repeated 3 times to ensure that there are no other impurity gases in the vacuum induction furnace. The protective gas is high-purity argon (purity greater than 99.999%), and the flow rate of argon is fast first and then slow. The flow rate of argon is 3000ml / min before 70% of the argon is introduced into the vacuum induction furnace, and the subsequent flow rate of argon is 2000ml / min;

[0073] Step 3. High-purity metal is melted by a vacuum induction melting process to obtain an alloy ingot, and the ingot is flipped 180 degrees and then melted again. This process is repeated 5 times to make the ingot melt more uniformly. In the first melting, the current is controlled at 220A to slowly melt the high-purity metal to prevent the volatilization of low-melting-point metals. In the second to fifth melting, the current is controlled at 290A to effectively melt the alloy to form a high-entropy alloy ingot with a uniform size of 300mmx200mmx60mm;

[0074] Step 4. The high-entropy alloy ingot is cooled to room temperature, polished to a smooth surface with 1000# sandpaper, ultrasonically cleaned with a methanol solution to remove possible impurities on the surface, rinsed with 75% ethanol, and then blown dry. The blowing dry temperature is maintained at 60℃. After blowing dry, a molten bulk high-entropy alloy ingot is obtained;

[0075] Step 5. The bulk as-cast high-entropy alloy ingot with a size of 300mmx200mmx60mm is subjected to high-temperature forging treatment. The furnace temperature is 650℃, the initial forging temperature is 1150℃, the final forging temperature is 700℃, the forging ratio is 2.5:1, and the cooling method is sand cooling;

[0076] Step 6. The high-entropy alloy ingot after forging and cooling is cut into a block with a size of 100mmx80mmx30mm, so that the size of the high-entropy alloy can be placed in a quartz tube;

[0077] Step 7. The quartz tube is connected to an argon gas vacuum pump to vacuumize the quartz tube to a vacuum degree greater than 10 -4 Pa. The process of vacuumizing the quartz tube is repeated 3 times to ensure that there is no impurity gas in the vacuum furnace. The protective gas is high-purity argon (purity greater than 99.999%). The flow rate of argon is fast at first and then slow. The flow rate of argon is 3000ml / min before 70% of argon is introduced, and the flow rate of subsequent argon is 2000ml / min;

[0078] Step 8. The quartz tube is heated. The heating rate is 20℃ / min before reaching 400℃, and the heating rate is 25℃ / min between 400-800℃. The high-entropy alloy is homogenized at 800℃ for 2 hours to obtain a heat-treated high-entropy alloy;

[0079] Step 9. The cooled ingot is ultrasonically cleaned. The alloy ingot is placed in a methanol solution and ultrasonically cleaned for 20min. Then it is rinsed with a 75% ethanol solution. Finally, a high-hardness AlxCoCrFeNiNby high-entropy alloy is obtained;

[0080] The detection results of Example 2 correspond to the Figure 3 and Figure 4, the XRD detection angle range is 20-100 degrees, and the scanning speed is 4 degrees per minute; the polished sample is etched with aqua regia for about 20s, and the microstructure morphology can be observed by scanning electron microscopy; the AlxCoCrFeNiNby high-entropy alloy has Laves phase and BCC phase structure, and according to the microstructure diagram, the microstructure is more optimal, complete and has no obvious defects;

[0081] Table 1. Comparison table of chemical composition of AlxCoCrFeNi of the present application (%)

[0082] Sample Al Fe Co Ni Cr Nb M (g / mol) 26.98 55.85 58.93 58.69 51.99 92.91 1# 12.56 21.66 22.86 22.76 20.16 0 2# 7.80 16.20 17.05 17.00 15.05 26.90

[0083] Table 2. Value table of vacuum melting parameters of the embodiment of the present application

[0084]

[0085] Table 3. Value table of high-temperature forging parameters of the embodiment of the present application

[0086] Example Charge temperature / °C Initial forging temperature / °C Final forging temperature / °C Forging ratio Cooling method 1# 600 1000 600 2 Water cooling 2# 650 1150 700 2.5 Sand cooling

[0087] Table 4. Value table of homogenization heat treatment parameters of the embodiment of the present application

[0088]

[0089]

[0090] Table 5. Vickers hardness test results of the embodiment of the present application

[0091] Example Vickers hardness / HV 1# 795 2# 1080

[0092] According to the above embodiment data and the content of the drawings, it can be obtained that the AlxCoCrFeNiNby high-entropy alloy and the preparation method provided by the present application improve the microstructure morphology of the as-cast AlxCoCrFeNiNby high-entropy alloy and improve the related mechanical properties, and finally the AlxCoCrFeNiNby high-entropy alloy with high hardness can be obtained.

[0093] The above only describes the preferred embodiments of the present application, and is not intended to limit the present application, and any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application shall be included in the protection scope of the present application.

Claims

1. A method for preparing a high hardness AlxCoCrFeNiNby high-entropy alloy, characterized in that, The method comprises the following steps: 1) according to the composition and content of the high-hardness AlxCoCrFeNiNby high-entropy alloy, a cast high-entropy alloy is prepared by vacuum induction melting; 2) the cast high-entropy alloy is further subjected to high-temperature forging treatment; 3) finally, the high-entropy alloy after forging cooling is subjected to homogenization heat treatment, thereby obtaining the high-hardness AlxCoCrFeNiNby high-entropy alloy; the expression of the high-hardness AlxCoCrFeNiNby high-entropy alloy is AlxCoCrFeNiNby, and the atomic percentage content of each element satisfies the conditions of Al: 0.07% to 19.35 at%, Co: 14.30% to 23.35 at%, Cr: 12.60% to 20.60 at%, Fe: 13.55% to 22.15 at%, Ni: 14.25% to 23.25 at%, and Nb: 26.90% to 44.00 at%; and further satisfies the following conditions: (1) the atomic ratio of Al:(CoCrFeNi):Nb is x:4:y; (2) 1≤x+y≤2; (3) the sum of the atomic percentages of each element is 100; in step 1), the vacuum induction melting process is at least 4 to 6 times of melting, wherein the current is controlled at 150 to 250 A during the first melting, and the current is controlled at 250 to 300 A during the remaining times of melting; after each melting is completed, the ingot is turned over by 180 degrees before the next melting is performed; in step 2), the high-temperature forging conditions are as follows: the furnace charging temperature is 600 to 700 DEG C, the initial forging temperature is 1000 to 1250 DEG C, the final forging temperature is 600 to 850 DEG C, the forging ratio is 2 to 3.5, and the forging cooling mode is water cooling or sand cooling; in step 3), the alloy is subjected to homogenization heat treatment at a heat treatment temperature of 600 to 800 DEG C under a protective gas condition for 2 to 4 hours, and then cooled to room temperature, thereby obtaining the high-hardness AlxCoCrFeNiNby high-entropy alloy in a heat-treated state; the heating mode is as follows: before reaching half of the heat treatment temperature, the heating speed is 10 to 20 DEG C / min; subsequently, the heating speed is 20 to 30 DEG C / min. 2.The method for preparing high hardness AlxCoCrFeNiNby high-entropy alloy according to claim 1, characterized in that: The vacuum degree in the vacuum induction melting furnace is less than 5x10 -3 Pa, and the protective gas is argon with a purity of more than 99.999%. 3.The method of claim 1, wherein the high hardness Al x CoCrFeNiN by high-entropy alloy is prepared by the following steps. The protective gas for heat treatment is argon with purity greater than 99.999% and vacuum degree less than 10 -4 Pa.

4. A high-hardness AlxCoCrFeNiNby high-entropy alloy prepared by the preparation method according to any one of claims 1 to 3. 5.The application of high hardness AlxCoCrFeNiNby high-entropy alloy according to claim 4, characterized in that: The high-hardness AlxCoCrFeNiNby high-entropy alloy is used for making wear-resistant molds, cutters or bearings. The high-hardness AlxCoCrFeNiNby high-entropy alloy is used for making wear-resistant molds, cutters or bearings.

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