High-toughness light refractory high-entropy alloy and preparation method thereof

Abstract

The invention provides a high-toughness light refractory high-entropy alloy and a preparation method thereof. The chemical formula of the high-entropy alloy is # imgabs0 #; the atomic molar ratio of the V element in the high-entropy alloy is more than or equal to 0.4 and less than or equal to 0.6. And Ti and Al elements with relatively low density are combined with V, Nb and Mo elements with relatively high melting points, so that the high-temperature performance of the alloy is ensured while the density is reduced. The preparation method comprises the following steps: sequentially carrying out ball milling and spark plasma sintering on alloy raw materials according to an atomic molar ratio to obtain the high-entropy alloy, the spark plasma sintering comprises first heating, second heating and cooling treatment which are carried out in sequence. The high-entropy alloy with the single centered cubic structure is prepared by combining ball milling and spark plasma sintering and combining and regulating the temperature increasing and decreasing process of the spark plasma sintering process, meanwhile, grains are effectively refined, the grain boundary is strengthened, and then the mechanical property of the alloy is improved.

Description

Technical Field

[0001] The present invention belongs to the technical field of high entropy alloys and preparation thereof, and relates to a high-strength, tough, lightweight, refractory high entropy alloy and a preparation method thereof. Background Art

[0002] High-entropy alloys (HEAs) typically consist of five or more metallic elements, with the atomic content of each metallic element ranging from 5% to 35%. This breaks with the design philosophy of traditional alloys, such as magnesium alloys, aluminum alloys, titanium alloys, and superalloys, which primarily rely on a single metallic element. They offer adjustable microstructure and performance. Refractory HEAs designed and developed based on high-melting-point elements exhibit superior strength, hardness, corrosion resistance, creep resistance, high-temperature structural stability, and high-temperature oxidation resistance to conventional nickel-based superalloys. They can meet the stringent requirements for heat-resistant structural materials in the aerospace, petrochemical, and other fields, and are expected to become the next generation of high-performance, high-temperature materials.

[0003] Refractory high-entropy alloys (HHAs) are primarily composed of high-density refractory elements such as Hf, W, Mo, and Ta, resulting in a high alloy density. Furthermore, the strong lattice distortion in HHAs hinders the movement of dislocations and deformation of the material. The irregular lattice arrangement makes atomic movement more difficult, resulting in poor room-temperature plasticity in HHAs.

[0004] Currently, refractory high-entropy alloy (HEA) blocks are primarily produced using vacuum arc melting and powder metallurgy. However, due to the high and widely varying melting points of the various components, HEAs produced using vacuum arc melting suffer from coarse grains, severe component segregation, and the susceptibility to casting defects such as shrinkage cavities and porosity, severely limiting further improvements in their performance. Powder metallurgy, a common process for preparing particle-reinforced composites, suffers from the slow heating rate and long holding time of tube furnace sintering, resulting in large grains in the resulting samples and preventing the production of HEAs with excellent comprehensive mechanical properties.

[0005] Mechanical alloying is a solid-state, non-equilibrium process that allows elements with widely differing melting points to be alloyed at relatively low temperatures. Spark plasma sintering, with its rapid heating rate, low sintering temperature, and short sintering time, effectively suppresses grain growth during the sintering process, resulting in a dense, uniformly structured bulk material. Combining mechanical alloying with spark plasma sintering can produce high-entropy alloy composites with superior performance.

[0006] In summary, developing a refractory high-entropy alloy with low cost, low density, and matching strength and toughness and a preparation method thereof is an urgent problem that needs to be solved by those skilled in the art. Summary of the Invention

[0007] The purpose of the present invention is to provide a high-strength, lightweight, refractory high-entropy alloy and a preparation method thereof, so as to solve the problems of poor room temperature plasticity, low strength and high density of refractory high-entropy alloys in the prior art.

[0008] In order to achieve the purpose of the invention, the present invention adopts the following technical solutions: A high-strength, light-weight, refractory high-entropy alloy, the chemical formula of which is TiAlV x NbMo; The atomic molar ratio of the V element in the high entropy alloy is 0.4≤x≤0.6, for example, it can be 0.42, 0.45, 0.48, 0.5, 0.52, 0.55 or 0.60, but is not limited to the listed values. Other unlisted values ​​within this numerical range are also applicable, preferably 0.5.

[0009] In the present invention, the atomic molar ratio of Ti, Al, V, Nb and Mo in the high entropy alloy is 1:1:x:1:1.

[0010] The high entropy alloy provided by the present invention combines Ti and Al elements with relatively low density and V, Nb and Mo elements with relatively high melting points, thereby reducing the density while ensuring the high-temperature performance of the alloy.

[0011] Furthermore, the structure of the high entropy alloy is a BCC phase (body-centered cubic structure); The average particle size of the sintered bulk high-entropy alloy is 2.2 to 2.8 μm, for example, 2.2 μm, 2.4 μm, 2.5 μm, or 2.8 μm, but is not limited to the listed values. Other values ​​not listed within this range are also applicable. The average particle size after sintering at 1000°C is 2.2 μm, the average particle size after sintering at 1100°C is 2.4 MPa, and the average particle size after sintering at 1200°C is 2.8 μm.

[0012] Furthermore, the density of the high entropy alloy is 5.50-5.78 g / cm 3 ; Density after sintering at 1000℃ is 5.50g / cm 3 , after sintering at 1100℃, the density is 5.66g / cm 3 , after sintering at 1200℃, the density is 5.78g / cm 3 ; The compressive yield strength of the high-entropy alloy at 25°C is 1800-1850 MPa; according to different sintering temperatures: the yield strength after sintering at 1000°C is 1800 MPa, the yield strength after sintering at 1100°C is 1830 MPa, and the yield strength after sintering at 1200°C is 1850 MPa.

[0013] The plastic strain of the high entropy alloy at 25°C is ≥17%, for example, it can be 17.5%, 18%, 18.5%, 19%, 20% or 21%, but is not limited to the listed values. Other values ​​not listed within this numerical range are also applicable; the plastic strain after sintering at 1000°C is 17%, the plastic strain after sintering at 1100°C is 17.5%, and the plastic strain after sintering at 1200°C is 18.1%; The specific strength of the high entropy alloy is ≥300 MPa·cm 3 / g, for example, 310 MPa·cm 3 / g, 320MPa·cm 3 / g, 330MPa·cm 3 / g, 350MPa·cm 3 / g or 360MPa·cm 3 / g, etc., but are not limited to the listed values. Other values ​​not listed in this range are also applicable. The specific strength after sintering at 1000℃ is 300MPa·cm 3 / g, and the specific strength after sintering at 1100℃ is 320MPa·cm 3 / g, and the specific strength after sintering at 1200℃ is 345MPa·cm 3 / g.

[0014] The invention makes the prepared high entropy alloy have light weight and excellent mechanical properties through the comprehensive effects of solid solution strengthening, grain boundary strengthening and precipitation strengthening by selecting and coordinating various elements.

[0015] A method for preparing the above-mentioned high entropy alloy comprises: sequentially ball milling and spark plasma sintering the alloy raw materials according to the atomic molar ratio to obtain the high entropy alloy; the spark plasma sintering comprises a first heating, a second heating and a cooling treatment performed sequentially.

[0016] The preparation method provided by the present invention combines ball milling and spark plasma sintering, and combines the regulation of the temperature rise and fall process of the spark plasma sintering process to effectively refine the grains, strengthen the grain boundaries, and thus improve the mechanical properties of the alloy, thereby producing a refractory high-entropy alloy with a single body-centered cubic structure, light weight, and matched strength and toughness.

[0017] In the present invention, the spark plasma sintering process is set to step by step to ensure that the alloy is fully sintered and effectively refine the grains, which is beneficial to improving the microstructure of the alloy material. The subsequent rapid cooling is beneficial to strengthening the alloy performance and preventing the alloy grains from growing.

[0018] Furthermore, the average particle size of the alloy raw material is 4.2 to 15 μm, for example, 10.5 μm, 11 μm, 11.5 μm, 12 μm, 13 μm, or 14 μm, but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable. The average particle size is 15 μm when the ball milling time is 10 hours, the average particle size is 9.2 μm when the ball milling time is 15 hours, the average particle size is 5 μm when the ball milling time is 20 hours, and the average particle size is 4.2 μm when the ball milling time is 30 hours.

[0019] Furthermore, the ball milling is carried out under a protective atmosphere; The protective atmosphere includes argon, and the ball milling is carried out in a sealed ball milling jar in a glove box with an argon concentration of 99.99%; The ball-to-material ratio of the ball mill is 15 to 30:1, for example, it can be 15:1, 18:1, 20:1, 22:1, 25:1 or 30:1, but is not limited to the listed values. Other values ​​not listed within the numerical range are also applicable; The grinding balls include stainless steel balls; The ball mill has a rotational speed of 360-400 r / min, for example, 360 r / min, 370 r / min, 380 r / min or 390 r / min, etc., but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0020] Furthermore, the ball milling time is 8 to 38 hours, for example, 8 hours, 10 hours, 12 hours, 15 hours, 18 hours, 20 hours, 25 hours, 30 hours, 35 hours or 38 hours, but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable; The ball milling method is intermittent ball milling; The intermittent ball milling is performed with a 15-minute interval after every 30-60 minutes of ball milling.

[0021] Furthermore, the vacuum degree of the spark plasma sintering is ≤4×10 -3 MPa; In the present invention, a pressure of 4-6 MPa is applied before the first heating, and then a vacuum treatment is performed. When the vacuum degree meets the requirement of ≤4×10 -3 MPa, and then the first temperature rise is carried out. A pressure of 4~6MPa is applied before vacuum treatment to prevent the upper and lower pressure heads of the graphite mold from tilting during vacuum treatment and the initial stage of sintering; the purpose of vacuum treatment is to prevent the powder from reacting with oxygen during the sintering process.

[0022] The spark plasma sintering pressure is 42-58 MPa, for example, 42 MPa, 45 MPa, 48 MPa, 50 MPa, 52 MPa, 55 MPa or 58 MPa, but is not limited to the listed values. Other values ​​not listed within the numerical range are also applicable. The first heating rate is 85-110°C / min, for example, 85°C / min, 90°C / min, 95°C / min, 100°C / min, 105°C / min, or 110°C / min, but is not limited to the listed values. Other values ​​not listed within the numerical range are also applicable. The end point of the first heating is 610-690°C, for example, 610°C, 620°C, 630°C, 640°C, 650°C, 660°C, 670°C, 680°C or 690°C, etc., but is not limited to the listed values, and other values ​​not listed in the numerical range are also applicable; The first heating holding time is 2.5 to 4.5 minutes, for example, it can be 2.5 minutes, 3 minutes, 3.5 minutes, 4 minutes or 4.5 minutes, but is not limited to the listed values. Other values ​​not listed within the numerical range are also applicable.

[0023] Furthermore, the heating rate of the second heating is 85-105°C / min, for example, 85°C / min, 90°C / min, 95°C / min, 100°C / min or 105°C / min, etc., but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable; The end point of the second heating is 1220-1380° C., for example, 1220° C., 1250° C., 1280° C., 1300° C., 1320° C., 1350° C., 1360° C., or 1380° C., but is not limited to the listed values. Other values ​​not listed within the numerical range are also applicable. The second heating holding time is 4 to 9 minutes, for example, 4 minutes, 5 minutes, 6 minutes, 7 minutes, 8 minutes, or 9 minutes, but is not limited to the listed values. Other values ​​not listed within the numerical range are also applicable. The cooling rate of the cooling treatment is 75~95℃ / min, for example, it can be 75℃ / min, 80℃ / min, 85℃ / min, 90℃ / min or 95℃ / min, but is not limited to the listed values. Other values ​​not listed within this numerical range are also applicable.

[0024] The terminal temperature of the cooling treatment is room temperature.

[0025] Furthermore, the preparation method comprises: ball milling and spark plasma sintering alloy raw materials with an average particle size of 10 to 15 μm in sequence according to an atomic molar ratio to obtain the high entropy alloy; The ball milling is carried out under a protective atmosphere; the ball-to-material ratio of the ball milling is 10-30:1, the rotation speed is 350-400 r / min, and the time is 5-40 h; the ball milling method is intermittent ball milling; The spark plasma sintering is carried out at a vacuum degree of ≤4×10 -3 MPa and a pressure of 40-60 MPa, and sequentially perform the first heating, second heating, and cooling treatments; The first heating process has a heating rate of 80-120°C / min, a heating end point of 600-700°C, and a holding time of 2-5 min; The second heating process has a heating rate of 80-110°C / min, an end point of the heating process of 1200-1400°C, and a holding time of 3-10 min; The cooling rate of the temperature reduction treatment is 70-100°C / min.

[0026] Compared with the prior art, the present invention has the following beneficial effects: (1) TiAlV provided by the present invention x NbMo high entropy alloy combines Ti and Al, which have lower density, with V, Nb, and Mo, which have higher melting points, to reduce density while ensuring high-temperature performance of the alloy. (2) The preparation method provided by the present invention combines ball milling and spark plasma sintering, and regulates the temperature ramping process parameters during the spark plasma sintering process to produce a refractory high-entropy alloy with fine grains, uniform structure, light weight, and matched strength and toughness. By combining ball milling and spark plasma sintering, and regulating the temperature ramping process during the spark plasma sintering process, a single body-centered cubic high-entropy alloy is produced, while effectively refining the grains and strengthening the grain boundaries, thereby improving the mechanical properties of the alloy. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 TiAlV prepared in Example 1 0.5 XRD pattern of NbMo high entropy alloy; Figure 2 TiAlV prepared in Example 1 0.5 SEM image of NbMo high-entropy alloy.

[0028] Figure 3 TiAlV prepared in Example 1 0.5 XRD pattern of NbMo high entropy alloy after sintering.

[0029] Figure 4 TiAlV prepared in Example 1 0.5 SEM image of NbMo high entropy alloy after sintering.

[0030] Figure 5 TiAlV prepared in Example 1 0.5 Compressive stress-strain curves of NbMo high-entropy alloys and comparison of specific strengths of different alloys. DETAILED DESCRIPTION

[0031] The technical solution of the present invention is further described below by way of specific embodiments. It should be understood by those skilled in the art that the embodiments are merely to help understand the present invention and should not be regarded as specific limitations of the present invention.

[0032] The ball mills in the following examples and comparative examples were equipped with a glove box, and the purity of the raw materials used was ≥99%. Example 1

[0033] This embodiment provides a high-strength, light-weight, refractory high-entropy alloy and a preparation method thereof. The chemical formula of the high-entropy alloy is TiAlV 0.5 NbMo; The preparation method comprises the following steps: (1) Ti powder with an average particle size of 10 μm, Al powder with an average particle size of 10 μm, V powder with an average particle size of 10 μm, Nb powder with an average particle size of 13 μm, and Mo powder with an average particle size of 15 μm were loaded into a ball mill according to the atomic molar ratio, and then stainless steel grinding balls were loaded. Then, intermittent ball milling was carried out for 20 h in an argon atmosphere with a purity of 99.99%, a ball-to-material ratio of 20:1, and a rotation speed of 380 r / min to obtain a high entropy alloy powder; The intermittent ball milling process is performed with a 15-minute break after every 40 minutes of ball milling. (2) The high entropy alloy powder described in step (1) is placed in a graphite mold of a sintering furnace, and a pressure of 5 MPa is applied and then vacuumed to a vacuum degree of 2×10 -3 MPa, and then at a vacuum degree of 2×10 -3 MPa and a pressure of 50 MPa to obtain a high entropy alloy by spark plasma sintering; The spark plasma sintering is a first heating, a second heating and a cooling process performed sequentially; The heating rate of the first heating is 100°C / min, the heating end point is 650°C, and the holding time is 3 minutes; the heating rate of the second heating is 90°C / min, the heating end point is 1300°C, and the holding time is 5 minutes; the cooling rate of the cooling treatment is 80°C / min, and the cooling end point is room temperature.

[0034] Figures 1 and 2The XRD and SEM images of the high entropy alloy prepared in this embodiment are respectively Figure 1-2 It can be seen that after 20 h of ball milling, only the diffraction peak corresponding to BCC was observed, indicating that the fully alloyed TiAlV was obtained by mechanical ball milling. 0.5 NbMo refractory high-entropy powder. During this process, repeated cold welding and fracturing achieve continuous refinement of the powder particles. As cold welding and fracturing reach a dynamic equilibrium, the powder's particle size and morphology no longer change significantly with increasing milling time. After 30 hours of milling, the average particle size of the powder reaches a steady state (2 μm).

[0035] Figures 3 and 4 The XRD and SEM images of the sintered high-entropy alloy are shown. The XRD patterns reveal that the sintered alloy is primarily composed of two disordered body-centered cubic structures (BCC1 and BCC2) and a hexagonal aluminum oxide (Al2O3) phase. Based on the contrast differences in the SEM images, the white region represents the matrix phase, corresponding to the disordered BCC1 phase; the gray region represents the precipitated phase, corresponding to the disordered BCC2 phase. The black phase exhibits strong aluminum- and oxygen-rich characteristics. Further analysis, combined with the stoichiometric ratio, confirms that it is a hexagonal aluminum oxide (Al2O3) phase. This is consistent with the XRD results, indicating that Al2O3 precipitated and remained as a stable phase during the sintering process. Example 2

[0036] This embodiment provides a high-strength, light-weight, refractory high-entropy alloy and a preparation method thereof. The chemical formula of the high-entropy alloy is TiAlV 0.6 NbMo; The preparation method comprises the following steps: (1) Ti powder with an average particle size of 12 μm, Al powder with an average particle size of 10 μm, V powder with an average particle size of 12 μm, Nb powder with an average particle size of 10 μm, and Mo powder with an average particle size of 15 μm were loaded into a ball mill according to the atomic molar ratio, and then stainless steel grinding balls were loaded. Then, intermittent ball milling was carried out for 40 h in an argon atmosphere with a purity of 99.99%, a ball-to-material ratio of 10:1, and a rotation speed of 350 r / min to obtain a high entropy alloy powder; The intermittent ball milling process is performed with a 15-minute break after every 60 minutes of ball milling. (2) The high entropy alloy powder described in step (1) is placed in a graphite mold of a sintering furnace, and a pressure of 5 MPa is applied and then vacuumed to a vacuum degree of 1×10 -3 MPa, and then the vacuum degree was 1×10 -3 MPa and a pressure of 40 MPa to obtain a high entropy alloy by spark plasma sintering; The spark plasma sintering is a first heating, a second heating and a cooling process performed sequentially; The heating rate of the first heating is 120°C / min, the heating end point is 700°C, and the holding time is 2 minutes; the heating rate of the second heating is 100°C / min, the heating end point is 1400°C, and the holding time is 3 minutes; the cooling rate of the cooling treatment is 90°C / min, and the cooling end point is room temperature. Example 3

[0037] This embodiment provides a high-strength, light-weight, refractory high-entropy alloy and a preparation method thereof. The chemical formula of the high-entropy alloy is TiAlV 0.4 NbMo; The preparation method comprises the following steps: (1) Ti powder with an average particle size of 10 μm, Al powder with an average particle size of 10 μm, V powder with an average particle size of 15 μm, Nb powder with an average particle size of 10 μm, and Mo powder with an average particle size of 15 μm were loaded into a ball mill according to the atomic molar ratio, and then stainless steel grinding balls were loaded. Then, intermittent ball milling was carried out for 10 h in an argon atmosphere with a purity of 99.99%, a ball-to-material ratio of 30:1, and a rotation speed of 400 r / min to obtain high entropy alloy powder; The intermittent ball milling process is performed with a 15-minute break after every 30-minute ball milling. (2) The high entropy alloy powder described in step (1) is placed in a graphite mold of a sintering furnace, and a pressure of 5 MPa is applied and then vacuumed to a vacuum degree of 4×10 -3 MPa, and then at a vacuum degree of 4×10 -3 MPa and a pressure of 60 MPa to obtain a high entropy alloy; The spark plasma sintering is a first heating, a second heating and a cooling process performed sequentially; The heating rate of the first heating is 90°C / min, the heating end point is 600°C, and the holding time is 4 minutes; the heating rate of the second heating is 80°C / min, the heating end point is 1200°C, and the holding time is 8 minutes; the cooling rate of the cooling treatment is 70°C / min, and the cooling end point is room temperature. Example 4

[0038] This embodiment provides a high-strength, lightweight, refractory high-entropy alloy and a preparation method thereof. The chemical formula of the high-entropy alloy is the same as that of Example 1; The preparation method is the same as that of Example 1 except that the end point of the first heating in step (2) is 500°C. Example 5

[0039] This embodiment provides a high-strength, lightweight, refractory high-entropy alloy and a preparation method thereof. The chemical formula of the high-entropy alloy is the same as that of Example 1; The preparation method is the same as that of Example 1 except that the holding time of the first heating in step (2) is 10 minutes. Example 6

[0040] This embodiment provides a high-strength, lightweight, refractory high-entropy alloy and a preparation method thereof. The chemical formula of the high-entropy alloy is the same as that of Example 1; The preparation method is the same as that of Example 1 except that the end point of the second heating in step (2) is 1100°C. Example 7

[0041] This embodiment provides a high-strength, lightweight, refractory high-entropy alloy and a preparation method thereof. The chemical formula of the high-entropy alloy is the same as that of Example 1; The preparation method is the same as that of Example 1 except that the end point of the second heating in step (2) is 1500°C. Example 8

[0042] This embodiment provides a high-strength, lightweight, refractory high-entropy alloy and a preparation method thereof. The chemical formula of the high-entropy alloy is the same as that of Example 1; The preparation method is the same as that of Example 1 except that the holding time of the second heating in step (2) is 15 minutes. Example 9

[0043] This embodiment provides a high-strength, lightweight, refractory high-entropy alloy and a preparation method thereof. The chemical formula of the high-entropy alloy is the same as that of Example 1; The preparation method is the same as that of Example 1 except that the heating rates of the first and second heating in step (2) are both 70°C / min. Example 10

[0044] This embodiment provides a high-strength, lightweight, refractory high-entropy alloy and a preparation method thereof. The chemical formula of the high-entropy alloy is the same as that of Example 1; The preparation method is the same as that of Example 1 except that the cooling rate of the cooling treatment in step (2) is 50°C / min.

[0045] Comparative Example 1 This comparative example provides a high-strength, light-weight, refractory high-entropy alloy and a preparation method thereof. The chemical formula of the high-entropy alloy is TiAlV 0.2 Except for NbMo, other conditions are the same as those in Example 1.

[0046] Comparative Example 2 This comparative example provides a high-strength, light-weight, refractory high-entropy alloy and a preparation method thereof. The chemical formula of the high-entropy alloy is TiZrV 0.5 Except for NbMo, other conditions are the same as those in Example 1.

[0047] Comparative Example 3 This comparative example provides a high-strength, light-weight, refractory high-entropy alloy and a preparation method thereof. The chemical formula of the high-entropy alloy is TiAlV 0.5 Except for TaMo, other conditions are the same as those in Example 1.

[0048] Comparative Example 4 This comparative example provides a high-strength, lightweight, refractory high-entropy alloy and a preparation method thereof. The chemical formula of the high-entropy alloy is the same as that of Example 1; The preparation method is the same as that of Example 1 except that the first temperature increase is not performed in step (2).

[0049] The high entropy alloys prepared in the above examples and comparative examples were subjected to density, compressive yield strength, plastic strain and specific strength performance tests. The density test was performed using an electronic analytical balance, and the compressive yield strength test was performed using a universal material testing machine at a temperature of 1×10 -3 s -1 Quasi-static compression was performed at a strain rate of 1000 nm, and stress-strain curves were collected simultaneously. The stress corresponding to 0.2% plastic deformation was taken as the compressive yield strength (σ0.2). The specific strength test method is specific strength = σb / ρ, where σb is the measured compressive fracture strength (taken as the maximum value of the stress-strain curve) and ρ is the measured density. The test results are shown in Table 1.

[0050] Table 1

[0051] From Table 1 we can see that: (1) The high entropy alloy provided by the present invention and its preparation method have matching strength, plasticity and density, and have high strength, high toughness and light weight at room temperature. The density of the high entropy alloy is 4~6g / cm 3 , compressive yield strength is 1800~1850MPa, plastic strain ≥17%, specifically Figure 5 (a) shows a typical engineering stress-strain curve of the high entropy alloy of the present invention, demonstrating its good mechanical response behavior at room temperature. Figure 5 (b) Comparing the specific strengths of high-entropy alloys with different compositions, it can be clearly seen that the high-entropy alloy designed in the present invention maintains higher strength while having a lower density, exhibiting more excellent specific strength performance, which is superior to high-entropy alloys with different compositions in existing literature.

[0052] (2) A comprehensive comparison of Example 1 with Examples 4 and 5 shows that when the terminal temperature of the first heating is too low, the alloy components will be segregated due to insufficient element diffusion, and a uniform solid solution structure cannot be formed, which is not conducive to the synergistic improvement of the strength and plasticity of the high-entropy alloy; when the holding time of the first heating is too long, the brittle phase transformation will be triggered by abnormal grain growth or excessive precipitation of the second phase, which is not conducive to the optimization of the toughness and processing performance of the high-entropy alloy.

[0053] (3) A comprehensive comparison of Example 1 and Examples 6-7 shows that when the end temperature of the second heating is too low (1100°C, Example 6), the density of the high-entropy alloy is low and the strength and plasticity are poor due to insufficient sintering densification. When the end temperature of the second heating is too high (1500°C, Example 7), the plasticity and strength of the high-entropy alloy decrease due to grain coarsening and pore growth. A comprehensive comparison of Example 1 and Example 8 shows that when the holding time of the second heating is too long, the excessive growth of the structure and the evolution of pores are not conducive to improving the comprehensive mechanical properties of the high-entropy alloy.

[0054] (4) A comprehensive comparison of Example 1 and Example 10 shows that when the cooling rate of the temperature reduction treatment is too slow, the grains continue to grow and the phase boundaries relax sufficiently, making it difficult to retain the strengthening phase, resulting in a decrease in the yield strength and specific strength of the high entropy alloy, and a slightly inferior overall mechanical property.

[0055] (5) From the comparison between Example 1 and Comparative Example 1, it can be seen that when the V content is reduced, the strength of the alloy decreases due to the weakening of the solid solution strengthening effect. At the same time, the element diffusion is more uniform but the strengthening effect is insufficient, and it is impossible to achieve an effective synergistic improvement in the strength and plasticity of the high entropy alloy. When the V content is too low, the plasticity of the alloy is limitedly improved, and the overall specific strength decreases, which is not conducive to the optimization of high strength, toughness and lightweight performance.

[0056] (6) From the comparison between Example 1 and Comparative Examples 2-3, it can be seen that when Zr is selected to replace Al, the atomic radius of Zr is larger and its density is significantly higher than Al, which leads to excessive lattice distortion and increased alloy density, thereby reducing the lightweight characteristics and comprehensive mechanical properties of the high entropy alloy; when Ta is selected to replace Nb, the melting point and atomic volume of Ta are higher than Nb, which leads to internal stress concentration and reduced phase stability of the alloy, thereby making the plasticity, toughness and heat resistance of the high entropy alloy inferior to those of Example 1. Therefore, the TiAlV 0.5 The NbMo component exhibits better comprehensive performance in terms of lightness, toughness and heat resistance.

[0057] The applicant declares that the present invention is intended to illustrate the detailed structural features of the present invention through the above-described embodiments, but the present invention is not limited to the above-described detailed structural features. This does not mean that the present invention must rely on the above-described detailed structural features in order to be implemented. Those skilled in the art should understand that any improvements to the present invention, equivalent replacements for selected components, additions of auxiliary components, and selection of specific embodiments, etc., fall within the scope of protection and disclosure of the present invention.

Claims

1. A high-strength, lightweight, refractory high-entropy alloy, characterized by: The chemical formula of the high entropy alloy is ; The atomic molar ratio of the V element in the high entropy alloy is 0.4≤x≤0.

6.

2. The high entropy alloy according to claim 1, wherein: The structure of the high entropy alloy is a BCC phase (body-centered cubic structure); The average particle size of the sintered bulk high entropy alloy is 2.2-2.8 μm.

3. The high entropy alloy according to claim 1 or 2, characterized in that: The density of the high entropy alloy is 5.50-5.78 ; The high entropy alloy has a compressive yield strength of 1800-1850 MPa at 25°C; The plastic strain of the high entropy alloy at 25°C is ≥17%; The specific strength of the high entropy alloy is ≥300 .

4. A method for preparing a high entropy alloy according to any one of claims 1 to 3, characterized in that: The method comprises the following steps: performing ball milling and spark plasma sintering on alloy raw materials in sequence according to an atomic molar ratio to obtain a high entropy alloy; and the spark plasma sintering comprises a first heating process, a second heating process and a cooling process in sequence.

5. The preparation method according to claim 4, characterized in that: The average particle size of the alloy raw material is 4.2-15 μm.

6. The preparation method according to claim 4 or 5, characterized in that: The ball milling is carried out under a protective atmosphere; The protective atmosphere comprises argon; The ball-to-material ratio of the ball mill is 15-30:1; The grinding balls include stainless steel balls; The rotation speed of the ball mill is 360-400 r / min.

7. The preparation method according to any one of claims 4 to 6, characterized in that: The ball milling time is 8-38h; The ball milling method is intermittent ball milling; The intermittent ball milling is performed with a 15 minute break after every 30-60 minutes of ball milling.

8. The preparation method according to any one of claims 4 to 7, characterized in that: The vacuum degree of the spark plasma sintering is ≤ MPa; The spark plasma sintering pressure is 42-58 MPa; The heating rate of the first heating is 85-110°C / min; The end point of the first heating is 610-690°C; The first heating holding time is 2.5-4.5 minutes.

9. The preparation method according to any one of claims 4 to 8, characterized in that: The second heating rate is 85-105°C / min; The end point of the second heating is 1220-1380°C; The second heating holding time is 4-9 minutes; The cooling rate of the cooling treatment is 75-95°C / min; The terminal temperature of the cooling treatment is room temperature.

10. The preparation method according to claim 4, characterized in that: The preparation method comprises: ball milling and spark plasma sintering alloy raw materials with an average particle size of 10-15 μm in sequence according to an atomic molar ratio to obtain the high entropy alloy; The ball milling is carried out under a protective atmosphere; the ball-to-material ratio of the ball milling is 10-30:1, the rotation speed is 350-400 r / min, and the time is 5-40 h; the ball milling method is intermittent ball milling; The spark plasma sintering is carried out at a vacuum degree of ≤ MPa and a pressure of 40-60 MPa, and sequentially perform the first heating, second heating, and cooling treatments; The first heating process has a heating rate of 80-120°C / min, a heating end point of 600-700°C, and a holding time of 2-5 min; The second heating process has a heating rate of 80-110°C / min, an end point of the heating process of 1200-1400°C, and a holding time of 3-10 min; The cooling rate of the temperature reduction treatment is 70-100°C / min.

Images