A low-density NbTiTaCrSiC-based refractory high-entropy superalloy

Abstract

The present invention relates to a low-density NbTiTaCrSiC series refractory high-entropy high-temperature alloy, which belongs to the field of high-entropy alloys. The present invention first designs the ternary matrix composition of the refractory high-entropy alloy. The matrix alloy composition is obtained by a high-throughput phase diagram calculation method; in order to simultaneously meet the requirements of low density, high oxidation resistance, good room temperature plasticity and high high-temperature strength, the alloy is composed of elements such as Nb, Ti, Ta, Cr, Si, V, Mo, W, Zr, C, B, etc., and is prepared by vacuum arc melting. The alloy is composed of BCC phase, Laves phase, silicide and carbide in the cast state, and has excellent mechanical properties. The alloy density is less than 8g / cm 3 The room temperature compressive yield strength is higher than 1000MPa, the fracture strain is greater than 20%, the compressive yield strength is greater than 700MPa at 800℃, and the average oxidation weight gain at 650℃ is less than 0.5g / m 2 ·h.

Description

Technical Field

[0001] The invention relates to a low-density NbTiTaCrSiC-based refractory high-entropy high-temperature alloy, belonging to the field of high-entropy alloys. Background Art

[0002] With the sixth-generation fighter jets on the agenda, various countries have also begun research and development of fifth-generation turbofan engines. However, the fifth-generation turbofan engine requires a turbine pre-turbine temperature of 2100K-2200K (1830℃-1930℃). Due to the limitation of its melting point, the performance of nickel-based alloys has been basically exhausted, making it difficult to meet the demand. In recent years, high-entropy alloys with multiple principal elements have become a new hot spot in the alloy field due to their nearly infinite composition space. Refractory high-entropy alloys have attracted increasing interest due to their high yield strength at high temperatures, and they have great potential in the future application of high-temperature alloys.

[0003] After more than a decade of research, researchers have developed a series of refractory high-entropy alloy systems, such as WNbMoTa, HfNbTaTiZr, and AlMoNbTaTiZr. However, finding a high-entropy alloy that simultaneously combines low density, high oxidation resistance, high room-temperature ductility, and excellent high-temperature performance remains elusive. To achieve high-temperature strength, the alloy requires a higher melting point. However, excessive Ta, Mo, and W content in the alloy increases the alloy density and the matrix brittleness, rendering it incapable of plastic deformation at room temperature. Introducing a secondary phase by adding Cr, Al, and Si can improve both room-temperature and high-temperature strength while also enhancing the alloy's oxidation resistance. However, excessive Si and Cr content can lead to a sharp decrease in the alloy's ductility due to the formation of coarse Laves phases and silicides. The nano-B2 phase introduced by Al is not stable at high temperatures and undergoes a phase transformation to a hexagonal phase during heat preservation. Therefore, the compositional design of refractory high-entropy alloys is crucial. Summary of the Invention

[0004] The purpose of the present invention is to provide a low-density NbTiTaCrSiC-based refractory high-entropy high-temperature alloy in order to solve the problems of high density, poor oxidation resistance and inconsistent room temperature and high temperature performance of existing refractory high-entropy alloys.

[0005] The purpose of the present invention is achieved through the following technical solutions.

[0006] A low-density NbTiTaCrSiC-based refractory high-entropy superalloy was developed. The ternary matrix composition of the refractory high-entropy alloy was first designed, requiring low density, high melting point, a small solidification range, a large single-phase range, and excellent oxidation resistance. The matrix alloy composition was designed using a high-throughput phase diagram calculation method. The specific steps are as follows:

[0007] Step 1: Use the Python combination module to generate a ternary refractory high-entropy alloy system for phase diagram calculation. The composition of the ternary refractory high-entropy alloy is expressed in atomic percentages. The number of elements used for phase diagram calculation is 9, and the step size for each element is set to 5%. Use the combination module to generate a nested list. Each sublist in the nested list consists of three numbers whose sum totals to 100, for a total of 14,364 sublists.

[0008] Step 2: Use the dictionary module in Python to combine the ternary refractory high entropy alloy system used for phase diagram calculation with each small list in the nested list to obtain the ternary refractory high entropy alloy composition used for phase diagram calculation.

[0009] Step 3: Using the Python pandas module, input the density, atomic number, and VEC of the ternary refractory high-entropy alloy elements used for phase diagram calculation to obtain the density and VEC of all ternary refractory high-entropy alloys. The density and VEC of ternary refractory high-entropy alloys are calculated using the following formula.

[0010] ρ=∑c i A i / (c i A i / ρ i )

[0011] VEC=∑c i VEC i

[0012] where c i is the atomic percentage of element i, A i is the atomic number of the element, ρ i is the density of element i, VEC i is the valence electron concentration of element i.

[0013] Step 4: Use the pyautogui module in Python to drive thermo-calc to calculate the phase diagram of all ternary refractory high entropy alloy compositions.

[0014] Step 5: Analyze the phase diagram calculation results obtained in Step 4 using the pandas module in Python to extract alloy data. The alloy data includes: melting point, solidification range, second phase, and second phase solution temperature.

[0015] Step 6: Using the pandas module in Python, integrate the density and VEC of all ternary refractory high-entropy alloys obtained in step 3, and the alloy data of all ternary refractory high-entropy alloys obtained in step 5 into an Excel file for system design and composition screening of ternary refractory high-entropy alloys.

[0016] The composition of the ternary refractory high entropy alloy obtained by screening is Nb a Ti b Ta c , where the atomic percentage of a is 25% to 75%, the atomic percentage of b is 25% to 60%, and the atomic percentage of c is 5% to 20%, and it is necessary to ensure that a+b+c=100%.

[0017] In order to improve the strength of the alloy, solid solution strengthening, precipitation strengthening and grain boundary strengthening can be achieved. Solid solution strengthening is mainly achieved through the addition of V, Mo, Zr, W, Cr, C and Si elements; precipitation strengthening is mainly achieved through the addition of Cr, Si and C elements, introducing Laves phase, silicide and carbide; grain boundary strengthening is achieved through the addition of a small amount of B element, which is concentrated at the grain boundary to enhance the grain boundary strength. The addition of Cr and Si elements will also improve the oxidation resistance of the alloy. The atomic percentage ranges of each element in the low-density refractory high-entropy high-temperature alloy are: 20% ≤ Nb ≤ 60%, 20% ≤ Ti ≤ 50%, 4% ≤ Ta ≤ 12%, 5% ≤ Cr ≤ 15%, 0.5% ≤ Si ≤ 3%, 0 <V≤5%,0<Mo≤3%,0<W≤2%,0<Zr≤4%,0.5%≤C≤3%,0.5%≤B≤2%。

[0018] The preparation method of the NbTiTaCrSiC refractory high entropy alloy material comprises the following steps:

[0019] Step 1: Select eleven elements including Nb, Ti, Ta, Cr, Si, V, Mo, W, Zr, C, and B, accurately weigh them according to atomic percentage, and place them into the copper crucible of a non-consumable vacuum arc melting furnace in order from low to high melting points.

[0020] Step 2: Close the furnace door, and after the non-consumable vacuum arc melting furnace reaches a high vacuum state, introduce high-purity argon gas with a purity of 99.99wt% as a protective gas.

[0021] Step 3: Melt the NbTiTaCrSiC alloy, increase the current until the alloy can be completely melted, and the single melting time of the alloy is 3 minutes. After the alloy is completely cooled, turn the ingot over by the robotic arm and continue melting using the same steps for 8 times. Do not turn on the magnetic stirring at the beginning and the last time, and turn on the magnetic stirring for the rest to ensure uniform melting.

[0022] Step 4: After the NbTiTaCrSiC alloy is smelted, wait for 20 minutes, and after it is completely cooled, open the furnace door and take out the sample to obtain the NbTiTaCrSiC alloy.

[0023] Beneficial effects

[0024] 1. The alloy material of the present invention primarily comprises Nb, Ti, Ta, Cr, Si, V, Mo, W, Zr, C, and B. The design strategy involves first designing the composition of the ternary alloy matrix, which must meet requirements for low density, good room-temperature ductility, and oxidation resistance. The alloy composition is then refined through solid solution strengthening, precipitation strengthening, and grain boundary strengthening. This compositional design strategy allows for accelerated optimization within a nearly unlimited compositional space, resulting in an alloy with room-temperature ductility, high-temperature strength, and oxidation resistance.

[0025] 2. The alloy presents a multiphase structure in the cast state, with Laves phase, silicide and carbide existing between dendrites. The density of NbTiTaCrSiC alloy is less than 8g / cm 3 The room temperature compressive yield strength is higher than 1000MPa, the fracture strain is greater than 20%, the compressive yield strength is greater than 700MPa at 800℃, and the average oxidation weight gain is less than 0.5g / m at 650℃. 2 h, comprehensive performance far exceeds that of most refractory high entropy alloys. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 It is Nb 40 Ti 30 Ta 10 As-cast microstructure diagram of Cr8Si2V2Mo3Zr2W1C1B1 alloy; Figure a is a 200x BSE diagram; Figure b is a 500x BSE diagram; Figure c is a 1000x BSE diagram;

[0027] Figure 2 It is Nb 40 Ti 30 Ta 10 Compressive stress-strain curve of Cr8Si2V2Mo3Zr2W1C1B1 alloy at room temperature;

[0028] Figure 3 It is Nb 40 Ti 30 Ta 10 Compressive stress-strain curve of Cr8Si2V2Mo3Zr2W1C1B1 alloy at 800℃;

[0029] Figure 4 It is Nb 40 Ti 30 Ta 10Oxidation weight gain curve of Cr8Si2V2Mo3Zr2W1C1B1 alloy after oxidation in air at 650℃ for 50h. DETAILED DESCRIPTION

[0030] The present invention will be further described below with reference to the accompanying drawings and embodiments.

[0031] Example 1

[0032] A low-density refractory high-entropy high-temperature alloy material, the atomic percentage expression of the alloy composition is Nb 40 Ti 30 Ta10Cr8Si2V2Mo3Zr2W1C1B1, the as-cast alloy structure is BCC phase, Laves phase, silicide and carbide. The specific steps of alloy composition design are as follows:

[0033] Step 1: Use the combination module in Python to generate a ternary refractory high-entropy alloy system for phase diagram calculation. The composition of the ternary refractory high-entropy alloy is expressed in atomic percentages. The number of elements in the ternary refractory high-entropy alloy used for phase diagram calculation is 9, and the step size of each element is set to 5%. Use the combination module to generate a nested list. Each small list in the nested list consists of three numbers whose sum is 100, and the nested list contains a total of 14,364 small lists.

[0034] Step 2: Use the dictionary module in Python to combine the ternary refractory high entropy alloy system used for phase diagram calculation with each small list in the nested list to obtain the ternary refractory high entropy alloy composition used for phase diagram calculation;

[0035] Step 3: Use the Python pandas module to input the density, atomic number, and VEC of the ternary refractory high-entropy alloy elements used for phase diagram calculation to obtain the density and VEC of all ternary refractory high-entropy alloys. The density and VEC of the ternary refractory high-entropy alloys are calculated using the following formulas.

[0036] ρ=∑ciAi / (ciAi / ρi)

[0037] VEC=∑ciVECi

[0038] Where ci is the atomic percentage of element i, Ai is the atomic number of the element, ρi is the density of element i, and VECi is the valence electron concentration of element i;

[0039] Step 4: Use the pyautogui module in Python to drive thermo-calc to calculate the phase diagram of all ternary refractory high entropy alloy compositions;

[0040] Step 5: Analyze the phase diagram calculation results obtained in step 4 using the pandas module in Python to extract alloy data; the alloy data includes: melting point, solidification range, second phase, and second phase solution temperature;

[0041] Step 6: Using the pandas module in Python, integrate the density and VEC of all ternary refractory high-entropy alloys obtained in step 3, and the alloy data of all ternary refractory high-entropy alloys obtained in step 5 into an Excel file to conduct system design and composition screening of ternary refractory high-entropy alloys;

[0042] The ternary refractory high entropy alloy obtained by screening is composed of NbTiTa, with Nb, Ti and Ta as the matrix components, and the alloy Nb 40 Ti 30 Ta 10 Cr8Si2V2Mo3Zr2W1C1B1, the cast alloy structure is BCC phase, Laves phase, silicide and carbide, such as Figure 1 shown.

[0043] The Nb 40 Ti 30 Ta 10 The preparation method of Cr8Si2V2Mo3Zr2W1C1B1 refractory high entropy alloy material comprises the following specific steps:

[0044] Step 1: Select eleven elements, including Nb, Ti, Ta, Cr, Si, V, Mo, W, Zr, C, and B, accurately weigh them according to atomic percentage, and place them into the copper crucible of a non-consumable vacuum arc melting furnace in the order of melting points from low to high, i.e. Si, Ti, Cr, V, Zr, B, Nb, Mo, Ta, W, and C.

[0045] Step 2: Close the furnace door, wait until the non-consumable vacuum arc melting furnace is evacuated to a high vacuum state, and then introduce high-purity argon gas with a purity of 99.99wt% as a protective gas.

[0046] Step 3: Nb 40 Ti 30 Ta 10 The Cr8Si2V2Mo3Zr2W1C1B1 alloy was melted, and the current was increased until the alloy was completely melted. The liquid state time of the alloy was 3 minutes for a single melting. After the alloy was completely cooled, the ingot was turned over by a robotic arm and the same melting steps were used to continue melting for 8 times. The magnetic stirring was not turned on at the beginning and the last time, and the magnetic stirring was turned on for the rest to ensure uniform melting.

[0047] Step 4: Wait for Nb 40 Ti 30 Ta 10After the Cr8Si2V2Mo3Zr2W1C1B1 alloy is smelted, wait for 20 minutes for it to cool completely, open the furnace door, take out the sample, and obtain Nb 40 Ti 30 Ta 10 Cr8Si2V2Mo3Zr2W1C1B1 alloy.

[0048] The alloy density was measured by Archimedes drainage method and was 7.9092 g / cm 3 The as-cast Nb 40 Ti 30 Ta 10 The structural analysis of Cr8Si2V2Mo3Zr2W1C1B1 alloy is as follows: Figure 1 As shown in the experiment, the alloy shows a typical dendritic structure in the cast state, with Laves phase, silicide and carbide existing between the dendrites. The mechanical properties of the alloy were tested at room temperature. Figure 2 As shown in the experiment, the room temperature compressive yield strength of the alloy is about 1030MPa and the fracture strain is about 20%. The compression mechanical properties of the alloy were tested at 800℃. Figure 3 As shown. Experiments show that the yield strength of the alloy is about 700MPa at 800℃. The alloy is oxidized for 50h in a heat treatment at 650℃. The oxidation weight gain curve of the alloy is as follows: Figure 4 As shown. Experiments show that the average oxidation rate is 0.38g / m 2 ·h, indicating that the alloy has good oxidation resistance.

[0049] Example 2

[0050] A low-density refractory high-entropy high-temperature alloy material, the atomic percentage expression of the alloy composition is Nb 30 Ti 40 Ta5Cr 12 Si3V1Mo2Zr2W2C2B1, the cast alloy structure is BCC phase, Laves phase, silicide and carbide.

[0051] The Nb 30 Ti 40 Ta5Cr 12 The preparation method of Si3V1Mo2Zr2W2C2B1 refractory high entropy alloy material comprises the following steps:

[0052] Step 1: Select eleven elements, including Nb, Ti, Ta, Cr, Si, V, Mo, W, Zr, C, and B, accurately weigh them according to atomic percentage, and place them into the copper crucible of a non-consumable vacuum arc melting furnace in the order of melting points from low to high, i.e. Si, Ti, Cr, V, Zr, B, Nb, Mo, Ta, W, and C.

[0053] Step 2: Close the furnace door, wait until the non-consumable vacuum arc melting furnace is evacuated to a high vacuum state, and then introduce high-purity argon gas with a purity of 99.99wt% as a protective gas.

[0054] Step 3: Nb 30 Ti 40 Ta5Cr 12 The Si3V1Mo2Zr2W2C2B1 alloy is melted, and the current is increased until the alloy can be completely melted. The liquid time of the alloy is 3 minutes for a single melting. After the alloy is completely cooled, the ingot is turned over by a robotic arm and the same melting steps are used to continue melting for 8 times. The magnetic stirring is not turned on at the beginning and the last time, and the magnetic stirring is turned on for the rest to ensure uniform melting.

[0055] Step 4: Wait for Nb 30 Ti 40 Ta5Cr 12 After the Si3V1Mo2Zr2W2C2B1 alloy is smelted, wait for 20 minutes for it to cool completely, open the furnace door, take out the sample, and obtain Nb 30 Ti 40 Ta5Cr 12 Si3V1Mo2Zr2W2C2B1 alloy.

[0056] The alloy density was measured by Archimedes drainage method and was 7.0398 g / cm 3 The alloy was tested for compressive mechanical properties at room temperature and 800°C. The results showed that the alloy had a compressive yield strength of about 1100 MPa at room temperature and a fracture strain of about 14%. Its yield strength at 800°C was about 730 MPa, and its average oxidation rate at 650°C for 50 hours was 0.44 g / m 2 ·h.

[0057] Example 3

[0058] A low-density dual-phase silicide reinforced refractory high-entropy alloy material, the atomic percentage expression of the alloy composition is Nb 29 Ti 35 Ta 11 Cr 14 Si1V2Mo2Zr2W1C1B2, the cast alloy structure is BCC phase, Laves phase, silicide and carbide.

[0059] The Nb 29 Ti 35 Ta 11 Cr 14 The preparation method of Si1V2Mo2Zr2W1C1B2 refractory high entropy alloy material comprises the following steps:

[0060] Step 1: Select eleven elements, including Nb, Ti, Ta, Cr, Si, V, Mo, W, Zr, C, and B, accurately weigh them according to atomic percentage, and place them into the copper crucible of a non-consumable vacuum arc melting furnace in the order of melting points from low to high, i.e. Si, Ti, Cr, V, Zr, B, Nb, Mo, Ta, W, and C.

[0061] Step 2: Close the furnace door, wait until the non-consumable vacuum arc melting furnace is evacuated to a high vacuum state, and then introduce high-purity argon gas with a purity of 99.99wt% as a protective gas.

[0062] Step 3: Nb 29 Ti 35 Ta 11 Cr 14 The Si1V2Mo2Zr2W1C1B2 alloy is melted, and the current is increased until the alloy can be completely melted. The liquid time of the alloy is 3 minutes for a single melting. After the alloy is completely cooled, the ingot is turned over by a robotic arm and the same melting steps are used to continue melting for 8 times. The magnetic stirring is not turned on at the beginning and the last time, and the magnetic stirring is turned on for the rest to ensure uniform melting.

[0063] Step 4: Wait for Nb 29 Ti 35 Ta 11 Cr 14 After the Si1V2Mo2Zr2W1C1B2 alloy is smelted, wait for 20 minutes for it to cool completely, open the furnace door, take out the sample, and obtain Nb 29 Ti 35 Ta 11 Cr 14 Si1V2Mo2Zr2W1C1B2 alloy.

[0064] The alloy density was measured by Archimedes drainage method and was 7.7405 g / cm 3 The alloy was tested for compressive mechanical properties at room temperature and 800°C. The results showed that the alloy had a compressive yield strength of about 1050 MPa at room temperature and a fracture strain of about 15%. Its yield strength at 800°C was about 710 MPa, and its average oxidation rate at 650°C for 50 hours was 0.42 g / m 2 ·h.

[0065] The above is a description of the preferred embodiments of the present invention. It should be noted that the present invention is not limited to the above embodiments. Any modifications, equivalent replacements, or improvements to the present invention that meet the scope requirements of the claims, the invention content, and the drawings should be included in the scope of protection of the present invention.

Claims

1. A composition design method for a low-density NbTiTaCrSiC-based refractory high-entropy superalloy, characterized by: The matrix composition design is performed through high-throughput phase diagram calculation. The specific steps are as follows: Step 1: Use the combination module in Python to generate a ternary refractory high-entropy alloy system for phase diagram calculation. The composition of the ternary refractory high-entropy alloy is expressed in atomic percentages. The number of elements in the ternary refractory high-entropy alloy used for phase diagram calculation is 9, and the step size of each element is set to 5%. Use the combination module to generate a nested list. Each small list in the nested list consists of three numbers whose sum is 100, and the nested list contains a total of 14,364 small lists. Step 2: Use the dictionary module in Python to combine the ternary refractory high entropy alloy system used for phase diagram calculation with each small list in the nested list to obtain the ternary refractory high entropy alloy composition used for phase diagram calculation; Step 3: Use the Python pandas module to input the density, atomic number, and VEC of the ternary refractory high-entropy alloy elements used for phase diagram calculation to obtain the density and VEC of all ternary refractory high-entropy alloys. The density and VEC of the ternary refractory high-entropy alloys are calculated using the following formulas. ρ=∑c i A i / (c i A i / r i ) VEC=∑c i THING i where c i is the atomic percentage of element i, A i is the atomic number of the element, ρ i is the density of element i, VEC i is the valence electron concentration of element i; Step 4: Use the pyautogui module in Python to drive thermo-calc to calculate the phase diagram of all ternary refractory high entropy alloy compositions; Step 5: Analyze the phase diagram calculation results obtained in step 4 using the pandas module in Python to extract alloy data; the alloy data includes: melting point, solidification range, second phase, and second phase solution temperature; Step 6: Using the pandas module in Python, integrate the density and VEC of all ternary refractory high-entropy alloys obtained in step 3, and the alloy data of all ternary refractory high-entropy alloys obtained in step 5 into an Excel file to conduct system design and composition screening of ternary refractory high-entropy alloys; The composition of the ternary refractory high entropy alloy obtained by screening is Nb a Ti b Ta c , where the atomic percentage of a is 25% to 75%, the atomic percentage of b is 25% to 60%, and the atomic percentage of c is 5% to 20%. It is necessary to ensure that a+b+c=100%; A low-density NbTiTaCrSiC-based refractory high-entropy superalloy is constructed with Nb, Ti and Ta as the matrix components.

2. A high entropy alloy obtained by the design method according to claim 1, characterized in that: The atomic percentage ranges of the elements in the high entropy alloy are as follows: 20%≤Nb≤60%, 20%≤Ti≤50%, 4%≤Ta≤12%, 5%≤Cr≤15%, 0.5%≤Si≤3%, 0 <V≤5%,0<Mo≤3%,0<W≤2%,0<Zr≤4%,0.5%≤C≤3%,0.5%≤B≤2%。 3. The high entropy alloy according to claim 2, wherein: The atomic percentage expression of the high entropy alloy composition is Nb 40 Ti 30 Ta 10 Cr8Si2V2Mo3Zr2W1C1B1.

4. The high entropy alloy according to claim 2, wherein: The atomic percentage expression of the high entropy alloy composition is Nb 30 Ti 40 Ta5Cr 12 Si3V1Mo2Zr2W2C2B1.

5. The high entropy alloy according to claim 2, wherein: The atomic percentage expression of the high entropy alloy composition is Nb 29 Ti 35 Ta 11 Cr 14 Si1V2Mo2Zr2W1C1B2.

6. A method for preparing an alloy according to any one of claims 3, 4 or 5, characterized in that: The following steps are involved: Step 1: Select Nb, Ti, Ta, Cr, Si, V, Mo, W, Zr, C and B elements, accurately weigh them according to atomic percentage, and place them into the copper crucible of a non-consumable vacuum arc melting furnace in order from low to high melting points; Step 2: Close the furnace door, and after the non-consumable vacuum arc melting furnace reaches a high vacuum state, introduce high-purity argon gas with a purity of 99.99wt% as a shielding gas; Step 3: Smelt the NbTiTaCrSiC alloy, increase the current until the alloy is completely melted, and the single melting time of the alloy is 3 minutes. After the alloy is completely cooled, the ingot is turned over by a robotic arm and the same melting steps are used to continue smelting for 8 times. The magnetic stirring is not turned on at the beginning and the last time, and the magnetic stirring is turned on for the rest to ensure uniform melting; Step 4: After the NbTiTaCrSiC alloy is smelted, wait for 20 minutes, and after it is completely cooled, open the furnace door and take out the sample to obtain the NbTiTaCrSiC alloy.

Images