Method for improving properties of NbTiTaCrSiC refractory high-entropy alloy by regulating precipitates through hot rolling and aging processes

Abstract

The present invention relates to a method for regulating precipitates through hot rolling and aging processes to improve the properties of NbTiTaCrSiC refractory high-entropy alloys, belonging to the field of high-entropy alloys. In order to solve the problem that the NbTiTaCrSiC refractory high-entropy alloy strengthened by Laves phase, silicide and carbide does not have room-temperature tensile properties, the present invention first conducts matrix composition design through high-throughput phase diagram calculation, and then adopts a method of combining hot rolling and aging processes to regulate precipitates to improve the properties of NbTiTaCrSiC refractory high-entropy alloys. This method can greatly improve the comprehensive properties of the alloy. The NbTiTaCrSiC alloy after hot rolling and aging processes has a room-temperature tensile yield strength exceeding 1100 MPa and a tensile fracture elongation greater than 10%. The tensile yield strength at 800 °C exceeds 800 MPa and the tensile fracture elongation is greater than 20%. The properties are far higher than those of the as-cast alloy without hot rolling and aging processes.

Description

Technical Field

[0001] The present invention relates to a method for regulating precipitates through hot rolling and aging processes to improve the properties of NbTiTaCrSiC refractory high-entropy alloys, and particularly to a method for regulating precipitates through the combination of hot rolling and aging processes to improve the properties of NbTiTaCrSiC refractory high-entropy alloys, belonging to the field of high-entropy alloys. Background Art

[0002] High-entropy alloys are composed of at least five elements in equiatomic or near-equiatomic ratios, and the concentration of each element is between 5% and 35%. Compared with traditional alloys, high-entropy alloys exhibit greater advantages in terms of mechanical strength, oxidation resistance, corrosion resistance, and wear resistance. In 2010, Senkov reported a new branch of refractory high-entropy alloys composed of 9 refractory elements. Due to the high melting points of refractory high-entropy alloys, they have greater strength at high temperatures compared to nickel-based alloys. Among them, WNbMoTa and WNbMoTaV exhibit strengths above 400 MPa at 1600 °C. Given the performance advantages of refractory high-entropy alloys at high temperatures and their nearly infinite compositional space, they are expected to become a new generation of high-temperature alloys.

[0003] However, after more than a decade of development, refractory high-entropy alloys also exhibit many problems, such as poor oxidation resistance, high density, and low room-temperature tensile fracture elongation. By adding elements such as Al, Cr, and Si to refractory high-entropy alloys, the density of the alloy can be reduced, while the oxidation resistance and strength of the alloy can be improved. However, the addition of elements such as Al, Cr, and Si will also introduce second phases in the alloy. For example, the addition of Al will introduce the B2 phase in the alloy, and the B2 phase will transform into a hexagonal phase during long-term heat preservation; the addition of Si will form network silicides at grain boundaries. The presence of these precipitates will cause a sharp decrease in the tensile fracture elongation of the alloy. Therefore, the regulation of precipitates in the alloy is particularly important. The present invention combines hot rolling and aging processes to regulate the Laves phase, silicides, and carbides in the alloy to achieve the improvement of alloy properties. Summary of the Invention

[0004] The purpose of the present invention is to solve the problem that the NbTiTaCrSiC refractory high-entropy alloy strengthened by the Laves phase, silicides, and carbides does not have room-temperature tensile properties, and to provide a method for regulating precipitates through the combination of hot rolling and aging processes to improve the properties of NbTiTaCrSiC refractory high-entropy alloys, which can greatly improve the comprehensive properties of the alloy.

[0005] To achieve the above purpose, the present invention is realized through the following technical solutions.

[0006] Method for improving properties of NbTiTaCrSiC-based refractory high-entropy alloy by regulating precipitates through hot rolling and aging processes, the specific steps are as follows:

[0007] 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 percentage. The number of elements in the ternary refractory high-entropy alloy 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, and each small list in the nested list consists of 3 numbers with a sum of 100. The nested list includes a total of 14364 small lists;

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

[0009] Step 3: Use the pandas module in Python to input the density, atomic number, and VEC of the elements in the ternary refractory high-entropy alloy 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 alloy are calculated by the following formulas.

[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, and VEC i is the valence electron concentration of element i;

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

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

[0015] Step 6: Integrate all the density and VEC of 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 through the pandas module in Python for the system design and composition screening of ternary refractory high-entropy alloys;

[0016] Step 7: 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% - 75%, the atomic percentage of b is 25% - 60%, and the atomic percentage of c is 5% - 20%, and it is necessary to ensure that a + b + c = 100%;

[0017] Taking Nb, Ti, and Ta as the matrix components, alloy composition design is carried out through solid solution strengthening, precipitation strengthening, and grain boundary strengthening. The atomic percentage ranges of each element in the NbTiTaCrSiC series of low-density refractory high-entropy superalloys 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%. The as-cast NbTiTaCrSiC series of alloys is composed of BCC phase, Laves phase, silicide, and carbide.

[0018] Step 8: Cut the as-cast NbTiTaCrSiC series of alloys into strips with a length of l mm, a width of w mm, and a thickness of t mm, wrap them with Ta foil and seal them in a quartz tube filled with argon, and perform heat treatment at 1200 °C for 24 h in a heat treatment furnace to achieve tissue homogenization. Among them, 10 < l < 100, 20 < w < 50, 5 < t < 40.

[0019] Step 9: Sheath the heat-treated alloy strips with an alloy with a thickness of n mm, and then weld them, where 1 < n < 10.

[0020] Step 10: Place the alloy with the sheath in a heat treatment furnace at 1050 - 1150 °C and keep it warm for 10 - 15 min, and then perform rolling. The deformation per pass is about 10%. After each rolling pass, put the alloy back into the heat treatment furnace and keep it warm for 1 min. The sample needs to be rolled in multiple passes, and the final deformation is controlled between 60% - 90%.

[0021] Step 11: After rolling is completed, remove the alloy sheath and surface oxide scale, wrap the alloy with Ta foil and seal it in a quartz tube filled with argon, and keep it warm in a heat treatment furnace at 1000 - 1150 °C for 80 - 240 min to achieve uniform nano-dispersion distribution of Laves phase, silicide, and carbide, and the comprehensive performance of the alloy is greatly improved.

[0022] Beneficial effects

[0023] The method combining hot rolling and aging processes of the present invention can achieve uniform distribution of precipitates in the matrix. After hot rolling of the alloy, the coarse Laves phase, silicides and carbides in the structure are broken and uniformly distributed on the matrix. During the subsequent aging process of the rolled alloy, recrystallization occurs to refine the grains. At the same time, affected by the solid solubility, uniformly distributed nano-Laves phase, silicides and carbides will precipitate in the alloy.

[0024] For the NbTiTaCrSiC-based alloy processed by hot rolling and aging processes, the tensile yield strength at room temperature exceeds 1100 MPa, and the tensile fracture elongation rate is greater than 10%. The tensile yield strength at 800 °C exceeds 800 MPa, and the tensile fracture elongation rate is greater than 20%. The performance is much higher than that of the as-cast alloy without hot rolling and aging processes. Description of the drawings

[0025] Figure 1 is the SEM image of Nb 40 Ti 30 Ta 10 Cr8Si2V2Mo3Zr2W1C1B1 alloy after hot rolling and aging. Among them, Figure a is a BSE image at 200 times magnification; Figure b is a BSE image at 500 times magnification; Figure c is a BSE image at 1000 times magnification.

[0026] Figure 2 is the room-temperature tensile property of Nb 40 Ti 30 Ta 10 Cr8Si2V2Mo3Zr2W1C1B1 alloy after hot rolling and aging.

[0027] Figure 3 is the 800 °C tensile property of Nb 40 Ti 30 Ta 10 Cr8Si2V2Mo3Zr2W1C1B1 alloy after hot rolling and aging. Detailed implementation manners

[0028] The present invention will be further described below in conjunction with the drawings and embodiments.

[0029] Example 1

[0030] A method for regulating precipitates by hot rolling and aging processes to improve the performance of NbTiTaCrSiC-based refractory high-entropy alloys, characterized by comprising the following steps:

[0031] Step 1: Generate a ternary refractory high-entropy alloy system for phase diagram calculation through the combination module in Python; the composition of the ternary refractory high-entropy alloy is expressed in atomic percentage. The number of elements in the ternary refractory high-entropy alloy for phase diagram calculation is 9, and the step size of each element is set to 5%. Generate a nested list through the combination module. Each small list in the nested list consists of 3 numbers with a sum of 100. The nested list contains a total of 14364 small lists;

[0032] Step 2: Combine the ternary refractory high-entropy alloy system for phase diagram calculation with each small list in the nested list through the dictionary module in Python to obtain the composition of the ternary refractory high-entropy alloy for phase diagram calculation;

[0033] Step 3: Input the density, atomic number, and VEC of the elements of the ternary refractory high-entropy alloy for phase diagram calculation through the pandas module in Python to obtain the density and VEC of all ternary refractory high-entropy alloys; the density and VEC of the ternary refractory high-entropy alloy are calculated through the following formulas;

[0034] ρ = ∑ciAi / (ciAi / ρi)

[0035] VEC = ∑ciVECi

[0036] 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;

[0037] Step 4: Drive thermo-calc to perform phase diagram calculation on all compositions of the ternary refractory high-entropy alloy through the pyautogui module in Python, and save the phase diagram calculation results in the form of excel;

[0038] Step 5: Analyze the phase diagram calculation results obtained in Step 4 through the pandas module in Python to extract alloy data; the alloy data includes: melting point, solidification range, and second-phase solution temperature;

[0039] Step 6: 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 through the pandas module in Python, and perform composition screening of the ternary refractory high-entropy alloy through the filtering function in excel;

[0040] Step 7: The composition of the ternary refractory high-entropy alloy obtained by screening is NbaTibTac, where the atomic percentage of a is 25% - 75%, the atomic percentage of b is 25% - 60%, and the atomic percentage of c is 5% - 20%. It is necessary to ensure that a + b + c = 100%;

[0041] Using Nb, Ti, and Ta as the matrix components, a low-density NbTiTaCrSiC-based refractory high-entropy superalloy is constructed, namely Nb 40 Ti 30 Ta 10 Cr8Si2V2Mo3Zr2W1C1B1; The as-cast alloy microstructure is BCC phase, Laves phase, silicide, and carbide.

[0042] Step 8: Cut the as-cast Nb 40 Ti 30 Ta 10 Cr8Si2V2Mo3Zr2W1C1B1 alloy into strips with a length of 20 mm, a width of 25 mm, and a thickness of 10 mm, wrap them with Ta foil and seal them in a quartz tube filled with argon, and perform heat treatment at 1200 °C for 24 h in a heat treatment furnace to achieve microstructure homogenization.

[0043] Step 9: Sheath the heat-treated alloy strips with an alloy with a thickness of 2 mm, and then weld them.

[0044] Step 10: Place the alloy with the sheath in a heat treatment furnace at 1075 °C and hold it for 10 min, and then perform rolling. The deformation per pass is about 10%. After each rolling pass, put the alloy back into the heat treatment furnace and hold it for 1 min. The sample needs to be rolled in multiple passes, and the final deformation is 60%.

[0045] Step 11: After rolling is completed, remove the alloy sheath and surface oxide scale, wrap the alloy with Ta foil and seal it in a quartz tube filled with argon, and hold it in a heat treatment furnace at 1000 °C for 80 min to achieve uniform nano-dispersion distribution of Laves phase, silicide, and carbide, and the comprehensive properties of the alloy are greatly improved.

[0046] Perform SEM characterization on Nb 40 Ti 30 Ta 10 Cr8Si2V2Mo3Zr2W1C1B1 after hot rolling and aging processes, as Figure 1 shown. The results show that the alloy has a uniform fine-grained microstructure, and Laves phase, silicide, and carbide are uniformly distributed in the matrix. Perform room temperature tensile property testing on Nb 40 Ti 30 Ta 10 Cr8Si2V2Mo3Zr2W1C1B1 after hot rolling and aging processes, asFigure 2 As shown. The yield strength of the alloy is about 1120 MPa, and the tensile fracture elongation is about 11%. For Nb40Ti after hot rolling and aging processes 30 Ta 10 Cr8Si2V2Mo3Zr2W1C1B1, the tensile property test at 800 °C is carried out as Figure 3 shown. The yield strength of the alloy is about 820 MPa, and the tensile fracture elongation is about 60%.

[0047] Example 2

[0048] A refractory high-entropy alloy of NbTiTaCrSiC system reinforced by Laves phase, silicide and carbide. The atomic percentage expression of the alloy composition is Nb 30 Ti 40 Ta5Cr 12 Si3V1Mo2Zr2W2C2B1. The as-cast alloy microstructure is BCC phase, Laves phase, silicide and carbide.

[0049] The Nb 30 Ti 40 Ta5Cr 12 Si3V1Mo2Zr2W2C2B1 alloy is processed by a method combining hot rolling and aging processes, including the following steps:

[0050] Step 1: Cut the as-cast Nb 30 Ti 40 Ta5Cr 12 Si3V1Mo2Zr2W2C2B1 alloy into strips with a length of 35 mm, a width of 30 mm, and a thickness of 30 mm, wrap them with Ta foil and seal them in a quartz tube filled with argon, and conduct heat treatment at 1200 °C for 24 h in a heat treatment furnace to achieve microstructure homogenization.

[0051] Step 2: Sheath the heat-treated alloy strips with an alloy with a thickness of 4 mm, and then weld them.

[0052] Step 3: Place the alloy with the sheath in a heat treatment furnace at 1100 °C for heat preservation for 15 min, and then roll it. The deformation per pass is about 10%. After each rolling pass, put the alloy back into the heat treatment furnace for heat preservation for 1 min. The sample needs to be rolled in multiple passes, and the final deformation is 60%.

[0053] Step 4: After rolling is completed, remove the alloy sheath and surface oxide scale, wrap the alloy with Ta foil and seal it in a quartz tube filled with argon, and keep it in a heat treatment furnace at 1100 °C for 90 min to achieve uniform nano-dispersion distribution of Laves phase, silicide and carbide, and the comprehensive performance of the alloy is greatly improved.

[0054] Nb after hot rolling and aging processes 30 Ti 40 Ta5Cr 12 Si3V1Mo2Zr2W2C2B1 was characterized by SEM. The results show that the alloy has a uniform fine-grained structure, and Laves phase, silicides and carbides are uniformly distributed in the matrix. Nb after hot rolling and aging processes 30 Ti 40 Ta5Cr 12 Si3V1Mo2Zr2W2C2B1 was tested for tensile properties at room temperature. The yield strength of the alloy is about 1100 MPa, and the tensile fracture elongation is about 13%. Nb after hot rolling and aging processes 30 Ti 40 Ta5Cr 12 Si3V1Mo2Zr2W2C2B1 was tested for tensile properties at 800 °C. The yield strength of the alloy is about 850 MPa, and the tensile fracture elongation is about 40%.

[0055] Example 3

[0056] A refractory high-entropy alloy of NbTiTaCrSiC system reinforced by Laves phase, silicides and carbides. The atomic percentage expression of the alloy composition is Nb 29 Ti 35 Ta 11 Cr 14 Si1V2Mo2Zr2W1C1B2. The as-cast alloy microstructure is BCC phase, Laves phase, silicides and carbides.

[0057] The Nb 29 Ti 35 Ta 11 Cr 14 Si1V2Mo2Zr2W1C1B2 alloy was processed by a method combining hot rolling and aging processes, including the following steps:

[0058] Step 1: Cut the as-cast Nb 29 Ti 35 Ta 11 Cr 14 Si1V2Mo2Zr2W1C1B2 alloy into strips with a length of 50 mm, a width of 30 mm and a thickness of 20 mm, wrap them with Ta foil and seal them in a quartz tube filled with argon, and conduct heat treatment at 1200 °C / 24 h in a heat treatment furnace to achieve microstructure homogenization.

[0059] Step 2: Sheath the heat-treated alloy strips with an alloy with a thickness of 3 mm, and then weld them.

[0060] Step 3: Place the alloy with the jacket in a heat treatment furnace at 1100 °C and hold for 15 min, then perform rolling. The deformation per pass is about 10%. After each rolling pass, put the alloy back into the heat treatment furnace and hold for 1 min. The sample needs to be rolled in multiple passes, and the final deformation is 60%.

[0061] Step 4: After rolling is completed, remove the alloy jacket and surface scale. Wrap the alloy with Ta foil and seal it in a quartz tube filled with argon. Hold it in a heat treatment furnace at 1000 °C for 200 min to achieve a uniform nano-dispersion distribution of Laves phase, silicide and carbide, and the comprehensive properties of the alloy are greatly improved.

[0062] For Nb 29 Ti 35 Ta 11 Cr 14 Si1V2Mo2Zr2W1C1B2 after hot rolling and aging processes, SEM characterization shows that the alloy has a uniform fine-grained structure, and Laves phase, silicide and carbide are uniformly distributed in the matrix. For Nb 29 Ti 35 Ta 11 Cr 14 Si1V2Mo2Zr2W1C1B2, perform room temperature tensile property tests. The yield strength of the alloy is about 1150 MPa, and the tensile fracture elongation is about 16%. For Nb 29 Ti 35 Ta 11 Cr 14 Si1V2Mo2Zr2W1C1B2, perform 800 °C tensile property tests. The yield strength of the alloy is about 860 MPa, and the tensile fracture elongation is about 35%.

[0063] The above is the description of the preferred embodiments of the present invention. Here, it should be noted that the present invention is not limited to the above embodiments. Any modifications, equivalent substitutions or improvements made to the present invention within the scope requirements of the claims, the description of the invention and the drawings should be included in the protection scope of the present invention.

Claims

1. A method for improving the properties of NbTiTaCrSiC refractory high-entropy alloys by regulating precipitates through hot rolling and aging processes, characterized in that: It includes the following steps: Step 1: Generate a ternary refractory high-entropy alloy system for phase diagram calculation through the combination module in Python; the composition of the ternary refractory high-entropy alloy is expressed in atomic percentage. The number of elements in the ternary refractory high-entropy alloy for phase diagram calculation is 9, and the step size of each element is set to 5%. A nested list is generated through the combination module, and each small list in the nested list consists of 3 numbers with a sum of 100. The nested list includes a total of 14,364 small lists; Step 2: Combine the ternary refractory high-entropy alloy system for phase diagram calculation with each small list in the nested list through the dictionary module in Python to obtain the composition of the ternary refractory high-entropy alloy for phase diagram calculation; Step 3: Input the density, atomic number, and VEC of the elements of the ternary refractory high-entropy alloy for phase diagram calculation through the pandas module in Python to obtain the density and VEC of all ternary refractory high-entropy alloys; the density and VEC of the ternary refractory high-entropy alloy are calculated through the following formulas; ρ = ∑c i A i / (c i A i / ρ i ) VEC = ∑c i VEC 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: Drive thermo-calc to perform phase diagram calculation on all compositions of the ternary refractory high-entropy alloy through the pyautogui module in Python, and save the phase diagram calculation results in the form of excel; Step 5: Analyze the phase diagram calculation results obtained in Step 4 through the pandas module in Python to extract alloy data; the alloy data includes: melting point, solidification interval, second-phase solution temperature; Step 6: Integrate all the densities and VECs of the ternary refractory high-entropy alloys obtained in Step 3 and all the alloy data of the ternary refractory high-entropy alloys obtained in Step 5 into an excel file through the pandas module in Python, and perform component screening of the ternary refractory high-entropy alloy through the filtering function in excel; Step 7: The ternary refractory high-entropy alloy obtained by screening has a composition of 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%; With Nb, Ti, and Ta as the matrix components, alloy composition design is carried out through solid solution strengthening, precipitation strengthening, and grain boundary strengthening. The atomic percentage ranges of each element in the NbTiTaCrSiC-based low-density refractory high-entropy superalloy 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%; the as-cast NbTiTaCrSiC-based alloy is composed of BCC phase, Laves phase, silicide, and carbide; Step 8: Cut the as-cast NbTiTaCrSiC-based alloy into strips with a length of l mm, a width of w mm, and a thickness of t mm, wrap it with Ta foil and seal it in a quartz tube filled with argon, and perform heat treatment at 1200 °C / 24 h in a heat treatment furnace to achieve tissue homogenization; where 10 < l < 100, 20 < w < 50, 5 < t < 40; Step 9: The heat-treated alloy bar is sheathed with an alloy having a thickness of n mm and then welded, where 1 < n < 10; Step 10: The alloy with the sheath is placed in a heat treatment furnace at 1050 - 1150 °C and kept warm for 10 - 15 min, and then rolled; the deformation per pass is 10%, and after each rolling pass, the alloy is put back into the heat treatment furnace and kept warm for 1 min; the sample needs to be rolled in multiple passes, and the final deformation is controlled between 60% and 90%; Step 11: After rolling is completed, the alloy sheath and surface oxide scale are removed, the alloy is wrapped with Ta foil and sealed in a quartz tube filled with argon, and kept warm in a heat treatment furnace at 1000 - 1150 °C for 80 - 240 min to achieve a uniform nano-dispersion distribution of Laves phase, silicide and carbide, and the comprehensive properties of the alloy are greatly improved.

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