Multi-index screening high-entropy alloy design method for high-temperature bearing performance requirements

Abstract

The invention discloses a multi-index screening high-entropy alloy design method for high-temperature bearing performance requirements, and relates to a multi-index screening high-entropy alloy design method. The invention aims to solve the problem of huge test cost caused by huge component design space of the high-entropy alloy. According to the method, the mechanical properties of the high-entropy alloy are calculated by adopting a first principle high-throughput method based on the virtual crystal approximation model, and the mechanical properties of various high-entropy alloys can be calculated at one time, so that the high-entropy alloy with ideal mechanical properties is quickly screened, the heavy workload of synthesis and mechanical property test experiments is reduced, and the experiment cost is remarkably reduced. The invention belongs to the technical field of bearings.

Description

TECHNICAL FIELD

[0001] The application relates to a multi-index screening high-entropy alloy design method and belongs to the technical field of bearings. BACKGROUND

[0002] In the field of high-end equipment such as aerospace engines, heavy-duty gas turbines and nuclear energy, key moving parts are subjected to the severe test of a continuous high-temperature environment. Taking the main shaft bearing of an aero-engine as an example, its working temperature has broken through 500 DEG C and continues to develop to above 800 DEG C. Under extreme working conditions, the traditional bearing materials have the technical bottlenecks of material softening and strength attenuation, phase transformation instability and size drift, lubrication system collapse and rapid attenuation of fatigue life. High-entropy alloys have great potential to break through the service limit of 900 DEG C due to their unique high-entropy effect, lattice distortion effect, delayed diffusion effect and cocktail effect. However, the huge component design space of high-entropy alloys will cause huge experimental costs, and high-throughput computational design technology is urgently needed to achieve a breakthrough. SUMMARY

[0003] The application is to solve the problem that the huge component design space of high-entropy alloys will cause huge experimental costs, and further proposes a multi-index screening high-entropy alloy design method for the performance requirements of high-temperature bearings.

[0004] The technical scheme adopted by the application to solve the above problem is that the steps of the application include: Step 1, determining the types of metal elements contained in the high-entropy alloy material system and the molar ratio of each element; Step 2, judging the crystal system of the high-entropy alloy according to the valence electron concentration of the high-entropy alloy, and constructing a metal single-element crystal structure model according to the crystal system of the high-entropy alloy; Step 3, modifying the Composition of the metal atoms in the metal single-element crystal structure model constructed in step 2 by using the 3D Atomistic window of the Materials Studio software according to the types and molar ratio quantities of the metal elements determined in step 1, to obtain a high-entropy alloy virtual crystal approximation model; Step 4, importing the high-entropy alloy virtual crystal approximation model constructed in step 3 into the same folder, and performing structure optimization on the high-entropy alloy virtual crystal approximation model to obtain a high-entropy alloy virtual crystal approximation model with the lowest energy; Step 5, applying a small deformation to the high-entropy alloy virtual crystal approximation model optimized in step 4 according to the symmetry of the crystal structure of the research object, and performing structure optimization on the deformed model to make it reach a stable state again, to obtain a stress-strain relationship; Step 6, fitting the stress-strain relationship obtained in step 5 by using the generalized Hooke's law to obtain the elastic stiffness constant and the elastic compliance constant ; Step 7, determining the mechanical stability of the high-entropy alloy according to the elastic stiffness coefficient obtained in step 6; Step 8, calculating the melting point of the high-entropy alloy according to the elastic stiffness coefficient obtained in step 6 ; Step 9, calculating the Young's modulus of the high-entropy alloy according to the elastic constant obtained in step 6 using the VRH criterion , shear modulus , bulk modulus and Poisson's ratio ; Step 10, calculating the Vickers hardness of the high-entropy alloy according to the shear modulus and bulk modulus in step 9 , calculating the fracture toughness of the high-entropy alloy according to the Young's modulus and Poisson's ratio in step 9 ; Step 11, high-throughput screening of the high-entropy alloy according to the mechanical stability, melting point , Young's modulus , Vickers hardness and fracture toughness obtained in steps 7, 8, 9 and 10 in turn.

[0005] Further, the metal elements in step 1 include at least 5 of Ti, Zr, Hf, V, Nb, Ta, Mo, W and Cr, and the molar ratio of each metal element is in the range of 5% to 35%.

[0006] Further, the valence electron concentration calculation formula in step 2 is , wherein c i is the molar ratio of the first i metal element, and VEC i is the valence electron number of the first i element; VEC<6.84 corresponds to BCC structure, VEC ≥ 8 corresponds to FCC structure, and 6.84 ≤ <8 corresponds to BCC and FCC dual-phase structure.

[0007] Further, the parameters for structure optimization in step 4 include: selecting PBE form in GGA for functional selection, selecting BFGS for optimization algorithm, selecting OTFG Norm-conserving for pseudo-potential, setting 1250eV for cutoff energy, k setting 20×20×20 for k-point, and setting 5×10 -6eV, the force convergence criterion is 0.01eV / A, the stress convergence precision is 0.02GPa, the displacement precision is 5*10 -4 eV, the self-consistent field cycle precision is 5*10 -7 eV, the self-consistent field maximum cycle number is 200.

[0008] Further, the number of micro-strains in step 5 is 6, the maximum strain amplitude is 0.3%, and the structure optimization parameters include: the functional selection is PBE form in GGA, the pseudo-potential selection is OTFG Norm-conserving, the cutoff energy is set to 1250eV, the k-point is set to 20*20*20, the energy convergence tolerance is 2*10 -6 eV, the force convergence criterion is 0.006eV / A, the displacement precision is 2*10 -4 eV, the self-consistent field cycle precision is 5*10 -7 eV, the self-consistent field maximum cycle number is 200.

[0009] The beneficial effects of the present application are: based on the determined element type, molar ratio and crystal system, according to the metal single crystal structure model, the metal single model is doped by using the Materials Studio calculation software, and a high-entropy alloy virtual crystal approximate model is obtained; then the structure of the high-entropy alloy virtual crystal approximate model is optimized, and a structure-stable high-entropy alloy virtual crystal approximate model is obtained; a micro-strain is applied to the structure-stable high-entropy alloy virtual crystal approximate model, and a geometry optimization is performed again to obtain stress, and the stress-strain relationship is fitted by using Hooke's law to obtain the elastic constant; the mechanical stability, melting point T m , Young's modulus E, Vickers hardness H V and fracture toughness K IC of the high-entropy alloy are calculated according to the elastic constant; and finally, the ideal target object is obtained by high-throughput screening of the high-entropy alloy according to the screening process.

[0010] The present application calculates the mechanical properties of high-entropy alloys by using the first-principle high-throughput method based on the virtual crystal approximate model, can calculate the mechanical properties of multiple high-entropy alloys at one time, thereby quickly screening the high-entropy alloys with ideal mechanical properties, reduces the heavy workload of synthesis and mechanical property test experiments, and significantly reduces the experimental cost. BRIEF DESCRIPTION OF DRAWINGS

[0011] Figure 1 is a high-entropy alloy screening process diagram; Figure 2 is a high-entropy alloy screening process diagram in the embodiment. DETAILED DESCRIPTION

[0012] Specific implementation one: as Figure 1 andFigure 2 As shown, a multi-index screening high-entropy alloy design method for high-temperature bearing performance requirements, the specific steps include: Step 1, determine the type of metal elements contained in the high-entropy alloy material system and the mole ratio of each element; Step 2, determine the crystal system of the high-entropy alloy according to the valence electron concentration of the high-entropy alloy, and construct a metal single crystal structure model according to the crystal system of the high-entropy alloy; Step 3, according to the type and mole ratio of the metal elements determined in step 1, modify the Composition of the metal atoms in the metal single crystal structure model constructed in step 2 by using the 3D Atomistic window of the Materials Studio software, to obtain a high-entropy alloy virtual crystal approximation model; Step 4, import the high-entropy alloy virtual crystal approximation model constructed in step 3 into the same folder, and perform geometric optimization on the high-entropy alloy virtual crystal approximation model to obtain the lowest energy high-entropy alloy virtual crystal approximation model, wherein the geometric optimization parameters include: the functional selection PBE form in GGA, the optimization algorithm selection BFGS, the pseudo-potential selection OTFG Norm-conserving, the cutoff energy is set to 1250 eV, k the point is set to 20x20x20, the energy convergence tolerance is 5x10 -6 eV, the force convergence standard is 0.01 eV / Å, the stress convergence accuracy is 0.02GPa, the displacement accuracy is 5x10 -4 Å, the maximum number of ion steps is 200, and the self-consistent field cycle accuracy is 5x10 -7 eV, the maximum number of self-consistent field cycles is 200; Step 5, according to the symmetry of the crystal structure of the research object, a small strain is applied to the high-entropy alloy virtual crystal approximation model optimized in step 4, and the deformed model is geometrically optimized to minimize the energy again to obtain the stress corresponding to different strains, wherein the number of strains is 6, the maximum strain is 0.3%, and the structure optimization parameters include: the functional selection PBE form in GGA, the pseudo-potential selection OTFG Norm-conserving, the cutoff energy is set to 1250 eV, k the point is set to 20x20x20, the energy convergence tolerance is 2x10 -6 eV, the force convergence standard is 0.006 eV / Å, the displacement accuracy is 2x10 -4 Å, the maximum number of ion steps is 200, and the self-consistent field cycle accuracy is 5x10 -7 eV, the maximum number of self-consistent field cycles is 200; Step 6, the stress-strain relationship obtained in step 5 is fitted by using the generalized Hooke's law to obtain the elastic constant of the high-entropy alloy; Step 7. Based on the elastic coefficient calculated in step 6, determine the mechanical stability of the high entropy alloy according to formula (1): (1), In formula (1), , , Both represent elastic stiffness constants; Step 8. Based on the elastic coefficient calculated in step 6, calculate the melting point T of the high entropy alloy according to formula (2) m : (2), Step 9. Based on the elastic coefficient calculation in step 6, the VRH criterion is used to calculate the Young's modulus E, shear modulus G, bulk modulus B and Poisson's ratio of the high entropy alloy according to formula (3) to formula (10) v ; (3), (4), (5), (6), (7), (8), (9), (10), In formulas (3) to (10), , , , , , are elastic stiffness constants, , , , , , , , , Both represent the elastic flexibility coefficient, , , represents the bulk modulus, , , represents the shear modulus; Step 10: Calculate the Vickers hardness H of the high entropy alloy based on the shear modulus G and bulk modulus B calculated in step 9 according to formula (11): VYoung's modulus E and Poisson's ratio calculated in step 9 v On this basis, the fracture toughness K of the high-entropy alloy is calculated according to formula (13) and formula (14) IC , formula (11)~formula (12): (11), (12), (13), (14), Wherein, a0=2GPa, beta=0.3, gamma=8.

[0013] Step 11, using Figure 1 The screening process shown in the figure is used to screen the high-entropy alloy according to the mechanical stability, melting point T m , Young's modulus E, Vickers hardness H V and fracture toughness K IC obtained in steps 7~10 in turn.

[0014] Wherein, the metal elements include at least 5 kinds of Ti, Zr, Hf, V, Nb, Ta, Mo, W, Cr, and the molar ratio of each metal element is in the range of 5%~35%, the high-entropy alloy mechanical property high-throughput calculation method of the application can calculate the mechanical properties of multiple different high-entropy alloys at one time.

[0015] Embodiment Embodiment 1 Step (1) selecting Zr, Hf, V, Nb, Ta, Mo, W 7 kinds of metal elements as high-entropy alloy components, and the element ratio is the same, that is, the equimolar ratio high-entropy alloy; Step (2) the valence electron concentration of the high-entropy alloy is greater than 8, and the BCC structure is constructed. The metal BCC structure metal single crystal model is constructed; Step (3) modifying the Composition of the metal atoms in the metal single crystal structure model constructed in step (2) by using the 3D Atomistic window of the Materials Studio software, obtaining a 21 high-entropy alloy virtual crystal approximation model; Step (4) importing the high-entropy alloy virtual crystal approximation model constructed in step (3) into the same folder, and geometrically optimizing the high-entropy alloy virtual crystal approximation model to obtain the high-entropy alloy virtual crystal approximation model with the lowest energy, wherein the geometric optimization parameters include: selecting PBE form in GGA for functional selection, selecting BFGS for optimization algorithm, selecting OTFG Norm-conserving for pseudopotential, and setting the cutoff energy to 1250 eV, kThe point is set to 20x20x20, and the energy convergence tolerance is 5x10 -6 eV, the force convergence criterion is 0.01 eV / Å, the stress convergence precision is 0.02 GPa, and the displacement precision is 5x10 -4 Å, the maximum number of ion steps is 200, and the self-consistent field cycle precision is 5x10 -7 eV, and the maximum number of self-consistent field cycles is 200. Step (5) According to the symmetry of the crystal structure of the research object, a small strain is applied to the high-entropy alloy virtual crystal approximation model optimized in step (4), and the deformed model is geometrically optimized to reach the energy minimization state again, to obtain the stress corresponding to different strains, wherein the number of strains is 6, and the maximum strain is 0.3%, and the structure optimization parameters include: the functional selection is PBE in GGA, the pseudo-potential selection is OTFG Norm-conserving, and the cutoff energy is set to 1250 eV, k The point is set to 20x20x20, and the energy convergence tolerance is 2x10 -6 eV, the force convergence criterion is 0.006 eV / Å, the displacement precision is 2x10 -4 Å, the maximum number of ion steps is 200, and the self-consistent field cycle precision is 5x10 -7 eV, and the maximum number of self-consistent field cycles is 200. Step (6) The stress-strain relationship obtained in step (5) is fitted by using the generalized Hooke's law to obtain the elastic constants of the high-entropy alloy. Step (7) According to the specific embodiment steps (7)~(10), the mechanical properties of the high-entropy alloy are calculated, and finally according to the specific embodiment step (11), the high-entropy alloy is screened, and 5 kinds of high-entropy alloys with excellent performance are obtained, as shown in Table 1.

[0016] Table 1 Screening results of Example 1

[0017] Example 2: Step (1) Select Ti, Zr, Hf, V, Nb, Ta, Mo, and W as the components of the high-entropy alloy, and the element ratio is the same, i.e. the equimolar ratio high-entropy alloy; Step (2) The valence electron concentration of the high-entropy alloy is greater than 8, and the BCC structure is constructed. Step (3) The Composition of the metal atoms in the metal single crystal structure model constructed in step (2) is modified by using the 3D Atomistic window of the Materials Studio software, to obtain a 56 high-entropy alloy virtual crystal approximation model. Step (4) according to the specific embodiment step (4) ~ (11) on high-entropy alloy structure optimization, elastic constant calculation, mechanical property calculation and high-throughput screening, finally get 8 kinds of high-entropy alloy, as shown in Table 2.

[0018] Table 2 screening results of example 2

[0019] The above is only the preferred embodiment of the present application, not any form of the present application is limited, although the present application has been disclosed as above, however, not to limit the present application, any skilled in the art, without departing from the scope of the present application, when the above-mentioned disclosed technical content to make some changes or modifications for equivalent variations of equivalent embodiments, but whatever is not out of the present application technical solution content, according to the technical essence of the present application, within the spirit and principles of the present application, to the above examples of any simple modification, equivalent replacement and improvement, etc., are still within the scope of the present application technical solution protection.

Claims

1. A multi-index screening high entropy alloy design method for high-temperature bearing performance requirements, characterized by: The multi-index screening high entropy alloy design method for high-temperature bearing performance requirements is implemented by the following steps: Step 1: Determine the types of metal elements contained in the high entropy alloy material system and the molar ratio of each element; Step 2: Determine the crystal system to which the high-entropy alloy belongs based on the valence electron concentration of the high-entropy alloy, and construct a metal element crystal structure model based on the crystal system of the high-entropy alloy; Step 3: Based on the types and molar ratios of the metal elements determined in Step 1, the composition of the metal atoms in the metal element crystal structure model constructed in Step 2 is modified using the 3D Atomistic window of Materials Studio software to obtain a high-entropy alloy virtual crystal approximation model; Step 4: Import the high entropy alloy virtual crystal approximation model constructed in step 3 into the same folder, perform structural optimization on the high entropy alloy virtual crystal approximation model, and obtain the high entropy alloy virtual crystal approximation model with the lowest energy; Step 5: According to the symmetry of the crystal structure of the research object, a slight deformation is applied to the high-entropy alloy virtual crystal approximation model optimized in step 4, and the structure of the deformed model is optimized to restore it to a stable state, thereby obtaining the stress-strain relationship; Step 6: Use the generalized Hooke's law to fit the stress-strain relationship obtained in step 5 to obtain the elastic stiffness constant of the high entropy alloy. and elastic compliance constant ; Step 7: determining the mechanical stability of the high entropy alloy according to the elastic stiffness coefficient calculated in step 6; Step 8: Calculate the melting point of the high entropy alloy based on the elastic stiffness coefficient calculated in step 6. ; Step 9: Calculate the Young's modulus of the high entropy alloy using the VRH criterion based on the elastic constants fitted in step 6. , shear modulus , bulk modulus and Poisson's ratio ; Step 10: Based on the shear modulus in step 9 and bulk modulus Calculating the Vickers Hardness of High Entropy Alloys , according to the Young's modulus in step 9 and Poisson's ratio Calculating the Fracture Toughness of High Entropy Alloys ; Step 11: The mechanical stability and melting point obtained in steps 7, 8, 9 and 10 are sequentially calculated. , Young's modulus , Vickers hardness and fracture toughness Perform high-throughput screening of high-entropy alloys.

2. The multi-index screening high entropy alloy design method for high-temperature bearing performance requirements according to claim 1 is characterized in that: The metal elements in step 1 include at least five of Ti, Zr, Hf, V, Nb, Ta, Mo, W, and Cr, and the molar ratio of each metal element is in the range of 5% to 35%.

3. The multi-index screening high entropy alloy design method for high-temperature bearing performance requirements according to claim 1 is characterized in that: The formula for calculating the valence electron concentration in step 2 is ,in c i For the i Molar ratio of metal elements, VEC i For the i The number of valence electrons of an element; VEC < 6.84 corresponds to BCC structure, VEC ≥ 8 corresponds to FCC structure, 6.84 ≤ < 8 corresponds to the BCC and FCC dual-phase structure.

4. The multi-index screening high entropy alloy design method for high-temperature bearing performance requirements according to claim 1 is characterized in that: The parameters for the structural optimization in step 4 include: the PBE form in GGA is selected as the functional, the BFGS is selected as the optimization algorithm, the OTFG Norm-conserving is selected as the pseudopotential, and the cutoff energy is set to 1250 eV. k The points are set to 20×20×20, and the energy convergence tolerance is 5×10 -6 eV, the force convergence standard is 0.01eV / Å, the stress convergence accuracy is 0.02GPa, and the displacement accuracy is 5×10 -4 Å, the maximum number of ion step iterations is 200, and the self-consistent field cycle accuracy is 5×10 -7 eV, and the maximum number of self-consistent field cycle steps is 200.

5. The multi-index screening high entropy alloy design method for high-temperature bearing performance requirements according to claim 1 is characterized in that: The number of small strains in step 5 is 6, the maximum strain amplitude is 0.3%, and the structural optimization parameters include: the PBE form in GGA is selected as the functional, the OTFG Norm-conserving pseudopotential is selected, the cutoff energy is set to 1250 eV, the k-point is set to 20×20×20, and the energy convergence tolerance is 2×10 -6 eV, the force convergence criterion is 0.006 eV / Å, and the displacement accuracy is 2×10 -4 Å, the maximum number of ion step iterations is 200, and the self-consistent field cycle accuracy is 5×10 -7 eV, and the maximum number of self-consistent field cycle steps is 200.

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