CN112395762A - High-entropy alloy mechanical property calculation method based on atom-in-sublattice occupying behavior - Google Patents
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Abstract
The invention relates to a method for calculating mechanical properties of a high-entropy alloy based on the occupation behavior of atoms in a sublattice, which comprises the following steps of: step S1, obtaining the phase structure of the alloy system to be calculated; s2, constructing a sublattice model and determining the proportion of the atomic number of each sublattice; step S3: constructing an end group compound of the alloy system; step S4, calculating the corresponding relation between the Gibbs free energy and the temperature of thermodynamic data of all terminal compounds; step S5, establishing a thermodynamic database of the terminal compound; step S6, calculating the occupation information of each atom in the sublattice; step S7, calculating the number of each atom in each sublattice, and combining randomly distributed sublattice atoms into alloy phase lattices to generate final unit cells of the system; and step S8, calculating thermodynamic property and mechanical property according to the obtained final unit cell of the system. The method is based on the occupying ordering behavior of atoms on the sublattice, and the accurate prediction of the performance of the high-entropy alloy material is realized.
Description
Technical Field
The invention relates to the field of calculation and prediction of metal materials, in particular to a method for calculating mechanical properties of a high-entropy alloy based on an atom-in-sublattice occupying behavior.
Background
The high-entropy alloy is a novel alloy design concept, has a plurality of composition elements, has components with equal atomic ratio or near equal atomic ratio, has relatively simple phase structure, and has a main phase composition of FCC, BCC or HCP solid solution. Depending on the composition of the high-entropy alloy and the heat treatment process, the high-entropy alloy may have one or more unique mechanical properties and chemical properties, such as high strength, high hardness, high-temperature softening resistance, radiation damage energy resistance, high-temperature oxidation resistance, and environmental corrosion resistance. However, many disputes exist in the research field of high-entropy alloy, and quantitative research on the relationship among alloy components, atomic arrangement in phases, phase structures and properties in the high-entropy alloy is lacked. Although a great deal of literature data is available to research the mechanical properties of the high-entropy alloy from the experimental perspective, the preparation and testing links of the high-entropy alloy involve the use of large and expensive analytical and testing instruments and complex data analysis techniques, so that reliable microstructure data and mechanical property data of the material are difficult to obtain economically and conveniently.
With the rapid development of material science and computers, a material calculation and simulation method based on the basic principles of classical thermodynamics, first-nature principle calculation and the like is expected to play a great role in the calculation design of the microstructure and the performance of a material, such as phase diagram calculation, prediction of the structure and the performance of the material, and further optimization of the components, the microstructure, the performance and the like of the designed material; on the other hand, when a material is calculated or simulated, a distribution model of atoms on a space lattice needs to be established, and the established model directly influences the reliability of a calculation result. In a few reports at present, quasi-random approximation (SQS) and Coherent Potential Approximation (CPA) are generally adopted to model the atomic distribution in the phase of the multi-principal-element high-entropy alloy, a completely disordered ideal mixed structure model is adopted, the model is only related to the number of atomic species and is unrelated to the atomic species, and obviously the model is not scientific and reasonable enough, because different elements are different in crystal structure, atomic structure, electronegativity and the like, the interaction among atoms is the same, so that the atomic arrangement deviates from the ideal random distribution, strong or weak occupied ordering tendency exists on the sublattice, the ordering tendency is changed from order to disorder along with the difference of heat treatment temperature, and the gibbs free energy of the system is the lowest and is in a stable structural state. Generally, alloy phases exhibit a strong tendency to occupy ordered sites at low temperatures and a strong tendency to occupy unordered sites at high temperatures. At present, the actual structure is difficult to embody by a completely ordered model and a completely disordered model adopted by intermetallic compounds or multi-principal-element high-entropy alloys in documents, so that when the performance of the high-entropy alloy materials is predicted, the calculation method is unreasonable, and the prediction result is not accurate enough.
Disclosure of Invention
In view of the above, the present invention aims to provide a method for calculating mechanical properties of a high-entropy alloy based on an occupying behavior of atoms in a sublattice, which establishes a distribution model of atoms in the sublattice and a whole lattice based on a precise occupied Fraction (SOF) on the basis of an occupied ordered distribution behavior in the sublattice and the whole lattice, thereby realizing accurate prediction of properties of the high-entropy alloy material.
In order to achieve the purpose, the invention adopts the following technical scheme:
a high-entropy alloy mechanical property calculation method based on the sublattice occupying behavior of atoms comprises the following steps:
step S1, obtaining the phase structure of the alloy system to be calculated;
step S2, constructing a sublattice model according to the obtained phase structure of the alloy system to be calculated and determining the proportion of the atomic number of each sublattice;
step S3: constructing an end group compound of an alloy system according to the sublattice model and the atomic ratio;
step S4, calculating the corresponding relation among thermodynamic data, volume and energy of all end compounds, and obtaining the corresponding relation between Gibbs free energy and temperature of the end compounds;
s5, fitting a functional relation of a phase diagram calculation method according to the obtained corresponding relation between the Gibbs free energy and the temperature to obtain each parameter of the functional relation and establish a thermodynamic database of the terminal compound;
step S6, calculating the occupation information of each atom in the sublattice according to the established thermodynamic database;
step S7, calculating the number of each atom in each sublattice according to the occupation information of each atom in the sublattice, distributing positions to the atoms according to the mode of atom random distribution on the same sublattice, combining the randomly distributed sublattice atoms into alloy phase lattice, and generating the final unit cell of the system;
and step S8, calculating thermodynamic property and mechanical property according to the obtained final unit cell of the system.
Further, the sublattice model includes
(1) The FCC structure high-entropy alloy adopts Cu3Au prototype L12Double sublattice model of structure:
wherein Mi respectively represents different alloy elements,
indicating that element Mi is at L12The fractional occupancy on the 1a sublattice of the structure,
indicating that element Mi is at L12Fractional occupancy on the 3c sublattice of the structure with a ratio of atomic numbers of the two sublattices of 1: 3;
(2) the BCC structure high-entropy alloy adopts a double-sublattice mode with NiAl as a prototype B2 structure
Type (2):
wherein Mi respectively represents different alloy elements,
represents the fractional occupancy of the element Mi on the 1a sublattice of the B2 structure,
represents the occupancy fraction of the element Mi on the 1B sublattice of the B2 structure, wherein the atomic number ratio of the two sublattices is 1: 1;
(3) the HCP structure high-entropy alloy adopts Ni3Sn as prototype D019Double sublattice model of structure:
wherein Mi respectively represents different alloy elements,
representing element Mi at D019The fractional occupancy on the 2c sublattice of the structure,
representing element Mi at D019The occupancy fraction on the 6h sublattice of the structure is 2:6 in atomic ratio of the two sublattices.
Further, the step S4 is specifically:
s41, carrying out structure optimization on each terminal compound until the precision is reached to obtain a balance volume;
step S42, selecting 10 volumes of each end group compound near the equilibrium volume, and respectively carrying out static calculation on the 10 volumes to obtain the energy corresponding to each volume;
step S43, calculating 10 volumes by using a density functional perturbation method of a phonon spectrum to obtain
Obtaining thermodynamic data;
and step S44, obtaining the corresponding relation between the Gibbs free energy G and the temperature T data of each end group compound by adopting a quasi-simple harmonic approximation method.
Further, the establishing of the thermodynamic database of the end group compound specifically comprises: G-T function relation based on phase diagram calculation method
G(T)＝A+BTlnT+CT2+DT3+ET-1+FT
And fitting all parameters in the G-T functional relation of the terminal compounds, deducting the simple substance reference state value by using the functional expression of all the terminal compounds, and writing the G-T expression after subtracting the reference state into a thermodynamic database in a TDB format.
Further, the step S8 is specifically:
step S81, according to the final crystal cell of the obtained system, carrying out structure optimization on the crystal cell to obtain a balanced crystal structure of the complex alloy phase;
step S82, changing different volumes of the balanced crystal structure, calculating total energy of different volumes, fitting a three-order Birch-Murnaghan solid state equation, and calculating the bulk modulus of the high-entropy alloy;
and step S83, calculating an elastic coefficient matrix of a related structure based on a strain-strain energy method, predicting the mechanical properties of the high-entropy alloy and the like.
Further, the step S82 is specifically: carrying out curve fitting on a solid state equation of the system, calculating to obtain total energy under different volumes, carrying out curve fitting on the Etot-V data, wherein the fitting model is a three-order Birch-Murnaghan solid state equation:
in the formula, E0For balanced total energy, V, of the crystal0For equilibrium volume, B is the bulk modulus, and B' is the first derivative to volume.
Further, step S83 is specifically that:
there are six independent components of stress, using σij(1, 2, 3) is represented by:
with six independent components of strain, using epsilonij(1, 2, 3) is represented by:
e＝(e1，e2，e3，e4，e5，e6)
the total energy front-to-back change of the system after applying strain to the material is expressed as:
for cubic system, comprising C11、C12And C44The elements of the three elastic constants are represented as:
substituting the delta E to obtain a relation between energy change and strain
First calculate C44When i and j are both equal to 4, C is the number of elements in the matrix44＝C55＝C66Substituting Δ E, setting E to (0, 0, 0, δ, δ, δ) yields:
thus:
similarly, let e be (e, e, 0, 0, 0, 0) to obtain:
thus:
on this basis, applying e ═ δ, δ, δ, 0, 0, yields:
therefore, the temperature of the molten metal is controlled,
three independent elastic constants C of cubic structure are obtained by solving the equations11、C12、C44；
Wherein the elastic modulus is represented by an elastic constant, and for a material with a cubic crystal structure, the relation between the bulk modulus B and the elastic constant is as follows:
the shear modulus G is related to the elastic constant by the formula:
wherein G isVAnd GRRespectively, Voigt and reus shear modulus, G is the Hill average shear modulus;
and finally, judging the property of the material according to the calculated ratio B/G of the bulk modulus to the shear modulus.
Further, the young's modulus E of the polycrystalline material is expressed by the corresponding elastic modulus:
unit cell material in transverse direction epsilontAnd axial direction εaThe ratio of the strain above is the poisson coefficient v of the material, i.e.:
or the poisson coefficient v is expressed by an elastic constant:
compared with the prior art, the invention has the following beneficial effects:
the invention establishes the distribution model of atoms on the sublattice and the integral lattice based on the precise occupied Fraction (SOF) on the basis of the occupied ordered distribution behavior on the sublattice and the integral lattice, thereby realizing the accurate prediction of the performance of the high-entropy alloy material,
drawings
FIG. 1 is a diagram of a calculation path of a CoCrFeNi high-entropy alloy design according to an embodiment of the present invention;
FIG. 2 is a graph showing the fractional occupancy of each element of the CoCrFeNi high-entropy alloy in each sublattice as a function of temperature according to an embodiment of the present invention;
FIG. 3 is a graph of the relationship between the thermodynamic function and the temperature of a CoCrFeNi high-entropy alloy in an embodiment of the invention;
FIG. 4 is a schematic diagram of the lattice occupying configuration of a CoCrFeNi high-entropy alloy constructed by using the SOF method at 298K in one embodiment of the present invention;
fig. 5 is a total energy curve of CoCrFeNi high-entropy alloy constructed by SOF method at 298K according to an embodiment of the present invention at different volumes (E-V curve E (E) (V));
fig. 6 is a strain-strain energy E- δ curve (E ═ E (δ) fitted curve) of CoCrFeNi high-entropy alloy constructed by SOF method at 298K in an embodiment of the present invention.
Detailed Description
The invention is further explained below with reference to the drawings and the embodiments.
In this embodiment, a high-entropy alloy of CoCrFeNi is taken as an example, and a method for calculating mechanical properties of the high-entropy alloy based on an occupying behavior of atoms in a sublattice is provided, including the following steps:
step S1, obtaining the CoCrFeNi high-entropy alloy as FCC _ L1 according to literature or other approaches2Structure, the ratio of atoms occupying vertex positions to atoms occupying face-center positions is 1: 3. (ii) a
Step S2, according to the obtained phase structure of the alloy system to be calculated, the FCC _ L1 of the CoCrFeNi high-entropy alloy2The structure is divided into two sets of sublattice structures, the first set of sublattice occupies the position of the body center 1a, the second set of sublattice occupies the position of 3c, and the atomic ratio of the sublattice is 1: 3. The sublattice model is
Step S3: according to the sublattice model and the atomic ratio, the end group compounds of 16 CoCrFeNi high-entropy alloys are constructed, as shown in figure 1, the phase structure of the end group compounds is also FCC _ L12And (5) structure. Search for Standard FCC _ L1 in the U.S. naval laboratory database2Structures, e.g. AuCu3Initial POSCAR files as end-group compounds; a POTCAR file of each end group compound was prepared in the PBE pseudopotential library.
Step S4, preparing input files INCAR and KPOINTS required by VASP calculation, and firstly, carrying out structural optimization on each terminal compound until the accuracy is reached to obtain a CONTCAR file with a balanced volume; selecting 10 volumes of each terminal compound near the equilibrium volume, respectively carrying out static calculation on the 10 volumes to obtain energy corresponding to each volume, and writing the energy into an e-v.dat file; calculating 10 volumes by using a phonon spectrum density functional perturbation method (Phonopy-dfpt) to obtain thermodynamic data; and finally, obtaining the corresponding relation between the Gibbs free energy G and the temperature T data of each end group compound by adopting a quasi-simple harmonic approximation (QHA).
Step S5, according to the G-T function relation of the phase diagram calculation method (CALPHAD)
G(T)＝A+BTlnT+CT2+DT3+ET-1+FT
Fitting each parameter in the G-T functional relation of all terminal compounds by Matlab software, deducting the reference state value of a simple substance by using the functional expression of each terminal compound, and writing the G-T expression into a thermodynamic database in a TDB format.
In this embodiment, the end group compound Co is preferably in the FCC structure3Cr is taken as an example, and the relative Gibbs free energy calculation formula is delta GT(Co3Cr)＝[GT(Co3Cr)-3×G298.15(Co)-G298.15(Cr)]/3, wherein Δ GT(Co3Cr) as end group compound Co3Relative Gibbs free energy function expression of Cr, GT(Co3Cr) as end group compound Co3Gibbs free energy function expression of Cr, G298.15(Co) is pure Co at room temperature(298.15K) Gibbs free energy function value, G, for Hexagonal Close Packed (HCP) stable Structure298.15(Cr) is a Gibbs free energy function value corresponding to BCC of a stable structure body center cubic structure of pure Cr at room temperature (298.15K), and thermodynamic units are normalized units J/(mol. atom).
Step S6, inputting the components of the four elements of Co, Cr, Fe and Ni according to the established TDB format thermodynamic database by using thermodynamic calculation software Thermo-Calc, wherein the components are all x-0.25; ten temperatures were selected from 298K-1498K every 100K. The occupancy y of each element in the sublattice is obtained, and the occupancy fraction is plotted with the temperature change by Origin, as shown in FIG. 2, and it can be seen that: the atom occupation is gradually changed from ordered to unordered along with the rise of the temperature, and the atom occupation rule is met. The Gibbs free energy, enthalpy of mixing and entropy of mixing of the CoCrFeNi system are also available in Thermo-Calc, as shown in FIG. 3, from which it can be seen: with increasing temperature, the Gibbs free energy of the CoCrFeNi system decreases, while the enthalpy and entropy of mixing increase.
And S7, according to the sublattice occupancy fraction obtained by thermodynamic calculation, atoms of different elements are randomly distributed on different lattice sublattices, and then a thermodynamic sublattice model of the CoCrFeNi system at 298K (namely, low temperature, the occupancy structure is biased to be ordered) is constructed by using an occupancy fraction method (SOF), so that preparation is provided for next and future performance calculation. For CoCrFeNi high-entropy alloy which is a single FCC phase in a temperature range, the alloy is prepared by adding the alloy to AuCu3The way of constructing 4 × 4 × 4 supercell with primitive cell obtains FCC _ L1 containing 256 atoms2And (5) structure. Where the 1a sublattice contains 64 atoms occupying the apex of the cubic lattice and the 3c sublattice contains 192 atoms occupying the face center of the cubic lattice. First, the standard FCC _ L1 is used2The 1a lattice site-occupying coordinates and the 3c lattice site-occupying coordinates in the structure are separated and are constructed as POSCAR-1a and POSCAR-3 c. Calculated occupancy configuration at 298K
(Co0.519Cr0.240Fe0.014Ni0.227)1a(Co0.160Cr0.253Fe0.329Ni0.258)3cAnd are rounded to twoThe number of atoms of each element in the sublattice is
(Co33Cr15Fe1Ni15)1a(Co31Cr49Fe63Ni49)3c，
And atoms are randomly distributed in two sub-lattices according to the occupied fraction by randomly scrambling the occupied coordinates of the same sub-lattice. Finally, the occupied coordinates of the atoms of the same element are arranged together, and two sublattices are nested, so that a thermodynamic sublattice model with occupied fractions is obtained, as shown in fig. 4.
And step S8, carrying out structural optimization on the POSCAR file constructed based on space-occupying fraction modeling (SOF), and then calculating the mechanical property of the CoCrFeNi system at 298K by using VASP software.
Firstly, carrying out solid state equation curve fitting on a system:
calculating by using a VASP software package to obtain total energy under different volumes, and performing curve fitting on the Etot-V data by using MATLAB software, wherein a fitting model is a three-order Birch-Murnaghan solid state equation:
total energy of equilibrium containing crystals in formula (E)0) Equilibrium volume (V)0) The structural, energy and physical mechanical properties such as the bulk modulus (B) and the first derivative (B') to the volume are important in material design. FIG. 5 shows the results of the fitting, and the elastic modulus B is 1.082eV/Angstrom3＝1.082×160.2189GPa＝173.68GPa。
Further, the relationship between the fine structure and the mechanical property of the high-entropy alloy is deeply researched by utilizing a stress-strain energy method. In which there are six independent components of stress, denoted byij(1, 2, 3) can be represented as:
with six independent components of strain, using epsilonij(1, 2, 3) can be represented as:
e＝(e1，e2，e3，e4，e5，e6)
the total energy front-to-back change of the system after straining the material can be expressed as:
for cubic system, comprising C11、C12And C44The matrix elements of the three elastic constants can be represented as:
substituting the delta E to obtain a relation between energy change and strain
Calculating C44When i and j are both equal to 4, C is the number of elements in the matrix44＝C55＝C66Substituting Δ E, setting E to (0, 0, 0, δ, δ, δ) yields:
thus:
similarly, it is assumed that e ═ can be (e, e, 0, 0, 0, 0):
thus:
on the basis of this, applying e ═ δ, δ, δ, 0, 0, we can obtain:
therefore, the temperature of the molten metal is controlled,
by solving the equations, three independent elastic constants C of cubic structure can be obtained11、C12、C44. By calculating and fitting, as shown in fig. 6, the elastic constants C11 ═ 233.3GPa, C12 ═ 135.6GPa, and C44 ═ 136.5GPa of CoCrFeNi are obtained;
wherein the elastic modulus can be expressed by an elastic constant, and for a cubic crystal structure material, the relation between the bulk modulus B and the elastic constant is as follows:
the shear modulus G is related to the elastic constant by the formula:
wherein G isVAnd GRRespectively, Voigt and reus shear modulus, and G is the Hill average shear modulus.
The young's modulus E of a polycrystalline material is expressed using the corresponding elastic modulus:
unit cell material in transverse direction epsilontAnd axial direction εaThe ratio of the strain above is the poisson coefficient v of the material, i.e.:
the poisson coefficient v can also be expressed by the elastic constant:
therefore, the bulk modulus B is 168.2GPa, the shear modulus G is 90.5GPa, the young modulus E is 230.1GPa, the B/G is 1.859, and the poisson ratio ν is 0.272 are calculated. The CoCrFeNi high-entropy alloy is known to be a brittle material through calculation because the ratio B/G of the bulk modulus to the shear modulus can be generally used for judging whether the material is ductile or brittle, namely when the B/G is more than 1.75, the material is a ductile material, and when the B/G is less than 1.75, the material is a brittle material.
According to the basic knowledge about theoretical mechanics, a high-entropy alloy system with an HCP structure comprises 5 independent elastic constants Cij (namely C11, C12, C13, C33 and C44), and the data of the 5 independent elastic constants can be obtained by referring to the calculation mode of FCC or BCC independent elastic coefficients of a cubic structure.
The above description is only a preferred embodiment of the present invention, and all equivalent changes and modifications made in accordance with the claims of the present invention should be covered by the present invention.
Claims (8)
1. A method for calculating mechanical properties of a high-entropy alloy based on the occupation behavior of atoms in a sublattice is characterized by comprising the following steps:
step S1, obtaining the phase structure of the alloy system to be calculated;
step S2, constructing a sublattice model according to the obtained phase structure of the alloy system to be calculated and determining the proportion of the atomic number of each sublattice;
step S3, constructing a terminal compound of the alloy system according to the sublattice model and the atomic ratio;
step S4, calculating the corresponding relation among thermodynamic data, volume and energy of all end compounds, and obtaining the corresponding relation between Gibbs free energy and temperature of the end compounds;
s5, fitting a functional relation of a phase diagram calculation method according to the obtained corresponding relation between the Gibbs free energy and the temperature to obtain each parameter of the functional relation and establish a thermodynamic database of the terminal compound;
step S6, calculating the occupation information of each atom in the sublattice according to the established thermodynamic database;
step S7, calculating the number of each atom in each sublattice according to the occupation information of each atom in the sublattice, distributing positions to the atoms according to the mode of atom random distribution on the same sublattice, combining the randomly distributed sublattices into alloy phase lattices, and generating final unit cells of the system;
and step S8, calculating thermodynamic property and mechanical property according to the obtained final unit cell of the system.
2. A method for calculating mechanical properties of a high-entropy alloy based on occupying space in sublattice by atoms according to claim 1, wherein the sublattice model comprises
(1) The FCC structure high-entropy alloy adopts Cu3Au prototype L12Double sublattice model of structure:
wherein Mi respectively represents different alloy elements,
indicating that element Mi is at L12The fractional occupancy on the 1a sublattice of the structure,
indicating that element Mi is at L12Fractional occupancy on the 3c sublattice of the structure with a ratio of atomic numbers of the two sublattices of 1: 3;
(2) the BCC structure high-entropy alloy adopts a double-sublattice model with NiAl as a prototype B2 structure:
wherein Mi respectively represents different alloy elements,
represents the fractional occupancy of the element Mi on the 1a sublattice of the B2 structure,
represents the occupancy fraction of the element Mi on the 1B sublattice of the B2 structure, wherein the atomic number ratio of the two sublattices is 1: 1;
(3) the HCP structure high-entropy alloy adopts Ni3Sn as prototype D019Double sublattice model of structure:
wherein Mi respectively represents different alloy elements,
representing element Mi at D019Occupation on the 2c sublattice of the structureThe number of bits in the bit-stream,
representing element Mi at D019The occupancy fraction on the 6h sublattice of the structure is 2:6 in atomic ratio of the two sublattices.
3. The method for calculating the mechanical property of the high-entropy alloy based on the occupying behavior of atoms in the sublattice according to claim 1, wherein the step S4 specifically comprises:
s41, carrying out structure optimization on each terminal compound until the precision is reached to obtain a balance volume;
step S42, selecting 10 volumes of each end group compound near the equilibrium volume, and respectively carrying out static calculation on the 10 volumes to obtain the energy corresponding to each volume;
step S43, calculating 10 volumes by using a density functional perturbation method of a phonon spectrum to obtain thermodynamic data;
and step S44, obtaining the corresponding relation between the Gibbs free energy G and the temperature T data of each end group compound by adopting a quasi-simple harmonic approximation method.
4. The method for calculating the mechanical property of the high-entropy alloy based on the occupying behavior of atoms in the sublattice according to claim 1, wherein the establishing of the thermodynamic database of the end group compounds is specifically as follows: G-T function relation based on phase diagram calculation method
G(T)＝A+BTlnT+CT2+DT3+ET-1+FT
And fitting all parameters in the G-T functional relation of the terminal compounds, deducting the simple substance reference state value by using the functional expression of all the terminal compounds, and writing the G-T expression after subtracting the reference state into a thermodynamic database in a TDB format.
5. The method for calculating the mechanical property of the high-entropy alloy based on the occupying behavior of atoms in the sublattice according to claim 1, wherein the step S8 specifically comprises:
step S81, according to the final crystal cell of the obtained system, carrying out structure optimization on the crystal cell to obtain a balanced crystal structure of the complex alloy phase;
step S82, changing different volumes of the balanced crystal structure, calculating total energy of different volumes, fitting a three-order Birch-Murnaghan solid state equation, and calculating the bulk modulus of the high-entropy alloy;
and step S83, calculating an elastic coefficient matrix of a related structure based on a strain-strain energy method, predicting the mechanical properties of the high-entropy alloy and the like.
6. The method for calculating the mechanical property of the high-entropy alloy based on the occupying behavior of atoms in the sublattice of the lattice according to claim 5, wherein the step S82 is specifically as follows: carrying out solid state equation curve fitting on the system, calculating to obtain total energy under different volumes, and calculating to obtain EtotAnd (4) carrying out curve fitting on the V data, wherein the fitting model is a third-order Birch-Murnaghan solid state equation:
in the formula, E0For balanced total energy, V, of the crystal0For equilibrium volume, B is the bulk modulus, and B' is the first derivative to volume.
7. The method for calculating the mechanical property of the high-entropy alloy based on the occupying behavior of atoms in the sublattice of the lattice according to claim 5, wherein the step S83 is specifically as follows:
there are six independent components of stress, using σij(1, 2, 3) is represented by:
with six independent components of strain, using epsilonij(1, 2, 3) is represented by:
e＝(e1，e2，e3，e4，e5，e6)
the total energy front-to-back change of the system after applying strain to the material is expressed as:
for cubic system, comprising C11、C12And C44The elements of the three elastic constants are represented as:
substituting the delta E to obtain a relation between energy change and strain
First calculate C44When i and j are both equal to 4, C is the number of elements in the matrix44＝C55＝C66Substituting Δ E, setting E to (0, 0, 0, δ, δ, δ) yields:
thus:
similarly, let e be (e, e, 0, 0, 0, 0) to obtain:
thus:
on this basis, applying e ═ δ, δ, δ, 0, 0, yields:
therefore, the temperature of the molten metal is controlled,
three independent elastic constants C of cubic structure are obtained by solving the equations11、C12、C44；
Wherein the elastic modulus is represented by an elastic constant, and for a material with a cubic crystal structure, the relation between the bulk modulus B and the elastic constant is as follows:
the shear modulus G is related to the elastic constant by the formula:
wherein G isVAnd GRRespectively, Voigt and reus shear modulus, G is the Hill average shear modulus；
And finally, judging the property of the material according to the calculated ratio B/G of the bulk modulus to the shear modulus.
8. A method for calculating mechanical properties of a high-entropy alloy based on occupying space of atoms in a sublattice according to claim 7, wherein the Young modulus E of the polycrystalline material is expressed by using the corresponding elastic coefficient:
unit cell material in transverse direction epsilontAnd axial direction εaThe ratio of the strain above is the poisson coefficient v of the material, i.e.:
or the poisson coefficient v is expressed by an elastic constant:
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