A method for constructing and evaluating alloy phase boundary / grain boundary irradiation damage behavior model

Abstract

The application belongs to the field of nuclear engineering, and particularly relates to a construction method and an evaluation method of an alloy phase boundary / grain boundary irradiation damage behavior model, which comprises the following steps: obtaining the crystal face and the crystal face angle of alpha-Mg in AZ31 according to an EBSD result graph of AZ31, obtaining the crystal face and the crystal face angle of (1100) Mg and (200) Li in LZ91 according to a TEM result graph of LZ91, constructing a phase boundary interface model of alpha-Mg and beta-Li, constructing a surface model through the crystal face obtained in S1, obtaining the number of surface atom layers, adding a vacuum isolation layer above the surface model, performing a convergence test on the surface model, and respectively establishing the interface models of AZ31 magnesium alloy and LZ91 magnesium-lithium alloy through the obtained results; S3: respectively doping one Mg vacancy, one Li vacancy, one Mg vacancy and one Li vacancy in the interface model obtained in S2, and constructing the alloy phase boundary / grain boundary irradiation damage behavior model.

Description

TECHNICAL FIELD

[0001] The application belongs to the field of nuclear engineering, and particularly relates to a method for constructing and evaluating a model of alloy phase boundary / grain boundary irradiation damage behavior. BACKGROUND

[0002] Nuclear power, as a new type of sustainable clean energy, is one of the important pillars of global electricity supply, and high-performance reactor structural materials play an important role in the safe and stable operation of nuclear power plants. Magnesium alloy is often used as a cladding material when uranium is used as a nuclear fuel in a CO2 gas-cooled reactor because of its stability in a water-free environment and good compatibility with uranium. At the operating temperature of the gas-cooled reactor, the magnesium alloy is required to have sufficient plasticity to prevent damage to the cladding during the deformation of the reactor core, and at the same time, the plasticity of the magnesium alloy should not decrease to a dangerous level under irradiation damage. However, the plastic deformation capacity of conventional HCP structure magnesium alloy is limited. Interfacial engineering is an effective method to improve the irradiation resistance of materials. By introducing a high density of grain boundaries, phase boundaries, free crystal surfaces and other interfaces in the material as traps for irradiation defects, the irradiation damage resistance of the material can be effectively controlled, and the stability of the microstructure and macroscopic properties of the material in a strong irradiation environment can be maintained.

[0003] However, the resistance of magnesium alloy grain boundaries, phase boundaries, free crystal surfaces and other interfaces to irradiation remains to be determined. The dual-phase magnesium-lithium alloy combines the characteristics of the two phases and exhibits extremely high plastic deformation capacity. The dislocation pile-up and strain concentration at the phase boundary of the alloy have a significant impact on the performance of the alloy. The resistance of the phase boundary in the magnesium-lithium alloy to irradiation also remains to be confirmed. The first-principles calculation method based on the density functional theory is a powerful tool for studying the properties of materials at the atomic scale, which can provide effective information on the physical nature of the above problems. Therefore, it is crucial to construct a reasonable calculation model of the magnesium alloy grain boundary / phase boundary before and after irradiation to study the resistance mechanism of the magnesium alloy to irradiation. SUMMARY

[0004] In view of the poor plasticity of the magnesium alloy after irradiation in the prior art and the unclear mechanism of the magnesium alloy grain boundary and phase boundary resistance to irradiation, the application provides a method for constructing and evaluating a model of alloy phase boundary / grain boundary irradiation damage behavior, comprising the following steps:

[0005] S1: According to the EBSD result graph of AZ31, the crystal face and crystal face angle of alpha-Mg in AZ31 are obtained, and according to the TEM result graph of LZ91, two crystal faces, i.e. and (200) Li the crystal face and crystal face angle, a phase boundary interface model of alpha-Mg and beta-Li is constructed;

[0006] S2: Using the crystal plane and orientation information obtained from S1, construct surface models, and construct face-centered cubic α-Mg and body-centered cubic β-Li supercell models respectively, along (0002). (200) Crystal plane cutting of α-Mg and β-Li supercell models to obtain two-phase supercell plate-like models with surfaces; then determine the number of atomic layers of the surface model, add a vacuum isolation layer on top of the surface model, and perform convergence tests on the surface model to obtain (0002) Mg An interface model of AZ31 magnesium alloy composed of crystal planes, and and (200) Li A model of the LZ91 magnesium-lithium alloy interface formed by crystal planes;

[0007] S3: By doping the interface model obtained in S2 with one Mg vacancy, one Li vacancy, or one Mg vacancy and one Li vacancy, respectively, an irradiation damage behavior model of alloy phase boundary / grain boundary was constructed.

[0008] Furthermore, the included angle of the α-Mg crystal planes described in S1 is 7.8°, and the α-Mg crystal plane is (0002). Mg .

[0009] Furthermore, as described in S1 and (200) Li The included angle of the crystal planes is 1°.

[0010] Furthermore, the thickness of the vacuum isolation layer described in S2 is

[0011] The convergence test described in S2 further determines whether convergence has occurred by measuring the surface energy of surface models with different numbers of layers. The formula for calculating the surface energy is as follows:

[0012]

[0013] In the formula, A represents the surface area; N bulk and N slab These are the number of atoms in the bulk structure and the surface structure, respectively; It is the total energy of atoms in the bulk structure; E tot E represents the total energy of the surface. suf (N) is the surface energy of the relevant surface model obtained after calculation.

[0014] Furthermore, the interface model of the AZ31 magnesium alloy described in S2 is (0002). Mg / (0002) Mg Grain boundaries, achieved by using 5 layers (0002) Mg Located on the 5th floor (0002) MgThe upper 5 layers (0002) Mg Rotated 7.8° to obtain.

[0015] Further, the interface model of the LZ91 magnesium-lithium alloy in S2 is and (200) Li By placing 6 layers (200) Li on the 3 layers The upper 6 layers (200) Li Rotated 1° to obtain.

[0016] An evaluation method of an alloy phase boundary / grain boundary irradiation damage behavior model, comprising the following steps: calculating the interface energy and adhesion work before and after irradiation by the alloy phase boundary / grain boundary irradiation damage behavior model, and judging the stability of the interface after irradiation by the difference value;

[0017] By comparing the electronic properties of the AZ31 grain boundary and the LZ91 phase boundary, the influence of vacancies induced by irradiation on the interface stability of the AZ31 grain boundary and the LZ91 phase boundary is obtained.

[0018] Further, the interface properties include interface energy, interface theoretical strength (adhesion work), and electronic properties include state density, differential charge density and Bader charge.

[0019] Advantages

[0020] (1) The construction method and evaluation method of the alloy phase boundary / grain boundary irradiation damage behavior model provided by the present application, in the geometric optimization, the method of controlling variables is used to test the energy convergence, so as to obtain a balanced and stable crystal structure, and by constructing the interface model of the grain boundary, and the structural convergence test of the surface model, the appropriate number of atomic layers is obtained, and by the convergence test of the surface model, the calculation cost is reduced and the calculation accuracy is improved, and a vacuum layer with a thickness of is added above each surface model to prevent the interaction of each surface. The influence of vacancies on the interface performance is obtained by the first principle, and one Mg vacancy, one Li vacancy, one Mg vacancy and one Li vacancy are doped to explore the damage effect of Au ion irradiation on the phase boundary of magnesium alloy.

[0021] (2) The application constructs a primary irradiation interface model for first-principle calculation, which has been successfully applied to the calculation and research of the irradiation damage behavior of AZ31 grain boundaries and LZ91 phase boundary. Through the data observed by experiments (EBSD, TEM), the information of the crystal planes and their angles constituting the interface is obtained, and the interface model is constructed to more specifically simulate the damage behavior of the real interface under irradiation. The model adopts one Mg vacancy, one Li vacancy, one Mg vacancy and one Li vacancy for doping respectively to explore the damage effect of Au ion irradiation on the phase boundary of magnesium alloy, realizes the effective simulation of the interface properties when containing different types of primary irradiation vacancy defects, and has the significant characteristics of low calculation cost and accurate calculation results. The application also provides a method for calculating and researching the influence of irradiation on the damage degree of the interface. By calculating the interface energy, interface theoretical strength (adhesion work) and Bader charge change amount of AZ31 grain boundary and LZ91 phase boundary before and after irradiation, the difference of the three is obtained, not only the resistance of the grain boundary and the phase boundary to the irradiation is analyzed, but also the influence of different types of vacancy irradiation defects on the interface properties and electronic properties is determined, which provides reliable and effective physical information on the damage degree of the primary irradiation defects to the interface at the atomic scale. BRIEF DESCRIPTION OF DRAWINGS

[0022] In order to more clearly illustrate the technical solutions of the example embodiments of the application, the following will briefly introduce the drawings needed to be used in the examples. It should be understood that the following drawings only show some embodiments of the application, and therefore should not be regarded as a limitation on the scope, and for those skilled in the art, other related drawings can also be obtained without creative labor. In the drawings:

[0023] Figure 1 The surface model graph in the convergence test of the application;

[0024] Figure 2 The surface energy graph of the surface of different atomic layers of the application;

[0025] Figure 3 The interface model graph of LZ91 and AZ31 of the application;

[0026] Figure 4 The interface energy and interface theoretical strength difference graph of AZ31 and LZ91 of the application;

[0027] Figure 5 The total state density (DOS) and partial wave state density (PDOS) graph of AZ31 of the application;

[0028] Figure 6 The differential charge density graph of AZ31 of the application;

[0029] Figure 7Differential charge density map of 001 plane of the present application;

[0030] Figure 8 Bader charge map of AZ31 of the present application;

[0031] Figure 9 Total density of states (DOS) and partial density of states (PDOS) map of LZ91 of the present application;

[0032] Figure 10 Differential charge density map of LZ91 of the present application;

[0033] Figure 11 Differential charge density map of 010 plane of the present application;

[0034] Figure 12 Bader map of LZ91 of the present application. DETAILED DESCRIPTION

[0035] The following will be combined with the embodiment 1 of the present application and the attached drawings to make a further understanding of the present application. Figures 1-12 The technical solutions of the present application are described clearly and completely, and obviously the described embodiments are only some of the embodiments of the present application, but not all the embodiments. Based on the embodiments in the present application, all the other embodiments obtained by the person skilled in the art without making creative efforts are within the protection scope of the present application.

[0036] The present application mainly uses the DS-PAW module of the multi-scale material design and simulation platform Device Studio software. Based on the autonomous calculation of the ground state solution, various electronic structure properties of the system can be obtained, such as the state density, the electronic local density, the partial charge (pcharge), the Bader charge analysis, the state density, the partial wave state density, etc.

[0037] Firstly, in order to obtain the ground state energy of the single atom, the geometric structure of the unit cell must be optimized, so as to ensure that the subsequent parameter selection is reliable; in the geometric optimization, the method of control variable is adopted to check the energy convergence, so as to obtain a balanced and stable crystal structure. For the selection of the cutoff energy, 400eV is selected according to the reference, and the K point value is automatically selected by the DS-PAW system according to different crystal structures; under the above parameters, the atomic ground state energy of Mg and Li atoms is-24.655eV and-204.67eV, respectively;

[0038] In order to construct the interface model of the grain boundary, the EBSD result map of AZ31 obtained by experiment is analyzed to obtain the crystal face angle of α-Mg in AZ31, and the two crystal faces with the smallest angle, i.e. the two crystal faces with the two angles of 7.8° and 7.8°, are selected as the two crystal faces of the grain boundary, and the two crystal faces are (0002) MgSimilarly, for the construction of the phase boundary interface model of α-Mg and β-Li, the TEM result of LZ91 is analyzed, and the two crystal planes with the smallest included angle are obtained and (200) Li The smallest included angle is 1°; in order to improve the calculation accuracy, the surface model is tested for structural convergence, and the result of the surface model convergence test is obtained; in the multiple layers within the acceptable error range, the layer with the least number of layers is selected; then, the surface model of the corresponding layer is stacked and spliced according to the crystal plane orientation relationship and the crystal plane included angle information obtained from S1, and a vacuum layer is added on one side of the surface along the

[001] direction, and the AZ31 magnesium alloy interface model composed of two (0002) Mg crystal planes with an included angle of 7.8° and the LZ91 magnesium-lithium alloy interface model composed of Mg and (200) Li crystal planes with an included angle of 1° are obtained.

[0039] Example 1

[0040] A method for constructing an alloy phase boundary / grain boundary irradiation damage behavior model, comprising the following steps:

[0041] S1: First, the EBSD result of single-phase magnesium alloy AZ31 and the TEM structure of two-phase magnesium-lithium alloy LZ91 are obtained, and then the crystal planes with the smallest included angle are selected according to the crystal plane orientation information in the figure; for AZ31 magnesium alloy, two (0002) Mg crystal planes with an included angle of 7.8° are selected to obtain the magnesium alloy grain boundary, and for LZ91 magnesium-lithium alloy, the and (200) Li crystal planes with an included angle of 1° are selected to obtain the magnesium alloy phase boundary;

[0042] S2: Determine the number of atomic layers of each crystal plane and construct the magnesium alloy grain boundary / phase boundary interface model, and add a vacuum layer with a thickness of on each surface model to prevent interaction between the surfaces; the surface model is constructed by the crystal planes obtained from S1, and the convergence test is performed on the surface model to measure whether the convergence is reached from the surface energy of the surface model with different numbers of layers; the specific expression formula of the surface energy calculation is as follows:

[0043]

[0044] In the formula, A represents the surface area; N bulk and N slab are the number of atoms in the bulk structure and the surface structure, respectively; is the total energy of the atoms in the bulk structure; E tot is the total energy of the surface; E suf(N) is the surface energy of the relevant surface model after calculation;

[0045] In combination Figure 1 The atomic layer numbers of different surface models in the convergence test process can be obtained and (200) Li Surface model, in combination Figure 2 The atomic layer numbers of different surface models in the convergence test process can be obtained and (200) Li The surface energy of the surface, from Figure 2 The atomic layer numbers suitable for different surface models are obtained from the surface energy results of 3 layers and 6 layers (200) Li For (0002) Mg The surface model thickness is selected as 5 atomic layers;

[0046] By obtaining the results of the surface model convergence test, by placing 5 layers (0002) Mg above 5 layers (0002) Mg , and then rotating the upper 5 layers (0002) Mg by 7.8° to obtain (0002) Mg / (0002) Mg Grain boundary, by placing 6 layers (200) Li above 3 layers , and then rotating the upper 6 layers (200) Li by 1° to obtain Phase boundary, according to the surface model, the lattice constants of the (200) Li surfaces are The lattice constants of the (0002) Mg surfaces are (0002) Mg The lattice constants of the (0002) Therefore The misfit degree of the phase boundary is 10.6%; according to the two-dimensional lattice misfit theory model proposed by Bremfitt et al., (0002) Mg / (0002) Mg Grain boundary and The influence of the interface misfit degree of the phase boundary on the calculation results can be ignored; considering the periodic boundary conditions, by slightly stretching or compressing Mg in the U and V directions, the coherent interface between the interfaces is realized, which makes up for the misfit degree of the interface; on this basis, by adding a vacuum isolation layer of , the interaction between the interfaces is effectively avoided;

[0047] S3: Using first-principles to explore the influence of vacancies on the interface performance in primary irradiation damage; therefore, based on the initial LZ91 phase boundary, one Mg vacancy, one Li vacancy, one Mg vacancy and one Li vacancy are doped respectively, and according to the type of doped vacancies, an alloy phase boundary / grain boundary irradiation damage behavior model is constructed, which is named as LZ91-Mg, LZ91-Li and LZ91-Mg-Li respectively, to explore the influence of Au ion irradiation on the phase boundary of magnesium alloy; similarly, based on the initial AZ31 grain boundary, one Mg vacancy is doped, which is named as AZ31-Mg, to explore the influence of Au ion irradiation on the grain boundary of magnesium alloy, as shown in Figure 3 Figure 3 (a) is LZ91, Figure 3 (b) is LZ91-Mg, Figure 3 (e) is LZ91-Li, Figure 3 (d) is LZ91-Mg-Li, Figure 3 (e) is AZ31, Figure 3 (f) is AZ31-Mg.

[0048] An evaluation method of an alloy phase boundary / grain boundary irradiation damage behavior model, comprising the following steps:

[0049] Firstly, the interface characteristics of the grain boundary interface and the phase boundary interface are obtained by characterizing the interface energy and the interface theoretical strength (adhesion work); the interface energy γ AB is an important thermodynamic parameter in metal materials, which reflects the increase of free energy caused by the disorder of atomic arrangement in the system, and the calculation formula can be expressed as:

[0050]

[0051] Wherein, A interface represents the interface area, is the total energy of the interface; and are the surface energies of different surfaces; N i is the number of i atoms in the interface model, and is the chemical potential of i atoms in the corresponding surface model, since the surface model selected by convergence test has the characteristics of bulk structure model, its value is equal to the energy of a single i atom;

[0052] The adhesion work W ad reflects the interface theoretical strength between the precipitated phase and the matrix, and the higher the value represents the stronger the interaction between the atoms on both sides of the interface, and the specific expression formula for calculation is as follows:

[0053]

[0054] In the formula, wherein, and ​The surface model total energy of A and B, respectively; E AB is the interfacial energy; A interface is the interfacial area;

[0055] The interfacial energy and adhesion work of AZ31 grain boundary and LZ91 phase boundary are calculated respectively, combined with Figure 4 It can be seen that the difference between the interfacial energy and adhesion work before and after irradiation is obtained by comparing the size of the interfacial energy and adhesion work before and after irradiation. The greater the difference, the worse the interface stability after irradiation, and the worse the resistance to irradiation;

[0056] In order to further analyze the influence of vacancies induced by irradiation on the interface properties of AZ31 grain boundary and LZ91 phase boundary, the differences in electronic properties such as state density, differential charge density and Bader charge of the interface model before and after irradiation are compared. Through the comparison of state density and differential charge density, the influence of irradiation on the stability of AZ31 grain boundary and LZ91 phase boundary is obtained. The influence degree of irradiation on the interface properties is measured by calculating the change of Bader charge;

[0057] Figure 4 The calculation results of AZ31 and LZ91 interfacial energy and adhesion work, from the calculation results, the change of AZ31 interfacial energy and adhesion work before and after irradiation can be seen, in general, smaller than LZ91, the influence of AZ31 interface stability after irradiation is smaller, which shows that the resistance of AZ31 grain boundary to irradiation is stronger than that of LZ91 phase boundary. In addition, in LZ91, the influence of doping Li vacancies on the interface properties and resistance to irradiation damage of LZ91 phase boundary is greater than that of doping Mg vacancies.

[0058] As the most important electronic structure characterization, the bonding state and interaction state in the electronic structure of state density have important influence on the stability of materials. Figure 5 (a-b) are the total density of states (DOS) and atomic partial density of states (PDOS) curves of AZ31 and AZ31-Mg, respectively. The blue dashed line represents the Fermi level. The valence electrons of each element in the AZ31 grain boundary are: Mg2p 6 3s 2 ;

[0059] From Figure 5It can be seen that the bonding electrons of AZ31 are mainly distributed in the range of -7.5-3.3 eV, and the bonding electrons of AZ31 in the range of -7.5--1.6 eV are mainly contributed by the s electrons of Mg; in the range of -1.6-3.3 eV, the bonding electrons of AZ31 are mainly contributed by the p electrons of Mg; in the range of -7.5-3.3 eV, the s and p electron states of Mg atom show obvious hybridization, indicating that Mg-Mg metal bond is formed. The bonding electron distribution of AZ31-Mg is similar to that of the initial AZ31 grain boundary, except that the hybridization area of the s and p electrons of Mg atom decreases by 0.67 after doping Mg vacancies; the more the overlapping area of the valence band, the stronger the hybridization, and the more stable the interface, indicating that the stability of AZ31 grain boundary decreases after doping Mg vacancies; the electron state density corresponding to the Fermi level of the initial AZ31 is 2.85 eV, and the electron state density corresponding to the Fermi level of AZ31-Mg is 2.73 eV, decreasing by 0.12 eV; the higher the electron state density corresponding to the Fermi level, the more unstable the system, but the change of the electron state density corresponding to the Fermi level of AZ31 before and after doping vacancies is small and can be ignored; in general, the stability of AZ31 interface decreases after doping vacancies, but the change is small;

[0060] Then the difference charge density and Bader charge of AZ31 are calculated; the difference charge density defines the redistribution of charge in the system after the atoms are arranged into a crystal, which can directly show the charge distribution and bonding ability; as shown in Figure 6 , the parts losing and gaining electrons can be obtained, and the value of the isosurface is From Figure 6 it can be found that in the initial AZ31 model, for most Mg atoms, the electrons are approximately uniformly distributed around them, and the gap density between adjacent Mg atoms is slightly high, showing typical metal bond characteristics; for the grain boundary part of the AZ31 model, the electrons are initially distributed around the isolated Mg atoms, and once the Mg atoms on the other surface are adsorbed to the(0002) Mg surface, the atoms on the(0002) Mg surface will transfer between them; it is worth noting that the charge transfer mainly occurs on the two surfaces, while the charge density of the internal atoms changes little, indicating that the adsorption of Mg atoms only affects the two surface atoms; similarly, for the AZ31-Mg model, after doping vacancies(0002) Mg , the adsorbed Mg atoms on the surface decrease, and the amount of charge transfer also decreases, resulting in a new surface structure; the more the charge transfer, the stronger the bonding ability of the atoms, which can indicate that the stability of the AZ31 surface decreases after doping vacancies.

[0061] To more intuitively observe the differential charge density, the (001) planes of the initial AZ31 and AZ31-Mg were respectively cut out, and the results are as follows. Figure 7 As shown. The contour lines of the initial AZ31 and AZ31-Mg surfaces are selected respectively. arrive and arrive Between. The results show that the two-dimensional differential charge maps of AZ31 and AZ31-Mg are... Figure 6 The results were consistent.

[0062] In addition, to quantify the charge transfer, this chapter calculates the Bader charge of AZ31, and the results are as follows: Figure 8 In AZ31, layer 5-6 of the 10-layer Mg atoms is the grain boundary. The Bader charge difference between layer 5 and layer 6 of AZ31 and AZ31-Mg is 0.473e and 0.466e, respectively. After doping with vacancies, it decreases by 0.007e, indicating that the charge transfer in AZ31 is more intense, which is consistent with the conclusion of differential charge density.

[0063] Similarly, the electronic properties of LZ91 before and after irradiation were calculated to analyze charge transfer and interface stability at the phase boundary. Figure 9 (ad) shows the total density of states (DOS) and atomic partial density of states (PDOS) curves for LZ91, LZ91-Mg, LZ91-Li, and LZ91-Mg-Li, respectively. The blue dashed line represents the Fermi level. The valence electrons of each element in the LZ91 phase boundary are: Mg2p 6 3s 2 and Li1s 2 2s 1 .

[0064] Depend on Figure 9 It is known that the bonding electrons of LZ91 are mainly distributed in the range of -10 to 2 eV. Within the range of -10 to -7.5 eV, the bonding electrons of LZ91 are mainly contributed by the s electrons of Mg. Within the range of -7.5 to 2 eV, significant hybridization of the s and p electron states of Mg and Li atoms occurs, indicating a bonding interaction between Mg and Li. Furthermore, the contribution of Mg atoms to the valence band is greater than that of Li atoms. Similarly, the bonding electrons of LZ91-Mg, LZ91-Li, LZ91-Mg-Li, and LZ91 within the range of -10 to -7.5 eV are mainly contributed by the s electrons of Mg, indicating the formation of Mg-Li ionic bonds. Within the range of -7.5 to -4 eV, there is no contribution from Li atoms, only from the s and p electrons of Mg. The hybridization area of ​​Mg and Li atoms is significantly reduced, indicating a substantial decrease in Mg-Li ionic bonds in LZ91 after doping with vacancies.

[0065] In addition, the reduced coincidence area of LZ91-Li is the same as that of LZ91-Mg-Li, which is larger than that of LZ91-Mg. Thus, it can be seen that the stability of the system is weakened after doping Mg and Li vacancies, and the effect of doping Li vacancies on the stability of LZ91 is greater than that of doping Mg vacancies. In the range of -4 to 2 eV, the s and p electron states of Mg atoms and the s and p electron states of Li atoms of the three interfacial models doped with vacancies show obvious hybridization, and in the range of -4 to 0 eV, the reduced coincidence areas of the three phase boundaries doped with vacancies are the same. Secondly, the electron state density corresponding to the Fermi level of the initial LZ91 phase boundary is 6.044 eV, and by doping Mg and Li vacancies, the Fermi surface moves towards the high energy level region, thereby increasing the state density of the corresponding Fermi surface. The state density corresponding to the Fermi level of LZ91-Mg, LZ91-Li and LZ91-Mg-Li is 6.296 eV, 6.656 eV and 6.381 eV, respectively, and the increase in the electron state density relative to the initial LZ91 phase boundary is 0.252 eV, 0.337 eV and 0.612 eV, respectively. Among them, the largest increase in the electron state density is LZ91-Li, which is twice that of the other two phase boundaries. This shows that the stability of the system is weakened after doping Mg and Li vacancies, and the effect of doping Li vacancies on the stability of the system is greater than that of doping Mg vacancies.

[0066] The differential charge density results of LZ91 are shown in Figure 10 Figure 10 The isosurface of (a-b) is Figure 10 The isosurface of (c-d) is Figure 10 (a) It can be found that in the initial LZ91 phase boundary, obvious charge transfer occurs around each Mg and Li atom, and the charge transfer amount of Li is greater than that of Mg, indicating that Mg and Li atoms will affect the charge density inside the other and the effect of Li atoms is greater than that of Mg atoms. There is also obvious charge transfer at the initial LZ91 phase boundary, indicating that Mg-Li bonds are formed at the phase boundary interface. It can be seen that the surrounding of Mg atoms is mainly blue electron cloud, while the surrounding of Li atoms is yellow electron cloud, indicating that at the phase boundary interface, Mg atoms lose electrons and Li atoms gain electrons. In addition, there is also a small amount of charge distribution in the vacuum layer. Similarly, the differential charge density of LZ91-Mg is shown in Figure 10 (b), the amount of charge transfer of the part doped with Mg vacancies at the interface is obviously reduced, and the amount of charge transfer of the surrounding atoms is increased. In addition, the internal charge density of Li atoms also changes obviously, the third layer (002) Li atoms lose more charge, while the sixth layer Li atoms lose less charge, and the charge distribution in the vacuum layer is almost 0. Thus, it can be seen that the stability of LZ91 is weakened after doping Mg vacancies. ​

[0067] The differential charge density of LZ91-Li is as follows Figure 10 As shown in (c), the overall charge density change is quite significant. After doping with a Li vacancy, the differential charge inside the Mg and Li atoms in the interface model disappears, indicating that in the LZ91-Li interface model, the charge distribution around the Mg and Li atoms is uniform, and no significant charge transfer occurs. When (1100) Mg and (200) Li After Li and Mg atoms are adsorbed onto the surface of LZ91-Mg-Li, charge transfer occurs at the phase boundary, forming Mg-Li bonds. The differential charge density of LZ91-Mg-Li is as follows: Figure 10 As shown in (d), its charge distribution is very similar to that of LZ91-Li, except that the amount of charge transfer is reduced at the Mg vacancy sites.

[0068] The (010) facets of four different models of LZ91 were extracted and analyzed. The results are as follows: Figure 11 As shown in (ad). To visually observe the effect of the differential charge density plot, contour lines for LZ91, LZ91-Mg, LZ91-Li, and LZ91-Mg-Li were selected respectively. arrive arrive arrive and arrive As shown in the figure, the doping of Li vacancies has a significant impact on the charge distribution within the LZ91 phase boundary, while the charge transfer at the doped Mg vacancies is reduced.

[0069] Figure 12 This represents the average Bader charge distribution of atoms in each layer of the four models of LZ91, where layer (1-6) is (200). Li layer(7-9) is Layers 6-7 are in LZ91 (200). Li and The point of contact. (By) Figure 12 (a) It can be seen that the Bader charge of the initial LZ91 drops sharply at layer 6-7, (200) Li The Bader charge is 3.115e. The Bader charge is 1.919e, indicating that Li atoms gain electrons while Mg atoms lose electrons in LZ91, with a Bader charge difference of 1.196e. The Bader charge of LZ91-Mg is generally not much different from that of the initial LZ91 phase boundary. In layers (1-6) and (7-9), i.e., inside Li and Mg atoms, the trend of Bader charge change is basically the same, with slight differences in value, indicating that the charge distribution is similar. In addition, inside Mg atoms, the Bader charge curve shows a slow upward trend, indicating that electrons around Mg atoms gradually transfer from the phase boundary to the interior of Mg atoms, which is consistent with the conclusion of differential charge. It is worth noting that in layer 7, i.e., the atomic layer doped with Mg vacancies, the Bader charge is significantly reduced. In layers 6-7, its (200) Li and The Bader charges are 3.260e and 1.632e, respectively, with a difference of 1.62e. The increased charge transfer at the phase boundary indicates that the doping of Mg vacancies at the phase boundary improves the stability of the phase interface.

[0070] For LZ91-Li and LZ91-Mg-Li, the trends in Bader charge variation differ significantly from those of the initial LZ91. In LZ91-Li, the Bader charge fluctuates considerably within layers (1-6), i.e., inside the Li atoms, indicating a significant charge transfer at the phase boundaries after Li doping. However, in layers (7-9), i.e. inside the Mg atoms, the Bader charge shows a decreasing trend, indicating that the charge around the Mg atoms gradually transfers from the interior of the Mg atoms to the phase boundaries, the opposite of the trend within the Mg atoms of the initial LZ91. In layer 7, i.e., the layer doped with Li vacancies, the Bader charge decreases significantly. The Bader charge in layers 6 and 7 (200...)... Li and The Bader charges of the two layers are 2.859e and 2.197e, respectively, differing by 0.662e. The decrease in charge transfer at the phase boundary indicates that the interface stability weakens after doping with Li vacancies. For LZ91-Mg-Li, charge transfer occurred in the atomic layers near the interface for both Li and Mg atoms. Unlike LZ91-Li, the Bader charge fluctuation of Mg atoms was more drastic than that of Li atoms. Notably, the Bader charge of layer 7, doped with Mg vacancies, was significantly increased, indicating a large amount of charge transferred there. In layers 6-7, the (200) Li and The Bader charges of the two interfaces are 2.937e and 2.619e, respectively, with a difference of 0.316e. The amount of charge transfer at the interface is reduced, indicating that the interface stability at the interface is weakened after doping Mg vacancies and Li vacancies compared with the initial LZ91 interface. Compared with the interface doped with Li vacancies, the interface stability is again weakened after doping one more Mg vacancy.

Claims

1. A method of constructing a model of alloy phase boundary / grain boundary irradiation damage behavior, characterized by, The method comprises the following steps: S1: According to the EBSD result map of AZ31, the crystal face and the crystal face angle of α-Mg in AZ31 are obtained, and according to the TEM result map of LZ91, two crystal faces, i.e. and the crystal face angle of (200) Li crystal face are obtained, and a phase boundary interface model of α-Mg and β-Li is constructed; S2: Construct the surface model by the crystal face and orientation information obtained by S1, and construct the α-Mg supercell model with hexagonal close-packed structure and the β-Li supercell model with body-centered cubic structure respectively, and cut the α-Mg and β-Li supercell models along the (0002), ,(200) crystal face respectively to obtain the two-phase supercell plate model containing surfaces; then determine the number of atomic layers of the surface model, add a vacuum isolation layer above the surface model, and test the convergence of the surface model to obtain the AZ31 magnesium alloy interface model composed of (0002) Mg crystal face, and and the LZ91 magnesium-lithium alloy interface model composed of (200) Li crystal face; The interface model of the AZ31 magnesium alloy is (0002) Mg (0002) Mg grain boundary, by rotating 5 layers (0002) Mg placed on 5 layers (0002) Mg above, and then rotating the 5 layers (0002) Mg above by 7.8°; The interface model of the LZ91 magnesium-lithium alloy is and (200) Li By placing 6 layers (200) Li on 3 layers above, and rotating the 6 layers (200) Li above by 1° to obtain; S3: constructing the alloy phase boundary / grain boundary irradiation damage behavior model by doping one Mg vacancy, one Li vacancy or one Mg vacancy and Li vacancy in the interface model obtained in S2 respectively.

2. The method of claim 1, wherein the alloy phase boundary / grain boundary irradiation damage behavior model is constructed by: The included angle of the crystal plane of the α-Mg described in S1 is 7.8°, and the crystal plane of the α-Mg is (0002) Mg .

3. The method of claim 1, wherein the alloy phase boundary / grain boundary irradiation damage behavior model is constructed by: as described in S1 and (200) Li crystal planes is 1°.

4. The method of claim 1, wherein the alloy phase boundary / grain boundary irradiation damage behavior model is constructed by: The vacuum insulation layer described in S2 has a thickness of 10 .

5. The method of claim 1, wherein the alloy phase boundary / grain boundary irradiation damage behavior model is constructed by: The convergence test in S2 judges whether the surface energy of the surface model with different layers is convergent or not, and the calculation formula of the surface energy is as follows: （1） wherein A represents the surface area; Nbulk and Nslab N is the number of atoms in the bulk structure and surface structure, respectively; Etot is the total energy of the atoms in the bulk structure; E tot Etot is the total energy of the atoms in the bulk structure; E is the surface energy of the relevant surface model obtained after the calculation.

6. A method of evaluating an alloy phase boundary / grain boundary irradiation damage behavior model, characterized by, The method comprises the following steps: The interface energy and adhesion work before and after irradiation are calculated by the alloy phase boundary / grain boundary irradiation damage behavior model obtained by any one of the methods in claims 1-5, the stability of the interface after irradiation is judged by the difference value, and the influence of the vacancies caused by irradiation on the interface properties of the AZ31 phase boundary and the LZ91 grain boundary is obtained by comparing the electronic properties of the AZ31 grain boundary and the LZ91 phase boundary.

7. The method of claim 6, wherein the alloy phase boundary / grain boundary irradiation damage behavior model is evaluated by: The interface properties include interface energy and interface theoretical strength, i.e. adhesion work, and the electronic properties include state density, differential charge density and Bader charge.

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