TiB2-based ultrahigh-temperature high-toughness ceramic as well as screening method and preparation method thereof

Abstract

The invention discloses a TiB2-based ultrahigh-temperature high-toughness ceramic and a screening method and a preparation method thereof, and relates to the technical field of ultrahigh-temperature ceramics, the TiB2-based ultrahigh-temperature high-toughness ceramic material is composed of Ti, B and one or more of Nb, Hf, Ta, Mo, W, Zr, V, Sc and Al, according to the screening method, the elasticity, mechanics and toughness of the TiB2-based ceramic doped with different types of alloy elements are calculated and obtained by adopting a high-throughput first principle, and mechanical properties changing along with components are established through component-property fitting based on CALPHAD; according to the preparation method, metal boride ceramic powder is subjected to high-energy ball milling and powder mixing and then is subjected to electric arc melting to prepare a ceramic block. Based on the screening and preparation method, the problems of high cost and long period caused by element screening in a traditional experiment can be reduced, and meanwhile, by adjusting the smelting temperature and the smelting time in the smelting process, the preparation of the single-phase TiB2-based ceramic block with uniform element distribution and high hardness and toughness can be realized.

Description

Technical Field

[0001] The present invention relates to the technical field of ultra-high temperature ceramics, and particularly relates to TiB2-based ultra-high temperature and high toughness ceramics and their screening method and preparation method. Background Art

[0002] Metal borides have become the focus of ceramic material research, and show extensive application potential especially in the fields of superhard materials, ultra-high temperature ceramics, wear-resistant materials, superconducting materials, etc. Among them, titanium diboride (TiB2) has attracted much attention due to its excellent physical properties, such as high hardness (≥30 GPa), high melting point (≥3000 °C), excellent creep resistance, and excellent electrical and thermal conductivity. These properties make TiB2 a potential candidate material for applications in extreme aerospace environments, cutting tools, thermal protection surfaces, electrodes, etc.

[0003] The excellent physical properties of TiB2 are attributed to its unique structural characteristics. TiB2 has a hexagonal AlB2-type structure (Hex-II: space group P6 / mmm), in which boron (B) atoms are located at the interstitial positions between titanium layers. This structure is composed of closely packed metal layers and planar boron layers separated, and boron atoms form a honeycomb network with strong B–B bonds within the layer. Research shows that the strong covalent interaction of Ti-B and B-B bonds is the source of its high hardness and high modulus. However, these crystal and electronic structure characteristics also result in low fracture toughness of TiB2 and sensitivity to subcritical crack growth. The high stacking fault energy generated by strong atomic interactions makes the generation of dislocations extremely difficult, thus limiting the engineering applications of TiB2.

[0004] Research shows that the fracture toughness of multi-component high-entropy borides (TiZrHfNbTa)B2 can be improved by increasing the lattice distortion degree of the structure and forming more complex chemical bonding. However, the selection of doping elements for high-entropy borides depends on experience, lacking data support and theoretical basis, and needs to be screened out through repeated experiments, resulting in a long research and development cycle, high research and development costs, and currently, high-entropy borides generally adopt the solid-phase sintering preparation method, resulting in low density of the prepared borides and easy generation of secondary phases. Summary of the Invention

[0005] The first aspect of the present invention lies in providing a screening method for TiB2-based ultra-high temperature and high toughness ceramics to solve the problems of long research and development cycle, high research and development cost, and low fracture toughness of TiB2-based ceramic materials.

[0006] The screening method for TiB2-based ultra-high temperature and high toughness ceramics includes the following steps:

[0007] Step 1, screening out the types of alloying elements doped into TiB2 by the method of first-principles calculation based on density functional theory;

[0008] Step 2: Through first-principles calculations combined with the CALPHAD composition-property modeling method, the property change law of TiB2 caused by different alloying element contents is established according to the types of alloying elements in step 1, and the appropriate alloying element content range is screened.

[0009] A preferred embodiment of the present invention is that step 1 specifically includes:

[0010] The material structure of TiB2 is obtained, and a supercell model of TiB2 is constructed through first-principles calculations based on density functional theory. Then, an alloy atom is doped to form a dilute solid solution model and the elastic properties are calculated. Subsequently, the hardness and fracture toughness are calculated based on the elasticity. Based on the calculation results, the types of alloy elements that improve toughness while reducing hardness by less than 10% are screened out.

[0011] A preferred embodiment of the present invention is that step 2 specifically includes: constructing (Ti x , M y )B2 structure, through first-principles calculation combined with CALPHAD composition-property modeling method, according to the types of alloying elements in step 1, the law of property changes of TiB2 with different alloying element contents is established, and the appropriate alloy content range is screened.

[0012] A preferred embodiment of the present invention is that the component-property modeling method is as shown in the following formula:

[0013] C lm = 0 C lm +△C lm (1)

[0014]

[0015] in To fit the endpoint properties, is the binary interaction parameter, x i and x j They are components of two components respectively.

[0016] The preferred embodiment of the present invention is to use the first principle calculation method of density functional theory, adopt Materials studio or VASP software to calculate, set the cutoff energy to 450eV, and the energy convergence standard of the structure to 10 -6 eV, the convergence criteria for the force is set to be below The number of self-consistent cycles was set to 100.

[0017] The second aspect of the present invention lies in providing a TiB₂-based ultra-high temperature and high toughness ceramic, which is screened by the screening method described in any one of the above, and the ceramic material is composed of elements Ti, B and one or more of the elements Nb, Hf, Ta, Mo, W, Zr, V, Sc, Al, expressed as: (Ti a Nb b Hf c Ta d Mo e W f Zr g V h Sc i Al j )B₂, where (a, j) ∈ (0 - 100%).

[0018] The third aspect of the present invention lies in providing a preparation method of a TiB₂-based ultra-high temperature and high toughness ceramic, which specifically includes the following steps:

[0019] Step 1, the raw materials for preparation are TiB₂ ceramic ultrafine powder with a purity of 99.9% or more, and transition metal boride ultrafine powder MB₂ with a purity of more than 99.9%, where M is one or several of Nb, Hf, Ta, Mo, W, Zr, V, Sc, Al;

[0020] Step 2, set the temperature of the drying oven at 50 - 80 °C, and dry the ceramic powder for 2 - 4 h;

[0021] Step 3, set the ball milling speed of the high-energy ball mill at 800 r / min and the ball milling time at 4 - 8 h to mix the raw materials evenly;

[0022] Step 4, use the arc melting method to melt the raw material powder prepared in Step 1 under argon protection to obtain a ceramic block.

[0023] The preferred embodiment of the present invention lies in that it further includes characterizing the phase and mechanical properties of the prepared (Ti x , M y )B₂ ultra-high temperature ceramic material block, specifically:

[0024] Slice and characterize the sample, and use X-ray diffraction XRD on a diffractometer to characterize all ingots to observe the phase composition of the material;

[0025] Adopt a Zeiss ultra-field emission gun scanning electron microscope for backscattered electron diffraction EBSD acquisition and energy dispersive X-ray spectroscopy EDS analysis;

[0026] Use a nano-indentor with a tip to conduct a nano-indentation test, and there are at least ten indentations on the boride of each sample.

[0027] The beneficial effects of the present invention are as follows:

[0028] The method for screening TiB2-based ultra-high temperature and high-toughness ceramics proposed by the present invention first quickly screens the alloy element composition through first-principles calculations based on density functional theory, greatly improving the long research and development cycle and high research and development costs caused by the "trial and error method". Moreover, the toughness of the (Ti x , M y )B2-based ceramic materials obtained by this method is significantly improved, and at the same time, the hardness does not decrease significantly, which greatly promotes the application of TiB2-based ceramic materials.

[0029] The strategy for improving toughness by alloying proposed by the present invention improves the lattice distortion degree of TiB2-based ceramic materials, improves the electronic structure of TiB2-based ceramic materials, realizes the reduction of the stacking fault energy of TiB2-based ceramic materials, thereby reducing the difficulty of dislocation activation, and can effectively reduce the strength of Ti-B bonding in TiB2-based ceramic materials. At the same time, an anti-bonding M-B bond (M is an alloy element) can be introduced. Through the above various effects, the toughness of TiB2-based ceramic materials is significantly improved.

[0030] The present invention uses TiB2 ceramic ultrafine powder and transition metal boride ultrafine powder (MB2) with a purity of 99.9% or more, ensuring the high purity of the final synthesized material. The high-energy ball milling process ensures the uniform mixing and particle size refinement of the powder, ensuring the full fusion of each component and the uniformity of the material in the subsequent arc melting method. By carrying out arc melting under argon protection, not only oxidation is avoided, but also the densification and mechanical properties of the material are improved. The present invention combines a variety of advanced characterization techniques such as X-ray diffraction (XRD), scanning electron microscopy (SEM), electron backscatter diffraction (EBSD), energy dispersive X-ray spectroscopy (EDS) and nanoindentation to comprehensively evaluate the phase, microstructure, element distribution and mechanical properties of the synthesized material. This method ensures that the quality and performance of the material meet high-standard requirements, providing reliable technical data support for engineering applications. Brief Description of the Drawings

[0031] Figure 1 Shows the dilute solid solution and disordered crystal structure models.

[0032] Figure 2 Are the hardness and fracture toughness of TiB2-based dilute solid solution ceramic materials based on first-principles calculations.

[0033] Figure 3 Are the hardness of (Ti x , M y )B2-based ultra-high temperature and high-toughness ceramic materials varying with the alloy element content.

[0034] Figure 4 is the fracture toughness of (Ti x , M y )B2-based ultra-high temperature and high toughness ceramic materials varying with the alloy element content.

[0035] Figure 5 are the XRD phase characterization results of TiB2, TiNbB2, TiTaB2, and TiNbTaB2 ceramic materials.

[0036] Figure 6 are the SEM and EDS characterization results of TiB2, TiNbB2, TiTaB2, and TiNbTaB2 ceramic materials.

[0037] Figure 7 are the nanoindentation stress-strain curves of TiB2, TiNbB2, TiTaB2, and TiNbTaB2 ceramic materials.

[0038] Figure 8 are the hardness and Young's modulus of TiB2, TiNbB2, TiTaB2, and TiNbTaB2 ceramic materials.

[0039] Figure 9 are the compressive stress-strain curves of TiB2, TiNbB2, TiTaB2, and TiNbTaB2 ceramic materials. Specific Embodiments

[0040] The preferred embodiments of the present invention will be described below with reference to the accompanying drawings. It should be understood that the preferred embodiments described below are only used to explain the present invention and do not limit the protection scope of the present invention.

[0041] The terms "first", "second", etc. in the specification, claims, and embodiments of the present application are used to distinguish similar objects, rather than to describe a specific order or sequence.

[0042] The present invention will be further described in detail below through preferred specific embodiments:

[0043] The screening method for TiB2-based ultra-high temperature and high toughness ceramics includes the following steps:

[0044] Step 1, screening out the types of alloying elements doped into TiB2 by the method of first-principles calculation based on density functional theory; the specific steps of Step 1 include:

[0045] Obtain the material structure of TiB2, and through the method of first-principles calculation based on density functional theory, construct a supercell model of TiB2, and then dope an alloy atom to form a dilute solid solution model and calculate the elastic properties. The dilute solid solution model is as shown in the appendixFigure 1 As shown, in this embodiment, 29 elements are selected, namely Al, Sc, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Y, Zr, Nb, Mo, Tc, Ru, Rh, Pd, Ag, Cd, La, Hf, Ta, W, Re, Os, Ir, Pt, Au. Subsequently, the hardness (H v ) and fracture toughness (K IC ) are calculated according to elasticity. The specific calculation formulas are as follows:

[0046]

[0047] where B is the bulk modulus, G is the shear modulus, and V0 is the volume.

[0048] The hardness and fracture toughness of the TiB2-based dilute solid solution ceramic material are as shown in the appendix Figure 2 .

[0049] Figure 3 is the hardness of the (Ti x , M y )B2-based ultra-high temperature and high-toughness ceramic material varying with the alloy element content.

[0050] Figure 4 is the fracture toughness of the (Ti x , M y )B2-based ultra-high temperature and high-toughness ceramic material varying with the alloy element content.

[0051] According to the calculation results, the types of alloy elements with toughness improvement and hardness reduction less than 10% are screened out.

[0052] Among them, the first-principles calculation method using density functional theory is adopted, and calculations are performed using Materials studio or VASP software. The cut-off energy is set to 450 eV, the energy convergence criterion for the structure is 10 -6 eV, the force convergence criterion is set to be lower than each atom , and the number of self-consistent cycles is set to 100.

[0053] In this embodiment, the material structure of TiB2 is obtained through an open-source database, and the open-source database includes MaterialsProject, OQMD, SprInger Materials, ICSD, and NIST.

[0054] Step 2: Through the first-principles calculation combined with the CALPHAD composition-property modeling method, the property change law of TiB2 with different alloy element contents is established according to the types of alloy elements in Step 1, and a suitable alloy element content range is screened.

[0055] Step 2 specifically includes: constructing the (Ti x , M y )B2 structure with different element contents through a disordered modeling method based on quasi-random approximation SQS, and establishing the law of property changes of TiB2 with different alloy element contents according to the types of alloy elements in Step 1 by combining first-principles calculations with the CALPHAD composition-property modeling method, and screening a suitable alloy content range.

[0056] The composition-property modeling method is shown in the following formula:

[0057] C lm = 0 C lm +△C lm (1)

[0058]

[0059] where is the property of the fitting endpoint, is the binary interaction parameter, x i and x j are the compositions of the two components respectively. The properties of the fitting endpoints are thermodynamic properties such as the enthalpy of mixing or mechanical properties such as modulus.

[0060] A TiB2-based ultra-high temperature and high-toughness ceramic, the TiB2-based ultra-high temperature and high-toughness ceramic is screened by the above-mentioned screening method, and the ceramic material is composed of elements Ti, B and one or more of the elements Nb, Hf, Ta, Mo, W, Zr, V, Sc, Al, expressed as: (Ti a Nb b Hf c Ta d Mo e W f Zr g V h Sc i Al j )B2, where (a, j) ∈ (0 - 100%).

[0061] A method for preparing a TiB2-based ultra-high temperature and high-toughness ceramic specifically includes the following steps:

[0062] Step 1, the raw materials used are TiB2 ceramic ultrafine powder with a purity of 99.9% or more, and transition metal boride ultrafine powder MB2 with a purity of more than 99.9%, where M is one or several of Nb, Hf, Ta, Mo, W, Zr, V, Sc, Al;

[0063] Step 2: Set the temperature of the drying oven to 50 - 80 °C and dry the ceramic powder for 2 - 4 h.

[0064] Step 3: Set the ball milling speed of the high - energy ball mill to 800 r / min and the ball milling time to 4 - 8 h to mix the raw materials evenly.

[0065] Step 4: Using the arc melting method, under argon protection, melt the raw material powder prepared in Step 1 to obtain a ceramic block.

[0066] It also includes characterizing the phase and mechanical properties of the prepared (Ti x , M y )B2 ultra - high - temperature ceramic material block, specifically:

[0067] Slice and characterize the sample. On a diffractometer, use X - ray diffraction (XRD) to characterize all ingots and observe the phase composition of the material.

[0068] Use a Zeiss ultra - field emission gun scanning electron microscope for back - scattered electron diffraction (EBSD) acquisition and energy - dispersive X - ray spectroscopy (EDS) analysis.

[0069] Use a nano - indenter with a tip to conduct nano - indentation tests, with at least ten indentations on the boride of each sample.

[0070] Specific Example 1:

[0071] In this example, Nb element is selected as the alloying element for toughness enhancement. The disordered models under different compositions are constructed through SQS, and the hardness and fracture toughness of the TiB2 ceramic material varying with the Nb composition are calculated by the CALPHAD - based composition - property fitting method. The optimal composition range is determined to be Ti:Nb = 1:1 in atomic percentage.

[0072] The preparation of (Ti, Nb)B2 ceramic blocks specifically includes the following steps:

[0073] Step 1: Select TiB2 ceramic ultrafine powder and NbB2 ultrafine powder with a purity of 99.9% or more as raw materials, and the mixing ratio in atomic percentage is TiB2:NbB2 = 1:1.

[0074] Step 2: Dry the raw material powder in a drying oven, set the temperature to 60 °C, and dry for 2 hours to remove the moisture in the raw materials.

[0075] Step 3: Place the dried TiB2 and NbB2 ultrafine powders into a high - energy ball mill, set the ball milling speed to 800 r / min, and the ball milling time to 6 hours to ensure that the powders are mixed evenly.

[0076] Step 4: Melt the ball-milled mixed powder by arc melting method under an argon protection atmosphere, control the temperature at 2500 °C, and obtain (Ti, Nb)B2 ceramic bulk.

[0077] Characterization of phase and mechanical properties:

[0078] Perform X-ray diffraction analysis on the melted (Ti, Nb)B2 ceramic bulk using an XRD-7000S diffractometer. The results are as Figure 4 shown. (Ti, Nb)B2 has the same characteristic peaks as TiB2, proving that they have the same structure.

[0079] Observe the microstructure of the (Ti, Nb)B2 ceramic using SEM and analyze the elemental composition of the material by EDS. The results are as Figure 5 shown. The distributions of Ti, Nb, and B elements are uniform without segregation, indicating that the structure is a single-phase solid solution structure.

[0080] Conduct a nanoindentation test to measure the hardness and elastic modulus of (Ti, Nb)B2. The results show that this material has high hardness and modulus. At the same time, according to the results of the stress-strain curve, (Ti, Nb)B2 has a higher strain rate than pure TiB2, indicating that its toughness has been improved.

[0081] Specific Example 2:

[0082] In this example, Ta element is selected as the alloying element for toughness enhancement. The disordered models under different compositions are constructed through SQS, and the hardness and fracture toughness of TiB2 ceramic materials varying with Ta composition are calculated by the CALPHAD-based composition-property fitting method. The optimal composition range is determined as Ti:Ta = 1:1 in atomic percentage.

[0083] Preparation of (Ti, Ta)B2 ceramic bulk, specifically including the following steps:

[0084] Step 1: Select TiB2 ceramic ultrafine powder and TaB2 ultrafine powder with a purity of 99.9% or higher as raw materials, and the mixing ratio is TiB2:TaB2 = 1:1 in atomic percentage.

[0085] Step 2: Dry the raw material powder in an oven, set the temperature at 60 °C, and dry for 2 hours to remove the moisture in the raw materials.

[0086] Step 3: Place the dried TiB2 and TaB2 ultrafine powders into a high-energy ball mill, set the ball milling speed at 800 r / min, and the ball milling time at 6 hours to ensure uniform mixing of the powders.

[0087] Step 4: Melt the ball-milled mixed powder by arc melting method under an argon protection atmosphere, control the temperature at 2500 °C, and obtain (Ti, Ta)B2 ceramic bulk.

[0088] Characterization of phase and mechanical properties:

[0089] Perform X-ray diffraction analysis on the melted (Ti, Ta)B2 ceramic bulk using an XRD-7000S diffractometer. The results are as Figure 4 shown. (Ti, Ta)B2 has the same characteristic peaks as TiB2, proving that they have the same structure.

[0090] Observe the microstructure of the (Ti, Ta)B2 ceramic using SEM and analyze the elemental composition of the material by EDS. The results are as Figure 5 shown. The elements Ti, Ta, and B are evenly distributed without segregation, indicating that the structure is a single-phase solid solution structure.

[0091] Conduct a nanoindentation test to measure the hardness and elastic modulus of (Ti, Ta)B2. The results show that this material has high hardness and wear resistance. At the same time, according to the results of the stress-strain curve, (Ti, Ta)B2 has a higher strain rate than pure TiB2, indicating that its toughness has been improved.

[0092] Specific Example 3

[0093] In this example, Ta and Nb elements are selected as alloying elements for toughness enhancement. An disordered model under different compositions is constructed by SQS, and the hardness and fracture toughness of TiB2 ceramic materials varying with the Ta and Nb compositions are calculated by a CALPHAD-based composition-property fitting method. The optimal composition range is determined as Ti:Ta:Nb = 1:1:1 in atomic percentage.

[0094] Preparation of (Ti, Ta, Nb)B2 ceramic bulk, specifically including the following steps:

[0095] Step 1: Select TiB2, TaB2, and NbB2 ultrafine powders with a purity of 99.9% or higher as raw materials, and the mixing ratio is TiB2:NbB2:TaB2 = 1:1:1 in atomic percentage.

[0096] Step 2: Dry the raw material powder in a drying oven, set the temperature at 60 °C, and dry for 2 hours to remove the moisture in the raw materials.

[0097] Step 3: Place the dried TiB2, NbB2, and TaB2 ultrafine powders into a high-energy ball mill, set the ball milling speed at 800 r / min, and the ball milling time at 6 hours to ensure uniform mixing of the powders.

[0098] Step 4: Melt the ball-milled mixed powder by arc melting method under an argon protection atmosphere, control the temperature at 2500 °C, and obtain (Ti, Ta, Nb)B2 ceramic bulk.

[0099] Characterization of phase and mechanical properties:

[0100] Perform X-ray diffraction analysis on the melted (Ti, Ta, Nb)B2 ceramic bulk using an XRD-7000S diffractometer. The results are as Figure 4 shown. (Ti, Nb, Ta)B2 has the same characteristic peaks as TiB2, proving that they have the same structure.

[0101] Observe the microstructure of (Ti, Ta, Nb)B2 ceramic using SEM and analyze the elemental composition of the material by EDS. The results are as Figure 5 shown. The elements Ti, Nb, Ta, and B are evenly distributed without segregation, indicating that the structure is a single-phase solid solution structure.

[0102] Perform nanoindentation tests to measure the hardness and elastic modulus of (Ti, Ta, Nb)B2. The results show that this material has high hardness and wear resistance. At the same time, according to the results of the stress-strain curve, (Ti, Ta, Nb)B2 has a higher strain rate than pure TiB2, indicating that its toughness has been improved.

[0103] Select undoped TiB2 ultra-high temperature ceramic in Comparative Example 1 for comparison with the ceramic materials in Examples 1-8. As shown in the following table:

[0104]

[0105] Conclusion:

[0106] Regarding the component dependence of hardness, except for Zr, the other eight elements show a trend of decreasing hardness when the alloying component increases. Among them, the solid solutions of Sc, Hf, and V are less sensitive to component changes. In terms of toughness, the solid solutions of Nb, Ta, and Mo show a significant increase at higher components. When the component exceeds 50%, its fracture toughness remains at a high level. Different from the trend of component dependence of hardness and toughness, Mo, Nb, and Ta, as alloying elements, simultaneously exhibit high hardness and high toughness, making them the best candidate elements when mixed with Ti in a 1:1 atomic ratio.

[0107] The incorporation of Ta and Nb causes these characteristic peaks to shift to the left, indicating that these three borides are single-phase solid solutions. Figure 5The SEM-EDS analysis results of TiB2, (TiTaB)2, (TiNbB)2, and (TiNbTa)B2 are shown. The SEM images indicate that no obvious secondary phase is observed in these multicomponent diborides, and the EDS characterization shows that the elements are evenly distributed on the scanned surface. This further verifies the accuracy of the stability calculation, indicating that the screened alloy components can form a stable single-phase solid solution. To evaluate the mechanical properties of the synthesized samples, nanoindentation tests were conducted. Figure 6 The load-displacement curves are shown, Figure 7 and the corresponding hardness and Young's modulus values are given. Figure 8 They are the hardness and Young's modulus of TiB2, TiNbB2, TiTaB2, and TiNbTaB2 ceramic materials. Figure 9 They are the compressive stress-strain curves of TiB2, TiNbB2, TiTaB2, and TiNbTaB2 ceramic materials. Due to the brittleness of the diborides, it is difficult to directly evaluate the toughness by the single-edge notched beam method. The sample processing is complex and the result reliability is low. Therefore, we qualitatively evaluate the toughness by analyzing the nanoindentation displacement difference under the same load; a larger displacement value indicates improved toughness.

[0108] The preferred embodiments of the present application are described in detail above in conjunction with the accompanying drawings. The typical well-known structures and common general knowledge technologies in the preferred embodiments are not described in detail here. Those of ordinary skill in the art can, under the inspiration given by this embodiment, improve and implement the technical solution of the present invention in combination with their own capabilities. Some typical well-known structures, well-known methods, or common general knowledge technologies should not be an obstacle to those of ordinary skill in the art to implement the present application.

[0109] The scope of protection required by this application shall be subject to the content of its claims, and the content recorded in the invention content, specific implementation manners, and the drawings of the specification is used to interpret the claims.

[0110] Within the scope of the technical concept of this application, several modifications can also be made to the specific implementation manners of this application, and these modified specific implementation manners should also be regarded as within the scope of protection of this application.

Claims

1. A screening method for TiB2-based ultra-high temperature and high toughness ceramics, characterized in that, Including the following steps: Step 1: Screen the types of alloying elements doped into TiB2 by the method of first-principles calculation based on density functional theory; Step 2: Establish the law of property change of TiB2 with different alloying element contents according to the types of alloying elements in Step 1 by combining first-principles calculation with CALPHAD composition-property modeling method, and screen the appropriate alloying element content range.

2. The screening method of TiB2-based ultra-high temperature and high toughness ceramics according to claim 1, characterized in that, The specific content of Step 1 includes: Obtain the material structure of TiB2, construct the supercell model of TiB2 by the method of first-principles calculation based on density functional theory, then dope an alloy atom to form a dilute solid solution model and calculate the elastic properties, and then calculate the hardness and fracture toughness according to the elastic calculation. Screen out the types of alloying elements with improved toughness and a hardness reduction of less than 10%.

3. The screening method of TiB2-based ultra-high temperature and high-toughness ceramics according to claim 2, characterized in that Step 2 specifically includes: constructing the (Ti x , M y )B2 structure, through first-principles calculation combined with CALPHAD composition-property modeling method, according to the types of alloying elements in step 1, the law of property changes of TiB2 with different alloying element contents is established, and the appropriate alloy content range is screened.

4. The screening method of TiB2-based ultra-high temperature and high-toughness ceramics according to claim 3, characterized in that The composition-property modeling method is shown by the following formula: C lm = 0 C lm + △C lm (1) wherein is the physical property of the fitting endpoint, is the binary interaction parameter, x i and x j are the compositions of the two components respectively.

5. The screening method of TiB2-based ultra-high temperature and high-toughness ceramics according to claim 2 or 3, characterized in that: Using the first-principles calculation method of density functional theory, calculations were performed using Materials studio or VASP software, the cut-off energy was set to 450 eV, and the energy convergence criterion for the structure was 10- 6 eV, and the force convergence criterion was set to be lower than per atom. The number of self-consistent cycles was set to 100.

6. TiB2-based ultra-high temperature and high-toughness ceramics, characterized in that: The TiB2-based ultra-high temperature and high toughness ceramic is screened by the screening method described in any one of the above 1-5, and the ceramic material is composed of elements Ti, B and one or more of the elements Nb, Hf, Ta, Mo, W, Zr, V, Sc, Al, expressed as: (Ti a Nb b Hf c Ta d Mo e W f Zr g V h Sc i Al j )B2, where (a, j) ∈ (0-100%).

7. Preparation method of TiB2-based ultra-high temperature and high toughness ceramics, characterized in that, Specifically including the following steps: Step 1: The raw materials for preparation are TiB2 ceramic ultrafine powder with a purity of 99.9% or more, and transition metal boride ultrafine powder MB2 with a purity of more than 99.9%, where M is one or more of Nb, Hf, Ta, Mo, W, Zr, V, Sc, Al; Step 2: Set the temperature of the drying oven to 50-80°C and dry the ceramic powder for 2-4h; Step 3: Set the ball milling speed of the high-energy ball mill to 800r / min and the ball milling time to 4-8h to mix the raw materials evenly; Step 4: Use the arc melting method to melt the raw material powder prepared in Step 1 under argon protection to obtain a ceramic block.

8. The preparation method of the TiB2-based ultra-high temperature and high toughness ceramic according to claim 7, characterized in that, It also includes characterizing the phase and mechanical properties of the prepared (Ti x , M y )B2 ultra-high temperature ceramic material bulk, specifically: Slice and characterize the sample. On the diffractometer, use X-ray diffraction XRD to characterize all ingots and observe the phase composition of the material; Perform backscattered electron diffraction EBSD acquisition and energy-dispersive X-ray spectroscopy EDS analysis using a Zeiss ultra-field emission gun scanning electron microscope; Use a nanoindenter with a tip to perform nanoindentation tests, with at least ten indentations on the boride of each sample.

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