A method for optimizing Ti2AlNb alloy composition based on first principle and phase diagram calculation

Abstract

A Ti2AlNb alloy composition optimization method based on first principle and phase diagram calculation relates to the first principle field, in particular to a Ti2AlNb alloy design method based on first principle and phase diagram calculation. In order to solve the problem of Ti2AlNb alloy composition optimization, the alloying elements of Ti2AlNb alloy are screened through Materials Studio and Thermo-Calc software, and then the composition of Ti2AlNb alloy is designed. Method: constructing a crystal model, alloying and doping the crystal model, calculating the electronic structure and mechanical properties of the crystal model before and after doping, screening the Ti2AlNb alloy system with better performance, and calculating the phase diagram of the screened Ti2AlNb alloy system. The application predicts and screens the alloying elements of Ti2AlNb alloy through material calculation method, and then designs the composition of Ti2AlNb alloy, which has certain theoretical guiding role for the alloying experiment of Ti2AlNb alloy, and helps to speed up the practical application of Ti2AlNb alloy alloying.

Description

TECHNICAL FIELD

[0001] The application relates to the field of first principles, in particular to a Ti2AlNb alloy design method based on first principles and phase diagram calculation. BACKGROUND

[0002] Ti2AlNb alloy is a light-weight high-temperature structural material developed on the basis of Ti3Al-based alloy, is considered to be one of the most potential aero-engine materials for replacing nickel-based high-temperature alloy at 650 DEG C to 750 DEG C, because of its high yield ratio, good room temperature plasticity and toughness, anti-creep performance, and good oxidation resistance and combustion resistance, and is an important material for key components such as compressor casing, integral blade disc and blade of future high-thrust-to-weight ratio aero-engine, but the phase transition mechanism of Ti2AlNb alloy is relatively complex, and there are problems of intrinsic brittleness and insufficient high-temperature mechanical properties. At present, the research on Ti2AlNb is focused on strengthening the alloy by alloying, and the composition optimization and microstructure control in the development process are still technical problems. On the one hand, the phase transition of the alloy is complex, and the evolution law of the microstructure has not been fully mastered, so how to effectively control the size, proportion, morphology, micro-distribution form and other microstructure details of each component phase in the alloy lacks theoretical basis. On the other hand, under the present situation that the microstructure details are difficult to control, the internal mechanism of the change of the strength and toughness of the alloy caused by the microstructure change is also difficult to explore clearly. SUMMARY

[0003] In order to solve the problem of composition optimization of Ti2AlNb alloy, the alloying elements of Ti2AlNb alloy are screened by MaterialsStudio and Thermo-Calc software, so as to realize the design of the composition of Ti2AlNb alloy.

[0004] The Ti2AlNb alloy composition optimization method based on first principles and phase diagram calculation is carried out according to the following steps:

[0005] Step one: constructing a crystal model

[0006] The crystal model of the three phases in the Ti2AlNb alloy is constructed, and the energy of the initial alloy system is obtained by geometric optimization of the crystal model of the three phases of the Ti2AlNb alloy by using the MaterialsStudio software;

[0007] Step two: alloying and doping the crystal model

[0008] The three-phase crystal models of the Ti2AlNb alloy are alloyed and doped with doping elements in the MaterialsStudio software, a plurality of doped crystal models are obtained, and the doped alloy system is obtained by geometric optimization of the doped crystal models;

[0009] Step three: calculating the energy and mechanical properties of the crystal models before and after doping

[0010] The Young's modulus, shear modulus, bulk modulus and Poisson's ratio of the three-phase crystal models of the Ti2AlNb alloy constructed in step one and the three-phase crystal models of the Ti2AlNb alloy after doping in step two are calculated by using the energy and elastic constants in the MaterialsStudio software;

[0011] Step four: screening the Ti2AlNb alloy system with excellent performance

[0012] According to the calculation results of steps one to three, the crystal model with excellent performance is screened, the doping element in the crystal model with excellent performance is the screened alloying element, and the alloying element is determined.

[0013] Step five: phase diagram calculation of the screened Ti2AlNb alloy system

[0014] The Thermo-Calc software is used to calculate the phase diagram of the crystal model with excellent performance screened in step four, and the phase content information and phase transition temperature information of the alloy system corresponding to the crystal model with excellent performance are obtained.

[0015] The beneficial effects of the present application are:

[0016] 1、The present application predicts and screens the alloying elements of the Ti2AlNb alloy by the method of material calculation, and then designs the composition of the Ti2AlNb alloy, which has certain theoretical guiding effect on the alloying experiment of the Ti2AlNb alloy, and helps to speed up the practical application of the alloying of the Ti2AlNb alloy.

[0017] 2、The present application can quickly predict the performance of materials by the method of material calculation according to the parameters such as Young's modulus and bulk modulus of the calculation system, which greatly shortens the material research and development cycle, reduces the research and development cost, and improves the research and development efficiency.

[0018] 3、The present application is based on computer simulation to explore new material structure and performance, which helps to discover new materials with excellent performance, or to optimize the performance of existing materials, so as to meet the needs of specific application scenarios.

[0019] 4、The application realizes component optimization and provides certain theoretical guidance for subsequent organization control. Through first principle calculation, the influence of the type of doped elements on the parameters such as system energy, electronic state density, differential charge density, Young's modulus, Poisson's ratio and the like can be obtained, different system parameters are compared, the doped elements are screened, the composition is optimized, and the influence of different doped elements on the phase composition, phase content and phase transition temperature of the system is calculated through the method of phase diagram calculation, thereby providing certain theoretical guidance for subsequent organization control. BRIEF DESCRIPTION OF DRAWINGS

[0020] Figure 1 The crystal model of the alpha2 phase in the Ti2AlNb alloy constructed in Example 1 is shown in the following table:

[0021] Figure 2 The crystal model of the alpha2 phase in the Ti2AlNb alloy constructed in Example 1 is shown in the following table:

[0022] Figure 3 The crystal model of the alpha2 phase in the Ti2AlNb alloy constructed in Example 1 is shown in the following table:

[0023] Figure 4 The pseudo-binary phase diagram of Ti-Mo of the Ti-22Al-15Nb-(0-5)Mo alloy in Example 1 is shown in the following table:

[0024] Figure 5 The pseudo-binary phase diagram of Ti-Zr of the Ti-22Al-15Nb-(0-5)Zr alloy in Example 1 is shown in the following table:

[0025] Figure 6 The temperature change section diagram of the Ti-Al-Nb ternary system in Example 1 is shown in the following table: DETAILED DESCRIPTION

[0026] The technical scheme of the application is not limited to the following specific embodiments, and any reasonable combination of the specific embodiments is also included.

[0027] Specific embodiment one: the Ti2AlNb alloy composition optimization method based on the first principle and phase diagram calculation in this embodiment is carried out according to the following steps:

[0028] Step one: constructing a crystal model

[0029] The crystal model of the three phases in the Ti2AlNb alloy is constructed, and the energy of the initial alloy system is obtained by geometric optimization of the crystal model of the three phases in the Ti2AlNb alloy by using the MaterialsStudio software;

[0030] Step two: alloying and doping the crystal model

[0031] In the MaterialsStudio software, the three-phase crystal models of the Ti2AlNb alloy are alloyed and doped with the doping elements to obtain a plurality of doped crystal models, and the doped crystal models are geometrically optimized to obtain the energy of the alloy system after doping;

[0032] Step three: calculating the energy and mechanical properties of the crystal models before and after doping

[0033] The Young's modulus, shear modulus, bulk modulus and Poisson's ratio of the three-phase crystal models of the Ti2AlNb alloy constructed in step one and the three-phase crystal models of the Ti2AlNb alloy after doping in step two are calculated using the energy and elastic constants in the MaterialsStudio software;

[0034] Step four: screening the Ti2AlNb alloy system with superior performance

[0035] According to the calculation results of steps one to three, the crystal model with superior performance is screened, the doping element in the crystal model with superior performance is the screened alloying element, and the alloying element is determined;

[0036] Step five: phase diagram calculation of the screened Ti2AlNb alloy system

[0037] The Thermo-Calc software is used to calculate the phase diagram of the crystal model with superior performance screened in step four to obtain the information of the phase content of the alloy system corresponding to the crystal model with superior performance and the phase transition temperature information.

[0038] The present embodiment has the following advantages:

[0039] 1. The present embodiment predicts and screens the alloying elements of the Ti2AlNb alloy through the material calculation method, and then designs the composition of the Ti2AlNb alloy, which has a certain theoretical guiding effect on the alloying experiment of the Ti2AlNb alloy, and helps to accelerate the practical application of the alloying of the Ti2AlNb alloy.

[0040] 2. According to the Young's modulus, bulk modulus and other parameters of the calculation system, the performance of the material can be quickly predicted through the material calculation method, which greatly shortens the material research and development cycle, reduces the research and development cost, and improves the research and development efficiency.

[0041] 3. The present embodiment is based on computer simulation to explore new material structures and properties, which helps to discover new materials with excellent performance or optimize the performance of existing materials to meet the needs of specific application scenarios.

[0042] 4、The embodiment realizes component optimization and provides certain theoretical guidance for subsequent organization control. Through first-principle calculation, the influence of the type of doped elements on the parameters such as system energy, electronic state density, differential charge density, Young's modulus, Poisson's ratio and the like can be obtained, different system parameters are compared, the doped elements are screened, the composition is optimized, and the influence of different doped elements on the phase composition, phase content and phase transition temperature of the system is calculated through the method of phase diagram calculation, thereby providing certain theoretical guidance for subsequent organization control.

[0043] Specific implementation method two: different from the specific implementation method one, the step one constructs the crystal model of the three phases in the Ti2AlNb alloy according to the crystal parameters of the crystal model of the three phases in the Ti2AlNb alloy in the modeling module of the Materials Studio software.

[0044] Specific implementation method three: different from the specific implementation method one or two, the three phases in the Ti2AlNb alloy are α2 phase, B2 phase and O phase.

[0045] Specific implementation method four: different from any one of the specific implementation methods one to three, the α2 phase is composed of Ti3Al, the B2 phase is composed of TiAl, and the O phase is composed of Ti2AlNb.

[0046] Specific implementation method five: different from any one of the specific implementation methods one to four, the parameters of the geometry optimization in the step one are as follows: the plane wave cutoff energy is selected as 500eV, the K points in the Brillouin zone are selected as the fine option, and the pseudo-potential is selected as the ultra-soft pseudo-potential ultrasoft.

[0047] Specific implementation method six: different from any one of the specific implementation methods one to five, the doping process in the step two is as follows: the original constituent atoms of the three phases of the Ti2AlNb alloy are replaced one by one by using the doping elements, and one doped crystal model is obtained after each replacement.

[0048] Specific implementation method seven: different from any one of the specific implementation methods one to six, the doping elements in the step two are Mo, V, Si, Fe, W, Ta, Zr and Y.

[0049] Specific implementation method eight: different from any one of the specific implementation methods one to seven, the parameters of the geometry optimization in the step two are as follows: the plane wave cutoff energy is selected as 500eV, the K points in the Brillouin zone are selected as the fine option, and the pseudo-potential is selected as the ultra-soft pseudo-potential ultrasoft.

[0050] Specific implementation method nine: different from any one of the specific implementation methods one to eight, the judgment method of the crystal model with excellent performance is as follows:

[0051] ① Compare the energy, Young's modulus, shear modulus, bulk modulus, and Poisson's ratio of the α2 phase, B2 phase, and O phase crystal models in the Ti2AlNb alloy before and after doping. Select the crystal model with lower energy after doping and higher Young's modulus, shear modulus, bulk modulus, and Poisson's ratio after doping as the crystal model with superior performance. The doping element in the crystal model with superior performance is the selected alloying element.

[0052] ② If there are multiple high-performance α2 phase crystal models, B2 phase crystal models, and O phase crystal models selected in step ①, then compare the Young's modulus of the multiple high-performance α2 phase crystal models, B2 phase crystal models, and O phase crystal models, and sort the doped α2 phase crystal models, B2 phase crystal models, and O phase crystal models according to Young's modulus. The doping elements contained in the top four α2 phase crystal models, the top four B2 phase crystal models, and the top four O phase crystal models are the selected alloying elements.

[0053] Specific Implementation Method 10: This implementation method differs from Specific Implementation Methods 1 to 9 in that the phase diagram described in step 5 is a temperature-varying cross-sectional diagram of the Ti-Al-Nb ternary system and a pseudo-binary phase diagram of Ti-alloying elements in an alloy system containing alloying elements.

[0054] Example 1:

[0055] This embodiment describes a method for optimizing the composition of Ti2AlNb alloys based on first-principles calculations and phase diagrams, following these steps:

[0056] Step 1: Constructing a crystal model

[0057] A three-phase crystal model of Ti2AlNb alloy was constructed, and the energy of the initial alloy system was obtained by geometrically optimizing the three-phase crystal model of Ti2AlNb alloy using MaterialsStudio software.

[0058] When constructing the crystal model of the three phases in the Ti2AlNb alloy, the model is constructed in the modeling module of the MaterialsStudio software based on the crystal parameters of the three phases in the Ti2AlNb alloy. The three phases α2, B2, and O are respectively hexagonal close-packed, body-centered cubic, and ordered orthorhombic structures. The crystal parameters include lattice constants and the positions occupied by different elements.

[0059] The Ti2AlNb alloy has three phases: α2 phase, B2 phase, and O phase. The composition of the α2 phase is Ti3Al, the composition of the B2 phase is TiAl, and the composition of the O phase is Ti2AlNb.

[0060] The parameters of the geometry optimization are as follows: the plane wave cutoff energy is selected as 500 eV, the K points in the Brillouin zone are selected as the fine option, and the pseudo-potential is selected as the ultrasoft pseudo-potential ultrasoft;

[0061] Step two: alloying doping on the crystal model

[0062] The crystal models of the three phases of the Ti2AlNb alloy are alloyed and doped with the doping elements in the Materials Studio software, to obtain a plurality of doped crystal models, and the energy of the alloy system after doping is obtained by geometry optimization on the doped crystal models;

[0063] The doping process is that the original constituent atoms of the three phases of the Ti2AlNb alloy are replaced one by one with doping elements, and a doped crystal model is obtained each time the replacement is performed once; the doping elements are Mo, V, Si, Fe, W, Ta, Zr and Y;

[0064] The parameters of the geometry optimization are as follows: the plane wave cutoff energy is selected as 500 eV, the K points in the Brillouin zone are selected as the fine option, and the pseudo-potential is selected as the ultrasoft pseudo-potential ultrasoft.

[0065] Step three: calculating the energy and mechanical properties of the crystal models before and after doping

[0066] The energy and elastic constants in the Materials Studio software are used to calculate the Young's modulus, shear modulus, bulk modulus and Poisson's ratio of the crystal models of the three phases of the Ti2AlNb alloy constructed in step one and the crystal models of the three phases of the Ti2AlNb alloy after doping in step two;

[0067] Step four: screening the Ti2AlNb alloy system with excellent performance

[0068] According to the calculation results of steps one to three, the crystal model with excellent performance is screened, and the doping element in the crystal model with excellent performance is the screened alloying element;

[0069] The judgment method of the crystal model with excellent performance is as follows:

[0070] ①, the energy, Young's modulus, shear modulus, bulk modulus and Poisson's ratio of the α2 phase, B2 phase and O phase crystal models of the Ti2AlNb alloy before and after doping are compared respectively, and the crystal model after doping with energy less than before doping and Young's modulus, shear modulus, bulk modulus and Poisson's ratio greater than before doping is selected as the crystal model with excellent performance, and the doping element in the crystal model with excellent performance is the screened alloying element;

[0071] ②, if the performance of the excellent α2 phase crystal model, B2 phase crystal model, O phase crystal model screened in step 1 are multiple, compare the Young's modulus of the multiple screened performance excellent α2 phase crystal model, B2 phase crystal model and O phase crystal model, and sort the doped α2 phase crystal model, B2 phase crystal model and O phase crystal model according to the Young's modulus, and the doping elements contained in the α2 phase crystal model ranked in the top four, the B2 phase crystal model ranked in the top four and the O phase crystal model ranked in the top four are the screened alloying elements;

[0072] The lower the energy of the alloy system, the more stable it is. Poisson's ratio can reflect the shear stability of the material lattice, Young's modulus can reflect the stiffness of the whole material, bulk modulus can reflect the deformation resistance of the material, and shear modulus can reflect the resistance of the material to external shear. Table 1 shows the energy and mechanical property calculation values of Ti2AlNb alloy three-phase (α2 phase, B2 phase and O phase) before and after doping, and finally Mo and Zr elements are screened out, which are more conducive to the improvement of alloy performance.

[0073] Table 1 Energy and mechanical properties of Ti2AlNb alloy three-phase before and after doping

[0074]

[0075]

[0076] Step five: phase diagram calculation of the screened Ti2AlNb alloy system

[0077] The Thermo-Calc software is used to calculate the phase diagram of the performance excellent crystal model screened in step four, and the phase content information and phase transition temperature information of the alloy system corresponding to the performance excellent crystal model are obtained with the change of temperature; Provide a certain theoretical basis for subsequent organization regulation.

[0078] The phase diagram is the Ti-Al-Nb ternary system temperature change section diagram, the Ti-Mo pseudo-binary phase diagram of Ti-Al-Nb-Mo quaternary system and the Ti-Zr pseudo-binary phase diagram of Ti-Al-Nb-Zr quaternary system, Figure 4 Ti-Mo pseudo-binary phase diagram of Ti-22Al-15Nb-(0-5)Mo alloy; Figure 5 Ti-Zr pseudo-binary phase diagram of Ti-22Al-15Nb-(0-5)Zr alloy. Figure 6The ternary system isothermal section diagram of Ti-Al-Nb in Example 1. After adding a small amount of Mo element in the Ti-Al-Nb base alloy, a new A15 phase and sigma phase will be generated in the alloy with an Al atomic ratio of 22, and the omega0 phase, gamma phase, sigma phase and A15 phase will be precipitated at a lower temperature in the alloy with an Al atomic ratio of 25, that is, the Mo element will promote the generation of the sigma phase and A15 phase. The Mo element will inhibit the generation of alpha2, reduce the content of alpha2 and precipitate at a lower temperature. There is no obvious influence on the precipitation temperature and decomposition temperature of B2 and O. After adding a small amount of Zr element in the Ti-Al-Nb base alloy, several new Al-Zr alloy phases will be generated, and with the increase of the Zr content, the atomic ratio of Zr in the Al-Zr alloy will also increase. The Zr element will also inhibit the generation of alpha2 phase, omega0 phase, gamma phase and other Ti-Al phases, and can only be precipitated at a lower temperature. There is no obvious influence on the precipitation temperature and decomposition temperature of B2 phase and O phase. The effect of a small amount of Zr doping element on alpha2 phase, B2 phase and O phase is similar to that of a small amount of Mo doping element.

Claims

1. A method for optimizing a composition of a Ti 2 AlNb alloy based on first-principle and phase diagram calculation, characterized in that: The Ti2AlNb alloy composition optimization method based on first principles and phase diagram calculation is performed according to the following steps: Step one: constructing a crystal model Constructing a crystal model of three phases in the Ti2AlNb alloy, and using the MaterialsStudio software to perform geometric optimization on the crystal model of the three phases in the Ti2AlNb alloy to obtain the energy of the initial alloy system; The three phases in the Ti2AlNb alloy in step one are alpha2 phase, B2 phase and O phase; Step two: alloying and doping the crystal model In the MaterialsStudio software, use the doping element to alloy and dope the crystal model of the three phases in the Ti2AlNb alloy, obtain a plurality of doped crystal models, and perform geometric optimization on the doped crystal models to obtain the energy of the alloy system after doping; The doping element is Mo; Step three: calculating the energy and mechanical properties of the crystal model before and after doping Using the energy and elastic constant in the MaterialsStudio software, the Young's modulus, shear modulus, bulk modulus and Poisson's ratio of the crystal model of the three phases in the Ti2AlNb alloy constructed in step one and the crystal model of the three phases in the Ti2AlNb alloy after doping in step two are calculated; Step four: screening the Ti2AlNb alloy system with excellent performance According to the calculation results of steps one to three, the crystal model with excellent performance is screened, the doping element in the crystal model with excellent performance is the screened alloying element, and the alloying element is determined; The judgment method of the crystal model with excellent performance is: ①, respectively, compare the energy, Young's modulus, shear modulus, bulk modulus and Poisson's ratio of the alpha2 phase, B2 phase and O phase crystal model of the Ti2AlNb alloy before and after doping, select the crystal model after doping whose energy is smaller than that before doping and whose Young's modulus, shear modulus, bulk modulus and Poisson's ratio are greater than those before doping as the crystal model with excellent performance, and the doping element in the crystal model with excellent performance is the screened alloying element; ②, if the alpha2 phase crystal model, B2 phase crystal model and O phase crystal model with excellent performance screened in step ① are multiple, compare the Young's modulus of the multiple screened alpha2 phase crystal model, B2 phase crystal model and O phase crystal model with excellent performance, and sort the doped alpha2 phase crystal model, B2 phase crystal model and O phase crystal model according to the Young's modulus, respectively. The doping element contained in the alpha2 phase crystal model ranked in the top four, the B2 phase crystal model ranked in the top four and the O phase crystal model ranked in the top four is the screened alloying element; Step five: phase diagram calculation of the screened Ti2AlNb alloy system Using Thermo-Calc software to perform phase diagram calculation on the crystal model with excellent performance screened in step four, and obtaining the phase content information and phase transition temperature information of the alloy system corresponding to the crystal model with excellent performance with temperature.

2. The first-principles and phase diagram calculation based Ti2AlNb alloy composition optimization method according to claim 1, characterized in that: When constructing the crystal model of the three phases in the Ti2AlNb alloy in step one, the crystal parameters of the crystal model of the three phases in the Ti2AlNb alloy are constructed in the modeling module of the MaterialsStudio software.

3. The first-principles and phase diagram calculation based Ti2AlNb alloy composition optimization method according to claim 1, characterized in that: The alpha2 phase component is Ti3Al, the B2 phase component is TiAl, and the O phase component is Ti2AlNb.

4. The first-principles and phase diagram computation based Ti2AlNb alloy composition optimization method of claim 1, wherein: The parameters of the geometry optimization in step one are as follows: the plane wave cutoff energy is selected as 500 eV, the K points in the Brillouin zone are selected as the fine option, and the pseudo-potential is selected as the ultrasoft pseudo-potential.

5. The first-principles and phase diagram computation based Ti2AlNb alloy composition optimization method of claim 1, wherein: The doping process in step two is as follows: the original constituent atoms of the three phases of the Ti2AlNb alloy are replaced one by one by using doping elements, and one doped crystal model is obtained after each replacement.

6. The first-principles and phase diagram computation based Ti2AlNb alloy composition optimization method of claim 1, wherein: The parameters of the geometry optimization in step two are as follows: the plane wave cutoff energy is selected as 500 eV, the K points in the Brillouin zone are selected as the fine option, and the pseudo-potential is selected as the ultrasoft pseudo-potential.

7. The first-principles and phase diagram computation based Ti2AlNb alloy composition optimization method of claim 1, wherein: The phase diagram in step five is a Ti-Al-Nb ternary system variable-temperature cross-section diagram and a Ti-alloying element pseudo-binary phase diagram in an alloy system containing alloying elements.

Images