Method for enhancing nickel aluminide matrix composite by carbon nanotubes based on molecular dynamics simulation

Abstract

The present invention belongs to the technical field of molecular dynamics simulation, and provides a method for carbon nanotube-reinforced nickel aluminide matrix composites based on molecular dynamics simulation. Specifically: using nickel aluminide (Ni<subgt;3< / subgt;Al) as the matrix and carbon nanotubes as the embedded bodies, by precisely controlling the position and diameter of the nanotubes, a structural model of carbon nanotube-reinforced nickel aluminide matrix composites is constructed by means of molecular dynamics simulation, realizing the uniform dispersion of carbon nanotubes in the nickel aluminide (Ni<subgt;3< / subgt;Al) matrix and avoiding the problem of carbon nanotube agglomeration in the matrix; meanwhile, enhancing the strength of the nickel aluminide matrix composites. In addition, by means of molecular dynamics simulation, the strength of carbon nanotube-reinforced nickel aluminide (Ni<subgt;3< / subgt;Al) matrix composites can be accurately predicted, and at the same time, the interaction mechanism between carbon nanotubes and the nickel aluminide (Ni<subgt;3< / subgt;Al) matrix in the composites can be better described, including the strengthening mechanism and the deformation mechanism.

Description

Technical Field

[0001] The present invention belongs to the technical field of molecular dynamics simulation, and provides a method for carbon nanotube-reinforced nickel aluminide matrix composites based on molecular dynamics simulation. Background Art

[0002] Nickel aluminide (Ni3Al) is an intermetallic compound with high strength, high hardness and good oxidation resistance, and is widely used in the fields of aerospace, automotive manufacturing and electronics. However, due to its brittleness and low fracture toughness, its scope of application is limited.

[0003] Nanotechnology is a technology for researching and applying materials at the nanoscale (1 - 100 nm). Due to their unique physical, chemical and mechanical properties, nanomaterials have broad application prospects in the field of materials science. Among them, nanotubes are a kind of nanomaterial with excellent properties. Due to their high strength, high flexibility and excellent electrical conductivity, they have important application value in reinforcing metal matrix composites. With the development of nanotechnology, it has become possible to introduce nanotubes into the nickel aluminide (Ni3Al) matrix to form nanotube-reinforced nickel aluminide (Ni3Al) matrix composites. Such composites can not only maintain the high strength and high hardness of nickel aluminide (Ni3Al), but also significantly improve its fracture toughness and fatigue resistance.

[0004] Nanotube-reinforced nickel aluminide (Ni3Al) matrix composites are traditionally prepared by mechanical alloying methods. For example, the prior art (Jiao Guangping. Research on the mechanical and physical properties of carbon nanotube-reinforced aluminum matrix composites [D]. Jilin: Changchun University of Technology, 2023) prepared carbon nanotube-reinforced aluminum matrix composites by magnetic stirring and spark plasma sintering technology, and explored the distribution and interfacial bonding of different amounts of carbon nanotubes in the aluminum matrix. Chinese invention patent CN111118380B discloses a carbon nanotube and phosphate co-reinforced nickel aluminide matrix composite and its preparation method, using carbon nanotubes and phosphates as co-reinforcing phases, nickel aluminum alloy as the matrix, the carbon nanotubes are 1 - 3 vol.% of the matrix volume, and the phosphate is 6 - 10 wt.% of the matrix mass. This composite has excellent tribological properties in a wide temperature range.

[0005] Although these methods can achieve uniform dispersion of nanotubes in the nickel aluminide (Ni3Al) matrix, due to the surface energy and interaction force of the nanotubes, it is easy to cause agglomeration of the nanotubes in the matrix, thus affecting the performance of the composite. In addition, most traditional mechanical alloying methods require high temperature, high pressure and long processing times, which not only increase the production cost but also limit their application in industrial production.

[0006] Therefore, how to achieve the uniform dispersion of nanotubes in a nickel aluminide (Ni3Al) matrix and how to reduce production costs are urgent problems to be solved in this field. In addition, the existing technologies do not have a deep enough understanding of the interaction mechanism between nanotubes and the nickel aluminide (Ni3Al) matrix, which also limits the further improvement of the performance of nanotube-reinforced nickel aluminide (Ni3Al) matrix composites.

[0007] Molecular dynamics simulation is a commonly used computational method for studying the motion and interaction of atoms and molecules at the nanoscale. Therefore, the microscopic structure and macroscopic properties of materials can be accurately predicted through molecular dynamics simulation, providing theoretical guidance for the design and optimization of nanotube-reinforced nickel aluminide (Ni3Al) composites. Summary of the Invention

[0008] Aiming at the problems existing in the prior art, the present invention provides a method for nanotube-reinforced nickel aluminide matrix composites based on molecular dynamics simulation, which realizes the uniform dispersion of carbon nanotubes (CNTs) in a nickel aluminide (Ni3Al) matrix. In addition, the strength of carbon nanotube (CNT)-reinforced nickel aluminide (Ni3Al) matrix composites can be accurately predicted, and the interaction mechanism between CNTs and the Ni3Al matrix can be clarified.

[0009] The present invention is realized through the following technical solutions:

[0010] A method for carbon nanotube-reinforced nickel aluminide matrix composites based on molecular dynamics simulation, comprising the following steps:

[0011] (1) Respectively construct a Ni3Al structural model and a carbon nanotube structural model. In the xy coordinate plane of the Ni3Al structural model, at the four vertices of a square region with a side length of 2.5 - 5 nm, within a range with a radius of 8 - 12 Å, delete the atoms in the z-axis direction and embed the carbon nanotubes to obtain a carbon nanotube-reinforced Ni3Al composite model;

[0012] (2) Set the potential functions of Ni3Al and carbon nanotubes and mix them, and set the basic simulation parameters to describe the Lennard Jones relationship between different atoms;

[0013] (3) Write a molecular dynamics calculation program to implement basic mechanical property tests and output basic property parameters;

[0014] (4) Process and analyze the parameters output from the tests and realize visualization to obtain the strengthening mechanism and deformation mechanism of carbon nanotube-reinforced nickel aluminide matrix composites.

[0015] Further, use Atomsk to construct the Ni3Al structure model and the carbon nanotube structure model, and set the lattice constant, lattice type, number of repeat units, number of atoms, and unit cell size of each structure model; among them, the number of repeat units of the carbon nanotube structure model is 2×2×1, the lattice type is m=n=8, armchair nanotube, the tube diameter is 8-12 Å, and the tube length is 70.2 Å.

[0016] Furthermore, the basic simulation parameters are as follows: adopt all-atom molecular dynamics, the unit system is metal, and at the same time, periodic boundary conditions are adopted in the x, y, and z directions. The cut-off radius is set to 10-12 Å, the neighbor list close number is 1.5-2.0 bin, and the simulation step size is 1-2 fs.

[0017] Further, the Ni3Al adopts the Meam potential function, and the carbon nanotube adopts the Airebo potential function; the Lennard Jones relationship between different atomic species is described by the Mix Arithmetic rule mixing potential function.

[0018] Specifically as follows:

[0019] ① The Ni3Al alloy adopts the Meam potential function, and the total energy of the Meam potential function E consists of the following three parts:

[0020]

[0021] Among them: is the embedding energy, indicating the energy i for an atom to be embedded in the electron cloud; is the background electron density i at the atom contributed by the electron clouds of surrounding atoms; i is the pair potential j between the atom and

[0022] depending on the distance between them

[0023]

[0024] Among them: is the material-related parameter; is the reference energy.

[0025] Furthermore, the background electron density is a many-body term that takes into account the electron cloud distribution of surrounding atoms, and its expression is:

[0026]

[0027] where: is the contribution of atom j to the electron density at a distance ; is the screening function, which is used to consider many-body effects.

[0028] Furthermore, the pair potential ( ) describes the direct interaction between two atoms, and its expression is:

[0029]

[0030] where: and are the effective charges of atoms i and j ; is the cutoff function, which is used to smoothly cutoff the potential function at the cutoff radius ; e is the elementary charge.[[ID=4�]]

[0031] ② The carbon nanotube adopts the Airebo potential function, and the total energy E of the Airebo potential function consists of the following three parts:

[0032]

[0033] where: is the Rebo part, which describes the interaction of covalent bonds; is the Lennard-Jones part, which describes the non-bonding interaction (van der Waals force); is the torsional potential part, which describes the influence of the intramolecular torsional angle.

[0034] Furthermore, the torsional potential part has the following expression:

[0035]

[0036] where: is the repulsive potential; is the attractive potential; is the Bond Order Parameter, which is used to describe the bond strength and many-body effects.

[0037] Furthermore, the Lennard-Jones part The expression is:

[0038]

[0039] where: is the depth of the potential well; is the equilibrium distance between atoms.

[0040] Furthermore, the torsional potential part The expression is:

[0041]

[0042] where: wijkl is the torsional angle; is the torsional potential function, usually in the form of a cosine function.

[0043] ③ The parameter combination between different types of atoms conforms to the Mix Arithmetic rule, and the expression is:

[0044]

[0045]

[0046] where, 、 and are the average equilibrium potential energy of atom i and atom j, the equilibrium potential energy of atom i, and the equilibrium potential energy of atom j, respectively; 、 and are the average equilibrium distance between atom i and atom j, the equilibrium distance of atom i, and the equilibrium distance of atom j, respectively.

[0047] Furthermore, after describing the Lennard Jones relationship between different atoms, the model is optimized.

[0048] Furthermore, the specific optimization of the model is: the conjugate gradient method is used as the energy minimization algorithm to perform preliminary structural optimization on the model, with an energy tolerance = 10 -10 -10 -8 and a force tolerance = 10 -10 -10 -8 , and the maximum number of iterations is 100000 to eliminate the unreasonable structure of the model and obtain a preliminary structural model; the energy minimization algorithm is the conjugate gradient method.

[0049] Furthermore, the preliminary structural model is relaxed at a temperature of 298 - 300 K for 1 - 2 ns under the NPT ensemble to obtain a stable structure.

[0050] Further, the molecular dynamics calculation program includes a tensile property test program and a compressive property test program; among them, the tensile test program and the compressive test program respectively use the tensile command and the compressive command in the Lammps software.

[0051] Furthermore, both the tensile test program and the compressive test program use the fixdeform command in the Lammps software, and the material is strained by simulating the deformation of the box.

[0052] Further, the basic mechanical property test is carried out under the NVT ensemble, with temperature control using the Nose - Hoover heat bath and integration using the V - Verlet method.

[0053] Specifically, after running the above - mentioned calculation programs (tensile property test program and compressive property test program) on the server for molecular dynamics calculation, the binary calculation results of the output parameters are obtained, and data analysis is performed on the calculation results.

[0054] More specifically, the data analysis process is as follows: For the above - output parameters, Python code is written to process and analyze the calculation results to obtain the stress - strain curve and Young's modulus. Software such as Ovito is used to visualize the tensile and compressive processes and phenomena such as dislocations during this mechanical change process, and through these, the strengthening mechanism and corresponding deformation mechanism of the alloy matrix composite material are obtained.

[0055] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0056] Through molecular dynamics simulation technology, carbon nanotubes (CNTs) are embedded in a nickel aluminide (Ni3Al) matrix to construct a model of a carbon nanotube (CNT)-reinforced nickel aluminide matrix composite (Ni3Al@CNT composite). By selecting a potential function and a suitable mixing method, the distribution and orientation of carbon nanotubes (CNTs) in the nickel aluminide (Ni3Al) matrix are precisely controlled (the Ni3Al lattice is divided into 4 square regions in the xy plane, and 4 CNT structural units are evenly embedded with the center of the square as the center of the diameter of the carbon nanotube (CNT)), achieving a uniform distribution of carbon nanotubes (CNTs) in the nickel aluminide (Ni3Al) matrix, solving the problem of agglomeration of carbon nanotubes (CNTs) in the nickel aluminide (Ni3Al) matrix, avoiding problems such as stress concentration and excessive local stress, and thus improving the compressive and tensile properties. At the same time, through the optimization of the model, it can more accurately describe the interaction relationship between atoms in the composite material, more accurately predict the mechanical properties such as the strength of the carbon nanotube (CNT)-reinforced nickel aluminide (Ni3Al) matrix composite, and better describe the interaction mechanism between the carbon nanotube (CNT) and the nickel aluminide (Ni3Al) matrix. Brief Description of the Drawings

[0057] Figure 1 is a flowchart of the method for molecular dynamics simulation of Ni3Al@CNT composite materials of the present invention;

[0058] Figure 2 is a schematic diagram of the structure of the Ni3Al@CNT composite material obtained by molecular dynamics simulation; where A is a top view and B is a front view;

[0059] Figure 3 is a tensile stress-strain curve diagram of Ni3Al alloy and Ni3Al@CNT composite material obtained by molecular dynamics simulation;

[0060] Figure 4 is a stress-strain curve diagram of Ni3Al@CNT composite material at different strain rates;

[0061] Figure 5 is a relationship curve diagram of the tensile strength and strain rate of Ni3Al@CNT composite material;

[0062] Figure 6 is a relationship curve diagram of the Young's modulus and strain rate of Ni3Al@CNT composite material;

[0063] Figure 7 is a visualization diagram of the tensile process of Ni3Al@CNT composite material and the corresponding dislocation diagram;

[0064] Figure 8Visualization diagram at the time of fracture and the corresponding dislocation diagram of the Ni3Al@CNT composite material. Specific implementation mode

[0065] The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. The described embodiments are only a part of the embodiments of the present invention, rather than all of the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0066] Example 1:

[0067] A method for carbon nanotube-reinforced nickel aluminide matrix composite based on molecular dynamics simulation, comprising the following steps:

[0068] (1) Respectively construct a Ni3Al structure model and a carbon nanotube structure model. In the xy coordinate plane of the Ni3Al structure model, with the four vertices of a square region with a side length of 2.5 - 5 nm as the centers and a radius range of 8 - 12 Å, delete the atoms in the z-axis direction and embed carbon nanotubes to obtain a carbon nanotube-reinforced Ni3Al composite material model;

[0069] (2) Set the potential functions of Ni3Al and carbon nanotubes and mix them, and set the basic simulation parameters to describe the Lennard Jones relationship between different atoms;

[0070] (3) Write a molecular dynamics calculation program to implement basic mechanical property tests and output of basic property parameters;

[0071] (4) Process and analyze the parameters output by the test and realize visualization to obtain the strengthening mechanism and deformation mechanism of the carbon nanotube-reinforced nickel aluminide matrix composite material.

[0072] Example 2:

[0073] A method for carbon nanotube-reinforced nickel aluminide matrix composite based on molecular dynamics simulation, comprising the following steps:

[0074] (1) Respectively construct a Ni3Al structure model and a carbon nanotube structure model. In the xy coordinate plane of the Ni3Al structure model, with the four vertices of a square region with a side length of 2.5 - 5 nm as the centers and a radius range of 8 - 12 Å, delete the atoms in the z-axis direction and embed carbon nanotubes to obtain a carbon nanotube-reinforced Ni3Al composite material model;

[0075] (2) Set the potential functions of Ni3Al and carbon nanotubes and mix them, and set the basic simulation parameters to describe the Lennard Jones relationship between different atoms;

[0076] (3) Write a molecular dynamics calculation program to implement basic mechanical property tests and output basic performance parameters;

[0077] (4) Process and analyze the parameters output from the tests and achieve visualization to obtain the strengthening mechanism and deformation mechanism of carbon nanotube reinforced Ni3Al matrix composites.

[0078] Furthermore, use Atomsk to construct the Ni3Al structure model and the carbon nanotube structure model, and set the lattice constant, lattice type, number of repeat units, number of atoms, and unit cell size of each structure model; among them, the number of repeat units of the carbon nanotube structure model is 2×2×1, the lattice type is m=n=8, Armchair, the tube diameter is 8 - 12 Å, and the tube length is 70.2 Å.

[0079] In some preferred embodiments of the present invention, embedding the carbon nanotube model into the Ni3Al structure model in step (1) specifically means: in the xy coordinate plane of the Ni3Al structure model, within the range with a radius of 8 Å centered at the coordinates (0.25, 0.25), (0.25, 0.75), (0.75, 0.25), and (0.75, 0.75), delete the atoms in the z-axis direction and embed the carbon nanotubes to obtain the carbon nanotube reinforced Ni3Al composite model.

[0080] Even further, the basic simulation parameters are as follows: adopt all-atom molecular dynamics, the unit system is metal, and at the same time, periodic boundary conditions are adopted in the x, y, and z directions, the cutoff radius is set to 10 - 12 Å, the neighbor list close number is 1.0 - 2.0 bin, and the simulation time step is 1 - 2 fs.

[0081] Furthermore, the Ni3Al adopts the Meam potential function, and the carbon nanotube adopts the Airebo potential function; the Lennard Jones relationship between different atomic species is described by mixing potential functions using the Mix Arithmetic rule.

[0082] Specifically as follows:

[0083] ① The Ni3Al alloy adopts the Meam potential function, and the total energy of the Meam potential function E consists of the following three parts:

[0084]

[0085] Among them: is the embedding energy, indicating the energy of the atom i embedded into the electron cloud; is the atom iThe background electron density at [location] is contributed by the electron clouds of surrounding atoms; is the atom i and j The pair potential between them depends on the distance between them .

[0086] Furthermore, the embedding energy is a function of the background electron density and is expressed as:

[0087]

[0088] where: is a material-related parameter; is the reference energy.

[0089] Even further, the background electron density is a many-body term that takes into account the electron cloud distribution of surrounding atoms and is expressed as:

[0090]

[0091] where: is the contribution of atom j to the electron density at distance ; is the screening function used to account for many-body effects.

[0092] Furthermore, the pair potential ( ) describes the direct interaction between two atoms and is expressed as:

[0093]

[0094] where: and are the effective charges of atoms i and j ; is the cutoff function used to smoothly truncate the potential function at the cutoff radius ; e is the elementary charge.

[0095] ② The carbon nanotube uses the Airebo potential function, and the total energy E of the Airebo potential function consists of the following three parts:

[0096]

[0097] where: This is the Rebo part, which describes the interaction of covalent bonds; This is the Lennard-Jones part, which describes the non-bonding interaction (van der Waals force); This is the torsional potential part, which describes the influence of the intramolecular torsional angle.

[0098] Furthermore, the torsional potential part The expression is:

[0099]

[0100] Where: is the repulsive potential; is the attractive potential; is the bond order parameter, which is used to describe the bond strength and many-body effects.

[0101] Furthermore, the Lennard-Jones part The expression is:

[0102]

[0103] Where: is the depth of the potential well; is the equilibrium distance between atoms.

[0104] Furthermore, the torsional potential part The expression is:

[0105]

[0106] Where: wijkl is the torsional angle; is the torsional potential function, usually in the form of a cosine function.

[0107] ③ The parameter combination between different types of atoms conforms to the Mix Arithmetic rule, and the expression is:

[0108]

[0109]

[0110] Where, , and are the average equilibrium potential energy of atom i and atom j, the equilibrium potential energy of atom i, and the equilibrium potential energy of atom j, respectively; , and the average equilibrium distance between the i and j atoms, the equilibrium distance of the i atom, and the equilibrium distance of the j atom, respectively.

[0111] Further, after obtaining the Lennard Jones relationship between different atoms, the structure of the model needs to be optimized, that is, energy minimization.

[0112] Furthermore, the specific optimization of the model is as follows: the energy minimization algorithm is used to perform preliminary structural optimization on the model, with energy tolerance = 10 -10 -10 -8 , force tolerance = 10 -10 -10 -8 , and the maximum number of iterations is 100,000 to eliminate the unreasonable structure of the model and obtain a preliminary structural model; the energy minimization algorithm is the conjugate gradient method.

[0113] Even further, the preliminary structural model is relaxed at a temperature of 298 - 300 K for 1 - 2 ns under the NPT ensemble to obtain a stable structure.

[0114] Further, the molecular dynamics calculation program includes a tensile property test program and a compression property test program; among them, the tensile test program and the compression test program respectively use the tensile command and the compression command in the Lammps software.

[0115] Even further, both the tensile test program and the compression test program use the fix deform command in the Lammps software to obtain strain for the material by simulating the deformation of the simulation box.

[0116] Further, the basic mechanical property test is carried out under the NVT ensemble, with temperature control using the Nose - Hoover heat bath and integration using the V - Verlet method.

[0117] Specifically, in molecular dynamics calculation, after running the above calculation programs (tensile property test program and compression property test program) on the server, the binary calculation results of the output parameters are obtained, and data analysis is performed on the calculation results.

[0118] More specifically, the data analysis process is as follows: for the above - output parameters, Python code is written to process and analyze the calculation results to obtain the stress - strain curve and Young's modulus, and software such as Ovito is used to visualize the tensile and compression processes and phenomena such as dislocations during this mechanical change process, and through these, the strengthening mechanism and corresponding deformation mechanism of the alloy matrix composite material are obtained.

[0119] Example 3:

[0120] The method of the present invention will be described in detail below according to a specific molecular dynamics simulation process of Ni3Al@CNT composite material and the simulation of tensile properties. For the specific calculation process not described in detail, refer to Example 2.

[0121] A method for molecular dynamics simulation of carbon nanotube reinforced nickel aluminide matrix composite material, the molecular dynamics simulation process is as Figure 1 shown, and the specific method is as follows:

[0122] (1) Construct a nanostructure model of Ni3Al and a carbon nanotube (CNT) structure model respectively, and embed the carbon nanotube into the nanostructure model of Ni3Al to obtain a Ni3Al@CNT composite material model; the specific steps are as follows:

[0123] Step S1: Use Atomsk software to construct a Ni3Al unit cell and a CNT unit cell respectively, and the relevant parameters are shown in Table 1.

[0124] Table 1 Relevant parameters of Ni3Al unit cell and CNT unit cell

[0125]

[0126] Step S2: Next, in the xy coordinate plane of the Ni3Al structure, centered at the four vertices of a square region with a side length of 5 nm, that is, at the four positions with coordinates (0.25, 0.25), (0.25, 0.75), (0.75, 0.25) and (0.75, 0.75), delete the atoms in the z-axis direction, and the deletion radius is 8 Å; then use the read_data command of the lammps program to combine the CNT structure model and the Ni3Al structure model 4 times to obtain a Ni3Al@CNT composite material model, as Figure 2 shown, where yellow represents aluminum atoms, blue represents nickel atoms, and red represents CNT.

[0127] (2) Set the potential functions of Ni3Al and CNT and mix them to describe the Lennard Jones relationship between different atoms. The specific process is as follows:

[0128] Adopt all-atom molecular dynamics, the unit system is metal, and periodic boundary conditions are adopted in the x, y, and z directions. The truncation radius is set to 12 Å, the neighbor list proximity number is 2.0 bin, and the simulation step size is 1 fs; first, use the conjugate gradient method to minimize the energy of the constructed model, energy tolerance = 1.0e -8 , force tolerance = 1.0e -8, with a maximum number of iterations of 100,000, eliminating the unreasonable structure of the model to obtain the initial structure model; then, the initial structure model was relaxed for 1 ns at a temperature of 298.15 K under the NPT ensemble to obtain a stable structure;

[0129] Then, under the NVT system, at a temperature of 298.15 K, a 1-ns tensile simulation was carried out. The command used was fix deform, the Nose-Hoover thermostat was used for temperature control, and the V-Verlet method was used for integration to obtain the Ni3Al@CNT composite material for mechanical property testing.

[0130] (3)Write a molecular dynamics calculation program to implement basic mechanical property testing, specifically including the following aspects:

[0131] Tensile test program: Use the tensile fix deform command in the Lammps software, with a strain rate of 10 10 -10 7 / s. Process the above output parameters, calculate the results and analyze them to obtain the stress-strain curve, tensile strength, and Young's modulus.

[0132] The strain rate is 10 8 / s. The tensile stress-strain curves of the Ni3Al alloy and the Ni3Al@CNT composite material obtained by molecular dynamics simulation are as Figure 3 shown. It can be seen that: CNTs are embedded in the Ni3Al alloy matrix, significantly strengthening the tensile strength of the Ni3Al alloy matrix, and there are stress fluctuations during the subsequent yield stage.

[0133] The tensile stress-strain curves of the Ni3Al@CNT composite material at different strain rates are as Figure 4 shown. It can be seen that: The stress increases linearly with strain during the initial elastic stage. As the strain increases, the stress reaches a peak and then drops sharply. The dropping process belongs to the yield stage of the material. The stress value corresponding to this peak is the ultimate strength of the material, and the strength at different strain rates is different. A high strain rate may cause the material to exhibit higher strength because the material may not have enough time to undergo plastic deformation at a high strain rate. The initial straight part of the curve represents the elastic region of the material. The larger the slope, the higher the Young's modulus of the material, that is, the stiffer the material.

[0134] At high strain rates, the material exhibits higher strength. This is because as the strain rate increases, the dislocation movement inside the material is restricted, resulting in stress concentration and increased strength. At high strain rates, an obvious strain rate strengthening effect will be shown, that is, as the strain rate increases, the strength increases significantly.

[0135] The relationship curve between the tensile strength of the Ni3Al@CNT composite material and the strain rate is shown in Figure 5 As shown, it can be seen that a high strain rate will cause changes in the strength and stress of the material, showing a higher tensile strength because the dislocation movement inside the material is restricted, resulting in stress concentration and increased strength.

[0136] The relationship curve between the Young's modulus and the strain rate is shown in Figure 6 As shown, it can be seen that the Young's modulus shows the following changes with the change of the strain rate:

[0137] At low strain rates (10 7 -10 8 / s), the material has enough time for elastic deformation, and the Young's modulus usually remains stable or changes little. At this time, the microstructure of the material (such as dislocation movement) can fully respond to the external load, and the Young's modulus mainly depends on the intrinsic stiffness of the material;

[0138] At medium strain rates (10 8 -10 9 / s), with the increase of the strain rate, the dislocation movement inside the material may be restricted, resulting in stress concentration and an increase in the Young's modulus. At this time, the material may show a certain strain rate strengthening effect, that is, the Young's modulus increases with the increase of the strain rate;

[0139] At high strain rates (10 9 -10 10 / s), the microstructure inside the material (such as dislocations, grain boundaries, etc.) cannot respond to the external load in time, and the material shows higher stiffness and lower plastic deformation ability. In addition, a high strain rate may cause a local temperature rise in the material (due to the conversion of plastic work into heat energy), which further affects the Young's modulus.

[0140] (4) Process and analyze the parameters of the test output and realize visualization to obtain the strengthening and deformation mechanisms of the composite material.

[0141] Use the Ovito software to visualize the above tensile process and the dislocation phenomenon during the tensile process. The results are as shown in Figure 7 and Figure 8 As shown. From Figure 7 and Figure 8 it can be seen that:

[0142] 4.1 Dislocation pinning effect

[0143] Molecular dynamics simulations show that carbon nanotubes act as rigid reinforcing phases in the Ni3Al matrix and form strong interfacial bonds with the matrix through Lennard Jones interactions. During the tensile process, dislocation lines (linear defects visible in the visualization diagrams) are blocked when they move to the carbon nanotube interface, forming a dislocation pile-up group ( Figure 7 the dense area shown in the dislocation diagram), and this pinning effect significantly improves the yield strength of the composite material.

[0144] 4.2 Stress transfer mechanism

[0145] By adopting the Mix Arithmetic rule to mix the Meam potential and the Airebo potential, the Ni-Al-C multiphase interface is accurately described. Figure 7 Visualization in Figure 3 shows that through its high modulus property, the carbon nanotube effectively transfers the external load to the entire matrix, making the stress more evenly distributed in the matrix (corresponding to

[0146] the higher stress plateau of the composite material in

[0147] In the fracture stage, at high strain rates: the dislocation multiplication rate is lower than the loading rate, and a dislocation tangling structure ( Figure 8 the network structure in the dislocation diagram) forms around the carbon nanotubes. This restricted dislocation movement delays crack initiation (corresponding to Figure 3 the higher fracture strain of the composite material in

[0148] 4.4 Carbon nanotube bridging effect

[0149] Figure 8 Visualization in Figure 3 shows that when the crack propagates to the carbon nanotube region, the interfacial bond maintained by Lennard Jones interactions causes the CNT to exhibit a pull-out behavior. The carbon nanotube bridges both sides of the crack, maintaining the high strength of the matrix while improving the fracture toughness. This process consumes additional energy (corresponding to

[0150] It should be noted that the above content is only used to illustrate the technical solution of the present invention, rather than limiting the protection scope of the present invention. Simple modifications or equivalent replacements made by those of ordinary skill in the art to the technical solution of the present invention do not depart from the essence and scope of the technical solution of the present invention.

Claims

1. A method for carbon nanotube-reinforced nickel aluminide matrix composite based on molecular dynamics simulation, characterized in that It includes the following steps: (1) Construct a Ni3Al structural model and a carbon nanotube structural model respectively. In the xy coordinate plane of the Ni3Al structural model, centered at the four vertices of a square region with a side length of 2.5 - 5 nm, within a range with a radius of 8 - 12 Å, delete the atoms in the z-axis direction and embed carbon nanotubes to obtain a carbon nanotube reinforced Ni3Al composite material model; Among them, the lattice type of the Ni3Al structural model is L12; (2) Set the potential functions of Ni3Al and carbon nanotubes and mix them, and set the basic simulation parameters to describe the Lennard Jones relationship between different atoms; the Ni3Al adopts the Meam potential function, and the carbon nanotubes adopt the Airebo potential function; the Lennard Jones relationship between different atomic species is described by mixing potential functions using the Mix Arithmetic rule; (3) Write a molecular dynamics calculation program to achieve basic mechanical property testing and output of basic property parameters; (4) Process and analyze the parameters output from the testing and achieve visualization to obtain the strengthening mechanism and deformation mechanism of the carbon nanotube reinforced nickel aluminide matrix composite; The total energy of the Meam potential function E consists of the following three parts: Wherein: is the Embedding Energy, representing the energy for an atom i to be embedded into the electron cloud; is the Background Electron Density at atom i contributed by the electron clouds of surrounding atoms; is the Pair Potential between atom i and j depending on the distance ; The embedding energy is a function of the background electron density and the expression is as follows: Wherein: is a material-related parameter; is a reference energy; Background electron density is a many-body term that takes into account the electron cloud distribution of surrounding atoms and is expressed as: Wherein: is an atom j contributes to the electron density at a distance ; is a screening function for considering many-body effects; The pair potential ( ) describes the direct interaction between two atoms and is expressed as: Wherein: and are atomic i and j effective charges; is a truncation function used to smoothly truncate the potential function at the cut-off radius ; e is the elementary charge; The total energy of the Airebo potential function E consists of the following three parts: Wherein: is the Rebo part, describing the interaction of covalent bonds; is the Lennard-Jones part, describing the non-bonding interaction (van der Waals force); is the torsional potential part, describing the influence of the intramolecular torsional angle.

2. The method according to claim 1, wherein Use Atomsk to construct the Ni3Al structural model and the carbon nanotube structural model, and set the lattice constant, lattice type, number of repeat units, number of atoms, and unit cell size of each structural model; among them, the number of repeat units of the carbon nanotube structural model is 2×2×1, the lattice type is m=n=8, armchair nanotube, the tube diameter is 8 - 12 Å, and the tube length is 70.2 Å.

3. The method according to claim 1, characterized in that, The basic simulation parameters are: adopt all-atom molecular dynamics, the unit system is metal, and at the same time, periodic boundary conditions are adopted in the x, y, and z directions, the cutoff radius is set to 10 - 12 Å, the neighbor list close number is 1.5 - 2.0 bin, and the simulation time step is 1 - 2 fs.

4. The method according to claim 1, wherein After describing the Lennard Jones relationship between different atoms, optimize the model.

5. The method according to claim 4, characterized in that, The optimization of the model is specifically as follows: The conjugate gradient method, which is an energy minimization algorithm, is used to preliminarily optimize the structure of the model with an energy tolerance of 10 -10 -10 -8 , a force tolerance of 10 -10 -10 -8 , and a maximum number of iterations of 100,000 to eliminate the unreasonable structure of the model and obtain a preliminary structural model.

6. The method according to claim 5, wherein Use the NPT ensemble to relax the preliminary structural model at a temperature of 298 - 300 K for 1 - 2 ns to obtain a stable structure.

7. The method according to claim 1, wherein The molecular dynamics calculation program includes a tensile property testing program and a compressive property testing program; among them, the tensile testing program and the compressive testing program respectively use the tensile command and the compressive command in the Lammps software.

8. The method according to claim 7, wherein Both the tensile testing program and the compressive testing program use the fix deform command in the Lammps software to obtain strain by simulating the deformation of the simulation box.

9. The method according to claim 1, characterized in that, The basic mechanical property testing is carried out in the NVT ensemble, using the Nose-Hoover heat bath to control the temperature and the V-Verlet method for integration.

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