Method for simulating carbon nanotube reinforced nickel-3 aluminum-based composite material based on molecular dynamics

Abstract

The invention belongs to the technical field of molecular dynamics simulation, and provides a method for simulating a carbon nanotube reinforced nickel-3-aluminum-based composite material based on molecular dynamics. The method specifically comprises the following steps: by taking nickel-3-aluminum (Ni3Al) as a matrix and a carbon nano tube as an embedding body, accurately controlling the position and the tube diameter of the nano tube, constructing a carbon nano tube reinforced nickel-3-aluminum-based composite material structure model by adopting a molecular dynamics simulation method, and realizing uniform dispersion of the carbon nano tube in the nickel-3-aluminum (Ni3Al) matrix, so as to obtain the carbon nano tube reinforced nickel-3-aluminum-based composite material. The problem of agglomeration of the carbon nanotubes in the matrix is avoided; and meanwhile, the strength of the nickel-3 aluminum-based composite material is enhanced. Besides, through a molecular dynamics simulation method, the strength of the carbon nanotube reinforced Ni3Al-based composite material can be accurately predicted, and meanwhile, interaction mechanisms, including a strengthening mechanism and a deformation mechanism, of the carbon nanotube and the Ni3Al-based composite material in the composite material can be better described.

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 (Ni 3 Al) is an intermetallic compound with high strength, high hardness and good oxidation resistance, and is widely used in the fields of aerospace, automobile manufacturing and electronics. However, due to its brittleness and low fracture toughness, its application scope 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 enhancing metal matrix composites. With the development of nanotechnology, it has become possible to introduce nanotubes into the nickel aluminide (Ni 3 Al) matrix to form nanotube-reinforced nickel aluminide (Ni 3 Al) matrix composites. Such composites can not only maintain the high strength and high hardness of nickel aluminide (Ni 3 Al), but also significantly improve its fracture toughness and fatigue resistance.

[0004] Nanotube-reinforced nickel aluminide (Ni 3 Al) 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 synergistically reinforced nickel-aluminum matrix composite material and its preparation method, using carbon nanotubes and phosphates as synergistic reinforcement 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 material has excellent tribological properties in a wide temperature range.

[0005] Although these methods can achieve the dispersion of nanotubes in nickel aluminide (Ni 3Uniform dispersion in the matrix, however, due to the surface energy and interaction forces of the nanotubes, it is easy for the nanotubes to agglomerate in the matrix, thus affecting the properties of the composite material. 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 the nickel aluminide (Ni 3 Al) matrix and how to reduce the production cost are urgent problems to be solved in this field at present. In addition, the existing technologies do not have a deep enough understanding of the interaction mechanism between the nanotubes and the nickel aluminide (Ni 3 Al) matrix, which also limits the further improvement of the properties of nanotube-reinforced nickel aluminide (Ni 3 Al) 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 microstructure 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 (Ni 3 Al) composites. Summary of the Invention

[0008] In view of 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 (CNT) in the nickel aluminide (Ni 3 Al) matrix. In addition, the strength of carbon nanotube (CNT)-reinforced nickel aluminide (Ni 3 Al) matrix composites can be accurately predicted, and the interaction mechanism between CNT and Ni 3 Al matrix can be clarified.

[0009] The present invention is realized through the following technical solutions: A method for carbon nanotube-reinforced nickel aluminide matrix composites based on molecular dynamics simulation, comprising the following steps: (1) Respectively construct a Ni 3 Al structural model and a carbon nanotube structural model. In the xy coordinate plane of the Ni 3 Al structural model, taking the four vertices of a square region with a side length of 2.5 - 5 nm as the centers and 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 Ni 3 Al composite material model; (2) Set Ni 3Mix the potential functions of Al and carbon nanotubes, set the basic simulation parameters, and describe the Lennard Jones relationship between different atoms; (3)Write a molecular dynamics calculation program to implement basic mechanical property tests and output basic performance parameters; (4)Process and analyze the parameters output from the tests and visualize them to obtain the strengthening mechanism and deformation mechanism of carbon nanotube reinforced nickel aluminide matrix composites.

[0010] Furthermore, use Atomsk to construct the Ni 3 Al structural model and 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.

[0011] Even further, the basic simulation parameters are as follows: use 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 time step is 1-2 fs.

[0012] Furthermore, the Ni 3 Al 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 the potential functions using the Mix Arithmetic rule.

[0013] Specifically as follows: ① The Ni 3 Al alloy adopts the Meam potential function, and the total energy of the Meam potential function E consists of the following three parts:

[0014] Among them: is the embedding energy, indicating the energy for an atom i to be embedded in the electron cloud; is the background electron density at the atom i , contributed by the electron clouds of surrounding atoms; is the pair potential between the atoms i and j , depending on the distance between them 。

[0015] Furthermore, the embedding energy is a function of the background electron density , and the expression is:

[0016] where: is a material-related parameter; is the reference energy.

[0017] Even further, the background electron density is a many-body term that takes into account the electron cloud distribution of surrounding atoms, and the expression is:

[0018] where: is the contribution of atom j to the electron density at a distance ; is the screening function (ScreeningFunction) used to consider many-body effects.

[0019] Furthermore, the pair potential ( ) describes the direct interaction between two atoms, and the expression is:

[0020] where: and are the effective charges of atoms i and j ; is the cutoff function used to smoothly cut off the potential function at the cutoff radius ; e is the elementary charge.

[0021] 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:

[0022] 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 torsion potential part, which describes the influence of the intramolecular torsion angle.

[0023] Furthermore, the torsion potential part has the expression:

[0024] Wherein: 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.

[0025] Furthermore, the Lennard-Jones part has the expression:

[0026] Wherein: is the potential well depth; is the equilibrium distance between atoms.

[0027] Furthermore, the torsional potential part has the expression:

[0028] Wherein: wijkl is the torsional angle; is the torsional potential function, which usually takes the form of a cosine function.

[0029] ③ The parameter combinations between different types of atoms conform to the Mix Arithmetic rule, and the expression is:

[0030]

[0031] Wherein, 、 and are respectively 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; 、 and are respectively the average equilibrium distance between atoms i and j, the equilibrium distance of atom i, and the equilibrium distance of atom j.

[0032] Furthermore, after describing the Lennard Jones relationship between different atoms, the model is optimized.

[0033] Furthermore, the specific optimization of the model is as follows: The preliminary structural optimization of the model is carried out using the energy minimization algorithm, with the energy tolerance = 10 -10 -10 -8 and the force tolerance = 10-10 -10 -8 , with a maximum number of iterations of 100,000, eliminating the unreasonable structure of the model to obtain a preliminary structural model; the energy minimization algorithm is the conjugate gradient method.

[0034] 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.

[0035] 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.

[0036] Furthermore, both the tensile test program and the compressive test program use the fixdeform command in the Lammps software to obtain strain for the material by simulating the deformation of the box.

[0037] Further, the basic mechanical property test is carried out under the NVT ensemble, using the Nose - Hoover heat bath for temperature control and the V - Verlet method for integration.

[0038] Specifically, the molecular dynamics calculation is to run the above calculation programs (tensile property test program and compressive property test program) on the server, obtain the binary calculation results of the output parameters, and perform data analysis on the calculation results.

[0039] More specifically, the data analysis process is as follows: for the above - output parameters, write Python code to process and analyze the calculation results to obtain the stress - strain curve and Young's modulus, use software such as Ovito to visualize the tensile and compressive processes and phenomena such as dislocations during this mechanical change process, and through these, obtain the strengthening mechanism and corresponding deformation mechanism of the alloy matrix composite material.

[0040] Compared with the prior art, the beneficial effects of the present invention are as follows: The present invention embeds carbon nanotubes (CNT) into the nickel aluminide (Ni 3 Al) matrix through molecular dynamics simulation technology, constructs a carbon nanotube (CNT) reinforced nickel aluminide matrix composite material (Ni 3 Al@CNT composite material) model, and through the selection of the potential function and a suitable mixing method, precisely controls the distribution and orientation of carbon nanotubes (CNT) in the nickel aluminide (Ni 3 Al) matrix (divide the Ni 3 Al lattice into 4 square regions on the xy plane, and use the center of the square as the center of the diameter of the carbon nanotube (CNT), and evenly embed 4 CNT structural units), realizing the carbon nanotubes (CNT) in the nickel aluminide (Ni3 uniformly distributed in the (Al) matrix, solving the problem of agglomeration of carbon nanotubes (CNTs) in the nickel aluminide (Ni 3 Al) matrix, avoiding the problems of stress concentration and excessive local stress, thereby 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 and can more accurately predict the mechanical properties such as the strength of the carbon nanotube (CNT)-reinforced nickel aluminide (Ni 3 Al) matrix composite material, so that the interaction mechanism between the carbon nanotube (CNT) and the nickel aluminide (Ni 3 Al) matrix is also better described. Description of the Drawings

[0041] Figure 1 is a flowchart of the method for molecular dynamics simulation of Ni 3 Al@CNT composite material of the present invention; Figure 2 is a schematic structural diagram of the Ni 3 Al@CNT composite material obtained by molecular dynamics simulation; where A is a top view and B is a front view; Figure 3 is for Ni 3 Al alloy and the Ni 3 Al@CNT composite material obtained by molecular dynamics simulation, a tensile stress-strain curve graph; Figure 4 is for Ni 3 Al@CNT composite material, a stress-strain curve graph at different strain rates; Figure 5 is for Ni 3 Al@CNT composite material, a relationship curve graph between tensile strength and strain rate; Figure 6 is for Ni 3 Al@CNT composite material, a relationship curve graph between Young's modulus and strain rate; Figure 7 is for Ni 3 Al@CNT composite material, a visualization graph of the tensile process and the corresponding dislocation graph; Figure 8 is for Ni 3 Al@CNT composite material, a visualization graph at the time of fracture and the corresponding dislocation graph. Detailed Embodiments

[0042] 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 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.

[0043] Embodiment 1: A method for preparing carbon nanotube reinforced nickel aluminide matrix composites based on molecular dynamics simulation, comprising the following steps: (1) Construct an Ni 3 Al structural model and a carbon nanotube structural model respectively. In the xy coordinate plane of the Ni 3 Al structural model, taking the four vertices of a square region with a side length of 2.5 - 5 nm as the centers and 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 Ni 3 Al composite material model; (2) Set the potential functions of Ni 3 Al and carbon nanotubes and mix them, and set the basic simulation parameters to describe the Lennard Jones relationship between different atoms; (3) Write a molecular dynamics calculation program to implement basic mechanical property tests and output basic property parameters; (4) Process and analyze the parameters output from the tests and visualize them to obtain the strengthening mechanism and deformation mechanism of the carbon nanotube reinforced nickel aluminide matrix composites.

[0044] Embodiment 2: A method for preparing carbon nanotube reinforced nickel aluminide matrix composites based on molecular dynamics simulation, comprising the following steps: (1) Construct an Ni 3 Al structural model and a carbon nanotube structural model respectively. In the xy coordinate plane of the Ni 3 Al structural model, taking the four vertices of a square region with a side length of 2.5 - 5 nm as the centers and 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 Ni 3 Al composite material model; (2) Set the potential functions of Ni 3 Al and carbon nanotubes and mix them, and set the basic simulation parameters to describe the Lennard Jones relationship between different atoms; (3) Write a molecular dynamics calculation program to implement basic mechanical property tests and output basic property parameters; (4)Process and analyze the parameters of the test output and achieve visualization to obtain the strengthening mechanism and deformation mechanism of the carbon nanotube-reinforced nickel aluminide matrix composite.

[0045] Further, use Atomsk to construct the Ni 3 Al 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, the tube diameter is 8 - 12 Å, and the tube length is 70.2 Å.

[0046] In some preferred embodiments of the present invention, step (1) embedding the carbon nanotube model into the Ni 3 Al structural model is specifically as follows: In the xy coordinate plane of the Ni 3 Al structural 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 Ni 3 Al composite material model.

[0047] 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 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.

[0048] Further, the Ni 3 Al 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 the Mix Arithmetic rule mixed potential function.

[0049] Specifically as follows: ① The Ni 3 Al alloy adopts the Meam potential function, and the total energy of the Meam potential function E consists of the following three parts:

[0050] Among them: is the embedding energy, indicating the energy of the atom i embedded in the electron cloud; is the atom iThe background electron density at [location], contributed by the electron clouds of surrounding atoms; is the atom i and j the pair potential between [atoms], depending on the distance between them .

[0051] Furthermore, the embedding energy is a function of the background electron density and is expressed as:

[0052] where: is a material-related parameter; is the reference energy.

[0053] 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:

[0054] where: is the contribution of atom j to the electron density at distance ; is the screening function, used to account for many-body effects.

[0055] Furthermore, the pair potential ( ) describes the direct interaction between two atoms and is expressed as:

[0056] 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.

[0057] 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:

[0058] where: is the Rebo part, describing the interaction of covalent bonds; is the Lennard-Jones part, describing non-bonded interactions (van der Waals forces); is the torsional potential part, describing the influence of the torsional angle within the molecule.

[0059] Furthermore, the torsional potential part has the expression:

[0060] where: is the repulsive potential; is the attractive potential; is the bond order parameter, used to describe the bond strength and many-body effects.

[0061] Furthermore, the Lennard-Jones part has the expression:

[0062] where: is the depth of the potential well; is the equilibrium distance between atoms.

[0063] Furthermore, the torsional potential part has the expression:

[0064] where: wijkl is the torsional angle; is the torsional potential function, usually in the form of a cosine function.

[0065] ③ The parameter combinations between different types of atoms conform to the Mix Arithmetic rule, and the expression is:

[0066]

[0067] 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.

[0068] Furthermore, after obtaining the Lennard Jones relationship between different atoms, it is necessary to optimize the structure of the model, that is, minimize the energy.

[0069] 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 100000. The unreasonable structure of the model is eliminated to obtain a preliminary structural model; the energy minimization algorithm is the conjugate gradient method.

[0070] 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.

[0071] Furthermore, 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.

[0072] Furthermore, both the tensile test program and the compression test program use the fixdeform command in the Lammps software to obtain strain by simulating the deformation of the box.

[0073] Furthermore, the basic mechanical property test is carried out under the NVT ensemble, with temperature control using the Nose - Hoover thermostat and integration using the V - Verlet method.

[0074] Specifically, after running the above calculation programs (tensile property test program and compression property test program) on the server in molecular dynamics calculation, the binary calculation results of the output parameters are obtained, and data analysis is performed on the calculation results.

[0075] 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 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.

[0076] Example 3: The following details the method of the present invention based on the molecular dynamics simulation process of a specific Ni 3 Al@CNT composite material and the simulation of tensile properties. The specific calculation process not detailed refers to Example 2.

[0077] A method for enhancing Ni₃Al-based composites with carbon nanotubes based on molecular dynamics simulation. The process of molecular dynamics simulation is as Figure 1 shown, and the specific method is as follows: (1) Construct a nanostructure model of Ni 3 ₃Al and a carbon nanotube (CNT) structure model respectively, and embed the carbon nanotubes into the Ni 3 ₃Al nanostructure model to obtain a Ni 3 ₃Al@CNT composite material model; the specific steps are as follows: Step S1: Use the Atomsk software to construct a Ni 3 ₃Al unit cell and a CNT unit cell respectively. The relevant parameters are shown in Table 1.

[0078] Table 1 Relevant parameters of Ni 3 ₃Al unit cell and CNT unit cell

[0079] Step S2: Next, in the xy coordinate plane of the Ni 3 ₃Al structure, centered at the four vertices of a square region with a side length of 5 nm, that is, 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 Ni 3 ₃Al structure model 4 times to obtain a Ni 3 ₃Al@CNT composite material model, as Figure 2 shown, where yellow represents aluminum atoms, blue represents nickel atoms, and red represents CNT.

[0080] (2) Set the potential functions of Ni 3 ₃Al and CNT, and mix them to describe the Lennard Jones relationship between different atoms. The specific process is as follows: Adopt all-atom molecular dynamics, with the unit system being metal. At the same time, periodic boundary conditions are adopted in the x, y, and z directions. The cut-off radius is set to 12 Å, the neighbor list close 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 an 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; 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 Ni 3 Al@CNT composite for mechanical property testing.

[0081] (3) Write a molecular dynamics calculation program to implement basic mechanical property testing, which specifically includes the following aspects: 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.

[0082] The stress-strain curves of Ni 8 / s under the condition of a strain rate of 10 3 Al alloy and Ni 3 Al@CNT composite obtained by molecular dynamics simulation are as Figure 3 shown. It can be seen that CNT is embedded in the Ni 3 Al alloy matrix, significantly strengthening the tensile strength of the Ni 3 Al alloy matrix, and there are stress fluctuations during the subsequent yield stage.

[0083] The stress-strain curves of Ni 3 Al@CNT composite 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.

[0084] At high strain rates, materials exhibit higher strength because the increase in strain rate restricts the movement of dislocations within the material, leading to stress concentration and increased strength. At high strain rates, an obvious strain rate strengthening effect is exhibited, that is, as the strain rate increases, the strength increases significantly.

[0085] Ni 3 The relationship curve between the tensile strength of the Ni@CNT composite material and the strain rate is shown in Figure 5 As shown, it can be seen that: high strain rates can cause changes in the strength and stress of materials, showing higher tensile strength because the movement of dislocations within the material is restricted, leading to stress concentration and increased strength.

[0086] 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: 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 external loads, and the Young's modulus mainly depends on the intrinsic stiffness of the material; At medium strain rates (10 8 -10 9 / s), as the strain rate increases, the movement of dislocations within the material may be restricted, resulting in stress concentration and an increase in the Young's modulus. At this time, the material may exhibit a certain strain rate strengthening effect, that is, the Young's modulus increases with the increase of the strain rate; At high strain rates (10 9 -10 10 / s), the microstructure within the material (such as dislocations, grain boundaries, etc.) cannot respond to external loads in a timely manner, and the material exhibits higher stiffness and lower plastic deformation ability. In addition, high strain rates may cause a local temperature increase in the material (due to the conversion of plastic work into heat energy), thereby further affecting the Young's modulus.

[0087] (4) Process and analyze the parameters of the test output and realize visualization to obtain the strengthening and deformation mechanisms of the composite material.

[0088] Visualize the above tensile process and the dislocation phenomenon during the tensile process using Ovito software, and the results are as shown in Figure 7 and Figure 8 As shown. From Figure 7 and Figure 8 it can be seen that: 4.1 Dislocation pinning effect It is shown by molecular dynamics simulation that carbon nanotubes in Ni 3As a rigid reinforcement phase in the Al matrix, it forms a strong interfacial bond with the matrix through Lennard Jones interaction. During the tensile process, when the dislocation lines (linear defects visible in the visualization diagram) move to the carbon nanotube interface, they are blocked and form 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.

[0089] 4.2 Stress transfer mechanism 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

[0090] the higher stress plateau of the composite material in 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 reticular structure in the dislocation diagram) is formed around the carbon nanotubes. This restricted dislocation movement delays the crack initiation (corresponding to Figure 3 the higher fracture strain of the composite material in

[0091] 4.4 Carbon nanotube bridging effect Figure 8 Visualization in Figure 3 shows that when the crack propagates to the carbon nanotube region, the interfacial bond maintained by Lennard Jones interaction causes the CNT to exhibit a pulling-out behavior. The carbon nanotubes bridge both sides of the crack, maintaining the high strength of the matrix while improving the fracture toughness. This process consumes additional energy (corresponding to

[0092] It should be noted that the above content is only used to illustrate the technical solution of the present invention, rather than a limitation on the protection scope of the present invention. Any simple modification or equivalent replacement made by those of ordinary skill in the art to the technical solution of the present invention does not depart from the essence and scope of the technical solution of the present invention.

Claims

1. A method for simulating carbon nanotube-reinforced nickel-aluminum-based composite materials based on molecular dynamics, characterized in that: The following steps are involved: (1) A Ni3Al structural model and a carbon nanotube structural model were constructed respectively. In the xy coordinate plane of the Ni3Al structural model, the atoms in the z-axis direction were deleted and carbon nanotubes were embedded in a square area with a side length of 2.5-5 nm and a radius of 8-12 Å, thereby obtaining a carbon nanotube-reinforced Ni3Al composite material model. (2) Setting the potential function of Ni3Al and carbon nanotubes and mixing them, setting the basic simulation parameters, and describing the Lennard Jones relationship between different atoms; (3) Write a molecular dynamics calculation program to achieve basic mechanical properties testing and basic performance parameter output; (4) The test output parameters are processed, analyzed and visualized to obtain the strengthening mechanism and deformation mechanism of the carbon nanotube-reinforced nickel-aluminum matrix composite material.

2. The method according to claim 1, characterized in that Atomsk was used to construct the Ni3Al structural model and the carbon nanotube structural model, and the lattice constant, lattice type, number of repeating units, number of atoms and unit cell size of each structural model were set; among them, the carbon nanotube structural model had a repeating unit number of 2×2×1, a lattice type of m=n=8, an armrest-type nanotube, a tube diameter of 8-12 Å, and a tube length of 70.2 Å.

3. The method according to claim 1, characterized in that The basic simulation parameters are: all-atom molecular dynamics, metal as the unit system, periodic boundary conditions in the x, y, and z directions, a cutoff radius of 10-12 Å, a neighbor list of 1.5-2.0 bins, and a simulation step of 1-2 fs.

4. The method according to claim 1, characterized in that 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 mixed potential function.

5. The method according to claim 4, characterized in that After describing the Lennard Jones relationships between different atoms, the model was optimized.

6. The method according to claim 5, characterized in that The specific optimization of the model is as follows: the energy minimization algorithm is used to perform preliminary structural optimization of the model, and the energy tolerance is 10 -10 -10 -8 , force tolerance = 10 -10 -10 -8 , the maximum number of iterations is 100000, the unreasonable structure of the model is eliminated, and a preliminary structural model is obtained; the energy minimization algorithm is the conjugate gradient method.

7. The method according to claim 6, characterized in that The preliminary structural model was relaxed at 298-300 K for 1-2 ns under the NPT ensemble to obtain a stable structure.

8. The method according to claim 1, characterized in that The molecular dynamics calculation program includes a tensile performance test program and a compression performance test program; wherein the tensile test program and the compression test program respectively use the tensile command and the compression command in the Lammps software.

9. The method according to claim 8, characterized in that The tensile test program and the compression test program both use the fix deform command in the Lammps software to simulate the deformation of the box so that the material acquires strain.

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

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