A molecular dynamics modeling method for precipitated phase systems based on thermodynamic calculations

Abstract

This invention relates to a molecular dynamics modeling method for precipitated phase systems based on thermodynamic calculations. By combining thermodynamic calculations with molecular dynamics simulations, this invention can better reveal the influence of the composition, size, and orientation distribution of the precipitated phase on the evolution of microscopic defects and macroscopic mechanical properties of the system. This allows for molecular dynamics simulations to more closely approximate actual materials, enabling a more detailed study of the interactions between precipitated phase particles and various microstructural defects and their impact on various performance indicators of the system. This provides stronger support for material design and optimization. Therefore, this invention has broad application prospects and significant practical value.

Description

Technical Field

[0001] This invention relates to a method for establishing a molecular dynamics simulation model, and particularly to a method for molecular dynamics modeling of precipitated phase systems of composite metallic materials based on thermodynamic calculations, belonging to the field of material performance prediction and simulation calculation. Background Technology

[0002] In materials science and physics, the study of thermodynamics and kinetics is crucial for understanding the properties and behavior of materials. Precipitated phases are an important microstructure in metallic materials, and their formation and evolution significantly affect the mechanical properties and other physicochemical properties of the materials. Therefore, developing a method that can accurately simulate precipitated phase systems is of great significance.

[0003] Currently, molecular dynamics methods are mainly used to simulate the interaction between precipitated phase systems and various microstructural defects and their impact on the system's mechanical properties. However, traditional molecular dynamics methods often neglect the influence of thermodynamic factors when simulating precipitated phase systems, leading to significant discrepancies between simulation and experimental results. Furthermore, a review of existing literature and testing of commercially available molecular dynamics modeling tools such as Atomsk and Material Studio revealed that it is not yet possible to directly establish molecular dynamics models containing precipitated phase particles with different size distributions and orientations. Therefore, developing a molecular dynamics modeling method for precipitated phase systems based on thermodynamic calculations is of great significance for improving simulation accuracy and predictive capabilities. Summary of the Invention

[0004] The purpose of this invention is to provide a molecular dynamics modeling method for precipitated phase systems based on thermodynamic calculations. This method combines thermodynamic calculations with molecular dynamics simulations, which can better reveal the influence of the composition, size, and orientation distribution of the precipitated phase on the evolution of microscopic defects and macroscopic mechanical properties of the system through molecular dynamics simulations.

[0005] To achieve the above objectives, the present invention employs the following technical solution:

[0006] A molecular dynamics modeling method for precipitated phase systems based on thermodynamic calculations is proposed. This method combines thermodynamic calculations with molecular dynamics simulations, and specifically includes the following steps:

[0007] 1) Based on the composition and temperature of the simulated material system, calculate the composition and volume fraction of the matrix phase and precipitated phase when the material is in thermodynamic equilibrium at that temperature using thermodynamic software.

[0008] 2) Based on the thermodynamic calculation results, a two-phase model of the alloy material is established. Each precipitated phase particle is simplified to a sphere. The matrix phase is designed to contain precipitated phase particles of two diameters, namely D1 and D2, where D2>D1. The ratio of the total volume of the two precipitated phase particles is a:b. Based on the diameter and volume ratio of the two precipitated phase particles and the size of the system, the number of precipitated phase particles of the two diameters in the system is calculated to be N1 and N2, respectively.

[0009] 3) Randomly generate N1+N2 points in the matrix phase, and ensure that the distance between each point is not less than the diameter D2 of the largest precipitated phase particle in the system to prevent the precipitated phase particles from overlapping.

[0010] 4) At points N1+N2 in the matrix phase, with each point as the center, remove a section of material with a diameter of D. i The matrix phase, D i =D1 or D i =D2, and fill in the diameter as D. i The precipitated phase particles are arranged to ensure that the final system contains N1 precipitated phase particles with a diameter of D1 and N2 precipitated phase particles with a diameter of D2.

[0011] 5) The method for preparing matrix phase and precipitate particles is as follows: The models of both matrix phase and precipitate are based on the single crystal model of element or compound, and some atoms are randomly replaced according to the thermodynamic composition (for substitutional solid solutions) or atoms are directly inserted into interstitial positions (for interstitial solid solutions); After the solid solution models of matrix phase and precipitate are established, molecular dynamics relaxation is required at the corresponding temperature to eliminate thermal stress.

[0012] For the precipitated phase particles, it is also necessary to extract a diameter of D from the established sufficiently large cubic precipitated phase model. i The spherical precipitate particles can be randomly rotated at different angles along the x, y, and z directions according to the simulation requirements, so that each precipitate particle has a different orientation.

[0013] 6) Relax the established molecular dynamics model to prevent atoms from being too close or overlapping at the interface between the matrix phase and the precipitated phase, thus ensuring the smooth progress of the molecular dynamics simulation.

[0014] The thermodynamic software used is Thermo-Calc.

[0015] In step 2), a two-phase model of the alloy material is established using Python programming combined with Atomsk software.

[0016] The two-phase model of the alloy material in step 2) is a cuboid with each side length between 10-1000 nm.

[0017] In step 6), the established molecular dynamics model is relaxed using LAMMPS software.

[0018] Compared with existing technologies, the beneficial effects of this invention are:

[0019] This invention combines thermodynamic calculations with molecular dynamics simulations, enabling a more accurate description of the composition, size, and orientation distribution characteristics of precipitated phase particles. This allows for molecular dynamics simulations to more closely approximate actual materials, and enables a more detailed study of the interactions between precipitated phase particles and various microstructural defects, as well as their impact on various performance indicators of the system. This provides stronger support for material design and optimization. Therefore, this invention has broad application prospects and significant practical value. Attached Figure Description

[0020] Figure 1 This is a view of the Laves precipitate model.

[0021] Figure 2 This is a model view of Laves precipitate particles with a diameter of 20 nm.

[0022] Figure 3 This is a model view of Laves precipitate particles with a diameter of 6 nm.

[0023] Figure 4 This is a view of the ferrite matrix phase model.

[0024] Figure 5 This is a model view of the Laves precipitate particle distribution in the ferrite matrix phase of Model 1.

[0025] Figure 6 This is a model view of the Laves precipitate particle distribution after the ferrite matrix phase is hidden in Model 1.

[0026] Figure 7 This is a model view of the Laves precipitate particle distribution in the ferrite matrix phase of Model 2.

[0027] Figure 8 This is a model view of the Laves precipitate particle distribution after the ferrite matrix phase is hidden in Model 2.

[0028] Figure 9 This is a model view of the Laves precipitate particle distribution in a ferrite matrix phase.

[0029] Figure 10 This is a model view of the Laves precipitate particle distribution after the removal of the ferrite matrix phase in Model 3. Detailed Implementation

[0030] The technical solutions of the present invention will be described in detail below through embodiments. The following embodiments are merely exemplary and used to explain and illustrate the technical solutions of the present invention, and should not be construed as limiting the technical solutions of the present invention.

[0031] Example:

[0032] A molecular dynamics model was established for the 17Cr4W material system at 650℃, in which the mass fractions of Fe, Cr, and W were 79%, 17%, and 4%, respectively.

[0033] 1. The composition and volume fraction of the ferrite matrix phase and the Laves precipitate phase were calculated using Thermo-Calc software, as shown in Table 1-4:

[0034] Table 1. Mole fraction and mass fraction of each component in the 17Cr4W material system at 650℃

[0035]

[0036] Table 2. Proportions of each phase in the 17Cr4W material system at 650℃

[0037]

[0038] Table 3. Mole fraction and mass fraction of each component in the ferrite matrix phase of the 17Cr4W material system at 650℃

[0039]

[0040]

[0041] Table 4. Mole fraction and mass fraction of each component in the Laves precipitate of the 17Cr4W material system at 650℃

[0042]

[0043] 2. Based on the thermodynamic calculation results, a two-phase model of 17Cr4W material was established using Python programming combined with Atomsk software. The Laves precipitates are small spheres with diameters of 6 nm and 20 nm, respectively. Three model systems were designed. Based on the diameter and volume ratio of the two precipitate particles and the system size, the number of precipitate particles of the two diameters in the system was calculated.

[0044] Model 1: The diameter of all Laves precipitate particles is 6 nm, such as... Figure 5 , Figure 6 As shown:

[0045] The system is a cube with a side length of 24.3 nm, containing 32 Laves precipitates with a diameter of 6 nm, and a total atomic number of approximately 1.23 million. Thirty-two points are randomly generated in the matrix phase, ensuring that the distance between each point is no less than the diameter of the largest precipitate in the system (6 nm) to prevent overlap. At each of these 32 points in the matrix phase, with that point as the center, a 6 nm diameter portion of the matrix phase is removed and replaced with a 6 nm diameter precipitate, ensuring that the final system contains 32 precipitates with a diameter of 6 nm.

[0046] Model 2: The diameter of all Laves precipitate particles is 20 nm, such as... Figure 7 , Figure 8 As shown:

[0047] The system is a cube with a side length of 43 nm, containing five Laves precipitates with a diameter of 20 nm. The total number of atoms in the system is approximately 6.74 million. Five points are randomly generated in the matrix phase, ensuring that the distance between each point is no less than 20 nm from the diameter of the largest precipitate in the system to prevent overlap of the precipitates. Then, at each of the five points in the matrix phase, with that point as the center, a 20 nm diameter portion of the matrix phase is removed and replaced with a 20 nm diameter precipitate, ensuring that the final system contains five 20 nm diameter precipitates.

[0048] Model 3: In the Laves precipitate, spheres with a diameter of 6 nm account for 30%, and spheres with a diameter of 20 nm account for 70% (volume ratio), such as... Figure 9 , Figure 10 As shown:

[0049] The system is a cube with a side length of 43 nm, containing 3 Laves precipitates with a diameter of 20 nm and 47 Laves precipitates with a diameter of 6 nm, for a total of approximately 6.74 million atoms. Fifty points are randomly generated in the matrix phase, ensuring that the distance between each point is no less than 20 nm from the diameter of the largest precipitate in the system to prevent overlap of precipitates. Sequentially, at each of the 50 points in the matrix phase, with that point as the center, 3 spherical matrix phase particles with a diameter of 20 nm and 47 spherical matrix phase particles with a diameter of 20 nm are removed, and the corresponding positions are filled with 3 precipitates with a diameter of 20 nm and 47 precipitates with a diameter of 20 nm.

[0050] 3. The method for preparing the ferrite matrix phase and Laves precipitate particles is as follows (e.g. Figures 1-4 As shown):

[0051] Ferrite matrix phase: A pure iron model with a BCC structure of appropriate size was constructed, and then 17.38% of the Fe atoms were randomly replaced with Cr atoms, and 0.97% of the Fe atoms were replaced with W atoms. Molecular dynamics was used to relax the ferrite matrix phase at 650 °C to eliminate thermal stress.

[0052] Laves precipitates: A pure iron model of the Laves phase structure of appropriate size was constructed, and then 9.54% of the Fe atoms were randomly replaced with Cr atoms, and 62.53% of the Fe atoms were replaced with W atoms. Molecular dynamics was used to relax the Laves precipitates at 650 °C to eliminate thermal stress.

[0053] Laves precipitate particles: In a sufficiently large cubic Laves precipitate model, spherical Laves precipitate particles with diameters of 6 nm and 20 nm were excavated. Before placing each Laves precipitate particle into a spherical cavity excavated in the matrix phase, the orientation of each Laves precipitate particle was determined by rotating it at different random angles along the x, y, and z directions.

[0054] 4. Relax the established molecular dynamics model using LAMMPS software to prevent atoms from being too close together or overlapping at the interface between the matrix phase and the precipitated phase, thus ensuring the smooth progress of the molecular dynamics simulation.

[0055] The above description is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any equivalent substitutions or modifications made by those skilled in the art within the scope of the technology disclosed in the present invention, based on the technical solution and inventive concept of the present invention, should be covered within the scope of protection of the present invention.

Claims

1. A molecular dynamics modeling method for precipitated phase systems based on thermodynamic calculations, characterized in that, This modeling method combines thermodynamic calculations with molecular dynamics simulations, and the specific method includes the following steps: 1) Based on the composition and temperature of the simulated material system, calculate the composition and volume fraction of the matrix phase and precipitated phase when the material is in thermodynamic equilibrium at that temperature using thermodynamic software; 2) Based on the thermodynamic calculation results, a two-phase model of the alloy material is established. Each precipitate particle is simplified to a sphere. The matrix phase is designed to contain precipitate particles of two different diameters, with diameters D1 and D2, where D2 > D1. Based on the diameters, volume ratios, and system size of the two precipitate particles, the number of precipitate particles of the two different diameters in the system is calculated to be N1 and N2, respectively. 3) Randomly generate N1+N2 points in the matrix phase, and ensure that the distance between each point is not less than the diameter D2 of the largest precipitated phase particle in the system to prevent the precipitated phase particles from overlapping. 4) At points N1+N2 in the matrix phase, with each point as the center, remove a section of material with a diameter of D. i The matrix phase, D i =D1 or D i =D2, and fill in the diameter as D. i The precipitated phase particles are arranged to ensure that the final system contains N1 precipitated phase particles with a diameter of D1 and N2 precipitated phase particles with a diameter of D2. 5) The method for preparing matrix phase and precipitate particles is as follows: The models of matrix phase and precipitate are based on the single crystal model of element or compound, and some atoms are randomly replaced or directly inserted into interstitial positions according to the thermodynamic composition; After the solid solution models of matrix phase and precipitate are established, molecular dynamics relaxation is required at the corresponding temperature to eliminate thermal stress. For the precipitated phase particles, it is also necessary to extract a diameter of D from the established sufficiently large cubic precipitated phase model. i The spherical precipitate particles can be randomly rotated at different angles along the x, y, and z directions according to the simulation requirements, so that each precipitate particle has a different orientation. 6) Relax the established molecular dynamics model.

2. The molecular dynamics modeling method for precipitated phase systems based on thermodynamic calculations according to claim 1, characterized in that, The thermodynamic software used is Thermo-Calc.

3. The molecular dynamics modeling method for precipitated phase systems based on thermodynamic calculations according to claim 1, characterized in that, In step 2), a two-phase model of the alloy material is established using Python programming combined with Atomsk software.

4. The molecular dynamics modeling method for precipitated phase systems based on thermodynamic calculations according to claim 1, characterized in that, The two-phase model of the alloy material in step 2) is a cuboid with each side length between 10-1000 nm.

5. The molecular dynamics modeling method for precipitated phase systems based on thermodynamic calculations according to claim 1, characterized in that, In step 6), the established molecular dynamics model is relaxed using LAMMPS software.

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