Simulation method, device, equipment and medium for growth of sintered neodymium iron boron crystal grains

Abstract

The invention relates to the technical field of phase field methods, in particular to a method, a device, equipment and a medium for simulating growth of sintered NdFeB crystal grains, and the method comprises the following steps: constructing a phase field simulation model of a NdFeB multi-element and multi-phase system, and describing total free energy of the NdFeB multi-element and multi-phase system; field variables in the neodymium iron boron multi-element and multi-phase system are determined, a kinetic equation of the phase-field simulation model is established, and the kinetic equation is based on the total free energy minimization principle and used for describing evolution of the field variables along with time and space; and solving the evolution process and size information of the microstructure of the neodymium iron boron crystal grains grown under the predetermined sintering condition based on the kinetic equation. According to the technical scheme, the evolution process and size information of the microstructures of the neodymium iron boron crystal grains growing under various preset sintering conditions can be accurately simulated, the reasonable sintering conditions can be adjusted and designed based on the simulation result so as to obtain the needed sintered neodymium iron boron crystal grains, and a simulation theory is achieved to guide a prediction experiment.

Description

Technical Field

[0001] The present disclosure relates to the technical field of phase field method, and in particular to a simulation method, device, equipment and medium for sintered NdFeB grain growth. Background Art

[0002] Sintered NdFeB permanent magnet materials are widely used in many fields such as motor industry, medical equipment, wind power generation, electric vehicles, aerospace, etc. due to their extremely high comprehensive performance. They are the permanent magnet materials with the best market application prospects. With the development of integration, miniaturization and intelligence of modern science and technology and information industry, the emergence of sintered NdFeB permanent magnet materials with ultra-high comprehensive performance has effectively promoted the development of more emerging industries. With the continuous advancement of science and technology, higher requirements are put forward for the magnetic properties of sintered NdFeB permanent magnet materials. High remanence, high coercive force and high magnetic energy product magnets have become an important trend for future development. Among them, the magnetic structure of sintered NdFeB magnets is closely related to the process and composition of sintered magnets. Therefore, process optimization of sintered NdFeB is one of the effective ways to improve the magnetic properties of sintered NdFeB magnets.

[0003] There are many factors that affect the final magnetic properties of NdFeB magnets during the sintering process, such as sintering time, sintering temperature, powder particle size distribution, sintering pressure, etc. If you want to obtain NdFeB sintered magnets with the desired performance, you need to comprehensively control these factors. The traditional NdFeB sintering industry mainly relies on experience for sintering, and the product needs to be tried and corrected many times from design to production. There is blindness, high cost and it is not conducive to improving the magnetic properties of sintered NdFeB. Therefore, how to reasonably adjust the process factors of designing sintered NdFeB has become a technical problem that needs to be solved urgently. Summary of the invention

[0004] In order to solve the problems in the related art, the embodiments of the present disclosure provide a method, device, equipment and medium for simulating the grain growth of sintered NdFeB.

[0005] In a first aspect, the present disclosure provides a method for simulating grain growth of sintered NdFeB, comprising:

[0006] Constructing a phase field simulation model of a NdFeB multi-component multi-phase system to describe the total free energy of the NdFeB multi-component multi-phase system;

[0007] Determine the field variables in the NdFeB multi-component and multi-phase system, and establish a kinetic equation of the phase field simulation model, wherein the kinetic equation is based on the total free energy minimization principle and is used to describe the evolution of the phase field variables over time and space;

[0008] The evolution process and size information of the microstructure of NdFeB grains grown under predetermined sintering conditions are solved based on the kinetic equation.

[0009] In a possible implementation, the method of solving the evolution process and size information of the microstructure of NdFeB grains grown under different sintering conditions based on the kinetic equation includes:

[0010] By controlling the variable method, fixing the sintering time and the initial grain size, the average grain size and microstructure of NdFeB grains at different sintering temperatures were simulated based on the kinetic equation to minimize the total free energy.

[0011] In a possible implementation, the method of solving the evolution process and size information of the microstructure of NdFeB grains grown under different sintering conditions based on the kinetic equation includes:

[0012] By controlling the variable method, fixing the sintering temperature and the initial grain size, and simulating the average grain size and microstructure of the NdFeB grains at different sintering times based on the kinetic equation to minimize the total free energy.

[0013] In a possible implementation, the phase field simulation model of the NdFeB multi-component multi-phase system is constructed to describe the total free energy of the multi-component multi-phase system, including:

[0014] A phase field simulation model was established based on the Ginzburg-Landau theory and the NdFeB multi-component and multi-phase system.

[0015] In a possible implementation, the total free energy F of the NdFeB multi-component multi-phase system is described as follows:

[0016]

[0017] Where F is the total free energy of the system, κ ρ and κ η are the surface and grain boundary energy gradient coefficients, respectively. Function f(ρ, {η(α)}) is the non-equilibrium volume chemical free energy density; f(ρ, {η(α)}) = Aρ 2 (1-ρ) 2 +B[ρ 2 +6(1-ρ)∑ α η 2 (α)-4(2-ρ)∑ α η 3 (α)+3(∑ α η 2 (α) 2 ]; A and B are constants, the density field ρ is a conservative field, η(α) is the phase field order parameter, η(α)=1 at the αth grain, η(α)=0 at other grains, and α is the total number of grains;

[0018] In a possible implementation, the kinetic equation includes:

[0019]

[0020] Where t is the sintering time, and M represents the coefficient related to material migration;

[0021] The relationship between M and the diffusion coefficient D is as follows:

[0022]

[0023] Where D is the diffusion coefficient, V m is the molar volume of NdFeB, R is the molar gas constant, and T is the sintering temperature;

[0024] The diffusion coefficient D is expressed as follows:

[0025] D=D V φ(ρ)+D vap [1-φ(ρ)]+D s ρ(1-ρ)+D gb ∑ α ∑ α≠α′ η α η α′ ;

[0026] Among them, D V , D vap , D s and D gb represent the bulk diffusion, gas diffusion, surface diffusion and grain boundary diffusion coefficients respectively, α′ represents the grain number except the αth grain, and φ(ρ) is the weight function.

[0027] In a second aspect, the present disclosure provides a device for simulating sintered NdFeB grain growth, comprising:

[0028] A model building module is configured to build a phase field simulation model of a NdFeB multi-component multi-phase system to describe the total free energy of the NdFeB multi-component multi-phase system;

[0029] An equation building module is configured to determine the field variables in the NdFeB multi-component and multi-phase system and to build a kinetic equation of the phase field simulation model, wherein the kinetic equation is based on the total free energy minimization principle and is used to describe the evolution of the phase field variables over time and space;

[0030] The growth simulation module is configured to solve the microstructure evolution process and size information of the NdFeB grains grown under predetermined sintering conditions based on the kinetic equation.

[0031] In a possible implementation, the growth simulation module is configured as follows:

[0032] By controlling the variable method, fixing the sintering time and the initial grain size, and simulating the average grain size and microstructure of NdFeB grains at different sintering temperatures based on the kinetic equation to minimize the total free energy;

[0033] In a possible implementation, the growth simulation module is configured as follows:

[0034] By controlling the variable method, fixing the sintering temperature and the initial grain size, and simulating the average grain size and microstructure of the NdFeB grains at different sintering times based on the kinetic equation to minimize the total free energy.

[0035] In a possible implementation, the phase field simulation model of the NdFeB multi-component multi-phase system is constructed to describe the total free energy of the multi-component multi-phase system, including:

[0036] A phase field simulation model was established based on the Ginzburg-Landau theory and the NdFeB multi-component and multi-phase system.

[0037] The total free energy F of the NdFeB multi-component multi-phase system is described as follows:

[0038]

[0039] Where F is the total free energy of the system, κ ρ and κ η are the surface and grain boundary energy gradient coefficients, respectively. Function f(ρ, {η(α)}) is the non-equilibrium volume chemical free energy density; f(ρ, {η(α)}) = Aρ 2 (1-ρ) 2 +B[ρ 2 +6(1-ρ)∑ α η 2 (α)-4(2-ρ)∑ α η 3 (α)+3(∑ α η 2 (α) 2 ]; A and B are constants, the density field ρ is a conservative field, η(α) is the phase field order parameter, η(α)=1 at the αth grain, η(α)=0 at other grains, and α is the total number of grains;

[0040] In a possible implementation, the kinetic equation includes:

[0041]

[0042] Where t is the sintering time, and M represents the coefficient related to material migration;

[0043] The relationship between M and the diffusion coefficient D is as follows:

[0044]

[0045] Where D is the diffusion coefficient, V m is the molar volume of NdFeB, R is the molar gas constant, and T is the sintering temperature;

[0046] The diffusion coefficient D is expressed as follows:

[0047] D=D V φ(ρ)+D vap [1-φ(ρ)]+D s ρ(1-ρ)+D gb ∑ α ∑ α≠α′ η α η α′ ;

[0048] Among them, D V , D vap , D s and D gb represent the bulk diffusion, gas diffusion, surface diffusion and grain boundary diffusion coefficients respectively, α′ represents the grain number except the αth grain, and φ(ρ) is the weight function.

[0049] In a third aspect, an embodiment of the present disclosure provides an electronic device, comprising a memory and a processor, wherein the memory is used to store one or more computer instructions, and wherein the one or more computer instructions are executed by the processor to implement a method as described in any one of the first aspects.

[0050] In a fourth aspect, an embodiment of the present disclosure provides a computer-readable storage medium on which computer instructions are stored. When the computer instructions are executed by a processor, a method as described in any one of the first aspects is implemented.

[0051] According to the technical solution provided by the embodiments of the present disclosure, the phase field simulation model and kinetic equation of the NdFeB multi-component and multi-phase system can be constructed to simulate the evolution process and size information of the microstructure of NdFeB grains grown under various predetermined sintering conditions. Based on the simulation results, the reasonable sintering conditions can be adjusted to obtain the required sintered NdFeB grains, so as to achieve simulation theory to guide predictive experiments and provide strong support for actual production and experimental research. The highly reliable and practical phase field simulation model can provide an effective tool for the development and improvement of sintering theory and provide a reasonable explanation for the physical phenomena observed in the sintering experiment. In actual industrial production, the perfect theoretical model and simulation method can predict the microstructure of sintered NdFeB grains, provide a basis for improving the sintering process, thereby improving the magnetic properties while reducing the R&D cycle and production costs, and meeting the industrialization requirements for the performance and processing costs of sintered NdFeB magnets.

[0052] It is to be understood that the foregoing general description and the following detailed description are exemplary and explanatory only and are not restrictive of the present disclosure. BRIEF DESCRIPTION OF THE DRAWINGS

[0053] Other features, objectives and advantages of the present disclosure will become more apparent through the following detailed description of non-limiting embodiments in conjunction with the accompanying drawings. In the accompanying drawings:

[0054] Figure 1 A flow chart of a method for simulating sintered NdFeB grain growth provided by an embodiment of the present disclosure is shown.

[0055] Figure 2 A diagram showing the grain size information of NdFeB grains at different sintering temperatures provided in this embodiment.

[0056] Figure 3 A curve chart showing the change of the average grain size of the sintered NdFeB grains provided in this embodiment with the sintering temperature.

[0057] Figure 4 SEM images of sintered NdFeB grains corresponding to three sintering temperatures are shown.

[0058] Figure 5 The figure shows the grain size information of NdFeB grains at different sintering times provided in this embodiment.

[0059] Figure 6 A curve chart showing the change of the average grain size of the sintered NdFeB grains provided in this embodiment with the sintering time.

[0060] Figure 7 The SEM images of sintered NdFeB grains corresponding to two sintering times are shown.

[0061] Figure 8 A structural block diagram of a device for simulating sintered NdFeB grain growth according to an embodiment of the present disclosure is shown.

[0062] Fig. 9 A structural block diagram of an electronic device according to an embodiment of the present disclosure is shown.

[0063] Fig.10 A schematic diagram showing the structure of a computer system suitable for implementing the method of the embodiment of the present disclosure is shown. DETAILED DESCRIPTION

[0064] Hereinafter, exemplary embodiments of the present disclosure will be described in detail with reference to the accompanying drawings so that those skilled in the art can easily implement them. In addition, for the sake of clarity, parts not related to the description of the exemplary embodiments are omitted in the accompanying drawings.

[0065] In the present disclosure, it should be understood that terms such as "include" or "have" are intended to indicate the presence of features, numbers, steps, behaviors, components, parts, or a combination thereof disclosed in the present specification, and are not intended to exclude the possibility that one or more other features, numbers, steps, behaviors, components, parts, or a combination thereof exist or are added.

[0066] It should also be noted that, in the absence of conflict, the embodiments and features in the embodiments of the present disclosure may be combined with each other. The present disclosure will be described in detail below with reference to the accompanying drawings and in combination with the embodiments.

[0067] Figure 1 FIG. 1 is a flow chart showing a method for simulating the growth of sintered NdFeB grains provided by an embodiment of the present disclosure. Figure 1 As shown, the simulation method for sintered NdFeB grain growth includes the following steps S101-S103:

[0068] In step S101, a phase field simulation model of a NdFeB multi-component multi-phase system is constructed to describe the total free energy of the NdFeB multi-component multi-phase system;

[0069] In step S102, the field variables in the NdFeB multi-component and multi-phase system are determined, and a kinetic equation of the phase field simulation model is established. The kinetic equation is based on the total free energy minimization principle and is used to describe the evolution of the field variables over time and space;

[0070] In step S103, the evolution process and size information of the microstructure of the NdFeB grains grown under predetermined sintering conditions are solved based on the kinetic equation.

[0071] In a possible implementation, the simulation method of sintered NdFeB grain growth can be applied to various electronic devices such as computers, computing devices, terminal devices, servers, service clusters, etc. for simulating sintered NdFeB grain growth.

[0072] In a possible implementation, the phase field method is a computational method for simulating the evolution of the microstructure of a material. The core idea of ​​this method is to describe the microstructure of the material by introducing a set of continuous field variables, rather than directly simulating the arrangement of atoms or molecules. The phase field method is based on the thermodynamics and kinetics of materials, and can give the direction and specific change path of the evolution of the microstructure inside the material, reproduce the evolution of the material's organization over time during various phase changes, and give a quantitative description thereof. That is, the phase field method can simulate the evolution of materials at a microscopic scale, while taking into account the thermodynamic and kinetic effects at a macroscopic scale. Therefore, this embodiment uses the phase field method to simulate the grain growth of sintered NdFeB grains.

[0073] In a possible implementation, when the phase field method is used to simulate the growth of sintered NdFeB grains, it is necessary to first construct a corresponding phase field simulation model, and the constructed phase field simulation model is applied to the NdFeB multi-component multi-phase system. Here, the phase field simulation model performs a phase field simulation on the grain growth process of sintered NdFeB grains. Thermodynamic and kinetic data corresponding to the phase field simulation model can be collected to describe the total system free energy of the NdFeB multi-component multi-phase system.

[0074] In one possible implementation, the field variable is a continuous variable used in phase field simulation to describe the microstructural characteristics of the material. There may be two field variables in this implementation. One is the density field, which takes the value of 1 in all solid phases and 0 in all liquid phases, so as to distinguish different phases. The other is the phase field order parameter η(α), where η(α)=1 at the αth grain and η(α)=0 at other grains, so as to represent different grains, and α is the total number of grains.

[0075] In one possible embodiment, the evolution of the phase field is controlled by kinetic equations, which are usually derived from variational principles of the total free energy functional and are used to describe the evolution of field variables in time and space based on the principle of minimization of the total free energy.

[0076] In a possible implementation, after the kinetic equation is established, the predetermined sintering conditions can be set as needed, and the kinetic equation can be solved by discrete iteration to output the evolution process and size information of the microstructure of the NdFeB grains grown under the predetermined sintering conditions.

[0077] This embodiment can simulate the evolution process and size information of the microstructure of NdFeB grains grown under various predetermined sintering conditions by constructing a phase field simulation model and kinetic equation of the NdFeB multi-component and multi-phase system. Based on the simulation results, reasonable sintering conditions can be adjusted to obtain the required sintered NdFeB grains, so as to achieve simulation theory to guide predictive experiments and provide strong support for actual production and experimental research. Highly reliable and practical phase field simulation models can provide effective tools for the development and improvement of sintering theory and provide reasonable explanations for the physical phenomena observed in sintering experiments. In actual industrial production, perfect theoretical models and simulation methods can predict the microstructure of sintered NdFeB grains, provide a basis for improving the sintering process, thereby improving the magnetic properties while reducing the R&D cycle and production costs, and meeting the industrialization requirements for the performance and processing costs of sintered NdFeB magnets.

[0078] In a possible implementation, step S103, i.e. solving the evolution process and size information of the microstructure of NdFeB grains grown under different sintering conditions based on the kinetic equation, can be implemented as follows:

[0079] By controlling the variable method, fixing the sintering time and the initial grain size, the average grain size and microstructure of NdFeB grains at different sintering temperatures were simulated based on the kinetic equation to minimize the total free energy.

[0080] In this embodiment, the microstructure refers to the internal structure and organizational morphology of NdFeB grains at a microscopic scale, which is composed of crystals, grain boundaries, grains, lattice defects, twins, precipitated phases, crystal orientations, etc.

[0081] In a possible implementation, step S103, i.e. solving the evolution process and size information of the microstructure of NdFeB grains grown under different sintering conditions based on the kinetic equation, can be implemented as follows:

[0082] By controlling the variable method, fixing the sintering temperature and the initial grain size, and simulating the average grain size and microstructure of the NdFeB grains at different sintering times based on the kinetic equation to minimize the total free energy.

[0083] In a possible implementation, the phase field simulation model of the NdFeB multi-component multi-phase system is constructed to describe the total free energy of the multi-component multi-phase system, including:

[0084] A phase field simulation model was established based on the Ginzburg-Landau theory and the NdFeB multi-component and multi-phase system.

[0085] In this embodiment, based on the Ginzburg-Landau theory, the microstructure evolution process and its internal mechanism of NdFeB magnetic materials are studied by using differential equations (i.e., kinetic equations), which has the advantage of not needing to track complex interfaces.

[0086] In a possible implementation, the total free energy F of the NdFeB multi-component multi-phase system is described as follows:

[0087]

[0088] Where F is the total free energy of the system, κ ρ and κ η are the surface and grain boundary energy gradient coefficients, respectively, and the function f(ρ, {η(α)}) is the nonequilibrium volume chemical free energy density, which defines the homogeneous coexistence terms (solids and systems) and multiple solid domains (grains with different crystal orientations); is the gradient symbol, d 3 r represents the integration over the volume.

[0089] f(ρ,{η(α)})=Aρ 2 (1-ρ) 2 +B[ρ 2 +6(1-ρ)∑ α η 2(α)-4(2-ρ)∑ α η 3 (α)+3(∑ α η 2 (α) 2 ];

[0090] Among them, A and B are constants, and the density field ρ is a conservative field.

[0091] In a possible implementation, the kinetic equation includes:

[0092]

[0093] Among them, t is the sintering time, and M represents the coefficient related to material migration; this formula is a variational solution of the density field ρ. It can be seen from the formula that the sintering time affects the evolution of the grains and thus affects the grain size.

[0094] The relationship between M and the diffusion coefficient D is as follows:

[0095]

[0096] Where D is the diffusion coefficient, V m is the molar volume of NdFeB, R is the molar gas constant, T is the sintering temperature, and this equation is the related equation for the effect of sintering temperature on grain size. The sintering temperature T mainly affects the grain size by affecting the diffusion coefficient.

[0097] The diffusion coefficient D can be expressed as follows:

[0098]

[0099] Where: D V , D vap , D s and D gb represent the bulk diffusion, gas diffusion, surface diffusion and grain boundary diffusion coefficients respectively, α′ represents the grain number except the αth grain, and φ(ρ) is the weight function.

[0100] In this embodiment, when η(α)=1, there will be α grains, and α free energy equations are obtained. The finite difference method is used for numerical simulation calculations, and the derivatives in the kinetic equations are discretized using the difference quotient of the function values ​​to obtain a set of algebraic equations with the function values ​​at the grid nodes as unknowns. The system is solved mathematically to obtain the average grain size. The specific calculation process is well understood by those skilled in the art and will not be described in detail here.

[0101] Two examples and two comparative examples are used below to illustrate that the simulation method provided by this embodiment can accurately simulate the grain growth process of sintered NdFeB grains.

[0102] Embodiment 1:

[0103] Based on the Ginzburg-Landau theory and the NdFeB multi-phase system, a phase field simulation model was established. The microstructure evolution process and average grain size of NdFeB were studied by differential equations (i.e., kinetic equations). Then, the grain size information of NdFeB grains at different sintering temperatures was simulated by the control variable method with fixed sintering time of 40 min and initial grain size of 2.9281 μm. Figure 2 and Figure 3 The grain size information shown is Figure 2 A diagram showing the grain size information of NdFeB grains at different sintering temperatures provided in this embodiment. Figure 3 The graph showing the average grain size of the sintered NdFeB grains provided in this embodiment as a function of the sintering temperature is shown. Figure 2 The grain size information of NdFeB grains at different sintering temperatures shown in the figure can be used to calculate the average grain size of NdFeB grains at different sintering temperatures, and then obtain Figure 3 The curve shown.

[0104] Comparative Example 1:

[0105] According to 29.5% PrNd, 1.5% M (M is one or more of Co, Cu, Al, Ga, Zr, Ti), the remaining ingredients are B and Fe, wherein the mass percentage of B and Fe is 0.95, and the above ingredients are prepared into a quick-setting sheet with an average thickness of 0.25-0.28 mm by using a medium-frequency induction melting furnace under argon protection, and the quick-setting sheet is placed in a hydrogen crushing furnace for hydrogen crushing and dehydrogenation to prepare a coarse granular powder with a particle size of millimeter level and a hydrogen content of less than 1000ppm, The obtained coarse granular powder is placed in a fluidized bed air flow mill with high-purity (99.995%) nitrogen as the power source for powdering, and NdFeB fine powder with an average particle size of 2.9 μm is prepared. The obtained fine powder is placed in a press with a magnetic field strength greater than 1.5 T for orientation molding to prepare a square compact. The obtained square compact is placed in a vacuum sintering furnace for sintering. The sintering time is 40 minutes. The sintering temperatures are 960°C, 1000°C and 1085°C, respectively, to obtain sintered NdFeB grains corresponding to three sintering temperatures, wherein, Figure 4 The SEM images of sintered NdFeB grains at three sintering temperatures are shown. Figure 4 The SEM images of the sintered NdFeB grains corresponding to the three sintering temperatures shown in the figure, and the average grain sizes of the NdFeB grains grown at the three sintering temperatures are calculated and shown in Table 1 below:

[0106] Temperature(℃) 960 1000 1085 Average grain size (μm) 2.89 2.99 3.12

[0107] Table 1

[0108] By comparing Example 1 with Comparative Example 1, it can be seen that the average grain size of the NdFeB grains simulated by phase field is basically consistent with the experimental measurement result of actual sintering.

[0109] Example 2

[0110] Based on the Ginzburg-Landau theory and the NdFeB multi-phase system, a phase field simulation model was established. The microstructure evolution process and average grain size of NdFeB were studied by differential equations (i.e., kinetic equations). Then, the grain size information of NdFeB grains at different sintering times was simulated by the controlled variable method with fixed sintering temperature of 1160°C and initial grain size of 2.9281μm. Figure 5 and Figure 6 The grain size information shown is Figure 5 The figure shows the grain size information of NdFeB grains at different sintering times provided in this embodiment. Figure 6 The graph showing the average grain size of the sintered NdFeB grains provided in this embodiment as a function of sintering time is shown. Figure 5 The grain size information of NdFeB grains at different sintering times shown in the figure can be used to calculate the average grain size of NdFeB grains at different sintering times, and then obtain Figure 6 The curve shown.

[0111] Comparative Example 2:

[0112] After preparing NdFeB fine powder with an average particle size of 2.9 μm according to the method described in Comparative Example 1, the obtained fine powder was placed in a press with a magnetic field strength greater than 1.5 T for orientation molding to prepare a block compact, and the obtained block compact was placed in a vacuum sintering furnace for sintering at a sintering temperature of 1160° C. The sintering time was 0 min and 30 min, respectively, to obtain sintered NdFeB grains corresponding to two sintering times, wherein: Figure 7 The SEM images of sintered NdFeB grains corresponding to two sintering times are shown. Figure 7 The SEM images of the sintered NdFeB grains corresponding to the two sintering times are shown in Table 2 below. The average grain sizes of the NdFeB grains grown under the two sintering times are calculated.

[0113] Time (min) 0min 30min Average grain size (μm) 2.83 3.13

[0114] Table 2

[0115] By comparing Example 2 with Comparative Example 2, it can be seen that the average grain size of the NdFeB grains simulated by phase field is basically consistent with the experimental measurement results of actual sintering.

[0116] The present disclosure also provides a simulation device for sintered NdFeB grain growth. Figure 8The structure block diagram of the simulation device for sintered NdFeB grain growth according to the embodiment of the present disclosure is shown, and the device can be implemented as part or all of an electronic device through software, hardware or a combination of both. Figure 8 As shown, the simulation device for sintered NdFeB grain growth comprises:

[0117] The model building module 801 is configured to build a phase field simulation model of the NdFeB multi-component multi-phase system and describe the total free energy of the NdFeB multi-component multi-phase system;

[0118] An equation building module 802 is configured to determine the field variables in the NdFeB multi-component and multi-phase system and to build a kinetic equation of the phase field simulation model, wherein the kinetic equation is based on the total free energy minimization principle and is used to describe the evolution of the field variables over time and space;

[0119] The growth simulation module 803 is configured to solve the evolution process and size information of the microstructure of the NdFeB grains grown under predetermined sintering conditions based on the kinetic equation.

[0120] In a possible implementation, the growth simulation module is configured as follows:

[0121] By controlling the variable method, fixing the sintering time and the initial grain size, and simulating the average grain size and microstructure of NdFeB grains at different sintering temperatures based on the kinetic equation to minimize the total free energy;

[0122] In a possible implementation, the growth simulation module is configured as follows:

[0123] By controlling the variable method, fixing the sintering temperature and the initial grain size, and simulating the average grain size and microstructure of the NdFeB grains at different sintering times based on the kinetic equation to minimize the total free energy.

[0124] In a possible implementation, the phase field simulation model of the NdFeB multi-component multi-phase system is constructed to describe the total free energy of the multi-component multi-phase system, including:

[0125] A phase field simulation model was established based on the Ginzburg-Landau theory and the NdFeB multi-component and multi-phase system.

[0126] In a possible implementation, the total free energy F of the NdFeB multi-component multi-phase system is described as follows:

[0127]

[0128] Where F is the total free energy of the system, κ ρ and κ ηare the surface and grain boundary energy gradient coefficients, respectively. Function f(ρ, {η(α)}) is the non-equilibrium volume chemical free energy density; f(ρ, {η(α)}) = Aρ 2 (1-ρ) 2 +B[ρ 2 +6(1-ρ)∑ α η 2 (α)-4(2-ρ)∑ α η 3 (α)+3(∑ α η 2 (α) 2 ]; A and B are constants, the density field ρ is a conservative field, η(α) is the phase field order parameter, η(α)=1 at the αth grain, η(α)=0 at other grains, and α is the total number of grains;

[0129] In a possible implementation, the kinetic equation includes:

[0130]

[0131] Where t is the sintering time, and M represents the coefficient related to material migration;

[0132] The relationship between M and the diffusion coefficient D is as follows:

[0133]

[0134] Where D is the diffusion coefficient, V m is the molar volume of NdFeB, R is the molar gas constant, and T is the sintering temperature;

[0135] The diffusion coefficient D is expressed as follows:

[0136]

[0137] Among them, D V , D vap , D s and D gb represent the bulk diffusion, gas diffusion, surface diffusion and grain boundary diffusion coefficients respectively, α′ represents the grain number except the αth grain, and φ(ρ) is the weight function.

[0138] The technical terms and technical features mentioned in the implementation manner of the present device are the same as or similar to those mentioned in the implementation manner of the above method. For the explanation and description of the technical terms and technical features involved in the present device, reference may be made to the explanation and description of the implementation manner of the above method, and they will not be repeated here.

[0139] The present disclosure also discloses an electronic device, Fig. 9 A structural block diagram of an electronic device according to an embodiment of the present disclosure is shown.

[0140] like Fig. 9 As shown, the electronic device 900 includes a memory 901 and a processor 902, wherein the memory 901 is used to store one or more computer instructions, wherein the one or more computer instructions are executed by the processor 902 to implement the method according to an embodiment of the present disclosure.

[0141] Fig.10 A schematic diagram showing the structure of a computer system suitable for implementing the method of the embodiment of the present disclosure is shown.

[0142] like Fig.10 As shown, the computer system 1000 includes a processing unit 1001, which can perform various processes in the above-mentioned embodiments according to a program stored in a read-only memory (ROM) 1002 or a program loaded from a storage part 1008 into a random access memory (RAM) 1003. In the RAM 1003, various programs and data required for the operation of the computer system 1000 are also stored. The processing unit 1001, the ROM 1002, and the RAM 1003 are connected to each other via a bus 1004. An input / output (I / O) interface 1005 is also connected to the bus 1004.

[0143] The following components are connected to the I / O interface 1005: an input part 1006 including a keyboard, a mouse, etc.; an output part 1007 including a cathode ray tube (CRT), a liquid crystal display (LCD), etc., and a speaker, etc.; a storage part 1008 including a hard disk, etc.; and a communication part 1009 including a network interface card such as a LAN card, a modem, etc. The communication part 1009 performs communication processing via a network such as the Internet. The drive 1010 is also connected to the I / O interface 1005 as needed. A removable medium 1011, such as a magnetic disk, an optical disk, a magneto-optical disk, a semiconductor memory, etc., is installed on the drive 1010 as needed, so that the computer program read therefrom is installed into the storage part 1008 as needed. Among them, the processing unit 1001 can be implemented as a processing unit such as a CPU, a GPU, a TPU, an FPGA, an NPU, etc.

[0144] In particular, according to an embodiment of the present disclosure, the method described above can be implemented as a computer software program. For example, an embodiment of the present disclosure includes a computer program product, which includes computer instructions, and the computer instructions are executed by a processor to implement the method steps described above. In such an embodiment, the computer program product can be downloaded and installed from a network through the communication part 1009, and / or installed from a removable medium 1011.

[0145] The flowcharts and block diagrams in the accompanying drawings illustrate the possible architecture, functions and operations of the systems, methods and computer program products according to various embodiments of the present disclosure. In this regard, each box in the flowchart or block diagram can represent a module, a program segment or a part of a code, and the module, a program segment or a part of the code contains one or more executable instructions for realizing the specified logical function. It should also be noted that in some alternative implementations, the functions marked in the box can also occur in a different order from the order marked in the accompanying drawings. For example, two boxes represented in succession can actually be executed substantially in parallel, and they can sometimes be executed in the opposite order, depending on the functions involved. It should also be noted that each box in the block diagram and / or flowchart, and the combination of boxes in the block diagram and / or flowchart can be implemented with a dedicated hardware-based system that performs a specified function or operation, or can be implemented with a combination of dedicated hardware and computer instructions.

[0146] The units or modules involved in the embodiments described in the present disclosure may be implemented by software or programmable hardware. The units or modules described may also be set in a processor, and the names of these units or modules do not constitute limitations on the units or modules themselves in some cases.

[0147] As another aspect, the present disclosure further provides a computer-readable storage medium, which may be a computer-readable storage medium included in the electronic device or computer system in the above embodiment; or a computer-readable storage medium that exists independently and is not assembled into a device. The computer-readable storage medium stores one or more programs, and the programs are used by one or more processors to execute the method described in the present disclosure.

[0148] The above description is only a preferred embodiment of the present disclosure and an explanation of the technical principles used. Those skilled in the art should understand that the scope of the invention involved in the present disclosure is not limited to the technical solution formed by a specific combination of the above technical features, but should also cover other technical solutions formed by any combination of the above technical features or their equivalent features without departing from the inventive concept. For example, the above features are replaced with the technical features with similar functions disclosed in the present disclosure (but not limited to) by each other.

Claims

1. A method for simulating grain growth of sintered NdFeB, characterized in that: include: Constructing a phase field simulation model of a NdFeB multi-component multi-phase system to describe the total free energy of the NdFeB multi-component multi-phase system; Determine the field variables in the NdFeB multi-component and multi-phase system, and establish a kinetic equation of the phase field simulation model, wherein the kinetic equation is based on the total free energy minimization principle and is used to describe the evolution of the phase field variables over time and space; The evolution process and size information of the microstructure of NdFeB grains grown under predetermined sintering conditions are solved based on the kinetic equation.

2. The method according to claim 1, characterized in that The method of solving the evolution process and size information of the microstructure of NdFeB grains grown under different sintering conditions based on the kinetic equation includes: By controlling the variable method, fixing the sintering time and the initial grain size, the average grain size and microstructure of NdFeB grains at different sintering temperatures were simulated based on the kinetic equation to minimize the total free energy.

3. The method according to claim 1, characterized in that The method of solving the evolution process and size information of the microstructure of NdFeB grains grown under different sintering conditions based on the kinetic equation includes: By controlling the variable method, fixing the sintering temperature and the initial grain size, and simulating the average grain size and microstructure of the NdFeB grains at different sintering times based on the kinetic equation to minimize the total free energy.

4. The method according to claim 1, characterized in that: The phase field simulation model of the NdFeB multi-component multi-phase system is constructed to describe the total free energy of the multi-component multi-phase system, including: A phase field simulation model was established based on the Ginzburg-Landau theory and the NdFeB multi-component and multi-phase system.

5. The method according to claim 4, characterized in that The total free energy F of the NdFeB multi-component multi-phase system is described as follows: Where F is the total free energy of the system, κ ρ and κ η are the surface and grain boundary energy gradient coefficients, respectively. Function f(ρ,{η(α)}) is the non-equilibrium volume chemical free energy density; f(ρ,{η(α)})=Aρ 2 (1-ρ) 2 +B[ρ 2 +6(1-ρ)∑ α η 2 (α)-4(2-ρ)∑ α η 3 (α)+3(∑ α η 2 (α) 2 ]; A and B are constants, the density field ρ is a conservative field, η(α) is the phase field order parameter, η(α)=1 at the αth grain, η(α)=0 at other grains, and α is the total number of grains.

6. The method according to claim 5, characterized in that The kinetic equations include: Where t is the sintering time, and M represents the coefficient related to material migration; The relationship between M and the diffusion coefficient D is as follows: Where D is the diffusion coefficient, V m is the molar volume of NdFeB, R is the molar gas constant, and T is the sintering temperature; The diffusion coefficient D is expressed as follows: Among them, D V , D vap , D s and D gb represent the bulk diffusion, gas diffusion, surface diffusion and grain boundary diffusion coefficients respectively, α′ represents the grain number except the αth grain, and φ(ρ) is the weight function.

7. A simulation device for sintered NdFeB grain growth, characterized in that: include: A model building module is configured to build a phase field simulation model of a NdFeB multi-component multi-phase system to describe the total free energy of the NdFeB multi-component multi-phase system; An equation building module is configured to determine the field variables in the NdFeB multi-component and multi-phase system and to build a kinetic equation of the phase field simulation model, wherein the kinetic equation is based on the total free energy minimization principle and is used to describe the evolution of the phase field variables over time and space; The growth simulation module is configured to solve the microstructure evolution process and size information of the NdFeB grains grown under predetermined sintering conditions based on the kinetic equation.

8. The device according to claim 7, characterized in that The growth simulation module is configured to: By controlling the variable method, fixing the sintering time and the initial grain size, the average grain size and microstructure of NdFeB grains at different sintering temperatures were simulated based on the kinetic equation to minimize the total free energy.

9. The device according to claim 7, characterized in that The growth simulation module is configured to: By controlling the variable method, fixing the sintering temperature and the initial grain size, and simulating the average grain size and microstructure of the NdFeB grains at different sintering times based on the kinetic equation to minimize the total free energy.

10. The device according to claim 7, characterized in that The phase field simulation model of the NdFeB multi-component multi-phase system is constructed to describe the total free energy of the multi-component multi-phase system, including: A phase field simulation model was established based on the Ginzburg-Landau theory and the NdFeB multi-component and multi-phase system.

11. The device according to claim 10, characterized in that The total free energy F of the NdFeB multi-component multi-phase system is described as follows: Where F is the total free energy of the system, κ ρ and κ η are the surface and grain boundary energy gradient coefficients, respectively. Function f(ρ,{η(α)}) is the non-equilibrium volume chemical free energy density; f(ρ,{η(α)})=Aρ 2 (1-ρ) 2 +B[ρ 2 +6(1-ρ)∑ α η 2 (α)-4(2-ρ)∑ α η 3 (α)+3(∑ α η 2 (α) 2 ]; A and B are constants, the density field ρ is a conservative field, η(α) is the phase field order parameter, η(α)=1 at the αth grain, η(α)=0 at other grains, and α is the total number of grains.

12. The device according to claim 11, characterized in that The kinetic equations include: Where t is the sintering time, and M represents the coefficient related to material migration; The relationship between M and the diffusion coefficient D is as follows: Where D is the diffusion coefficient, V m is the molar volume of NdFeB, R is the molar gas constant, and T is the sintering temperature; The diffusion coefficient D is expressed as follows: Among them, D V , D vap , D s and D gb represent the bulk diffusion, gas diffusion, surface diffusion and grain boundary diffusion coefficients respectively, α′ represents the grain number except the αth grain, and φ(ρ) is the weight function.

13. An electronic device, characterized in that: The method comprises a memory and a processor, wherein the memory is used to store one or more computer instructions, wherein the one or more computer instructions are executed by the processor to implement the method according to any one of claims 1 to 6.

14. A readable storage medium, characterized in that: Computer instructions are stored thereon, and when the computer instructions are executed by a processor, the method described in any one of claims 1 to 6 is implemented.

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