Microstructure prediction method of high-entropy alloy, directional solidification process optimization method and preparation method of high-entropy alloy bar

Abstract

The present invention relates to a method for predicting the microstructure of high-entropy alloys, a method for optimizing the directional solidification process, and a method for preparing high-entropy alloy bars. The method for predicting the microstructure includes the following steps: calculating and extracting the physical properties of high-entropy alloys through JMatPro software; inputting the physical properties into the parameter settings of COMSOL software, and simulating the induction melting process of high-entropy alloys through COMSOL software until a completely molten high-entropy alloy melt is obtained; simulating the directional solidification process of the high-entropy alloy melt through ProCAST finite element software to obtain the microstructure of the high-entropy alloy under corresponding process conditions. Through the combined simulation of JMatPro, COMSOL, and ProCAST software, the present invention realizes the full-process prediction from material properties, melting process to microstructure, providing a more efficient and low-cost technical approach for the prediction, research and development, and preparation of high-entropy alloy microstructures.

Description

Technical Field

[0001] The present invention relates to a method for predicting the microstructure of a high-entropy alloy, a method for optimizing the directional solidification process, and a method for preparing a high-entropy alloy bar, and particularly relates to a method for predicting the microstructure of a bulk magnetostrictive high-entropy alloy, a method for optimizing the directional solidification process, and a method for preparing a high-entropy alloy bar, belonging to the field of high-entropy alloys. Background Art

[0002] In the field of materials science, the microstructure, as the core element of the internal structure of materials, plays a crucial role in the properties of materials. The microstructure of materials includes the size, morphology, orientation, phase composition and distribution of grains, etc., which directly affect the mechanical, physical and chemical properties of materials. In magnetostrictive materials, the microstructure is particularly important because the magnetostrictive properties of materials are closely related to the grain orientation, phase structure and equiaxed crystal ratio. By optimizing the microstructure of materials, the isotropy, fatigue resistance and bulk magnetostrictive effect of materials can be effectively improved.

[0003] At present, the research on magnetostrictive materials mostly focuses on traditional alloys, such as rare-earth alloys like iron-nickel, iron-dysprosium-holmium, and some single-crystal materials. Although these materials show excellent magnetostrictive properties, they also have many limitations. First of all, traditional materials often have high brittleness, especially in single-crystal structures, and the problem of high brittleness limits the processing and service life of materials. Secondly, the corrosion resistance of traditional alloys is poor, and their performance will significantly decline in some corrosive environments. In addition, traditional alloys show instability under extreme environments (such as high temperature or strong magnetic field conditions), which easily leads to material performance degradation or failure. In contrast, as an emerging material, high-entropy alloys, with their diversified composition and high-entropy effect, exhibit excellent mechanical properties, oxidation resistance and thermal stability, and have attracted much attention in the field of materials research in recent years. More importantly, the bulk magnetostrictive properties of high-entropy alloys can be significantly improved by optimizing the composition and process parameters, so as to meet the needs of a wider range of industrial applications. Therefore, studying the bulk magnetostrictive characteristics of high-entropy alloys has become a research hotspot in recent years.

[0004] In the research of high-entropy alloys, by adjusting the composition and process conditions of high-entropy alloys, the volume magnetostrictive properties of high-entropy alloys can be improved. However, in practical applications, the microstructure of high-entropy alloys remains the key factor determining their properties. Microstructural characteristics such as grain size, crystal orientation, phase distribution, and equiaxed grain ratio of high-entropy alloys directly affect the mechanical and magnetic properties of the materials. Generally, for high-entropy alloys with better volume magnetostrictive properties, the following regularities are presented in their microstructure: a larger equiaxed grain ratio and a higher grain uniformity. Traditional experimental methods mainly directly observe the final microstructure through actual melting and directional solidification processes. Although this method can provide intuitive results, it has the following limitations: 1. High experimental cost: Each experiment requires actual melting and directional solidification processes, which not only take a long time and are costly but also make it difficult to quickly obtain microstructure and magnetostrictive property data under various process parameters. 2. Unclear relationship between microstructure and process parameters: Traditional experimental methods often can only provide the final microstructure state, making it difficult to effectively establish an accurate correlation between process parameters, the microstructure of high-entropy alloys, and volume magnetostrictive properties, thus limiting process optimization. 3. Difficult process monitoring: During the actual induction melting process, the state of the high-entropy alloy melt is difficult to observe in real time, especially key information such as whether the high-entropy alloy is completely melted and the temperature field distribution in different regions is difficult to obtain.

[0005] Chinese Patent Application CN113343524A discloses a method for optimizing the directional solidification process of Fe-Al-Ta ternary alloys based on simulation. Through the ProCAST software, it can simulate the directional solidification process and grain growth state of Fe-Al-Ta ternary alloys. By designing models and adjusting simulation parameters, the solidification microstructure of Fe-Al-Ta ternary alloys with different compositions under different directional solidification process parameters can be predicted. However, this patent only considers the directional solidification process and does not consider the state of whether the Fe-Al-Ta ternary alloy is completely melted and the temperature field distribution before directional solidification, nor does it consider the heat treatment steps of the ingot during the directional solidification process. The preparation of high-entropy alloys usually involves induction melting and directional solidification processes successively (generally carried out in a liquid metal directional solidification furnace). The state of the high-entropy alloy melt obtained by induction melting and the heat treatment steps during the directional solidification process both have significant effects on the microstructure of the high-entropy alloy products obtained after directional solidification. Therefore, the method of this patent is actually difficult to accurately predict and optimize the microstructure of high-entropy alloys.

[0006] Chinese Invention Patent CN113987892B discloses a method for establishing a 3D model of vacuum arc remelting to control segregation of superalloys. According to the actual dimensions of the mold during the vacuum arc remelting of superalloys (such as 508mm, 660mm, 460mm, etc.), a finite element model of the ingot during the vacuum arc remelting of superalloys is established using SolidWorks and Procast software, and the change process of the ingot in the metal molten pool is intuitively reflected through the finite element model. This patent is directed to the vacuum arc remelting process, which belongs to a different process type from the induction melting and directional solidification processes of high-entropy alloys. Therefore, the method for establishing a 3D model of vacuum arc remelting to control segregation of superalloys in this patent is also not applicable to the prediction and optimization of the microstructure of high-entropy alloys.

[0007] Therefore, how to effectively predict and optimize the microstructure of high-entropy alloys to improve their magnetostrictive properties has become a key challenge in current research. Summary of the Invention

[0008] Aiming at the deficiencies of the prior art, one of the purposes of the present invention is to provide an efficient prediction method for the microstructure of high-entropy alloys; the second purpose of the present invention is to provide an optimization method for the directional solidification process of high-entropy alloys; the third purpose of the present invention is to provide a preparation method for high-entropy alloy bars.

[0009] To solve the above technical problems, the technical solution of the present invention is as follows:

[0010] The method for predicting the microstructure of high-entropy alloys includes the following steps:

[0011] S1. Calculate and extract the physical property parameters of the high-entropy alloy to be predicted through JMatPro software;

[0012] Among them, the physical property parameters include the solidus and liquidus temperatures, density curve, thermal conductivity curve, electrical conductivity curve, and enthalpy curve of the high-entropy alloy changing with temperature; generally, the solidus and liquidus temperatures can be obtained from each curve such as the electrical conductivity curve.

[0013] S2. Input the physical property parameters into the material parameter settings of COMSOL software, and simulate the induction melting process of the high-entropy alloy through COMSOL software until a completely molten high-entropy alloy melt is obtained, and record the temperature of the high-entropy alloy melt at this time; optionally, record the melting time at this time.

[0014] S3. Simulate the directional solidification process of the high-entropy alloy melt through ProCAST finite element software to obtain the microstructure of the high-entropy alloy under corresponding process conditions.

[0015] Among them, the temperature of the high-entropy alloy melt obtained in step S2 is used as the initial temperature for casting in the simulation process of step S3; the high-entropy alloy is a volume magnetostrictive high-entropy alloy.

[0016] Further, the composition of the high-entropy alloy is FeCo(AlCrNi) x M y , where x = 0.1~1.5 and y = 0~0.05; M is one or more of Cu, Co, Mn, Mo, Nb, Ni, Si, Ti, V, W, B, C, P, and S.

[0017] Further, in S2,

[0018] Input the physical property parameters into the parameter settings of COMSOL software, and construct a two-dimensional axisymmetric geometric model of the induction melting unit of the liquid metal directional solidification furnace;

[0019] Perform mesh generation on the constructed two-dimensional axisymmetric geometric model, and set the material types of the various components of the two-dimensional axisymmetric geometric model;

[0020] Select the electromagnetic field and heat transfer field, set the induction melting regime, and perform multi-physics coupling;

[0021] Adopt frequency domain research, set the frequency, calculation time, and step size of induction heating, and perform calculations of the electric field, magnetic field, and solid heat transfer field;

[0022] View the results of the frequency domain research, observe the temperature field change of the high-entropy alloy during the melting process until the high-entropy alloy melt is completely melted, and record the temperature of the high-entropy alloy melt at this time;

[0023] Among them, the induction melting regime is segmented heating; the liquid metal directional solidification furnace includes a furnace cavity, an induction melting unit, and a directional solidification unit, and the induction melting unit and the directional solidification unit are arranged in the furnace cavity.

[0024] Further, the two-dimensional axisymmetric geometric model includes an induction melting air domain (corresponding to the furnace cavity of the induction melting unit), a crucible arranged in the induction melting air domain, the crucible is filled with high-entropy alloy, the outer wall of the crucible is covered with a sand layer, a copper coil is wound around the crucible, water is arranged inside the copper coil, and the sand layer is located between the crucible and the copper coil; preferably, the material of the crucible is magnesium oxide; preferably, the sand layer is a magnesia sand layer.

[0025] Further, the water flow rate in the copper coil is 4 - 6 kg / min, and the water temperature at the inlet of the copper coil is 20 - 35 °C.

[0026] Furthermore, the induction melting regime is to first heat at a power of 8 - 12 kW for 2 - 7 min, then heat at a power of 13 - 17 kW for 3 - 7 min, and finally heat at a power of 18 - 22 kW for 3 - 7 min;

[0027] Preferably, when using frequency domain research, set the frequency of induction heating to 3000 - 5000 Hz, the calculation time to 10 - 20 min, and the step size to 0.5 - 1.5 min.

[0028] Furthermore, in S3,

[0029] Using ProCAST finite element software, construct a three - dimensional geometric model of the directional solidification unit of the liquid metal directional solidification furnace;

[0030] Perform mesh division on the three - dimensional geometric model, and set the material types of each component of the three - dimensional geometric model and the heat transfer coefficient between components;

[0031] Set the directional solidification process parameters, turn on the CAFE switch of the high - entropy alloy, and set the CAFE - related parameters of the high - entropy alloy;

[0032] Run, and view the microstructure of the high - entropy alloy under the corresponding process conditions in the Viewer (post - processing module) of ProCAST finite element software;

[0033] Among them, the directional solidification process parameters include heat treatment temperature, heat treatment time, rising rate, falling rate, rotation rate; the CAFE - related parameters of the high - entropy alloy include surface nucleation undercooling, surface nucleation undercooling variance, surface nucleation density, bulk nucleation undercooling, bulk nucleation undercooling variance, bulk nucleation density;

[0034] Among them, the three - dimensional geometric model includes a thermal insulation shell, a directional solidification air domain (corresponding to the furnace cavity of the directional solidification unit) located inside the thermal insulation shell, and a corundum mold for accommodating the high - entropy alloy. A liquid metal shell is provided below the thermal insulation shell. The liquid metal shell contains liquid metal, and the top of the liquid metal shell is connected to the directional solidification air domain. The corundum mold is located inside the directional solidification air domain, and the lower end of the corundum mold can extend into the liquid metal shell and can move up and down relative to the liquid metal shell.

[0035] Optionally, the falling rate refers to the rate at which the corundum mold descends from the directional solidification air domain into the liquid metal shell.

[0036] Furthermore, view the grain uniformity and equiaxed crystal ratio of the microstructure.

[0037] Furthermore, use the inverse calculation module of ProCAS finite element software to solve and obtain the heat transfer coefficient.

[0038] Optionally, the process of the directional solidification process includes the following steps: pouring the high-entropy alloy melt in the crucible into the corundum mold; then lowering the corundum mold into the liquid metal shell so that the corundum mold is completely immersed in the liquid metal; then, lifting the corundum mold upward so that the corundum mold completely enters the directional solidification air domain for heat treatment. Optionally, the corundum mold is lifted upward at a rate of 1500-2500 μm / s. Generally, this parameter has little effect on the microstructure of the high-entropy alloy and can be selected according to needs.

[0039] Further, in S3, the directional solidification method adopts high-temperature gradient directional solidification of liquid metal. The rising rate of the corundum mold is 1-2500 μm / s, the falling rate is 1-2500 μm / s; the rotation rate is 1-100 rpm.

[0040] Based on the same inventive concept, the present invention also provides: an optimization method for the directional solidification process of high-entropy alloys, using the above-mentioned microstructure prediction method to predict the microstructure of a certain high-entropy alloy under different directional solidification processes; then, comparing, the directional solidification process with the most ideal obtained microstructure is the optimized directional solidification process.

[0041] Thus, the directional solidification process of a high-entropy alloy with a certain composition can be optimized.

[0042] Optionally, compare the equiaxed crystal ratio and grain size uniformity in the microstructure to determine the most ideal microstructure. Generally, the higher the equiaxed crystal ratio and the higher the grain size uniformity in the microstructure, the more ideal.

[0043] Optionally, the liquid metal is GaInSn. Optionally, in the liquid metal, the gallium content is 65-72 vol%, the indium content is 20-22 vol%, and the tin content is 8-12 vol%.

[0044] Based on the same inventive concept, the present invention also provides: a preparation method of high-entropy alloy bars, including the optimized directional solidification process described above.

[0045] Thus, it helps to obtain high-entropy alloy bars (directionally solidified high-entropy alloy bars) with a high equiaxed crystal ratio and high grain size uniformity in the microstructure.

[0046] Optionally, first obtain the high-entropy alloy melt by induction melting, and then perform directional solidification on the high-entropy alloy melt using the optimized directional solidification process described above.

[0047] The present invention aims at the directional solidification process of high-entropy alloy molten metal. Process experiments are carried out using a directional solidification furnace for molten metal. By combining simulation software such as JMatPro, COMSOL, and ProCAST, the properties of the material, the induction melting, and the directional solidification process are comprehensively simulated. Through the simulation of the COMSOL software, the problems that the melting process and the temperature field distribution cannot be directly observed during the induction melting process are solved. Combining the material parameters provided by the JMatPro software, and then through the COMSOL software, the melting time of the alloy and the temperature state after melting can be effectively predicted, which can provide accurate initial conditions for the casting temperature of the high-entropy alloy during the directional solidification simulation of the ProCAST software, and prepare for accurately predicting the final microstructure of the high-entropy alloy. The simulation of the ProCAST software overcomes the problem that the relationship between process parameters and the alloy microstructure cannot be clarified in traditional experiments. At the same time, the MATLAB software can be used subsequently to quantitatively analyze the microstructure results obtained by the ProCAST software, establish the correlation between process parameters and the microstructure, and thus provide guidance for optimizing the directional solidification process. Through the combined simulation of the JMatPro, COMSOL, and ProCAST software, the present invention realizes the full-process prediction from material properties, melting process to microstructure, providing a more efficient and low-cost technical approach for the preparation of high-entropy alloys. And through this prediction method, it can be used to more simply optimize the directional solidification process, effectively reduce the process optimization cost, and improve the efficiency.

[0048] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0049] (1) The present invention uses the COMSOL software to simulate the induction melting process in the directional solidification furnace for molten metal, solving the problem that the melting state and temperature field distribution of the high-entropy alloy during the induction melting process cannot be monitored in real time in traditional experiments. The simulation can ensure the temperature uniformity of the melt, reduce the non-uniformity of the microstructure, provide guarantee for the performance consistency of the final material, and obtain the temperature of the high-entropy alloy melt, providing an accurate initial temperature for the subsequent directional solidification process.

[0050] (2) The present invention uses the ProCAST finite element software to simulate the directional solidification process, solving the problem that it is difficult to establish a quantitative relationship between the directional solidification process parameters and the microstructure distribution. It can accurately simulate the influence of different process parameters on the microstructure (grain uniformity and equiaxed crystal ratio), so as to predict the microstructure morphology under different process parameter conditions, and can be used to more quickly optimize the directional solidification process. This process avoids the limitations of traditional experimental methods, can effectively guide the process optimization, and provides accurate data support for improving the volume magnetostrictive performance of the material.

[0051] (3) The present invention can provide strong support for the composition design of volume magnetostrictive high-entropy alloys. By means of computer-aided materials science such as the ProCAST finite element software, the microstructural evolution of high-entropy alloys with different compositions can be simulated, and the properties of high-entropy alloys can be predicted, thereby guiding the optimization design of high-entropy alloys, improving the comprehensive properties of high-entropy alloys, enhancing the R & D efficiency, and contributing to the more precise design of high-entropy alloys. BRIEF DESCRIPTION OF THE DRAWINGS

[0052] Figure 1 It is a flowchart of a method for predicting the microstructure of a high-entropy alloy and a method for optimizing the directional solidification process according to the present invention.

[0053] Figure 2 It is the density curve of Fe 35 Co 35 Al 10 Cr 10 Ni 10 calculated by JMatPro software in Example 1 of the present invention.

[0054] Figure 3 It is the thermal conductivity curve of Fe 35 Co 35 Al 10 Cr 10 Ni 10 calculated by JMatPro software in Example 1 of the present invention.

[0055] Figure 4 It is the conductivity curve of Fe 35 Co 35 Al 10 Cr 10 Ni 10 calculated by JMatPro software in Example 1 of the present invention.

[0056] Figure 5 It is the curve of the enthalpy value varying with temperature of Fe 35 Co 35 Al 10 Cr 10 Ni 10 calculated by JMatPro software in Example 1 of the present invention.

[0057] Figure 6 It is a two-dimensional axisymmetric simplified model of the induction melting unit in COMSOL software in Example 1 of the present invention.

[0058] Figure 7 It is the Fe 35 Co 35 Al 10 Cr10 Ni 10 Phase change process (left) and temperature distribution map (right).

[0059] Figure 8 This is the three-dimensional simplified model of the directional solidification unit in ProCAST finite element software in Example 1 of the present invention.

[0060] Figure 9 This is the alloy microstructure field obtained under the process conditions of Example 1 calculated by ProCAST finite element software.

[0061] Figure 10 This is the simulation result diagram of the high-entropy alloy under the optimal process parameters in Example 2 of the present invention.

[0062] Figure 11 This is the metallographic microscope result diagram of the high-entropy alloy under the optimal process parameters in Example 2 of the present invention.

[0063] In the figure: 1 - density curve, 2 - thermal conductivity curve, 3 - electrical conductivity curve, 4 - curve of enthalpy value changing with temperature, 5 - induction melting air domain, 6 - sand layer, 7 - crucible, 8 - high-entropy alloy, 9 - water, 10 - copper coil, 11 - directional solidification air domain, 12 - heat preservation shell, 13 - high-entropy alloy melt, 14 - corundum mold, 15 - liquid metal, 16 - liquid metal shell. Specific implementation manners

[0064] The present invention will be described in detail below with reference to the embodiments. It should be noted that, without conflict, the embodiments in the present invention and the features in the embodiments can be combined with each other. For the convenience of description, words such as "upper", "lower", "left", and "right" in the following text only indicate the same direction as the upper, lower, left, and right directions of the attached drawings themselves, and do not limit the structure.

[0065] Example 1

[0066] The method for predicting the microstructure of the high-entropy alloy in this example includes the following steps:

[0067] Step 1: Calculation of physical properties parameters of the high-entropy alloy. Input the composition of the high-entropy alloy (Fe 35 Co 35 Al 10 Cr 10 Ni 10 ) into JMatPro 13.0 software to calculate its physical properties parameters. The calculation results of the physical properties parameters are as Figures 2 to 5 shown. It can be seen from the figure that through JMatPro 13.0 software, physical properties parameters such as the solidus and liquidus temperatures, density curve 1, thermal conductivity curve 2, electrical conductivity curve 3, and curve 4 of the enthalpy value changing with temperature of the high-entropy alloy can be calculated. FromFigures 2 to 5 It can be seen that the solid-liquidus temperature of the high-entropy alloy 8 is 1219 °C.

[0068] Step 2: Simulation of the induction melting process. Substitute the calculated physical properties of the high-entropy alloy into the COMSOL 6.2 software. The steps for simulating the induction melting process using the COMSOL 6.2 software are as follows:

[0069] ① Since the induction melting unit of the target liquid metal directional solidification furnace has axisymmetric characteristics, when using the COMSOL6.2 software for simulation, using a two-dimensional axisymmetric model can significantly reduce the number of meshes while ensuring the accuracy of the calculation results. Therefore, when constructing the geometry of the induction melting unit of the target liquid metal directional solidification furnace, a simplified two-dimensional axisymmetric model is adopted, as Figure 6 shown; specifically, the two-dimensional axisymmetric simplified model includes an induction melting air domain 5, a crucible 7 arranged in the induction melting air domain 5. The crucible 7 contains the high-entropy alloy 8. The outer wall of the crucible 7 is covered with a sand layer 6. A copper coil 10 is wound around the crucible 7, and water 9 is arranged inside the copper coil 10. The sand layer 6 is located between the crucible 7 and the copper coil 10; the material of the crucible 7 is magnesium oxide; the sand layer 6 is a magnesia layer; the target liquid metal directional solidification furnace includes a furnace cavity, an induction melting unit, and a directional solidification unit. The induction melting unit and the directional solidification unit are arranged in the furnace cavity; the entire furnace cavity is in a vacuum environment;

[0070] ② Mesh the above two-dimensional axisymmetric simplified model. An extremely fine mesh size can be used. Among them, the maximum element size is 0.01 m, and the average mesh quality is 0.9413; set the material of the crucible 7 to magnesium oxide, the copper coil 10 is a water-cooled copper coil, the internal material of the copper coil is water 9, and the inside of the crucible 7 is the high-entropy alloy 8;

[0071] ③ Select electromagnetic field and heat transfer field for multi-physics coupling. Set the power of the induction heating coil to 10kW(5min)-15kw(5min)-20kW(5min) (that is, induction heating is carried out in three stages, the heating time of each stage is 5min, and the heating power of each stage is 10, 15, 20kW in turn), the water flow rate in the copper coil is 5 kg / min, and the water temperature at the inlet of the copper coil is 25 °C; the temperature of the outer wall surface of the liquid metal directional solidification furnace is 25°C;

[0072] ④ Adopt frequency domain research. The frequency of the induction heating coil is 4000 Hz, the calculation time is 15 min, and the step size is 1min to perform electromagnetic-thermal multi-physics calculation;

[0073] ⑤ The liquid phase distribution and temperature distribution of the high-entropy alloy after induction melting calculated by the COMSOL 6.2 software are as Figure 7 shown, from Figure 7As can be seen on the right side, Fe 35 Co 35 Al 10 Cr 10 Ni 10 At 15 minutes, the highest temperature reached 1370 °C, and the highest temperature was located at the top edge of the alloy. Figure 7 Fe is shown on the left side 35 Co 35 Al 10 Cr 10 Ni 10 The liquid phase is evenly distributed and has completely turned into a liquid state. The real-time monitoring of the alloy melting state and temperature field distribution is realized through COMSOL 6.2 software until the high-entropy alloy melt is completely melted. Finally, the melting time is recorded as 15 minutes and the temperature of the high-entropy alloy melt is 1370 °C. This temperature will be used as the initial condition for Step 3.

[0074] Step 3: Input the temperature of the high-entropy alloy melt (1370 °C) into the ProCAST 2021 finite element software to conduct a simulation of the directional solidification process. The specific simulation steps include:

[0075] ① Build a three-dimensional geometric model according to the directional solidification unit of the liquid metal directional solidification furnace, as Figure 8 shown; specifically, the three-dimensional geometric model includes a thermal insulation shell 12, a directional solidification air domain 11 located inside the thermal insulation shell 12, and a corundum mold 14 (with a height of 300 mm) for accommodating the high-entropy alloy. A liquid metal shell 16 is provided below the thermal insulation shell 12, and a liquid metal 15 (chemical formula: GaInSn, proportion: gallium 68.5 vol%, indium 21.5 vol%, tin 10 vol%) is contained in the liquid metal shell 16. The top end of the liquid metal shell 16 is connected to the directional solidification air domain 11. The corundum mold 14 is located inside the directional solidification air domain 11, and the corundum mold 14 can extend into the liquid metal shell 16 and can move up and down relative to the liquid metal shell 16.

[0076] ② Conduct mesh division on the three-dimensional geometric model, set the maximum element size to 0.05 m, and there are a total of 165,320 mesh elements; assign material properties to each region respectively. Set the thermal insulation shell 12 and the mold box as mold, set the high-entropy alloy melt 13 as Alloy, and set the directional solidification air domain 11 and the liquid metal 15. Set the material properties of each part, and set the initial temperature according to the actual temperature of the thermal insulation furnace, 1400 °C. The initial temperatures of the thermal insulation shell 12 and the corundum mold 14 are both set to the initial 1400 °C. After the corundum mold 14 completely descends, set the temperatures of the directional solidification air domain 11, the thermal insulation shell 12, and the corundum mold 14 to the heat treatment temperature of 1200 °C, and set the temperature of the high-entropy alloy melt 13 to the above-mentioned high-entropy alloy melt temperature of 1370 °C;

[0077] ③Since the heat transfer coefficient cannot be directly obtained, the inverse calculation module in the ProCAST 2021 finite element software is used for solution. After solution, the heat transfer coefficient between the corundum mold 14 and the high-entropy alloy melt 13 is 2000 W / (m 2 ·K), the heat transfer coefficient between the corundum mold 14 and the directional solidification air domain 11 is 50 W / (m 2 ·K), and the heat transfer coefficient between the corundum mold 14 and the liquid metal 15 is 5000 W / (m 2 ·K);

[0078] ④Apply Geometrical boundary conditions. Specifically, set the Translate v(t) (descending rate) of the mold box to 84 um / s. After descending 300 mm (at this time, the corundum mold just completely enters the liquid metal); immediately lift the corundum mold 14 into the directional solidification air domain 11 at a rising rate of 2000 um / s for heat treatment at a temperature of 1200 °C for 1 h, with a Rotation (rotation rate) of 10 rpm and a temperature gradient of about 300 K / cm; in the material settings, turn on the CAFE switch of Fe 35 Co 35 Al 10 Cr 10 Ni 10 and set the CAFE-related parameters for it. Among them, the surface nucleation undercooling is set to 2.5 K, the undercooling variance is set to 1 K, the surface nucleation density is set to 7×10 8 1 / m 2 ; the bulk nucleation undercooling is set to 1.5 K, the bulk nucleation undercooling variance is set to 1.5 K, and the bulk nucleation density is set to 9×10 9 1 / m 3 ;

[0079] Among them, the descending rate refers to the rate at which the corundum mold 14 descends from the directional solidification air domain 11 into the liquid metal shell 16;

[0080] ⑤Run and view the microstructure at the top of the high-entropy alloy under this process condition in the Viewer. The results are as Figure 9 shown.

[0081] Example 2

[0082] A method for optimizing the directional solidification process of a high-entropy alloy uses the microstructure prediction method described in Example 1 to predict the microstructures of a certain high-entropy alloy under different directional solidification processes; then, compare, and the directional solidification process with the most ideal obtained microstructure is the optimized directional solidification process.

[0083] Specifically, orthogonal experiments were used to systematically study the effects of directional solidification parameters (heat treatment temperature, heat treatment time, descent rate, rotation rate) on the microstructure of high-entropy alloys. Each factor was divided into 3 levels. According to the four-factor and three-level design, the L9(3^4) orthogonal table was used, and the experimental scheme is shown in Table 1 below.

[0084] Table 1 Design of L9 Orthogonal Experiment Scheme

[0085]

[0086] Based on the above parameters, the calculation of the directional solidification microstructure field of liquid metal was carried out. The microstructure distribution results calculated by the ProCAST 2021 finite element software were exported. The MATLAB software was used to quantitatively analyze the grain distribution map generated by the simulation results, mark the grains and extract their properties, and calculate the grain size, uniformity, and equiaxed grain ratio in the grain distribution map. The equiaxed grain ratio is defined as: the area of equiaxed grains Ae to the total crystal area At , and the calculation formula is: .

[0087] The grain size uniformity is defined as: the ratio of the average value of the grain size ( ) to the standard deviation of the grain size ( ), and the calculation formula is: uniformity .

[0088] The results of the orthogonal experiment are shown in Table 2.

[0089] Table 2 Simulation Results of Orthogonal Experiment

[0090]

[0091] As can be seen from Table 2, it can be seen from the data that different heat treatment and processing parameters have significant effects on the equiaxed grain ratio and grain size uniformity. Lower heat treatment temperature, shorter heat treatment time, low descent rate, and low rotation rate may be more conducive to increasing the equiaxed grain ratio, while medium heat treatment temperature, longer heat treatment time, low descent rate, and medium rotation rate may be more helpful to obtain a uniform grain size distribution. According to the orthogonal experiment table, under the conditions of heat treatment temperature of 1100 °C, heat treatment time of 30 minutes, descent rate of 50 µm / s, and rotation rate of 10 rpm, the microstructure simulation result diagram obtained is as shown in Figure 10 , and the results with a higher equiaxed grain ratio (51.78%) and the highest uniformity (0.7974) can be obtained, indicating that this combination is the optimal condition to achieve the goal in the current experiment and can be used as the optimized process.

[0092] Further experimental verification was carried out on the above-optimized process. For the obtained optimal process parameters (heat treatment temperature of 1100 °C, heat treatment time of 30 minutes, descent rate of 50 µm / s, rotation rate of 10 rpm), an induction melting (actual experiment was carried out according to the melting process of Example 1) and directional solidification experiment (using the above optimal process parameters) were conducted using a liquid metal directional solidification furnace with the same structure and size as the model used in the simulation process. The actual microstructure of the high-entropy alloy was observed through a metallographic microscope. The actual microstructure is as Figure 11 shown. Using Matlab software, a part of the microstructure of the high-entropy alloy observed by the actual microscope was taken to calculate the equiaxed crystal ratio and the grain size uniformity. The calculation results show that the equiaxed crystal ratio is 50.92%, and the grain size uniformity is 0.7824. The error between the simulation result and the actual result is less than 5%, indicating that the above high-entropy alloy microstructure prediction method and process optimization method of the present invention have the advantages of rapidity, reliability, and accuracy, and can effectively improve the R & D efficiency.

[0093] The content clarified in the above embodiments should be understood that these embodiments are only used to illustrate the present invention more clearly, rather than to limit the scope of the present invention. After reading the present invention, various equivalent forms of modification of the present invention by those skilled in the art all fall within the scope defined by the appended claims of this application.

Claims

1. A method for predicting the microstructure of a high entropy alloy, characterized in that: The steps include: S1. Calculate and extract the physical property parameters of the high entropy alloy to be predicted by JMatPro software; Among them, the physical property parameters include the solid and liquidus temperatures, density curve, thermal conductivity curve, electrical conductivity curve and enthalpy value versus temperature curve of the high entropy alloy; S2, inputting the physical property parameters into the material parameter setting of COMSOL software, simulating the induction melting process of the high entropy alloy by COMSOL software, until a completely molten high entropy alloy melt is obtained, and recording the temperature of the high entropy alloy melt at this time; The physical property parameters are input into the material parameter setting of COMSOL software, and a two-dimensional axisymmetric geometric model of the induction melting unit of the liquid metal directional solidification furnace is constructed; Meshing the constructed two-dimensional axisymmetric geometric model, and setting the material type of each component of the two-dimensional axisymmetric geometric model; Select electromagnetic field and heat transfer field, set up induction melting system, and conduct multi-physical field coupling; Use frequency domain research to set the frequency, calculation time, and step size of induction heating to calculate the electric field, magnetic field, and solid heat transfer field; Check the frequency domain research results, observe the temperature field changes of the high entropy alloy during the smelting process, until the high entropy alloy is completely melted, and record the temperature of the high entropy alloy melt at this time; S3, simulating the directional solidification process of the high entropy alloy melt by ProCAST finite element software to obtain the microstructure of the high entropy alloy under corresponding process conditions; The temperature of the high entropy alloy melt obtained in step S2 is used as the initial casting temperature during the simulation process of step S3; and the high entropy alloy is a volume magnetostrictive high entropy alloy.

2. The microstructure prediction method according to claim 1, characterized in that: The composition of high entropy alloy is FeCo(AlCrNi) x M y , wherein x=0.1~1.5, y=0~0.05; M is one or more of Cu, Co, Mn, Mo, Nb, Ni, Si, Ti, V, W, B, C, P, and S.

3. The microstructure prediction method according to claim 1, characterized in that: The two-dimensional axisymmetric geometric model comprises an induction melting air domain (5), a crucible (7) arranged in the induction melting air domain (5), the crucible (7) containing a high entropy alloy, the outer wall of the crucible (7) covered with a sand layer (6), a copper coil (10) wound on the crucible (7), water (9) arranged in the copper coil (10), and the sand layer (6) located between the crucible (7) and the copper coil (10).

4. The microstructure prediction method according to claim 1, characterized in that: The induction melting system is to heat at 8-12kW for 2-7min, then at 13-17kW for 3-7min, and finally at 18-22kW for 3-7min. When using frequency domain research, the frequency of induction heating is set to 3000-5000 Hz, the calculation time is 10-20 min, and the step size is 0.5-1.5 min.

5. The microstructure prediction method according to any one of claims 1, 3-4, characterized in that: In S3, ProCAST finite element software is used to construct a three-dimensional geometric model of the directional solidification unit of the liquid metal directional solidification furnace; Meshing the three-dimensional geometric model, and setting the material type of each component of the three-dimensional geometric model and the heat transfer coefficient between the components; Set the directional solidification process parameters, turn on the CAFE switch of the high entropy alloy, and set the CAFE related parameters of the high entropy alloy; Run and view the microstructure of high entropy alloy under corresponding process conditions in the Viewer of ProCAST finite element software; Among them, the directional solidification process parameters include heat treatment temperature, heat treatment time, descending rate, ascending rate and rotation rate; the CAFE-related parameters of high entropy alloys include face nucleation undercooling, face nucleation undercooling variance, face nucleation density, body nucleation undercooling, body nucleation undercooling variance and body nucleation density; The three-dimensional geometric model includes a heat-insulating shell (12), a directional solidification air domain (11) located in the heat-insulating shell (12), and a corundum mold (14) for containing a high-entropy alloy. A liquid metal shell (16) is provided below the heat-insulating shell (12). The liquid metal shell (16) contains liquid metal (15). The top of the liquid metal shell (16) is connected to the directional solidification air domain (11). The corundum mold (14) is located in the directional solidification air domain (11). The lower end of the corundum mold (14) can extend into the liquid metal shell (16) and can move up and down relative to the liquid metal shell (16).

6. The microstructure prediction method according to claim 5, characterized in that: In S3, the directional solidification method adopts liquid metal high temperature gradient directional solidification, the rising rate of the corundum mold is 1-2500 μm / s, the descending rate is 1-2500 μm / s; the rotation rate is 1-100 rpm.

7. A method for optimizing the directional solidification process of a high entropy alloy, characterized in that: The microstructure prediction method as described in any one of claims 1 to 6 is used to predict the microstructure of a certain high entropy alloy under different directional solidification processes; then, by comparison, the directional solidification process with the most ideal microstructure is the optimized directional solidification process.

8. A method for preparing a high entropy alloy rod, characterized in that: Comprising the optimized directional solidification process as described in claim 7.

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