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

Abstract

The invention relates to a microstructure prediction method of a high-entropy alloy, a directional solidification process optimization method and a preparation method of a high-entropy alloy bar. The microstructure prediction method comprises the following steps: calculating and extracting physical property parameters of the high-entropy alloy through JMatPro software; the physical property parameters are input into parameter setting of COMSOL software, and the induction melting process of the high-entropy alloy is simulated through the COMSOL software until a completely-molten high-entropy alloy melt is obtained; the directional solidification process of the high-entropy alloy melt is simulated through ProCAST finite element software, and the microstructure of the high-entropy alloy under the corresponding technological condition is obtained. According to the method, through joint simulation of JMatPro, COMSOL and ProCAST software, prediction of the whole process from material attributes to the smelting process to the microstructure is achieved, and a more efficient and low-cost technical approach is provided for prediction, research, development and preparation of the microstructure of the high-entropy alloy.

Description

Technical Field

[0001] The present invention relates to a method for predicting the microstructure of a high entropy alloy, a method for optimizing a directional solidification process and a method for preparing a high entropy alloy rod, and in particular to a method for predicting the microstructure of a volume magnetostrictive high entropy alloy, a method for optimizing a directional solidification process and a method for preparing a high entropy alloy rod, and belongs to the field of high entropy alloys. Background Art

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

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

[0004] In the study of high entropy alloys, the volume magnetostriction of high entropy alloys can be improved by adjusting the composition and process conditions of high entropy alloys. However, in practical applications, the microstructure of high entropy alloys is still the key factor determining their performance. The microstructure characteristics of high entropy alloys, such as grain size, crystal orientation, phase distribution, and equiaxed crystal ratio, directly affect the mechanical and magnetic properties of the material. Generally, the better the volume magnetostriction of the high entropy alloy, the larger the equiaxed crystal ratio and the higher the grain uniformity. The traditional experimental method mainly observes the final microstructure directly through the actual melting and directional solidification process. 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 is not only time-consuming and costly, but also difficult to quickly obtain microstructure and magnetostriction performance data under multiple process parameters. 2. The relationship between microstructure and process parameters is unclear: Traditional experimental methods can only provide the final microstructure state, and it is difficult to effectively establish the precise relationship between process parameters and the microstructure and volume magnetostrictive properties of high-entropy alloys, thereby limiting the optimization of the process. 3. Difficulty in process monitoring: In the actual induction melting process, the state of the high-entropy alloy melt is difficult to observe in real time, especially whether the high-entropy alloy is completely melted, the temperature field distribution in different regions and other key information are difficult to obtain.

[0005] Chinese invention patent application CN113343524A discloses a method for optimizing the directional solidification process of Fe-Al-Ta ternary alloy based on simulation. The method can simulate the directional solidification process and grain growth state of Fe-Al-Ta ternary alloy through ProCAST software. By designing and modeling, and adjusting the simulation parameters, the solidification structure of Fe-Al-Ta ternary alloy with different compositions under different directional solidification process parameters can be predicted. However, the patent only considers the directional solidification process, and does not consider whether the Fe-Al-Ta ternary alloy is completely melted before directional solidification, the temperature field distribution and other states, 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 (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 have a significant impact on the microstructure of the high entropy alloy product obtained after directional solidification. Therefore, the method of the patent is actually difficult to accurately predict and optimize the microstructure of the high entropy alloy.

[0006] Chinese invention patent CN113987892B discloses a method for establishing a 3D model of vacuum arc remelting to control the segregation of high-temperature alloys. According to the actual size of the crystallizer (such as 508mm, 660mm, 460mm, etc.) during the vacuum arc remelting of high-temperature alloys, SolidWorks and Procast software are used to establish a finite element model of the ingot during the vacuum arc remelting of high-temperature alloys. The finite element model intuitively reflects the change process of the ingot in the metal molten pool. The patent is aimed at the vacuum arc remelting process, which is a different process type from the induction melting and directional solidification process of high-entropy alloys. Therefore, the method of establishing a 3D model of vacuum arc remelting to control the segregation of high-temperature alloys in this patent cannot be applied 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] In view of the deficiencies in the prior art, one of the objects of the present invention is to provide an efficient prediction method for the microstructure of a high entropy alloy; a second object of the present invention is to provide a method for optimizing the directional solidification process of a high entropy alloy; a third object of the present invention is to provide a method for preparing a high entropy alloy rod.

[0009] In order to solve the above technical problems, the technical solution of the present invention is as follows: The microstructure prediction method of high entropy alloy includes the following steps: 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 solidus and liquidus temperatures, density curve, thermal conductivity curve, electrical conductivity curve and enthalpy value versus temperature curve of the high entropy alloy; generally, the solidus and liquidus temperatures can be obtained from the electrical conductivity curve and other curves; S2, inputting the physical property parameters into the material parameter setting of COMSOL software, simulating the induction melting process of the high entropy alloy through 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; optionally, also recording the melting time 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.

[0010] Furthermore, the composition of the 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.

[0011] Furthermore, in S2, The physical property parameters are input into the parameter setting of COMSOL software, and a two-dimensional axisymmetric geometric model of an induction melting unit of a 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 melt is completely melted, and record the temperature of the high entropy alloy melt at this time; Among them, the induction melting system is segmented heating; the liquid metal directional solidification furnace includes a furnace chamber, an induction melting unit and a directional solidification unit, and the induction melting unit and the directional solidification unit are arranged in the furnace chamber.

[0012] Furthermore, the two-dimensional axisymmetric geometric model includes an induction melting air domain (corresponding to the furnace chamber of the induction melting unit), a crucible arranged in the induction melting air domain, the crucible is filled with a 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 in 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 magnesium sand layer.

[0013] Furthermore, the flow rate of water in the copper coil is 4-6 kg / min, and the water temperature at the inlet of the copper coil is 20-35°C.

[0014] Further, the induction melting system 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; Preferably, when frequency domain research is adopted, 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.

[0015] Furthermore, 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 (post-processing module) of ProCAST finite element software; Among them, the directional solidification process parameters include heat treatment temperature, heat treatment time, rising rate, falling 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; Among them, the three-dimensional geometric model includes an insulation shell, a directional solidification air domain located in the insulation shell (corresponding to the furnace chamber of the directional solidification unit) and a corundum mold for accommodating a high-entropy alloy. A liquid metal shell is provided below the insulation shell, and liquid metal is contained in the liquid metal shell. The top of the liquid metal shell is connected to the directional solidification air domain. The corundum mold is located in 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.

[0016] Optionally, the descent rate refers to the rate at which the corundum mold is lowered from the directional solidification air domain into the liquid metal shell.

[0017] Furthermore, check the grain uniformity and equiaxed grain ratio of the microstructure.

[0018] Furthermore, the back calculation module of ProCAS finite element software was used to solve and obtain the heat transfer coefficient.

[0019] Optionally, 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.

[0020] Furthermore, 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.

[0021] Based on the same inventive concept, the present invention also provides: a method for optimizing the directional solidification process of a high entropy alloy, using the microstructure prediction method as described above 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.

[0022] Therefore, the directional solidification process of a high entropy alloy component of a certain composition can be optimized.

[0023] Optionally, the proportion of equiaxed crystals and the uniformity of grain size in the microstructure are compared to determine the most ideal microstructure. Generally, the higher the proportion of equiaxed crystals in the microstructure, the higher the uniformity of grain size, and the more ideal it is.

[0024] 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%.

[0025] Based on the same inventive concept, the present invention also provides: a method for preparing a high entropy alloy rod, comprising the optimized directional solidification process as described above.

[0026] This helps to obtain a high entropy alloy rod (high entropy alloy directional solidification rod) with a high proportion of equiaxed crystals and high uniformity of grain size in the microstructure.

[0027] Optionally, a high entropy alloy melt is first obtained by induction melting, and then the high entropy alloy melt is directionally solidified using the optimized directional solidification process as described above.

[0028] The present invention is directed to the liquid metal directional solidification process of high entropy alloy, and a liquid metal directional solidification furnace is used to perform process experiments. By combining simulation software such as JMatPro, COMSOL and ProCAST, the properties of the material, induction melting and directional solidification processes are fully simulated. Through COMSOL software simulation, the problem that the melting process and temperature field distribution cannot be directly observed during induction melting is solved. Combined with the material parameters provided by JMatPro software, the melting time of the alloy and the temperature state after melting can be effectively predicted by COMSOL software, which can provide accurate initial conditions for the casting temperature of the high entropy alloy during the directional solidification simulation of ProCAST software, and prepare for accurately predicting the final microstructure of the high entropy alloy. The ProCAST software simulation overcomes the problem that the relationship between the process parameters and the alloy microstructure cannot be clearly defined in traditional experiments. At the same time, MATLAB software can be used to quantitatively analyze the microstructure results obtained by ProCAST software, establish the relationship between the process parameters and the microstructure, and then provide guidance for optimizing the directional solidification process. The present invention realizes the prediction of the whole process from material properties, smelting process to microstructure through the joint simulation of JMatPro, COMSOL and ProCAST software, providing a more efficient and low-cost technical approach for the preparation of high-entropy alloys. And the prediction method can be used to optimize the directional solidification process more simply, effectively reduce the cost of process optimization, and improve efficiency.

[0029] Compared with the prior art, the present invention has the following beneficial effects: (1) The present invention uses COMSOL software to simulate the induction melting process in the liquid metal directional solidification furnace, which solves 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 a 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.

[0030] (2) The present invention uses ProCAST finite element software to simulate the directional solidification process, which solves the problem of difficulty in establishing a quantitative relationship between directional solidification process parameters and microstructure distribution. It can accurately simulate the influence of different process parameters on microstructure (grain uniformity and equiaxed crystal ratio), thereby predicting the microstructure morphology under different process parameter conditions, which can be used to optimize the directional solidification process more quickly. This process avoids the limitations of traditional experimental methods, can effectively guide process optimization, and provide accurate data support for improving the volume magnetostrictive properties of materials.

[0031] (3) The present invention can provide strong support for the composition design of volume magnetostrictive high-entropy alloys. By using computer materials science tools such as 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 optimal design of high-entropy alloys, improving the comprehensive properties of high-entropy alloys, improving research and development efficiency, and contributing to a more accurate design of high-entropy alloys. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Figure 1 The present invention is a flow chart of a method for predicting the microstructure of a high entropy alloy and a method for optimizing a directional solidification process.

[0033] Figure 2 is Fe calculated by JMatPro software in Example 1 of the present invention 35 Co 35 Al 10 Cr 10 Ni 10 Density curve graph.

[0034] Figure 3 is Fe calculated by JMatPro software in Example 1 of the present invention 35 Co 35 Al 10 Cr 10 Ni 10 Thermal conductivity curve of .

[0035] Figure 4 is Fe calculated by JMatPro software in Example 1 of the present invention 35 Co 35 Al 10 Cr 10 Ni 10 The conductivity curve of .

[0036] Figure 5 is Fe calculated by JMatPro software in Example 1 of the present invention 35 Co 35 Al 10 Cr 10 Ni 10 A graph showing the enthalpy of a substance changing with temperature.

[0037] 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.

[0038] Figure 7 is Fe calculated by COMSOL software in Example 1 of the present invention 35 Co 35 Al 10 Cr10 Ni 10 Phase change process (left) and temperature distribution diagram (right).

[0039] Figure 8 It is a three-dimensional simplified model of the directional solidification unit in the ProCAST finite element software in Example 1 of the present invention.

[0040] Fig. 9 The alloy structure field obtained under the process conditions of Example 1 calculated by ProCAST finite element software.

[0041] Fig.10 This is a diagram of the high entropy alloy simulation results under the optimal process parameters in Example 2 of the present invention.

[0042] Fig.11 This is a metallographic microscope result of the high entropy alloy under the optimal process parameters in Example 2 of the present invention.

[0043] In the figure: 1-density curve, 2-thermal conductivity curve, 3-electrical conductivity curve, 4-curve of enthalpy 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-insulation shell, 13-high entropy alloy melt, 14-corundum mold, 15-liquid metal, 16-liquid metal shell. DETAILED DESCRIPTION

[0044] The present invention will be described in detail below in conjunction with the embodiments. It should be noted that the embodiments and features of the embodiments of the present invention can be combined with each other without conflict. For the convenience of description, if the words "upper", "lower", "left" and "right" appear in the following, they only indicate that the upper, lower, left and right directions are consistent with the drawings themselves, and do not limit the structure.

[0045] Example 1 The microstructure prediction method of the high entropy alloy of this embodiment includes the following steps: Step 1: Calculation of physical properties of high entropy alloy. 35 Co 35 Al 10 Cr 10 Ni 10 ) The composition of 8 was input into JMatPro 13.0 software to calculate its physical properties. The calculation results of physical properties are as follows: Figures 2 to 5 As shown in the figure, it can be seen that the physical properties of the high entropy alloy such as solid and liquidus temperature, density curve 1, thermal conductivity curve 2, electrical conductivity curve 3 and enthalpy value with temperature curve 4 can be calculated by JMatPro 13.0 software. Figures 2 to 5 It can be seen that the solidus-liquidus temperature of high entropy alloy 8 is 1219°C.

[0046] Step 2: Induction melting process simulation. The calculated physical properties of the high entropy alloy are introduced into COMSOL 6.2 software. The steps of using COMSOL 6.2 software to simulate the induction melting process include: ① Since the induction melting unit of the target liquid metal directional solidification furnace has an axisymmetric characteristic, when simulating with COMSOL6.2 software, the use of a two-dimensional axisymmetric model can significantly reduce the number of grids 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 used, such as Figure 6 As 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, a high entropy alloy 8 is contained in the crucible 7, the outer wall of the crucible 7 is covered with a sand layer 6, a copper coil 10 is wound around the crucible 7, water 9 is arranged in the copper coil 10, and 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 magnesium sand layer; the target liquid metal directional solidification furnace includes a furnace chamber, an induction melting unit and a directional solidification unit, and the induction melting unit and the directional solidification unit are arranged in the furnace chamber; the entire furnace chamber is in a vacuum environment; ② The above two-dimensional axisymmetric simplified model is meshed using an extremely fine mesh size, wherein the maximum unit size is 0.01 m and the average mesh quality is 0.9413; the material of the crucible 7 is magnesium oxide, the copper coil 10 is a water-cooled copper coil, the internal material of the copper coil is water 9, and the crucible 7 contains a high entropy alloy 8; ③ The electromagnetic field and heat transfer field are used for multi-physical field coupling, and the power of the induction heating coil is set 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, and 20kW respectively), the water flow rate in the copper coil is 5 kg / min, and the water temperature at the entrance of the copper coil is 25 ℃; the outer wall temperature of the liquid metal directional solidification furnace is 25 ℃; ④ Using frequency domain research, the frequency of the induction heating coil is 4000 Hz, the calculation time is 15 min, and the step size is 1 min to perform electromagnetic thermal multi-physics field calculations; ⑤ The liquid phase distribution and temperature distribution of the high entropy alloy after induction melting calculated by COMSOL 6.2 software are as follows Figure 7 As shown by Figure 7 As can be seen on the right, Fe 35 Co 35 Al 10 Cr 10 Ni 10At 15 min, the maximum temperature reaches 1370 ℃, and the maximum temperature is located at the top edge of the alloy. Figure 7 Fe is shown on the left 35 Co 35 Al 10 Cr 10 Ni 10 The liquid phase is evenly distributed and has completely turned into a liquid state. The alloy melting state and temperature field distribution are monitored in real time by COMSOL 6.2 software until the high entropy alloy melt is completely melted. The final melting time is recorded as 15 min and the high entropy alloy melt temperature is 1370 °C, which will be used as the initial condition for step 3.

[0047] Step 3: Bring the high entropy alloy melt temperature (1370 °C) into the ProCAST 2021 finite element software to simulate the directional solidification process. The specific simulation steps include: ① Build a three-dimensional geometric model according to the directional solidification unit of the liquid metal directional solidification furnace, such as Figure 8 As shown; specifically, 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 (with a height of 300 mm) for accommodating 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 (with a chemical formula of GaInSn and a ratio of 68.5 vol%, gallium, 21.5 vol%, indium, and 10 vol%). 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 corundum mold 14 can extend into the liquid metal shell 16 and can move up and down relative to the liquid metal shell 16.

[0048] ② Mesh the three-dimensional geometric model, set the maximum unit size to 0.05 m, and there are 165320 mesh units in total; assign material properties to each area, set the insulation shell 12 and the mold box to mold, set the high entropy alloy melt 13 to 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 insulation furnace temperature of 1400 ℃. The initial temperatures of the insulation shell 12 and the corundum mold 14 are all set to the initial 1400 ℃. After the corundum mold 14 is completely lowered, the temperatures of the directional solidification air domain 11, the insulation shell 12 and the corundum mold 14 are set to the heat treatment temperature of 1200 ℃, and the temperature of the high entropy alloy melt 13 is set to the above-mentioned high entropy alloy melt temperature of 1370 ℃; ③ Since the heat transfer coefficient cannot be obtained directly, the inverse calculation module in the ProCAST 2021 finite element software is used to solve it. After solving, the heat transfer coefficient between the corundum mold 14 and the high entropy alloy melt 13 is 2000 W / (m2 ·K), the heat transfer coefficient between the corundum mold 14 and the directional solidification air region 11 is 50 W / (m 2 ·K), the heat transfer coefficient between the corundum mold 14 and the liquid metal 15 is 5000 W / (m 2 K); ④ Apply Geometrical boundary conditions. Specifically, set the Translate v(t) (descent rate) of the mold box to 84 um / s, and after descending 300 mm (at this time, the corundum mold is just completely in the liquid metal); immediately lift the corundum mold 14 into the directional solidification air domain 11 at a rising rate of 2000 um / s, and perform heat treatment at a temperature of 1200 ℃ for 1 h, with a rotation rate of 10 rpm and a temperature gradient of about 300K / cm; in the material settings, turn on Fe 35 Co 35 Al 10 Cr 10 Ni 10 The CAFE switch is set, and the CAFE related parameters are set. The surface kernel supercooling is set to 2.5 K, the supercooling variance is set to 1 K, and the surface kernel density is set to 7×10 8 1 / m 2 , the supercooling of the body core is set to 1.5 K, the variance of the supercooling of the body core is set to 1.5 K, and the density of the body core is set to 9×10 9 1 / m 3 ; The descending rate refers to the rate at which the corundum mold 14 descends from the directional solidification air region 11 into the liquid metal shell 16; ⑤ Run and view the microstructure of the top of the high entropy alloy under the process conditions in the Viewer. The results are as follows Fig. 9 shown.

[0049] Example 2 A method for optimizing the directional solidification process of a high entropy alloy, using the microstructure prediction method described in Example 1 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.

[0050] 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 three levels. Based on four factors and three levels, the L9 (3^4) orthogonal table was used. The experimental scheme is shown in Table 1.

[0051] Table 1 L9 orthogonal experimental design

[0052] According to the above parameters, the liquid metal directional solidification organization field is calculated, and the microstructure distribution results calculated by ProCAST 2021 finite element software are exported. The grain distribution map generated by the simulation results is quantitatively analyzed using MATLAB software, the grains are marked and the properties are extracted, and the grain size, uniformity and equiaxed crystal ratio in the grain distribution map are calculated, where the equiaxed crystal ratio is defined as: equiaxed crystal area Ae Total crystal area At The ratio is calculated as: .

[0053] Grain size uniformity is defined as: the average value of the grain size ( ) and the standard deviation of grain size ( ), the calculation formula is: uniformity .

[0054] The orthogonal experiment results are shown in Table 2.

[0055] Table 2 Orthogonal experiment simulation results

[0056] As can be seen from Table 2, it can be seen from the data that different heat treatment and processing parameters have a significant effect on the equiaxed crystal 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 improving the equiaxed crystal ratio, while medium heat treatment temperature, longer heat treatment time, low descent rate and medium rotation rate may be more conducive to obtaining a uniform grain size distribution. According to the orthogonal experimental 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 results are shown in the figure below. Fig.10 As shown, the results with a higher proportion of equiaxed crystals (51.78%) and the highest uniformity (0.7974) can be obtained, which indicates that this combination is the optimal condition to achieve the goal in the current experiment and can be used as an optimized process.

[0057] The optimized process was further verified by experiments. The optimal process parameters (heat treatment temperature 1100°C, heat treatment time 30 minutes, descent rate 50µm / s, rotation rate 10 rpm) were used in a liquid metal directional solidification furnace with the same structure and size as the model used in the simulation process to carry out actual induction melting (actual experiment according to the melting process of Example 1) and directional solidification experiment (carried out using the above optimal process parameters), and the actual microstructure of the high entropy alloy was observed by metallographic microscope. The actual microstructure is as follows: Fig.11As shown, Matlab software is used to calculate the equiaxed crystal ratio and grain size uniformity of a part of the high entropy alloy microstructure observed by an actual microscope. The calculation results show that the equiaxed crystal ratio is 50.92%, the grain size uniformity is 0.7824, and the error between the simulation result and the actual result is less than 5%, indicating that the 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 research and development efficiency.

[0058] The contents explained in the above embodiments should be understood as these embodiments are only used to more clearly illustrate the present invention, and are not used to limit the scope of the present invention. After reading the present invention, various equivalent forms of modifications to the present invention by those skilled in the art all fall within the scope defined by the features attached to 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; 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: In S2, The physical property parameters are input into the parameter setting of COMSOL software, and a two-dimensional axisymmetric geometric model of an induction melting unit of a 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.

4. The microstructure prediction method according to claim 3, 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).

5. The microstructure prediction method according to claim 3, 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.

6. The microstructure prediction method according to any one of claims 3 to 5, 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).

7. The microstructure prediction method according to claim 6, 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.

8. 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 7 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.

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

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