Vacuum rheo-die casting method and device for thin-walled aluminum alloy parts

Abstract

The application discloses a vacuum rheo-die casting forming method and device for aluminum alloy thin-wall parts, belongs to the field of metal injection molding process and heat treatment technology, and specifically comprises the following steps: firstly, aluminum alloy powder is melted into liquid, a mathematical model is constructed to calculate the solid phase rate, the casting mold is preheated and vacuumized when the solid phase rate approaches a threshold value, and the obtained semi-solid slurry is introduced into a die casting chamber of a die casting machine, low-temperature inert gas is supplemented into the casting mold to take away the heat of the mold when the aluminum alloy melt enters the casting mold, the casting mold is rotated at high speed, the semi-solid slurry is attached to the inner wall of the casting mold by centrifugal force to be cooled and solidified, the solidification time is estimated through a preliminary casting solidification model, the temperature of the casting mold is lowered after the semi-solid slurry is completely solidified, the aluminum alloy melt is rapidly cooled, solid solution treatment and aging treatment of the aluminum alloy casting are completed in the casting mold, and finally, the casting is automatically demolded and taken out through a mechanical arm on the device.

Description

Technical Field

[0001] This invention belongs to the field of metal injection molding technology and heat treatment technology, specifically relating to a vacuum rheological die casting method and apparatus for thin-walled aluminum alloy parts. Background Technology

[0002] With the rapid development of the automotive and 5G communication industries, the demand for lightweighting is increasing, and the urgent need for thin-walled aluminum alloy parts has become an important area of ​​development. Thin-walled aluminum alloy parts are precision castings with high requirements for dimensional accuracy and surface quality. However, during the casting process, the surface tension of the liquid metal creates a damping effect, resulting in a Laplace force that hinders the filling flow of the thin section.

[0003] Therefore, traditional rheological die casting processes, due to the low temperature and high viscosity of the semi-solid slurry, have poor filling capacity. Moreover, the flow and heat transfer processes during filling interfere with each other, which easily leads to casting defects such as under-casting, cold shuts, and shrinkage cavities in the castings. This seriously affects the application of rheological die casting technology and the quality of the castings. Therefore, effective measures must be taken to improve the process in order to enhance the filling capacity of the semi-solid slurry. Summary of the Invention

[0004] Therefore, the present invention provides a vacuum rheological die casting method and apparatus for thin-walled aluminum alloy parts to solve the problem of filling defects of semi-solid slurry in the prior art.

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

[0006] According to a first aspect of the invention,

[0007] This invention discloses a vacuum rheological die casting method for thin-walled aluminum alloy parts, comprising:

[0008] A fixed proportion of aluminum alloy powder is added to a crucible, and the aluminum alloy powder is melted in a melting furnace under a protective atmosphere.

[0009] After the aluminum alloy melt is completely melted into a liquid, the temperature of the aluminum alloy melt is monitored in real time, and a low-temperature inert gas is introduced into the aluminum alloy melt. The process continues until the temperature of the aluminum alloy melt decreases, and the time elapsed is statistically significant. The mixture is converted into a semi-solid slurry, and a mathematical model is established to calculate the solid fraction of the semi-solid slurry, so that the objective function... Minimize, applying the objective function:

[0010] ;

[0011] in, These are the process parameters for aluminum alloy melt. The average solid fraction, Let be the vector function of the solid fraction distribution region. The standard deviation of the solid fraction. , , The weighting coefficients represent the degree of emphasis placed on "accuracy", "uniformity" and "efficiency", respectively.

[0012] when When it approaches the threshold, The semi-solid slurry obtained in the area is introduced into the die casting chamber of the die casting machine and preheated to cast the mold. At the same time, the mold is evacuated. Then, the injection parameters of the die casting machine are adjusted, and finally the semi-solid slurry is injected into the mold.

[0013] When the aluminum alloy melt enters the casting mold, a low-temperature inert gas is added to the casting mold to remove the heat of the mold. At the same time, the casting mold rotates at high speed, and the semi-solid slurry is attached to the inner wall of the casting mold by centrifugal force, so that the semi-solid slurry cools and solidifies. Based on this, a preliminary casting solidification model is constructed to describe the solidification process of the semi-solid slurry.

[0014] The casting mold stops rotating, and the temperature of the casting mold is reduced by water cooling or air cooling to quickly cool the aluminum alloy melt. After the aluminum alloy melt solidifies, the remaining semi-solid slurry is injected into the casting mold again.

[0015] The casting mold is kept warm for a period of time before the casting is removed.

[0016] Furthermore, the process of establishing a mathematical model for calculating the solid fraction of the semi-solid slurry includes:

[0017] Construct the energy conservation equation and apply the following formula: , bring in The temperature field equation is obtained as follows: ;

[0018] The equilibrium solid fraction is compared using the lever model, and the formula is: Then substitute The temperature field equation Transformed into solid-phase field equation Specifically:

[0019] ,in, and These are the liquidus temperature and the solidus temperature. It is the melt density. It is time. It is the velocity vector of the melt. Phase change latent heat release value, The enthalpy reduction function, Thermal conductivity, , and These represent the curl, gradient, and divergence of the melt, respectively.

[0020] A bubble dynamics model is constructed to determine the bubble force based on bubble size, floating velocity, and gas holdup. The applicable formula is: + + ,in, The density of the semi-solid aluminum alloy melt. The relative velocity vector difference between gas and liquid. Volume fraction of inert gases Bubble diameter, Let be the curl of the flow field. For the total acceleration of gases and liquids, Turbulent dissipation force coefficient, Turbulent kinetic energy of the liquid phase gradient of gas phase volume fraction The drag coefficient is a function of the Reynolds number. The lift coefficient, This is the virtual mass force coefficient;

[0021] Establish the momentum conservation equation, and apply the formula: The velocity field of the semi-solid slurry after the introduction of inert gas was obtained. ,in, For static pressure, For viscous stress tensor, It is the vector of gravitational acceleration;

[0022] According to the solid fraction field equation of the semi-solid slurry and velocity field equations Small-scale experiments were conducted to verify the model and correct the empirical coefficients, thereby obtaining the process parameters. , so that the objective function minimize.

[0023] Furthermore, the protective gas is argon;

[0024] The inert gas is nitrogen gas, which is heated by the compressor before entering the semi-solid slurry.

[0025] Furthermore, before the semi-solid slurry enters the casting mold, the casting mold is preheated at a temperature of 0 to 200 degrees Celsius, and at the same time, the casting mold is evacuated, with the vacuum level maintained between 20 and 50 MPa.

[0026] Furthermore, the process of constructing the preliminary casting solidification model includes:

[0027] An inert gas is injected into the casting mold, and the heat is carried away by the inert gas. The formula for estimating the rate of heat release is: ,in, It is the gas mass flow rate. It is the specific heat capacity of inert gases. and These are the temperatures at which the gas enters and exits the melt, respectively.

[0028] Construct a latent heat release model for phase change and calculate the calorific value release rate. The applied formula is ,in, The latent heat distribution function;

[0029] The melt in the casting mold is considered as a homogeneous system, and the overall energy balance equation is constructed as follows:

[0030] ,in, The heat capacity of the melt. For cooling rate, For the heat dissipation rate of the casting mold;

[0031] Record the two time points at which the semi-solid slurry enters the casting mold. and And obtain the temperature by measuring the temperature of the casting mold. ,when At that time, the semi-solid slurry initially added to the casting mold solidifies.

[0032] Furthermore, a temperature sensor is embedded in the casting model. When the temperature of the casting model is between 465°C and 480°C, it is first kept at that temperature. After keeping at that temperature for 10 to 60 minutes, the temperature of the casting mold is then rapidly reduced.

[0033] Furthermore, after the aluminum alloy melt solidifies, the remaining semi-solid slurry is injected into the casting mold again, so that the temperature of the casting mold is in the range of 150°C to 190°C, and a second stage of heat preservation is performed.

[0034] Furthermore, after the aluminum alloy melt solidifies, the remaining semi-solid slurry is injected into the casting mold multiple times, and the temperature of the casting mold is maintained within the range of 150°C to 190°C.

[0035] Furthermore, the aluminum alloy powder contains 9.6%–12.0% Si, 1.5%–3.5% Cu, ≤1.3% Fe, ≤0.3% Mg, ≤0.5% Mn, ≤1.0% Zn, and ≤0.5% Ni, and the melting temperature of the aluminum alloy powder is 700℃–720℃.

[0036] According to a second aspect of the invention,

[0037] This invention discloses an apparatus that applies the above-mentioned vacuum rheological die casting method for thin-walled aluminum alloy parts.

[0038] When the mold is removed and the casting is taken out, the device automatically opens the mold and uses a robotic arm to take out the finished casting.

[0039] The present invention has the following advantages:

[0040] The vacuum rheological die casting method for thin-walled aluminum alloy parts provided by this invention integrates a gas-induced semi-solid slurry preparation device with die casting technology and performs vacuum treatment. Based on this, the aluminum alloy thin-walled parts prepared by the vacuum rheological die casting method eliminate casting defects such as incomplete filling, cold shuts, lock holes, and porosity caused by the poor filling ability of semi-solid slurry in traditional rheological die casting. At the same time, a differential vector equation model is established to describe this process, so as to quantify the die casting process. This can significantly improve the existing rheological die casting technology and solve the problem of poor filling ability caused by the low temperature and high viscosity of semi-solid slurry. Attached Figure Description

[0041] To more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are merely exemplary, and those skilled in the art can derive other embodiments based on the provided drawings without creative effort.

[0042] The structures, proportions, sizes, etc. illustrated in this specification are only for the purpose of assisting those skilled in the art in understanding and reading the content disclosed herein, and are not intended to limit the conditions under which the present invention can be implemented. Therefore, they have no substantial technical significance. Any modifications to the structure, changes in the proportions, or adjustments to the size, without affecting the effects and objectives that the present invention can produce, should still fall within the scope of the technical content disclosed in the present invention.

[0043] Figure 1 A schematic diagram of the vacuum rheological die casting apparatus for thin-walled aluminum alloy parts provided by the present invention.

[0044] Figure 2A flowchart of a vacuum rheological die casting method for thin-walled aluminum alloy parts provided by the present invention;

[0045] Figure 3 A flowchart illustrating the mathematical model for constructing the solid fraction of a semi-solid slurry, as provided by this invention.

[0046] Figure 4 The flowchart for constructing a preliminary casting solidification model provided by the present invention. Detailed Implementation

[0047] It should be noted that, unless otherwise specified, the embodiments and features described in this application can be combined with each other. The present invention will now be described in detail with reference to the accompanying drawings and embodiments.

[0048] It should be noted that the following detailed descriptions are exemplary and intended to provide further explanation of this application. Unless otherwise specified, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application pertains.

[0049] It should be noted that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the exemplary embodiments according to this application. As used herein, the singular form is intended to include the plural form as well, unless the context clearly indicates otherwise. Furthermore, it should be understood that when the terms "comprising" and / or "including" are used in this specification, they indicate the presence of features, steps, operations, devices, components, and / or combinations thereof.

[0050] It should be noted that the terms "first," "second," etc., in the specification, claims, and accompanying drawings of this application are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence. It should be understood that such data can be interchanged where appropriate so that the embodiments of this application described herein can be implemented, for example, in sequences other than those illustrated or described herein.

[0051] Furthermore, the terms “including” and “having” and any variations thereof are intended to cover non-exclusive inclusion, such as a process, method, system, product, or apparatus that includes a series of steps or units, which is not necessarily limited to those steps or units that are explicitly listed, but may include other steps or units that are not explicitly listed or that are inherent to such process, method, product, or apparatus.

[0052] For ease of description, spatial relative terms such as "above," "on top of," "on the upper surface of," "above," etc., may be used here to describe the spatial positional relationship of a device or feature to other devices or features as shown in the figure. It should be understood that spatial relative terms are intended to include different orientations in use or operation in addition to the orientation of the device as described in the figure.

[0053] For example, if a device in the accompanying drawings is inverted, a device described as "above" or "on top of" other devices or structures will subsequently be positioned as "below" or "under" other devices or structures. Thus, the exemplary term "above" can include both "above" and "below". The device may also be positioned differently, rotated 90 degrees, or in other orientations, and the spatial relative descriptions used herein will be interpreted accordingly.

[0054] Please refer to this as well. Figures 3-4 This invention discloses a vacuum rheological die casting method for thin-walled aluminum alloy parts. The purpose of this invention is to address the casting defects such as undercasting, cold shuts, and shrinkage cavities, as well as insufficient filling capacity, that exist in the forming process of thin-walled aluminum alloy parts. This invention develops a vacuum rheological die casting method for thin-walled aluminum alloy parts, integrating a gas-induced semi-solid slurry preparation device with die casting technology. The technical solution disclosed in this invention will be described below with specific embodiments, and the specific steps include:

[0055] In a specific embodiment of this invention, starting from step S1, aluminum alloy powder is first added to a crucible according to a fixed ratio, and under a protective atmosphere, the aluminum alloy powder is melted in a melting furnace until it is completely melted into a liquid. In step S2, the molten aluminum alloy is introduced into a die-casting machine, and its temperature is monitored in real time. Simultaneously, a low-temperature inert gas is introduced into the molten aluminum alloy. As the temperature of the molten aluminum alloy decreases, it gradually enters a semi-solid state until a statistical time has elapsed. It is then transformed into a semi-solid slurry. Next, in step S3, this transformation process is described using a mathematical model. Specifically, the solid fraction of the semi-solid slurry is calculated using the mathematical model, so that the objective function... Minimize, and apply the objective function as:

[0056] ;

[0057] in, These are the process parameters for aluminum alloy melt. The average solid fraction, Let be the vector function of the solid fraction distribution region. The standard deviation of the solid fraction. , , The weighting coefficients represent the degree of emphasis placed on "accuracy," "uniformity," and "efficiency," respectively. In determining... , , After determining the weighting coefficients, proceed to step S4 to input the process parameters P and the objective function. At the minimum, it should be noted that the process parameter P includes many process parameters that can change the solid fraction, such as aeration time, aeration rate, and initial melt temperature. After approaching the threshold, Within the specified range, the physical state of the semi-solid slurry converted from molten aluminum alloy is optimal, therefore it can be used to... The semi-solid slurry obtained in the region is introduced into the die-casting chamber of the die-casting machine, and the casting mold is preheated. The casting mold is then evacuated, and the injection parameters of the die-casting machine are adjusted simultaneously in step S5. Finally, the semi-solid slurry is injected into the casting mold. In steps S6 and S7, after the aluminum alloy melt enters the casting mold, a low-temperature inert gas is added to the mold to remove heat. Simultaneously, the casting mold rotates at high speed, using centrifugal force to adhere the semi-solid slurry to the inner wall of the mold, allowing it to cool and solidify. This results in a denser surface structure of the casting. Furthermore, residual air bubbles in the semi-solid slurry are separated from the mold by centrifugal force, along with slag and oxides. In step S7, a preliminary casting solidification model is constructed to describe the solidification process of the semi-solid slurry and to estimate the solidification time. After the semi-solid slurry has completely solidified, the process proceeds to step S8. At this point, the casting mold stops rotating, and the temperature of the casting mold is reduced by water cooling or air cooling to rapidly cool the aluminum alloy melt, thereby completing the solution treatment of the aluminum alloy casting. In step S9, after the aluminum alloy melt has solidified, the remaining semi-solid slurry is injected into the casting mold again, which allows the temperature of the aluminum alloy casting to rise again, so as to perform aging treatment on the aluminum alloy casting. That is, in step S10, the casting mold is kept at a certain temperature. After a period of time, the aluminum alloy casting obtains the strengthening phase generated by the decomposition of the supersaturated solid solution, which greatly improves the strength and hardness. Finally, the mold is removed and the casting is taken out.

[0058] In some embodiments, the protective gas in the melting furnace is argon, and the inert gas is nitrogen. After being compressed and heated, nitrogen enters the semi-solid slurry to rapidly bring the aluminum alloy melt into a semi-solid state. In this embodiment, ADC12 aluminum alloy is preferably used as the raw material, containing 9.6%–12.0% Si, 1.5%–3.5% Cu, ≤1.3% Fe, ≤0.3% Mg, ≤0.5% Mn, ≤1.0% Zn, and ≤0.5% Ni, with the remainder being elemental aluminum and unavoidable impurities. Optionally, A380 aluminum alloy can also be used as the raw material, containing 7.5%–9.5% Si, 3.0%–4.0% Cu, ≤2.0% Fe, ≤0.1% Mg, ≤0.5% Mn, ≤3.0% Zn, and ≤0.5% Ni. During pretreatment, refer to... Figure 1 First, remove the dirt from the surface of the alloy, then place it in an induction furnace and heat it to 700 ℃. After the alloy is completely melted, degas, remove slag, and scrape off the slag. When the aluminum alloy powder is completely melted into liquid, seal and fix the gas-induced semi-solid slurry preparation device and the melt collection device. The melt in the crucible flows along the heat preservation channel of the melting furnace through the gate on the sealing block of the semi-solid slurry preparation device into the melt collection device of the die casting equipment. Nitrogen gas is introduced into the melt to obtain a semi-solid slurry. Then, open the melt shut-off valve and pour the semi-solid slurry into the injection chamber of the die casting machine. Seal the injection chamber, open the vacuum valve to evacuate the mold cavity and the injection chamber, and start the injection punch to cast the workpiece.

[0059] In a specific embodiment of the present invention, the process of establishing a mathematical model for calculating the solid fraction of a semi-solid slurry includes the following steps: first, step S31 is performed to detect the temperature of the melt; then, in step S32, an energy conservation equation is constructed, using the following formula: , bring in The temperature field equation is obtained as follows: ;

[0060] Based on this, proceed to step S33, applying the lever model to compare the equilibrium solid fractions, using the following formula: Then substitute The temperature field equation Transformed into solid-phase field equation Specifically:

[0061] ;

[0062] in, and These are the liquidus temperature and the solidus temperature. It is the melt density. It is time. It is the velocity vector of the melt. Phase change latent heat release value, The enthalpy reduction function, Thermal conductivity, , and These represent the curl, gradient, and divergence of the melt, respectively.

[0063] In step S34, a bubble dynamics model is constructed, and the bubble force is determined based on the bubble size, floating velocity, and gas holdup. The applicable formula is:

[0064] + + ;

[0065] in, The density of the semi-solid aluminum alloy melt. The relative velocity vector difference between gas and liquid. Volume fraction of inert gases Bubble diameter, Let be the curl of the flow field. For the total acceleration of gases and liquids, Turbulent dissipation force coefficient, Turbulent kinetic energy of the liquid phase gradient of gas phase volume fraction The drag coefficient is a function of the Reynolds number. The lift coefficient, This represents the virtual mass force coefficient. Proceed to step S35 to establish the momentum conservation equation, applying the formula:

[0066] ;

[0067] The velocity field of the semi-solid slurry after the introduction of inert gas was obtained. ,in, For static pressure, For viscous stress tensor, This represents the gravitational acceleration vector. A small-scale experiment was conducted in step S36, and the solidity field equation of the semi-solid slurry was used. and velocity field equations This allows for the verification of the model and the correction of empirical coefficients, resulting in the acquisition of process parameters. , so that the objective function minimize.

[0068] In one specific embodiment of this invention, before the semi-solid slurry enters the casting mold, the casting mold is preheated to a temperature of 0-200 degrees Celsius. Simultaneously, a vacuum is applied to the casting mold, maintaining a vacuum level between 20-50 MPa. A temperature sensor is embedded in the casting mold. When the temperature of the casting mold is between 465°C and 480°C, it is first held at that temperature for 10-60 minutes. Then, the temperature of the casting mold is rapidly reduced, thereby completing the solution treatment of the aluminum alloy material.

[0069] In this embodiment, after the aluminum alloy melt solidifies, the remaining semi-solid slurry is injected into the casting mold again, maintaining the casting mold temperature within the range of 150°C to 190°C and performing a second stage of heat preservation. Specifically, the casting mold is insulated to maintain a stable internal temperature. Optionally, after the aluminum alloy melt solidifies, the remaining semi-solid slurry can be injected into the casting mold multiple times to continuously inject heat into the casting mold, thereby maintaining the casting mold temperature within the range of 150°C to 190°C.

[0070] In some embodiments, the process of constructing a preliminary casting solidification model includes the following steps: first, in step S71, inert gas is injected into the casting mold to remove heat. The formula for estimating the rate of heat release is: ,in, It is the gas mass flow rate. It is the specific heat capacity of inert gases. and These are the temperatures at which the gas enters and exits the melt, respectively.

[0071] Then, in step S72, a latent heat release model for phase change is constructed, and the calorific value release rate is calculated. The applied formula is ,in, Given the latent heat distribution function, the melt in the casting mold is thus considered as a homogeneous system, and in step S73, the total energy balance equation is constructed:

[0072] ,in, The heat capacity of the melt. For the cooling temperature drop rate, The heat dissipation rate of the casting mold.

[0073] In step S74, the two time points when the semi-solid slurry enters the casting mold are recorded. and And obtain the temperature by measuring the temperature of the casting mold. In step S75, the general solution of the differential equation is obtained, and when When the semi-solid slurry is first added to the casting mold, it indicates that the slurry has solidified.

[0074] Based on the same inventive concept, this invention discloses a device, referring to... Figure 1 When applying the vacuum rheological die casting method for thin-walled aluminum alloy parts proposed above, it should be noted that when the casting is removed from the mold, the device automatically opens the mold and uses a robotic arm to remove the finished casting.

[0075] Although the present invention has been described in detail above with general descriptions and specific embodiments, modifications or improvements can be made to it, which will be obvious to those skilled in the art. Therefore, all such modifications or improvements made without departing from the spirit of the present invention fall within the scope of protection claimed by the present invention.

Claims

1. A vacuum rheological die casting method for thin-walled aluminum alloy parts, characterized in that, include: A fixed proportion of aluminum alloy powder is added to a crucible, and the aluminum alloy powder is melted in a melting furnace under a protective atmosphere. After the aluminum alloy powder is completely melted into an aluminum alloy melt, the temperature of the aluminum alloy melt is monitored in real time, and a low-temperature inert gas is introduced into the aluminum alloy melt. While waiting for the temperature of the aluminum alloy melt to decrease, a mathematical model is established to calculate the solid fraction of the aluminum alloy melt, so that the objective function... Minimize and calculate the statistical time required for the aluminum alloy melt to transform into a semi-solid slurry. The objective function is: ； in, These are the process parameters for aluminum alloy melt. The average solid fraction, Let be the vector function of the solid fraction distribution region. The standard deviation of the solid fraction. , , The weighting coefficients represent the degree of emphasis placed on accuracy, uniformity, and efficiency, respectively. when When it approaches the threshold, The semi-solid slurry obtained in the area is introduced into the die casting chamber of the die casting machine and preheated to cast the mold. At the same time, the mold is evacuated. Then, the injection parameters of the die casting machine are adjusted, and finally the semi-solid slurry is injected into the mold. When the aluminum alloy melt enters the casting mold, a low-temperature inert gas is added to the casting mold to remove the heat of the mold. At the same time, the casting mold rotates at high speed, and the semi-solid slurry is attached to the inner wall of the casting mold by centrifugal force, so that the semi-solid slurry cools and solidifies. Based on this, a preliminary casting solidification model is constructed to describe the solidification process of the semi-solid slurry. The casting mold stops rotating, and the temperature of the casting mold is reduced by water cooling or air cooling to quickly cool the aluminum alloy melt. After the aluminum alloy melt solidifies, the remaining semi-solid slurry is injected into the casting mold again. The casting mold is kept warm for a period of time before the casting is removed.

2. The vacuum rheological die casting method for thin-walled aluminum alloy parts according to claim 1, characterized in that, The process of establishing a mathematical model for calculating the solid fraction of the semi-solid slurry includes: Construct the energy conservation equation and apply the following formula: , bring in The temperature field equation is obtained as follows: ; The equilibrium solid fraction is compared using the lever model, and the formula is: Then substitute The temperature field equation Transformed into solid-phase field equation Specifically: ,in, and These are the liquidus temperature and the solidus temperature. It is the melt density. It is time. It is the velocity vector of the melt. Phase change latent heat release value, The enthalpy reduction function, Thermal conductivity, , and These represent the curl, gradient, and divergence of the melt, respectively. A bubble dynamics model is constructed to determine the bubble force based on bubble size, floating velocity, and gas holdup. The applicable formula is: + + ； in, The density of the semi-solid aluminum alloy melt. The relative velocity vector difference between gas and liquid. Volume fraction of inert gases Bubble diameter, Let be the curl of the flow field. For the total acceleration of gases and liquids, Turbulent dissipation force coefficient, Turbulent kinetic energy of the liquid phase gradient of gas phase volume fraction The drag coefficient is a function of the Reynolds number. The lift coefficient, This is the virtual mass force coefficient; Establish the momentum conservation equation, and apply the following formula: ： The velocity field of the semi-solid slurry after the introduction of inert gas was obtained. ,in, For static pressure, For viscous stress tensor, It is the vector of gravitational acceleration; According to the solid fraction field equation of the semi-solid slurry and velocity field equations Small-scale experiments were conducted to verify the model and correct the empirical coefficients, thereby obtaining the process parameters. , so that the objective function minimize.

3. The vacuum rheological die casting method for thin-walled aluminum alloy parts according to claim 2, characterized in that: The protective atmosphere is argon; The inert gas is nitrogen gas, which is heated by the compressor before entering the semi-solid slurry.

4. The vacuum rheological die casting method for thin-walled aluminum alloy parts according to claim 3, characterized in that, Before the semi-solid slurry enters the casting mold, the casting mold is preheated at a temperature of 0-200 degrees Celsius. At the same time, the casting mold is evacuated and the vacuum degree is maintained between 20-50 MPa.

5. The vacuum rheological die casting method for thin-walled aluminum alloy parts according to claim 4, characterized in that, The process of constructing the preliminary casting solidification model includes: An inert gas is injected into the casting mold, and the heat is carried away by the inert gas. The formula for estimating the rate of heat release is: ； in, It is the gas mass flow rate. It is the specific heat capacity of inert gases. and These are the temperatures at which the gas enters and exits the melt, respectively. Construct a latent heat release model for phase change and calculate the calorific value release rate. The applied formula is ,in, The latent heat distribution function; The melt in the casting mold is considered as a homogeneous system, and the overall energy balance equation is constructed as follows: ； in, The heat capacity of the melt. For cooling rate, For the heat dissipation rate of the casting mold; Record the two time points at which the semi-solid slurry enters the casting mold. and And obtain the temperature by measuring the temperature of the casting mold. ,when At that time, the semi-solid slurry initially added to the casting mold solidifies.

6. The vacuum rheological die casting method for thin-walled aluminum alloy parts according to claim 5, characterized in that, A temperature sensor is embedded in the casting mold. When the temperature of the casting mold is between 465°C and 480°C, it is first kept at that temperature. After keeping at that temperature for 10 to 60 minutes, the temperature of the casting mold is then rapidly reduced.

7. The vacuum rheological die casting method for thin-walled aluminum alloy parts according to claim 6, characterized in that, After the aluminum alloy melt solidifies, the remaining semi-solid slurry is injected into the casting mold again, so that the temperature of the casting mold is in the range of 150°C to 190°C, and a second heat preservation is performed.

8. The vacuum rheological die casting method for thin-walled aluminum alloy parts according to claim 6, characterized in that, After the aluminum alloy melt solidifies, the remaining semi-solid slurry is injected into the casting mold multiple times, and the temperature of the casting mold is maintained in the range of 150°C to 190°C.

9. The vacuum rheological die casting method for thin-walled aluminum alloy parts according to claim 1, characterized in that, The aluminum alloy powder contains 9.6%–12.0% Si, 1.5%–3.5% Cu, ≤1.3% Fe, ≤0.3% Mg, ≤0.5% Mn, ≤1.0% Zn, and ≤0.5% Ni. The melting temperature of the aluminum alloy powder is 700℃–720℃.

10. An apparatus for using the vacuum rheological die casting method for thin-walled aluminum alloy parts as described in claim 6, characterized in that, When removing the casting from the mold, the device automatically opens the mold and uses a robotic arm to remove the finished casting.

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