Mg-gd-y-zn-zr series alloy and method for improving flowability of die casting thereof

Abstract

The application discloses a Mg-Gd-Y-Zn-Zr series alloy die-casting fluidity improving method, characterized in that 0.5-1.5% of Ca elements in mass percentage are added in the VW92 alloy to improve the die-casting fluidity of the alloy.The application also discloses a high-fluidity Mg-Gd-Y-Zn-Zr series alloy with good die-casting fluidity, namely, the alloy is composed of the VW92 alloy and 0.5-1.5% of Ca elements in mass percentage.The application can better improve the die-casting fluidity of the Mg-Gd-Y-Zn-Zr series alloy and improve product quality.

Description

Technical Field

[0001] This invention relates to the field of automotive magnesium rare earth alloy casting technology, and in particular to a Mg-Gd-Y-Zn-Zr alloy and a method for improving its die casting fluidity. Background Technology

[0002] Magnesium alloys are characterized by their light weight, high specific strength, good vibration damping performance, and excellent electrical and thermal conductivity, and are currently widely used in aerospace, automotive manufacturing, and 3C (computer, communication, and consumer electronics) fields. With the deepening of energy conservation and emission reduction efforts, magnesium alloys, as the lightest commercially available metal structural material, can play a crucial role in lightweight automotive design, significantly reducing carbon emissions and bringing greater economic benefits.

[0003] With the increasing demands on magnesium alloy applications and the continuous development of material processing equipment, cast magnesium alloy components are becoming increasingly complex in shape and gradually expanding in size from small to large, ultra-large, and structurally integrated. This places high demands on the fluidity of magnesium alloys themselves. During the casting process, the solidification of the molten magnesium alloy generates enormous solidification shrinkage forces. When these forces exceed the alloy's critical resistance, fatal defects such as hot cracking are easily produced, severely hindering the formability and application of magnesium alloys. Good fluidity allows the remaining liquid phase at the end of solidification to effectively compensate for hot cracks, significantly reducing the tendency of magnesium alloys to hot crack. Furthermore, the primary casting method for magnesium alloys is currently die casting. For the forming of complex and ultra-large magnesium alloy castings, alloy fluidity also has a significant impact on the quality of die castings. During die casting, the magnesium alloy melt must possess high fluidity to ensure rapid filling of the mold, especially for structures containing small holes or uneven wall thicknesses, where the fluidity requirement is even higher. Therefore, improving the fluidity of magnesium alloys is of great significance for improving the quality of complex and ultra-large magnesium alloy castings and developing key technologies for magnesium alloy casting.

[0004] VW92 alloy, as a high-strength cast magnesium alloy in the Mg-Gd-Y-Zn-Zr series, has a wide range of applications. However, due to its high rare earth element content, this alloy has poor fluidity, a high tendency to hot cracking, and poor die-casting formability, which seriously hinders its application.

[0005] Therefore, how to improve the shortcomings of VW92 magnesium alloy, enhance its alloy fluidity, thereby reducing defects in alloy casting products and improving product quality has become a problem that needs to be considered and solved by those skilled in the art. Summary of the Invention

[0006] In view of the shortcomings of the prior art, the technical problem to be solved by the present invention is: how to provide a Mg-Gd-Y-Zn-Zr alloy and a method for improving its die casting fluidity, so as to better improve the fluidity performance of the Mg-Gd-Y-Zn-Zr alloy during die casting and improve product quality.

[0007] To solve the above-mentioned technical problems, the present invention adopts the following technical solution:

[0008] A method for improving the die casting fluidity of Mg-Gd-Y-Zn-Zr alloys is characterized by adding 0.5-1.5% by mass of Ca element to VW92 alloy to improve its die casting fluidity.

[0009] The VW92 alloy described in the scheme, namely Mg-9Gd-2Y-1Zn-0.5Zr alloy, comprises the following components in the indicated mass ratios: Gd: 9.0%-10.0%, Y: 1.5%-2.50%, Zn: 0.8%-1.5%, Zr: 0.4%-0.5%, with the balance being Mg and unavoidable impurities, the content of which is less than or equal to 0.05%. Thus, by adding a small amount of Ca to the VW92 alloy, on the one hand, the introduction of the low-melting-point eutectic phase of Mg2Ca with a relatively large diffusion coefficient can drive the flow of the magnesium rare earth phase with a small diffusion coefficient, allowing sufficient time for the eutectic alloy to fill the mold cavity before crystallization; on the other hand, magnesium alloys with high rare earth element content have always had the problem of high melt viscosity. However, after introducing the relatively low-viscosity Mg2Ca phase, the Mg2Ca phase can be distributed between the magnesium rare earth phases before the melt solidifies, reducing the bonding force between the magnesium rare earth phases and thus reducing the overall high viscosity of the melt. Therefore, it can greatly improve its fluidity and improve the die-casting performance, as has been proven by fluidity tests.

[0010] Among alloys of the same type, differences in chemical composition lead to variations in crystallization characteristics and fluidity. Generally, alloy crystallization occurs within a specific temperature range, and the primary crystals formed during crystallization impede the flow of molten metal. Eutectic alloys, however, crystallize at a constant temperature, without the formation of primary crystals, resulting in less resistance to the molten metal. Furthermore, eutectic alloys have lower melting points, allowing sufficient time to fill the mold cavity before crystallization at the same pouring temperature, thus exhibiting superior casting performance. The further the alloy's composition deviates from the eutectic point, the wider its crystallization temperature range, and the worse its fluidity. Therefore, while meeting performance requirements, casting alloys should ideally be eutectic alloys or alloys with compositions close to eutectic.

[0011] Therefore, this invention also discloses a high-fluidity Mg-Gd-Y-Zn-Zr alloy with good die-casting fluidity, which is composed of 0.5-1.5% Ca by mass on the basis of the existing VW92 alloy; the VW92 alloy includes the following components in the following mass proportions: Gd: 9.0%-10.0%, Y: 1.5%-2.50%, Zn: 0.8%-1.5%, Zr: 0.4%-0.5%, with the balance being Mg and unavoidable impurities, the content of which is less than or equal to 0.05%.

[0012] Alternatively, the Mg-Gd-Y-Zn-Zr alloy is composed of VW92 alloy with the addition of 1.0% by mass of Ca, specifically comprising the following components in the following mass proportions: Gd: 9.12%, Y: 2.05%, Zn: 1.05%, Zr: 0.51%, Ca: 0.96%, with the balance being Mg and unavoidable impurities, the content of which is less than or equal to 0.05%.

[0013] Alternatively, the Mg-Gd-Y-Zn-Zr alloy is composed of VW92 alloy with the addition of 1.5% by mass of Ca, specifically comprising the following components in the following mass proportions: Gd: 9.44%, Y: 2.4%, Zn: 1.21%, Zr: 0.44%, Ca: 1.54%, with the balance being Mg and unavoidable impurities, the content of which is less than or equal to 0.05%.

[0014] Furthermore, the high-fluidity Mg-Gd-Y-Zn-Zr alloy is cast using the following casting steps:

[0015] 1) Batching: VW92 alloy and Mg-Ca master alloy are used as raw materials, and the raw materials are batched according to the alloy composition ratio to ensure that the total amount of impurity elements Si and Fe is less than 0.05%;

[0016] 2) Remove impurities from raw materials, remove the oxide layer on the metal surface of the materials, and then dry them for later use;

[0017] 3) Melt the raw materials to obtain a melt;

[0018] 4) Melt purification: The melt is purified by removing slag before casting.

[0019] 5) After spraying the mold cavity with release agent, the mold is cast, cooled and demolded to obtain the target magnesium rare earth alloy product.

[0020] Thus, in this method, VW92 alloy and Mg-Ca master alloy are used as raw materials. This is because the melting point of magnesium matrix is ​​only about 650℃, while the melting point of pure Ca is higher than that of magnesium. In order to allow calcium to fully enter the magnesium matrix, Mg-Ca master alloy with a low melting point is selected as raw material to facilitate the full mixing of the two.

[0021] Further, in step 2), the specific operating steps are as follows: first, use a grinding wheel to remove the oxide layer on the surface of the material; put the VW92 alloy and Mg-Ca intermediate alloy into a drying oven, set the temperature to 250℃, preheat for 30 minutes to remove moisture, and then set aside for use.

[0022] Because magnesium is chemically reactive with a flash point of around 500℃, directly heating magnesium alloys that have been exposed to air for a long time can easily cause combustion during the smelting process. This not only severely affects the quality of the magnesium alloy but also poses a serious experimental risk. Therefore, removing moisture from magnesium alloy raw materials is essential to ensure the smooth progress of subsequent smelting and the quality of the alloy.

[0023] Further, in step 3), the specific operating steps are as follows: preheat the melting furnace at 500℃ for 30 minutes. Prepare a solution of boron nitride and alcohol at a mass ratio of 1:2, and apply it evenly to the inner wall of the low-carbon steel crucible with a brush, then dry it (place it in a drying oven to dry); place the dehydrated VW92 alloy into the air-dried iron crucible, and under the protection of a CO2+SF6 (100:1) mixed gas, raise the temperature of the melting furnace to 730℃, hold it at this temperature until the VW92 alloy melts, add the dried Mg-Ca master alloy, melt it, and obtain the melt.

[0024] Adding the intermediate alloy later in this way facilitates the thorough mixing of alloying elements and ensures the accuracy of the alloying element content.

[0025] Further, in step 4), the specific operation steps are as follows: the mixed solution of boron nitride and alcohol is evenly applied to the slag removal spoon (with a long handle of low carbon steel) and the inner and outer surfaces of the stirring rod (with low carbon steel). After the material melts, the slag on the surface of the melt is removed using the above-mentioned steel spoon. The stirring rod (with low carbon steel) is used to stir for 5 minutes to obtain the target alloy melt. After standing for 30 minutes at a temperature of 730°C, it is ready for casting.

[0026] This allows air trapped during stirring to be allowed to settle and be expelled, preventing the formation of oxide impurities and porosity. Furthermore, it allows the incorporated alloying elements to diffuse fully, resulting in a homogeneous alloy.

[0027] Further, in step 5), the specific operating steps are as follows: the magnesium alloy release agent is evenly sprayed onto the inner wall of the single-spiral flowability test mold to facilitate cooling and demolding. The mold is preheated to 250°C, and after the target alloy melt has been held at this temperature, it is poured into the 250°C mold at a temperature of 730°C. After cooling, the target magnesium alloy product is obtained by demolding.

[0028] At 730℃, the alloy melt exhibits good fluidity, allowing for better filling and achieving optimal experimental testing results when poured into the mold. Preheating the mold not only extends its lifespan but also effectively prevents splashing during high-temperature molten metal casting. For the alloy, this prevents cold cracking caused by sudden cooling. A post-effect temperature of 250℃ increases the quantity and dispersion of the eutectic phase in the alloy structure, allowing it to better compensate for hot cracking and improve the performance of the alloy product.

[0029] Therefore, compared with the prior art, the present invention has at least the following advantages: The high-strength as-cast VW92 alloy provided in this application, by adding trace amounts of Ca, yields VW92-1.0Ca and VW92-2.0Ca magnesium alloys with good fluidity. When no Ca is added, the measured flow distance of this magnesium alloy is 402 mm; when the Ca content is controlled at 1.0 wt%, the measured flow distance is 501 mm; and when the Ca content is controlled at 1.5 wt%, the measured flow distance is 564 mm. The present invention improves the fluidity of the VW92 magnesium alloy, effectively reducing the alloy's tendency to hot crack, improving the quality of die-cast parts, and providing favorable conditions for the integrated casting of ultra-large complex magnesium alloy components. Attached Figure Description

[0030] Figure 1 This is a flowability sample of the VW92 alloy obtained in Experimental Example 1 of the present invention.

[0031] Figure 2 The image shows a sample of a high-fluidity Mg-Gd-Y-Zn-Zr alloy provided in Experimental Example 2 of this invention.

[0032] Figure 3 The image shows a sample of a high-fluidity Mg-Gd-Y-Zn-Zr alloy provided in Experimental Example 3 of this invention.

[0033] Figure 4 This is a schematic diagram of the self-made single-spiral flowability test mold used in Experiment Examples 1, 2 and 3 of the present invention.

[0034] Figure 5This is a schematic diagram of a die-casting mold with vibration function developed by the applicant to further improve the die-casting fluidity of Mg-Gd-Y-Zn-Zr alloys.

[0035] Figure 6 for Figure 5 A schematic diagram of the cavity surface of the moving mold.

[0036] Figure 7 for Figure 5 A cross-sectional view of the bottom of the inner cavity of the moving mold, used to show the structure of the air inlet and outlet pipes.

[0037] Figure 8 for Figure 5 A schematic diagram of the structure of a single-rod vibration device. Detailed Implementation

[0038] The present invention will now be described in further detail with reference to specific embodiments.

[0039] Implementation method: A method for improving the die casting fluidity of Mg-Gd-Y-Zn-Zr alloys, characterized in that 0.5-1.5% by mass of Ca element is added to VW92 alloy to improve its die casting fluidity.

[0040] The VW92 alloy described in the scheme, namely Mg-9Gd-2Y-1Zn-0.5Zr alloy, comprises the following components in the indicated mass ratios: Gd: 9.0%-10.0%, Y: 1.5%-2.50%, Zn: 0.8%-1.5%, Zr: 0.4%-0.5%, with the balance being Mg and unavoidable impurities, the content of which is less than or equal to 0.05%.

[0041] Specifically, by adding 0.5-1.5% by mass of Ca to the above VW92 alloy, a high-fluidity Mg-Gd-Y-Zn-Zr alloy with good die-casting fluidity is obtained.

[0042] In practice, the high-fluidity Mg-Gd-Y-Zn-Zr alloy is cast using the following casting steps:

[0043] 1) Batching: VW92 alloy and Mg-Ca master alloy are used as raw materials, and the raw materials are batched according to the alloy composition ratio to ensure that the total amount of impurity elements Si and Fe is less than 0.05%;

[0044] 2) Raw material impurity removal: First, use a grinding wheel to remove the oxide layer on the surface of the material; put the VW92 alloy and Mg-Ca master alloy into a drying oven, set the temperature to 250℃, and preheat for 30 minutes to remove moisture;

[0045] 3) Preheat the melting furnace at 500℃ for 30 minutes. Prepare a solution of boron nitride and alcohol at a mass ratio of 1:2, and apply it evenly to the inner wall of a low-carbon steel crucible using a brush. Place the dehydrated VW92 alloy into an air-dried iron crucible. Under the protection of a CO2+SF6 (100:1) mixed gas, raise the furnace temperature to 730℃ and hold it until the VW92 alloy melts. Then, add the dried Mg-Ca master alloy and melt to obtain the melt.

[0046] 4) Melt purification: The mixed solution of boron nitride and alcohol is evenly applied to the slag removal spoon with a long handle of low carbon steel and the inner and outer surfaces of the low carbon steel stirring rod. After the material melts, the slag on the surface of the melt is removed using the above-mentioned steel spoon. The melt is stirred for 5 minutes using the low carbon steel stirring rod to obtain the target alloy melt. After standing for 30 minutes at a temperature of 730℃, it is ready for casting.

[0047] 5) Mold preheating: Spray the magnesium alloy release agent evenly on the inner wall of the single spiral flowability test mold to facilitate cooling and demolding. Preheat the mold to 250°C. After the target alloy melt has been held at this temperature, pour it into the 250°C mold at 730°C. After cooling, demold to obtain the target magnesium alloy product.

[0048] To further verify the effectiveness of the present invention, the applicant conducted the following experimental examples based on the above embodiments. To facilitate the testing of its die-casting fluidity, a fluidity testing mold was used in the experimental examples; see [link to relevant documentation]. Figure 4 The flowability test mold has a single spiral cavity, with a casting gate connected to the center of the spiral for casting. After obtaining the test sample through die casting, the alloy flow distance is measured using a fine thread and a measuring tape.

[0049] Experimental Example 1

[0050] In this experimental example, the existing VW92 alloy was used directly for the test, i.e., without adding 0.5-1.5% Ca element; specifically, it was composed of the following components (raw materials) by mass percentage: Gd: 9.0%-10.0%, Y: 1.5%-2.50%, Zn: 0.8%-1.5%, Zr: 0.4%-0.5%, with the balance being Mg and unavoidable impurities, the content of which is less than or equal to 0.05%. Then, the casting steps in the above embodiment were used to cast the target magnesium alloy sample.

[0051] Experiment Example 2

[0052] In this experimental example, based on the above-described implementation method, the raw material composition is further defined as an existing VW92 alloy with the addition of 1.0% by mass of Ca. Specifically, the raw material composition by mass is: Gd: 9.12%, Y: 2.05%, Zn: 1.05%, Zr: 0.51%, Ca: 0.96%, with the balance being Mg and unavoidable impurities, the content of which is less than or equal to 0.05%. The casting process described in the above-described implementation method is then used to obtain the target magnesium alloy sample.

[0053] Experimental Example 3

[0054] In this experimental example, based on the above-described implementation method, the raw material composition is further defined as an existing VW92 alloy with the addition of 1.5% by mass of Ca. Specifically, the raw material composition by mass is: Gd: 9.44%, Y: 2.4%, Zn: 1.21%, Zr: 0.44%, Ca: 1.54%, with the balance being Mg and unavoidable impurities, the content of which is less than or equal to 0.05%. The casting process described in the above-described implementation method is then used to obtain the target magnesium alloy sample.

[0055] Flow performance test:

[0056] The test samples obtained by die casting in Experiments 1-3 above are shown in the attached figures. Figure 1-3 As shown in the figure. For the samples obtained in Experiments 1, 2, and 3, a thin thread was used to wrap around the center of the flow path, and the starting and ending positions were marked. The flow distance of the marked thread was then measured using a measuring tape. The measurement results for Experiments 1, 2, and 3 are shown in Table 1.

[0057] Table 1. Flow distance test results of Experiments 1-3

[0058] project Flow distance (mm) Experimental Example 1 402 Experiment Example 2 501 Experimental Example 3 564

[0059] As can be seen from Table 1, the VW92-1.0Ca alloy of Experimental Example 2 and the VW92-1.5Ca alloy of Experimental Example 3 have better fluidity than the VW92 alloy of Experimental Example 1, with improvements of 24.6% and 40.3% respectively. That is, Experimental Examples 2-3 have good fluidity, which can effectively improve defects such as hot cracking generated during the solidification process of magnesium alloys and meet the fluidity requirements of die casting of Mg-Gd-Y-Zn-Zr alloys with high rare earth content.

[0060] In practice, to further improve the die-casting flow properties of Mg-Gd-Y-Zn-Zr alloys, the inventors' team developed a die-casting mold with vibration capabilities. This mold applies vibration during die-casting, enhancing the flow of molten metal in thinner and finer areas within the mold cavity and improving product quality.

[0061] Specifically, this vibration-enabled die-casting mold, see Figure 5-8 The system includes a matching fixed mold 1 and a moving mold 2, which form a cavity 3 after mold closing. The mold closing surfaces of the fixed mold 1 and the moving mold are also provided with a sprue 4 and a sprue gate 5. It also includes an ejector pin vibration device mounted on the moving mold 2 (or the fixed mold). The ejector pin vibration device includes an ejector pin 6 perpendicularly facing the cavity surface, and a vibration device located at the rear end of the ejector pin 6. See also... Figure 7 In this embodiment, the cavity is a cavity containing multiple irregularly shaped components.

[0062] In this way, during die casting, the mold can directly apply vibration to the molten metal filling the cavity via ejector pins. This breaks down and refines the gas and oxide film entrained during die casting, distributing them evenly throughout the melt. This avoids structural defects, improves the flow and filling performance of the molten metal, refines the grain size, and enhances the quality of die casting. Because the vibration of the mold cavity is applied via ejector pins, ejector pins and vibration devices can be specifically installed at locations requiring localized reinforcement, facilitating the enhancement of specific areas in the casting.

[0063] The front end of the push rod 6 is provided with an abutment 7 whose width increases along the circumferential direction.

[0064] In this way, increasing the contact area between the front end of the push rod 6 and the molten metal can better apply vibration to the molten metal, while avoiding the situation where the solidified layer on the surface of the molten metal is punctured due to the low contact area, which would affect the surface quality of the casting product.

[0065] The vibration device includes an inflation chamber 8 located at the rear of the push rod 6. A piston 9 is slidably fitted into the inflation chamber at the rear end of the push rod. A return spring 10 abuts between the front end of the inflation chamber and the front end surface of the piston. An air inlet pipe 11 is also provided at the rear end of the inflation chamber behind the piston. An air outlet pipe 12 is also provided on the inner wall of the inflation chamber. When the return spring 10 is not compressed, the air outlet pipe 12 is located in front of the piston 9. When the return spring is compressed to the point where the piston is located at the air outlet pipe position, the front end face of the push rod (the front side of the abutment joint) abuts against the mold cavity surface.

[0066] In this way, when the vibration device is working, it controls the air intake through the air inlet pipe, increasing the air pressure in the inflation chamber and pushing the piston forward. The return spring is compressed. When the piston moves to the air outlet pipe position, the abutment is located on the mold cavity surface. At this time, the ejector rod abuts against the surface of the molten metal in the cavity through the abutment. If the piston continues to move forward, it will connect the air outlet pipe and the inflation chamber to release air. After the inflation chamber is depressurized, the piston retracts under the action of the return spring, and the air outlet pipe is immediately closed, causing the gas pressure in the inflation chamber to increase again, pushing the piston again and exposing the air outlet pipe to release air. This achieves repeated axial vibration of the ejector rod, which is transmitted to the molten metal in the mold cavity, improving the flow performance of the melt and thus improving the die-casting quality. After die-casting, when demolding, the air outlet pipe is closed first, and the air inlet pipe is used to inject air to eject the die-cast product. Therefore, the above-mentioned vibration device is integrated into the ejection mechanism, which allows the ejector rod to not only realize the normal ejection function of the product, but also serve as a vibration transmission device to improve the die-casting quality.

[0067] Among them, an air outlet 13 is provided between the air outlet pipe 12 and the inner wall of the inflation chamber. The air outlet 13 is a groove formed by the inward concavity of the inner wall of the inflation chamber.

[0068] In this way, the vent outlet ensures that the venting is uniformly distributed throughout the entire circumference, guaranteeing the uniformity of vibration, preventing polarization, and extending the service life of the device. Secondly, this structure greatly increases the venting area and improves venting efficiency, allowing the vent outlet to be exposed only a very small distance axially to complete the venting, ensuring that the vibration is within a very small amplitude range and preventing excessive amplitude from damaging the surface quality of the product.

[0069] The abutment 7 is matched and set in a mounting groove on the mold cavity surface; the push rod 6 is set in two sections, and a slidable sleeve structure 14 is provided between the front half and the rear half. When the return spring is not stressed, the distance from the piston position to the air outlet position is the sleeve sliding fit stroke distance.

[0070] In this way, the above structure allows the piston to push forward and compress the return spring after the inflation chamber begins to inflate. When the piston reaches the outlet pipe position, the front and rear halves of the ejector rod have just completed the sliding engagement stroke of the sleeve structure. At this point, the front and rear halves of the ejector rod are in contact and can apply force to the abutment. Under the repeated deflation of the outlet pipe, the piston vibrates and acts on the mold cavity surface through the ejector rod and the abutment. This recessed design limits the abutment when the ejector rod retracts, ensuring that its front surface is always on the mold cavity surface (and forms part of the mold cavity surface), preventing damage to the cavity surface from the abutment's back-and-forth movement. The ejector rod is designed as a telescopic structure, with a telescopic stroke equal to the piston stroke. During operation, the piston provides sufficient compression force to the return spring by traveling a certain distance. This ensures that the vibration generated when the piston reaches the outlet pipe position has a high frequency, giving the vibration a stronger disturbance effect on the molten metal, more efficiently breaking dendrites, and resulting in higher fluidity of the molten metal. The broken dendrites become new crystallization nuclei, further refining the metal grain structure. This ensures that vibration improves the performance of die-cast products.

[0071] The push rod 6 has an elastic material section 15. By compressing this elastic material section, more space is provided for the push rod to be compressed, allowing it to generate outward vibration more effectively. This ensures that the output vibration has room for adjustment and control, and better guarantees the vibration effect.

[0072] The piston's front end, the push rod 6, has a threaded section. An adjusting sleeve 16 is screwed onto this threaded section, and the rear end of the return spring abuts against the adjusting sleeve 16. This allows adjustment of the axial position of the piston on the push rod by rotating the adjusting sleeve, which in turn adjusts the piston's initial position through the action of the return spring. This effectively adjusts the distance from the piston's initial position to the outlet pipe position. This distance affects the force of the return spring when the piston reaches the outlet pipe position, thus affecting the vibration frequency. A greater return spring force results in a higher vibration frequency and faster vibration.

[0073] The air inlet pipe 11 is equipped with a pressure control valve 17, and the air outlet pipe 12 is equipped with a flow control valve 18.

[0074] In this way, the air pressure control valve can regulate the amount of air pressure input through the intake pipe, thereby regulating the vibration intensity. Simultaneously, the flow control valve can regulate the amount of air released through the outlet pipe, thus regulating the vibration amplitude.

[0075] The ejector pin vibration devices are installed in multiple locations within the mold cavity where die-casting performance is weak. As mentioned earlier, these weak locations include, but are not limited to, locations with irregular structures (leading to poor molten material filling), locations with reduced thickness or width (causing premature solidification of the molten material), locations where the product requires higher local strength, and locations where pre-installed embedded reinforcing components are added to the die-cast product. In practice, the distribution, size, shape, and number of ejector pin vibration devices can be adjusted according to the specific structure of the mold cavity and the performance requirements of the product, thereby better achieving targeted vibration reinforcement effects at specific locations.

[0076] In addition, during implementation, the moving mold is connected to the die-casting machine via bolts. The fixed mold surface is provided with a cavity corresponding to the parting surface of the die-cast part, and the fixed mold is fixed to one side of the die-casting machine via bolts. Half of the ingate cavity is provided below both the moving mold and the fixed mold. When the moving mold and the fixed mold are closed, a complete ingate is formed, which connects the pressure chamber of the die-casting machine to the ingate of the mold. During implementation, the moving mold is composed of multiple connected parts, facilitating the installation of the internal ejector vibration device.

[0077] Furthermore, it should be noted that the applicant has separately applied for patent protection for the aforementioned die-casting mold with vibration function. Therefore, if the mold is implemented independently, it will still fall within the scope of the applicant's protection.

Claims

1. A high-fluidity Mg-Gd-Y-Zn-Zr alloy with good die-casting fluidity, characterized in that, It is composed of VW92 alloy with 1-1.5% Ca by mass added; the VW92 alloy comprises the following components in the following mass proportions: Gd: 9.0%-10.0%, Y: 1.5%-2.50%, Zn: 0.8%-1.5%, Zr: 0.4%-0.5%, with the balance being Mg and unavoidable impurities, the content of which is less than or equal to 0.05%; Alternatively, the following component Gd can be used in the following mass ratio: 9.12%, Y: 2.05%, Zn: 1.05%, Zr: 0.51%, Ca: 0.96%, balance Mg and unavoidable impurities, the content of which is less than or equal to 0.05%; Alternatively, the following component Gd can be used in the following mass ratio: 9.44%, Y: 2.4%, Zn: 1.21%, Zr: 0.44%, Ca: 1.54%, balance being Mg and unavoidable impurities, the content of which is less than or equal to 0.05%; The casting process is carried out using the following steps: 1) Batching: VW92 alloy and Mg-Ca master alloy are used as raw materials, and the raw materials are batched according to the alloy composition ratio to ensure that the total amount of impurity elements Si and Fe is less than 0.05%; 2) Remove impurities from raw materials, remove the oxide layer on the metal surface of the materials, and then dry them for later use; 3) Melt the raw materials to obtain a melt; 4) Melt purification: The melt is purified by removing slag before casting. 5) After spraying the mold cavity with release agent, the mold is cast, cooled and demolded to obtain the target magnesium rare earth alloy product; In step 2), the specific operating steps are as follows: First, use a grinding wheel to remove the oxide layer on the surface of the material; put the VW92 alloy and Mg-Ca master alloy into a drying oven, set the temperature to 250℃, preheat for 30 minutes to remove moisture and set aside. In step 3), the specific operating steps are as follows: Preheat the melting furnace at 500℃ for 30 minutes. Prepare a solution of boron nitride and alcohol at a mass ratio of 1:2, and apply it evenly to the inner wall of the low-carbon steel crucible with a brush, then let it dry; place the dehydrated VW92 alloy into the air-dried iron crucible, raise the temperature of the melting furnace to 730℃ under the protection of CO2+SF6 mixed gas, hold it at the temperature until the VW92 alloy melts, add the dried Mg-Ca master alloy, melt and obtain the melt.

2. The high-fluidity Mg-Gd-Y-Zn-Zr alloy as described in claim 1, characterized in that, In step 4), the specific operating steps are as follows: the mixed solution of boron nitride and alcohol is evenly applied to the slag removal spoon and the inner and outer surfaces of the stirring rod. After the material melts, the slag on the surface of the melt is removed using the steel spoon. The stirring rod is used to stir for 5 minutes to obtain the target alloy melt. After standing for 30 minutes at a temperature of 730℃, it is ready for casting.

3. The high-fluidity Mg-Gd-Y-Zn-Zr alloy as described in claim 1, characterized in that, In step 5), the specific operation steps are as follows: the magnesium alloy release agent is evenly sprayed on the inner wall of the single spiral flowability test mold to facilitate cooling and demolding; the mold is preheated to 250°C, and after the target alloy melt is kept at a constant temperature, it is poured into the 250°C mold at a temperature of 730°C. After cooling, the target magnesium alloy product is obtained by demolding.

4. A method for improving the fluidity of Mg-Gd-Y-Zn-Zr alloys in die casting, characterized in that, Adding Ca to VW92 alloy improves its die-casting fluidity and produces a high-fluidity Mg-Gd-Y-Zn-Zr alloy as described in any one of claims 1-3.

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