High-toughness light-weight die-cast aluminum alloy for motor end cover and preparation method thereof

Abstract

The application relates to the technical field of aluminum alloy, in particular to a high-strength and high-toughness light-weight die-casting aluminum alloy for motor end covers and a preparation method thereof. The preparation method comprises the following steps: melting industrial pure aluminum, metallic silicon, electrolytic copper, aluminum-manganese alloy and aluminum-iron alloy to obtain a base melt; after cooling, aluminum-magnesium alloy is sequentially added for main alloying, and aluminum-silicon coated calcium-vanadium composite particles are added for micro-alloying; after refining, rotary blowing degassing and ultrasonic homogenization treatment, high-vacuum die-casting forming is carried out, and then low-temperature stabilization treatment is carried out, so that the high-strength and high-toughness light-weight die-casting aluminum alloy for motor end covers is obtained. The application realizes the synergistic improvement of the heat conduction performance, the strength and toughness and the stability of the aluminum alloy by matching the alloy raw materials and the preparation steps, pre-combining the Ca source and the V source and modifying the Al-Si coating, combining the stage melting, the melt purification, the ultrasonic homogenization and the high-vacuum die-casting process, and is suitable for industrial production.

Description

Technical Field

[0001] This application relates to the field of aluminum alloy technology, specifically to a high-strength, high-toughness, lightweight die-cast aluminum alloy for motor end caps and its preparation method. Background Technology

[0002] Motor end caps are important structural and sealing components in motor assemblies, typically used to support bearings, enclose the housing, assist in heat dissipation, and bear assembly loads. As new energy vehicle drive motors and high-performance industrial motors develop towards higher speeds, higher power densities, and lighter weights, motor end caps not only need to meet the requirements of one-time die-casting of complex thin-walled structures, but also need to possess high strength, good toughness, low defect sensitivity, and good dimensional stability.

[0003] Currently, motor end caps and similar housing parts generally use Al-Si or Al-Si-Cu die-cast aluminum alloys, combined with vacuum die casting, melt purification, and subsequent heat treatment or machining processes to improve product performance. Existing technological development mainly focuses on two directions: one is to reduce internal defects by optimizing the die casting process, melt purification, and solidification control; the other is to improve material microstructure and processing properties through raw material pretreatment, the addition of modifiers, and post-treatment processes.

[0004] For example, patent application CN121491303A discloses a vacuum die-casting method for high-reliability aluminum alloy motor end caps. This method reduces defects such as micropores, inclusions, and shrinkage cavities in the hot spot area by performing acoustic levitation purification of the aluminum alloy melt, online detection of the melt's acoustic purity, and magnetic field-induced zoned solidification in the mold's hot spot area. This approach focuses on melt purification and solidification process control during die casting, which is beneficial for improving the density, airtightness, and mechanical properties of the casting. However, this method mainly targets defect suppression during the forming process and involves less attention to the optimization of the composition system and microalloying design of the die-cast aluminum alloy itself. In particular, it falls short in terms of how to stably introduce active elements with microstructure regulation effects to further achieve a synergistic improvement in strength and toughness.

[0005] Patent application CN119093683A discloses a die-casting process for a small end cover plate for a motor. This process involves mechanically cleaning, pickling, and drying the cast aluminum raw material, and adding a modifier composed of strontium and vanadium during the melting process. After die-casting, the material undergoes heat treatment, shaping, and CNC machining to improve the product's hardness, corrosion resistance, and dimensional stability. This approach focuses on optimizing the raw material pretreatment, modification treatment, and post-die-casting processing. However, the modifier addition method is relatively direct, lacking specific design to address issues such as active element burn-off, uneven diffusion, and insufficient microalloying utilization. Furthermore, its measures for controlling melt gas content and inclusions, as well as suppressing internal defects during die-casting, are relatively limited, making it difficult to simultaneously meet the comprehensive requirements of high strength, toughness, low defects, and high reliability for complex thin-walled motor end covers.

[0006] Therefore, although existing technologies have improved the die-casting of motor end caps from the perspectives of die-casting process control or raw materials and post-processing, the following problems still exist: On the one hand, conventional Al-Si or Al-Si-Cu die-casting aluminum alloys are difficult to balance between high strength and high toughness; on the other hand, elements such as Ca and V, which have the potential to regulate microstructure, are prone to problems such as large burn-off, uneven dispersion and unstable effect when directly added, making it difficult to fully exert their role in refining microstructure, improving brittle phases and enhancing overall performance.

[0007] Therefore, there is an urgent need to provide a high-strength, high-toughness, lightweight die-cast aluminum alloy suitable for motor end caps and its preparation method, so as to further improve the strength, toughness, density and dimensional stability of the material while ensuring die-casting formability. Summary of the Invention

[0008] This application aims to overcome at least one of the deficiencies of the prior art and provide a high-strength, high-toughness, lightweight die-cast aluminum alloy for motor end caps and its preparation method. By combining alloy raw materials and preparation steps, Ca source and V source are pre-composite and Al-Si coating modification is performed. Combined with staged melting, melt purification, ultrasonic homogenization and high vacuum die-casting process, the thermal conductivity, strength, toughness and stability of aluminum alloy are synergistically improved, making it suitable for industrial production.

[0009] In a first aspect, embodiments of this application provide a method for preparing a high-strength, high-toughness, lightweight die-cast aluminum alloy for motor end caps, achieved through the following technical solution: A method for preparing a high-strength, high-toughness, lightweight die-cast aluminum alloy for motor end caps includes the following steps: (1) Industrial pure aluminum, metallic silicon, electrolytic copper, aluminum-manganese alloy and aluminum-iron alloy are preheated and put into a melting furnace, melted at 740-780℃ and held at the temperature to obtain the basic melt; (2) Adjust the temperature to 720-750℃ and add aluminum-magnesium alloy for main alloying; then adjust the temperature to 700-725℃ and add aluminum-silicon coated calcium-vanadium composite particles for micro alloying to obtain composite melt. (3) Add refining agent to purify the composite melt, remove the slag, perform rotary blowing degassing, and then ultrasonic homogenize for 8-18 minutes; after standing for 15-35 minutes, perform high vacuum die casting on the melt under vacuum conditions not higher than 60 mbar and injection pressure of 75-110 MPa. After demolding, perform low temperature stabilization treatment at 140-175℃ for 2-6 hours to obtain high strength and toughness lightweight die-cast aluminum alloy for motor end caps.

[0010] The method for preparing high-strength, high-toughness, lightweight die-cast aluminum alloy for motor end caps according to the embodiments of this application has at least the following beneficial effects: This application adopts a process route that combines basic melting, main alloying, microalloying, melt purification, rotary jet degassing, ultrasonic homogenization, high vacuum die casting, and low-temperature stabilization treatment. This allows for the coordinated control of alloy composition, improvement of melt quality, regulation of solidification structure, and suppression of forming defects. It can effectively reduce the gas content and inclusion level in the melt, reduce defects such as porosity and shrinkage in the casting, and improve the density and comprehensive mechanical properties of the casting.

[0011] In the microalloying stage, this application uses aluminum-silicon coated calcium-vanadium composite particles. By pre-compositing the Ca source and V source and performing Al-Si coating treatment, the oxidation loss of Ca element under high temperature conditions can be reduced after adding aluminum liquid, while improving the dispersion and diffusion conditions of V element in the melt. This improves the stability, effective utilization and distribution uniformity of microalloying elements, and provides a basis for subsequent microstructure optimization.

[0012] This application utilizes the synergistic microalloying effect of Ca and V to regulate the solidification structure, which can refine the primary α-Al grains, improve the morphology of the eutectic structure, and to a certain extent reduce the destructive effect of brittleness on the matrix continuity, thereby improving the uniformity of the structure. This allows the material to achieve a synergistic improvement in strength and toughness while maintaining good die-casting formability, and is beneficial for improving fatigue crack resistance and service reliability.

[0013] This application combines ultrasonic homogenization with high-vacuum die casting. Ultrasonic homogenization helps to promote the homogenization of the internal structure and composition of the melt, disperse local agglomerates, and improve inclusion distribution, while high-vacuum die casting helps to reduce air entrapment and porosity defects. The synergistic effect of the two can further improve the filling integrity, internal quality, and dimensional accuracy of complex thin-walled motor end caps.

[0014] This application employs a low-temperature stabilization treatment after die casting, which can release some of the residual stress from die casting while avoiding problems such as blistering and deformation that are easily caused by conventional high-temperature heat treatment. This improves the dimensional stability of the casting and the structural stability during subsequent use, making it more suitable for mass production and engineering applications of die castings such as motor end caps.

[0015] The overall process of this application takes into account both material properties and manufacturing adaptability. It is not only conducive to obtaining die-cast aluminum alloy end cap products with high strength, toughness, light weight and low defects, but also suitable for one-time forming of motor end caps with complex structures. It has positive significance for improving product consistency and production efficiency.

[0016] According to some embodiments of this application, the preheating temperature of the industrial pure aluminum, metallic silicon, electrolytic copper, aluminum-manganese alloy and aluminum-iron alloy in step (1) is 180-260°C and the preheating time is 1.5-3h.

[0017] This preheating condition helps remove adsorbed moisture and some volatile impurities from the surface of the raw materials, reducing temperature shocks during furnace entry and the resulting melt turbulence, gas absorption, and oxidation inclusions. At the same time, it can improve the melting efficiency of each component and the temperature stability of the melt, promoting the uniform melting of elements such as Si, Cu, Mn, and Fe into the base melt, providing a stable compositional basis for subsequent main alloying, microalloying, and melt purification treatment, thereby helping to reduce internal defects in castings and improve the uniformity of the microstructure and the forming quality.

[0018] According to some embodiments of this application, the Al content in the industrial pure aluminum is not less than 99 wt%, for example 99.3 wt%, 99.5 wt%, or 99.7 wt%.

[0019] According to some embodiments of this application, the industrial pure aluminum is 85 to 90 parts by weight, for example 86, 87, 88 or 89 parts.

[0020] According to some embodiments of this application, the Si content in the metallic silicon is not less than 98.5 wt%, for example 98.5 wt%, 98.8 wt%, or 99 wt%.

[0021] According to some embodiments of this application, the metallic silicon is 8 to 10.5 parts by weight, for example 9 parts, 9.5 parts or 10 parts.

[0022] According to some embodiments of this application, the Cu content in the electrolytic copper is not less than 99.9 wt%, for example 99.9 wt%, 99.95 wt%, or 99.99 wt%.

[0023] According to some embodiments of this application, the electrolytic copper is 2.8 to 4.2 parts by weight, for example 3 parts, 3.5 parts or 4 parts.

[0024] According to some embodiments of this application, the weight percentage of manganese in the aluminum-manganese alloy is 10% to 20%, for example, 10%, 15% or 20%.

[0025] According to some embodiments of this application, the aluminum-manganese alloy comprises 2.3 to 5 parts by weight, for example 2.5 parts, 3 parts or 4 parts.

[0026] According to some embodiments of this application, the weight percentage of iron in the aluminum-iron alloy is 10% to 20%, for example, 10%, 15% or 20%.

[0027] According to some embodiments of this application, the aluminum-iron alloy is 0.4 to 1.6 parts by weight, for example 0.5 parts, 1 part or 1.5 parts.

[0028] According to some embodiments of this application, the magnesium weight percentage in the aluminum-magnesium alloy is 15% to 25%, for example, 15%, 20% or 25%.

[0029] According to some embodiments of this application, the aluminum-magnesium alloy is 1.8 to 4 parts by weight, for example 2 parts, 2.5 parts or 3 parts.

[0030] According to some embodiments of this application, the aluminum-silicon coated calcium-vanadium composite particles are 0.8 to 2.5 parts by weight, for example, 0.8 parts, 1 part or 2 parts.

[0031] By limiting the content of corresponding elements in aluminum-manganese alloys, aluminum-iron alloys, and aluminum-magnesium alloys, and further limiting the proportions of industrial pure aluminum, metallic silicon, electrolytic copper, aluminum-manganese alloys, aluminum-iron alloys, aluminum-magnesium alloys, and aluminum-silicon coated calcium-vanadium composite particles, it is beneficial to balance strength, toughness, and lightweight requirements while ensuring alloy fluidity and die-casting formability. Specifically, Si and Cu are beneficial for improving alloy strength and casting performance; Mn and Fe are beneficial for controlling the morphology of iron-containing phases and improving anti-sticking properties; Mg is beneficial for improving the strengthening effect; and aluminum-silicon coated calcium-vanadium composite particles are beneficial for improving the stability of Ca and V additions and their microstructure control effects. The synergistic effect of these components can refine the microstructure, reduce defect sensitivity, and improve the density, comprehensive mechanical properties, and dimensional stability of castings.

[0032] According to some embodiments of this application, the aluminum-silicon coated calcium-vanadium composite particles are made from the following raw materials: Al-Ca master alloy powder, Al-V master alloy powder, Al-Si master alloy powder, and Al-Mg master alloy powder. The Al-Si master alloy powder forms a coating layer, which helps reduce the oxidation loss of Ca in the melt and improves the wettability and melting uniformity of the composite particles after they enter the melt. The Al-Mg master alloy powder helps promote the interfacial bonding between the particles and the molten aluminum and the diffusion of elements. The combined effect of Al-Ca and Al-V master alloy powders can improve the stability and uniformity of the addition and distribution of Ca and V elements in the melt, thereby further refining the grains, improving the eutectic structure, and enhancing the strength, toughness, and casting quality of the alloy.

[0033] Furthermore, the weight ratio of the Al-Ca master alloy powder, the Al-V master alloy powder, the Al-Si master alloy powder, and the Al-Mg master alloy powder is 20–35:10–25:45–65:2–8. This compounding ratio balances the effective content of the Ca and V active components with the stability of the coating system. The Al-Si master alloy powder facilitates continuous coating and improves the solubility and dispersibility of the composite particles, while the Al-Mg master alloy powder enhances interparticle bonding and improves the interfacial wetting effect after molten entry. This reduces Ca burn-off and local V enrichment, promotes the uniform release and dispersion of Ca and V in the molten aluminum, and improves the consistency and stability of the microalloying effect, thus refining the microstructure and enhancing the overall mechanical properties of the casting.

[0034] Furthermore, the Ca content in the Al-Ca master alloy powder is 8 to 15 wt%, for example, 10 wt%, 10 to 12 wt%, or 14 wt%.

[0035] Furthermore, the V content in the Al-V master alloy powder is 5 to 15 wt%, for example 10 wt%, 8 to 12 wt%, or 14 wt%.

[0036] Furthermore, the Si content in the Al-Si master alloy powder is 10-20 wt%, for example 12 wt%, 10-15 wt%, or 18 wt%.

[0037] Furthermore, the Mg content in the Al-Mg master alloy powder is 3 to 10 wt%, for example, 5 wt%, 4 to 6 wt%, or 8 wt%.

[0038] The above limitations are beneficial for balancing the stability of composite particle preparation, the reactivity of addition, and the effect of element release after molten metal addition. Specifically, controlling the Ca content in Al-Ca master alloy powder to 8–15 wt% helps to reduce the risk of oxidation loss and excessively rapid reaction while ensuring the supply of Ca element; controlling the V content in Al-V master alloy powder to 5–15 wt% helps to improve the introduction efficiency and dispersion uniformity of V element in aluminum melt; controlling the Si content in Al-Si master alloy powder to 10–20 wt% helps to form a stable coating layer and improve the compatibility between composite particles and aluminum melt; and controlling the Mg content in Al-Mg master alloy powder to 3–10 wt% helps to achieve smooth addition and precise composition control in the main alloying process. By limiting these ranges, the microalloying effect and melt stability can be further improved.

[0039] According to some embodiments of this application, the preparation method of the aluminum-silicon coated calcium-vanadium composite particles includes: under an inert atmosphere, mixing Al-Ca master alloy powder, Al-V master alloy powder, Al-Mg master alloy powder and 20-30 wt% Al-Si master alloy powder and ball milling for 1-3 hours, pressing into composite particle core material with a particle size of 5-20 mm; preheating the composite particle core material to 420-500°C and placing it in a rolling coating device, adding the remaining Al-Si master alloy powder, and rolling coating at a temperature of 450-560°C to soften the surface of the Al-Si master alloy powder and continuously adhere it to the surface of the composite particle core material; subsequently, through secondary compaction and short-time heat preservation densification treatment, forming an Al-Si coating layer with a thickness of 0.2-1.0 mm on the surface of the composite particle core material, and obtaining aluminum-silicon coated calcium-vanadium composite particles after cooling.

[0040] This application improves the structural stability and feeding operability of microalloying additives by pre-mixing and pressing Al-Ca, Al-V, and Al-Mg master alloy powders into composite particle cores, and then forming a continuous Al-Si coating layer on their surface. The Al-Si coating layer isolates and protects Ca elements after addition to molten aluminum, reducing their high-temperature oxidation loss, while improving the carrying, introduction, and diffusion distribution conditions of V elements, thus increasing the recovery rate and dispersion uniformity of Ca and V. After secondary compaction and short-term heat treatment for densification, the coating layer and core material are more stably bonded, facilitating the smooth melting and uniform release of composite particles in the melt, thereby better refining the microstructure, improving microstructure uniformity, and enhancing the overall performance of the alloy.

[0041] Furthermore, the rotational speed of the rolling coating is 15–40 r / min, and the coating time is 10–30 min.

[0042] Furthermore, the pressure of the secondary compaction is 20–80 MPa.

[0043] Furthermore, the short-term heat preservation densification treatment is carried out under an inert atmosphere at a temperature of 480–580°C for 5–10 minutes.

[0044] According to some embodiments of this application, after the aluminum-silicon coated calcium-vanadium composite particles in step (2) are added, they are kept at a constant temperature for 3 to 8 minutes.

[0045] This method facilitates the complete melting of the coating layer and promotes the uniform release and diffusion of Ca and V elements into the molten aluminum, making the microalloying process more stable. If the holding time is too short, the composite particles cannot fully dissipate, easily causing localized compositional inhomogeneity and affecting the refining and modification effects; if the holding time is too long, it easily increases the oxidation and burn-off of Ca elements, which is not conducive to the effective utilization of microalloying elements. Controlling the holding time within 3–8 minutes can balance particle dissipation, element diffusion, and burn-off control, improving the addition efficiency and distribution uniformity of Ca and V elements, thereby contributing to the refinement of the microstructure, improvement of the eutectic morphology, and enhancement of the alloy's strength and toughness.

[0046] According to some embodiments of this application, the amount of refining agent added in step (3) is 0.15% to 0.5% of the weight of the composite melt, for example, 0.15%, 0.2% to 0.4% or 0.5%.

[0047] According to some embodiments of this application, the refining agent in step (3) is a chloride-fluoride composite aluminum alloy refining agent. The use of the chloride-fluoride composite aluminum alloy refining agent in step (3) to purify the composite melt is beneficial for promoting the aggregation, flotation, and separation of oxide inclusions in the melt, reducing the hydrogen content in the melt, and improving the cleanliness of the melt. Simultaneously, this refining agent, in conjunction with subsequent rotary blowing degassing and ultrasonic homogenization treatment, can further reduce gas and inclusion residues in the melt, lower the probability of defects such as porosity and slag inclusions during die casting, and improve the density and uniformity of the casting structure. This, in turn, helps to improve the mechanical properties, dimensional stability, and forming reliability of the die-cast aluminum alloy used for motor end caps.

[0048] Furthermore, the chloride salt is selected from at least one of potassium chloride, sodium chloride, and magnesium chloride.

[0049] Furthermore, the fluoride salt is selected from at least one of sodium hexafluoroaluminate and potassium fluorosilicate.

[0050] The combination of chloride and fluoride salts can effectively cover, slag-forming, and purify the melt, promoting the flotation and separation of oxide inclusions, reducing the content of gas and non-metallic inclusions in the melt, and improving the purity of the melt. At the same time, the fluoride salts help improve the melt fluidity and interfacial wetting state, and promote the uniform diffusion of microalloying elements, thereby improving the stability of die casting, the density of castings, and the uniformity of microstructure.

[0051] According to some embodiments of this application, the rotary jet degassing in step (3) uses high-purity argon or argon-nitrogen mixture, with a gas flow rate of 1-3 L / min and a degassing time of 8-20 min.

[0052] These conditions allow for sufficient contact between dispersed bubbles and molten aluminum, improving hydrogen removal efficiency and promoting the flotation and removal of non-metallic inclusions, thereby effectively reducing the gas content and inclusion level of the melt. Simultaneously, the aforementioned process parameters balance degassing effectiveness with melt stability, avoiding problems such as secondary gas entrapment, increased oxidation, and excessive melt disturbance caused by excessive flow rate or time. This improves filling stability during subsequent die casting, reduces internal defects such as porosity in the casting, and ultimately enhances the density, mechanical properties, and product consistency of the motor end cover casting.

[0053] According to some embodiments of this application, the frequency of the ultrasonic homogenization process in step (3) is 18-24 kHz and the power is 1.2-3 kW.

[0054] Ultrasonic homogenization treatment can generate stable and effective cavitation and acoustic flow effects on the melt before die casting, promoting uniform distribution of composition and temperature within the melt, breaking up local agglomerates and improving the distribution of inclusions. It also helps refine the solidification structure and reduce sensitivity to defects such as porosity and shrinkage. Within the aforementioned frequency and power range, the intensity of the ultrasonic action is ensured while avoiding excessive melt disturbance caused by insufficient treatment or excessive energy. This contributes to improving the density, microstructure uniformity, dimensional stability, and overall mechanical properties of the die-cast motor end cap.

[0055] According to some embodiments of this application, in the high vacuum die casting process described in step (3), the mold preheating temperature is 180-240°C, the low-speed injection speed is 0.1-0.4 m / s, the high-speed injection speed is 2.5-5 m / s, and the mold dwell time is 8-18 s.

[0056] In the high-vacuum die casting process, controlling the mold preheating temperature to 180–240℃ helps improve the stability of melt filling and avoids defects such as cold shuts and under-casting caused by excessively low mold temperatures. It also prevents excessively high mold temperatures from causing sticking and localized coarsening of the microstructure. Controlling the low-speed injection speed to 0.1–0.4 m / s and the high-speed injection speed to 2.5–5 m / s helps balance cavity venting and rapid filling, reducing air entrapment, splashing, and turbulence, and improving the internal density of the casting. Controlling the mold dwell time to 8–18 seconds ensures complete solidification of the casting and reduces the risk of demolding deformation and cracking. The combined effect of these parameters further improves the forming integrity, dimensional accuracy, and product consistency of complex thin-walled motor end caps.

[0057] According to some embodiments of this application, the low-temperature stabilization treatment in step (3) is to keep warm at 150-165°C for 3-5 hours.

[0058] By employing a low-temperature stabilization treatment at 150–165℃ for 3–5 hours after die casting, residual stress inside the casting can be released without causing blistering, significant deformation, or excessive changes in the microstructure of the die-cast aluminum alloy. This reduces stress concentration caused by rapid solidification and demolding cooling, thereby improving the microstructure and dimensional stability. At the same time, the treatment temperature and time are relatively mild, having little impact on the surface quality and internal density of the casting. This helps maintain the original forming accuracy of the die-casting and improves the consistency of subsequent machining and structural reliability during use. It is particularly suitable for the mass production of complex thin-walled die-casting parts such as motor end caps.

[0059] Secondly, embodiments of this application provide a high-strength, high-toughness, lightweight die-cast aluminum alloy for motor end caps manufactured using the above-described method for preparing a high-strength, high-toughness, lightweight die-cast aluminum alloy for motor end caps.

[0060] The high-strength, high-toughness, lightweight die-cast aluminum alloy used for the motor end cover according to the embodiments of this application has at least the following beneficial effects: This application utilizes aluminum-silicon coated calcium-vanadium composite particles for microalloying, combined with melt purification, rotary jet degassing, ultrasonic homogenization, high-vacuum die casting, and low-temperature stabilization treatment. This results in a more uniform alloy composition distribution, refined microstructure, and reduced internal defects such as porosity, shrinkage, and inclusions, thus achieving a balance of high strength, good toughness, and high density. Furthermore, the alloy exhibits good dimensional stability, meeting the requirements for lightweighting, forming integrity, and reliability in complex thin-walled motor end caps.

[0061] In this article, the numerical ranges mentioned all include the endpoint values ​​and cover any subranges within that range, such as the ranges obtained by arbitrarily combining the specifically listed numerical values.

[0062] Unless otherwise specified, the weight parts of raw materials mentioned herein shall be understood as the weight ratio between the raw materials. For example, 85-90 parts of industrial pure aluminum indicates the relative amount of industrial pure aluminum used in the raw materials for preparing the die-cast aluminum alloy. Based on 0.8-2.5 parts of aluminum-silicon coated calcium-vanadium composite particles, this can be understood as the weight ratio of industrial pure aluminum to aluminum-silicon coated calcium-vanadium composite particles being 85-90:0.8-2.5. Attached Figure Description

[0063] To more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings used in the description of the embodiments will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0064] Figure 1This is a comparison chart of the tensile strength and elongation after fracture data of the die-cast aluminum alloys prepared in Examples 1-4 and Comparative Examples 1-4 of this application; Figure 2 This is a comparison chart of the Brinell hardness and density data of the die-cast aluminum alloys prepared in Examples 1-4 and Comparative Examples 1-4 of this application. Detailed Implementation

[0065] To make the objectives, technical solutions, and advantages of this application clearer, a further detailed description will be provided below in conjunction with specific embodiments. The embodiments described herein are merely some examples of this application and should not be construed as limiting the scope of protection of this application. Unless otherwise specified, the raw materials used in the embodiments are all commercially available, and the equipment and testing methods used are conventional equipment and methods in the art.

[0066] Example 1 This embodiment provides a high-strength, high-toughness, lightweight die-cast aluminum alloy for motor end caps, which is made from the following raw materials in parts by weight: 88 parts of industrial pure aluminum, 9 parts of metallic silicon, 3.5 parts of electrolytic copper, 4 parts of aluminum-manganese alloy, 1 part of aluminum-iron alloy, 3 parts of aluminum-magnesium alloy, and 1.5 parts of aluminum-silicon coated calcium-vanadium composite particles. Among them, the Al content in industrial pure aluminum is 99.5 wt%, the Si content in metallic silicon is 98.8 wt%, the Cu content in electrolytic copper is 99.95 wt%, the manganese weight percentage in aluminum-manganese alloy is 15%, the iron weight percentage in aluminum-iron alloy is 15%, and the magnesium weight percentage in aluminum-magnesium alloy is 20%. Preparation of aluminum-silicon coated calcium-vanadium composite particles: Under an inert atmosphere, Al-Ca master alloy powder, Al-V master alloy powder, Al-Mg master alloy powder and 25wt% Al-Si master alloy powder were mixed and ball-milled for 2 hours, and then pressed into composite particle core materials with an average particle size of 10mm. The composite particle core materials were preheated to 460℃ and placed in a rolling coating device. The remaining Al-Si master alloy powder was added, and rolling coating was performed at a temperature of 500℃, a rotation speed of 30r / min, and a coating time of 20min, so that the surface of Al-Si master alloy powder was softened and continuously adhered to the surface of the composite particle core material. Subsequently, a secondary compaction was performed at a pressure of 50MPa, and a short-term heat preservation densification treatment was carried out at a temperature of 530℃ and under an inert atmosphere for 8min, so that an Al-Si coating layer with a thickness of 0.2-1mm was formed on the surface of the composite particle core material. After cooling, aluminum-silicon coated calcium-vanadium composite particles were obtained. The weight ratio of Al-Ca master alloy powder, Al-V master alloy powder, Al-Si master alloy powder and Al-Mg master alloy powder is 28:18:55:5. The Al-Ca master alloy powder contains 12 wt% Ca, the Al-V master alloy powder contains 10 wt% V, the Al-Si master alloy powder contains 15 wt% Si, and the Al-Mg master alloy powder contains 7 wt% Mg. The refining agent is composed of potassium chloride, sodium chloride and sodium hexafluoroaluminate in a weight ratio of 1:1:1. The preparation method of high-strength, high-toughness, lightweight die-cast aluminum alloy for motor end caps is as follows: (1) Industrial pure aluminum, metallic silicon, electrolytic copper, aluminum-manganese alloy and aluminum-iron alloy are preheated at 220℃ for 2.5h and then put into a melting furnace, melted at 760℃ and held at the temperature to obtain the basic melt; (2) Adjust the temperature to 735℃, add aluminum-magnesium alloy for main alloying; then adjust the temperature to 715℃, add aluminum-silicon coated calcium-vanadium composite particles and keep warm for 6 minutes for micro alloying to obtain composite melt. (3) Add 0.35% of the weight of the composite melt as a refining agent to purify the composite melt. After removing the slag, use argon-nitrogen mixed gas for rotary blowing degassing. The gas flow rate is 2L / min and the degassing time is 14min. Then, use ultrasonic homogenization for 13min. The frequency of ultrasonic homogenization is 21kHz and the power is 2.1kW. After standing for 25min, use high vacuum die casting to form the melt under vacuum of 50mbar and injection pressure of 90MPa. During the die casting process, the mold preheating temperature is 210℃, the low-speed injection speed is 0.3m / s, the high-speed injection speed is 4m / s, and the mold dwell time is 13s. After demolding, use low-temperature stabilization treatment at 160℃ for 4h to obtain high-strength and high-toughness lightweight die-cast aluminum alloy for motor end caps.

[0067] Example 2 This embodiment provides a high-strength, high-toughness, lightweight die-cast aluminum alloy for motor end caps, which is made from the following raw materials in parts by weight: 90 parts of industrial pure aluminum, 8 parts of metallic silicon, 4.2 parts of electrolytic copper, 2.3 parts of aluminum-manganese alloy, 1.6 parts of aluminum-iron alloy, 1.8 parts of aluminum-magnesium alloy, and 2.5 parts of aluminum-silicon coated calcium-vanadium composite particles. Among them, industrial pure aluminum contains 99 wt% Al, metallic silicon contains 99 wt% Si, electrolytic copper contains 99.9 wt% Cu, aluminum-manganese alloy contains 20% manganese by weight, aluminum-iron alloy contains 10% iron by weight, and aluminum-magnesium alloy contains 25% magnesium by weight. Preparation of aluminum-silicon coated calcium-vanadium composite particles: Under an inert atmosphere, Al-Ca master alloy powder, Al-V master alloy powder, Al-Mg master alloy powder and 20wt% Al-Si master alloy powder were mixed and ball-milled for 3 hours, and then pressed into composite particle cores with an average particle size of 5mm. The composite particle cores were preheated to 500℃ and placed in a rolling coating device. The remaining Al-Si master alloy powder was added, and rolling coating was performed at 450℃, 40r / min, and 10min, so that the surface of Al-Si master alloy powder was softened and continuously adhered to the surface of the composite particle cores. Subsequently, a secondary compaction at a pressure of 80MPa was performed, followed by a short-term heat preservation densification treatment at 480℃ under an inert atmosphere for 10min, so that an Al-Si coating layer with a thickness of 0.2-1.0mm was formed on the surface of the composite particle cores. After cooling, aluminum-silicon coated calcium-vanadium composite particles were obtained. The weight ratio of Al-Ca master alloy powder, Al-V master alloy powder, Al-Si master alloy powder and Al-Mg master alloy powder is 20:25:45:8. The Al-Ca master alloy powder contains 8 wt% Ca, the Al-V master alloy powder contains 15 wt% V, the Al-Si master alloy powder contains 10 wt% Si, and the Al-Mg master alloy powder contains 10 wt% Mg. The refining agent is composed of magnesium chloride, sodium hexafluoroaluminate and potassium fluorosilicate in a weight ratio of 2:1:1. The preparation method of high-strength, high-toughness, lightweight die-cast aluminum alloy for motor end caps is as follows: (1) Industrial pure aluminum, metallic silicon, electrolytic copper, aluminum-manganese alloy and aluminum-iron alloy are preheated at 180°C for 3 hours and then put into a melting furnace, melted at 740°C and held at that temperature to obtain the basic melt. (2) Adjust the temperature to 750℃, add aluminum-magnesium alloy for main alloying; then adjust the temperature to 700℃, add aluminum-silicon coated calcium-vanadium composite particles and keep warm for 8 minutes for micro alloying to obtain composite melt. (3) Add 0.15% of the weight of the composite melt as a refining agent to purify the composite melt. After removing the slag, use high-purity argon gas for rotary blowing degassing. The gas flow rate is 3L / min and the degassing time is 8min. Then, use ultrasonic homogenization for 18min. The frequency of ultrasonic homogenization is 18kHz and the power is 3kW. After standing for 15min, use high vacuum die casting to form the melt under vacuum of 60mbar and injection pressure of 75MPa. During the die casting process, the mold preheating temperature is 240℃, the low-speed injection speed is 0.1m / s, the high-speed injection speed is 5m / s, and the mold dwell time is 8s. After demolding, use low-temperature stabilization treatment at 175℃ for 2h to obtain high-strength, high-toughness, lightweight die-cast aluminum alloy for motor end caps.

[0068] Example 3 This embodiment provides a high-strength, high-toughness, lightweight die-cast aluminum alloy for motor end caps, which is made from the following raw materials in parts by weight: 85 parts of industrial pure aluminum, 10.5 parts of metallic silicon, 2.8 parts of electrolytic copper, 5 parts of aluminum-manganese alloy, 0.4 parts of aluminum-iron alloy, 4 parts of aluminum-magnesium alloy, and 0.8 parts of aluminum-silicon coated calcium-vanadium composite particles. Among them, industrial pure aluminum contains 99.7 wt% Al, metallic silicon contains 98.5 wt% Si, electrolytic copper contains 99.99 wt% Cu, aluminum-manganese alloy contains 10% manganese by weight, aluminum-iron alloy contains 20% iron by weight, and aluminum-magnesium alloy contains 15% magnesium by weight. Preparation of aluminum-silicon coated calcium-vanadium composite particles: Under an inert atmosphere, Al-Ca master alloy powder, Al-V master alloy powder, Al-Mg master alloy powder and 30wt% Al-Si master alloy powder were mixed and ball-milled for 1 hour, and then pressed into composite particle core material with an average particle size of 20mm. The composite particle core material was preheated to 420℃ and placed in a rolling coating device. The remaining Al-Si master alloy powder was added, and rolling coating was performed at a temperature of 560℃, a rotation speed of 15r / min, and a coating time of 30min, so that the surface of Al-Si master alloy powder was softened and continuously adhered to the surface of the composite particle core material. Subsequently, a second compaction was performed at a pressure of 20MPa, and a short-term heat preservation densification treatment was carried out at a temperature of 580℃ under an inert atmosphere for 5min, so that an Al-Si coating layer with a thickness of 0.2-1.0mm was formed on the surface of the composite particle core material. After cooling, aluminum-silicon coated calcium-vanadium composite particles were obtained. The weight ratio of Al-Ca master alloy powder, Al-V master alloy powder, Al-Si master alloy powder and Al-Mg master alloy powder is 35:10:65:2. The Al-Ca master alloy powder contains 15 wt% Ca, the Al-V master alloy powder contains 5 wt% V, the Al-Si master alloy powder contains 20 wt% Si, and the Al-Mg master alloy powder contains 3 wt% Mg. The refining agent is composed of potassium chloride and potassium fluorosilicate in a weight ratio of 1:2. The preparation method of high-strength, high-toughness, lightweight die-cast aluminum alloy for motor end caps is as follows: (1) Industrial pure aluminum, metallic silicon, electrolytic copper, aluminum-manganese alloy and aluminum-iron alloy are preheated at 260℃ for 1.5h and then put into a melting furnace, melted at 780℃ and held at the temperature to obtain the basic melt; (2) Adjust the temperature to 720℃, add aluminum-magnesium alloy for main alloying; then adjust the temperature to 725℃, add aluminum-silicon coated calcium-vanadium composite particles and keep warm for 3 minutes for micro alloying to obtain composite melt; (3) Add 0.5% of the weight of the composite melt as a refining agent to purify the composite melt. After removing the slag, use argon-nitrogen mixed gas for rotary blowing degassing. The gas flow rate is 1L / min and the degassing time is 20min. Then, use ultrasonic homogenization for 8min. The frequency of ultrasonic homogenization is 24kHz and the power is 1.2kW. After standing for 35min, use high vacuum die casting to form the melt under vacuum of 30mbar and injection pressure of 110MPa. During the die casting process, the mold preheating temperature is 180℃, the low-speed injection speed is 0.4m / s, the high-speed injection speed is 2.5m / s, and the mold retention time is 18s. After demolding, use low-temperature stabilization treatment at 140℃ for 6h to obtain a high-strength, high-toughness, lightweight die-cast aluminum alloy for motor end caps.

[0069] Example 4 This embodiment provides a high-strength, high-toughness, lightweight die-cast aluminum alloy for motor end caps, which is made from the following raw materials in parts by weight: 89 parts of industrial pure aluminum, 10 parts of metallic silicon, 3 parts of electrolytic copper, 3 parts of aluminum-manganese alloy, 1 part of aluminum-iron alloy, 3 parts of aluminum-magnesium alloy, and 1 part of aluminum-silicon coated calcium-vanadium composite particles. Among them, industrial pure aluminum contains 99.3 wt% Al, metallic silicon contains 98.7 wt% Si, electrolytic copper contains 99.95 wt% Cu, aluminum-manganese alloy contains 14% manganese by weight, aluminum-iron alloy contains 18% iron by weight, and aluminum-magnesium alloy contains 22% magnesium by weight. Preparation of aluminum-silicon coated calcium-vanadium composite particles: Under an inert atmosphere, Al-Ca master alloy powder, Al-V master alloy powder, Al-Mg master alloy powder and 26wt% Al-Si master alloy powder were mixed and ball-milled for 2 hours, and then pressed into composite particle core materials with an average particle size of 15mm. The composite particle core materials were preheated to 480℃ and placed in a rolling coating device. The remaining Al-Si master alloy powder was added, and rolling coating was performed at a temperature of 510℃, a rotation speed of 20r / min, and a coating time of 20min, so that the surface of Al-Si master alloy powder was softened and continuously adhered to the surface of the composite particle core material. Subsequently, a second compaction was performed at a pressure of 50MPa, and a short-term heat preservation densification treatment was carried out at a temperature of 530℃ under an inert atmosphere for 7min, so that an Al-Si coating layer with a thickness of 0.2-1.0mm was formed on the surface of the composite particle core material. After cooling, aluminum-silicon coated calcium-vanadium composite particles were obtained. The weight ratio of Al-Ca master alloy powder, Al-V master alloy powder, Al-Si master alloy powder and Al-Mg master alloy powder is 30:20:60:4. The Al-Ca master alloy powder contains 10 wt% Ca, the Al-V master alloy powder contains 12 wt% V, the Al-Si master alloy powder contains 14 wt% Si, and the Al-Mg master alloy powder contains 5 wt% Mg. The refining agent is composed of sodium chloride, magnesium chloride and potassium fluorosilicate in a weight ratio of 1:1:1. The preparation method of high-strength, high-toughness, lightweight die-cast aluminum alloy for motor end caps is as follows: (1) Industrial pure aluminum, metallic silicon, electrolytic copper, aluminum-manganese alloy and aluminum-iron alloy are preheated at 210℃ for 2.5h and then put into a melting furnace, melted at 760℃ and held at the temperature to obtain the basic melt; (2) Adjust the temperature to 730℃, add aluminum-magnesium alloy for main alloying; then adjust the temperature to 710℃, add aluminum-silicon coated calcium-vanadium composite particles and keep warm for 5 minutes for micro alloying to obtain composite melt. (3) Add 0.4% of the weight of the composite melt as a refining agent to purify the composite melt. After removing the slag, use high-purity argon gas for rotary blowing degassing. The gas flow rate is 2L / min and the degassing time is 16min. Then, use ultrasonic homogenization for 12min. The frequency of ultrasonic homogenization is 20kHz and the power is 2.5kW. After standing for 22min, use high vacuum die casting to form the melt under vacuum of 55mbar and injection pressure of 85MPa. During the die casting process, the mold preheating temperature is 220℃, the low-speed injection speed is 0.2m / s, the high-speed injection speed is 3m / s, and the mold retention time is 15s. After demolding, use low-temperature stabilization treatment at 150℃ for 5h to obtain high-strength, high-toughness, lightweight die-cast aluminum alloy for motor end caps.

[0070] Comparative Example 1 (different from Example 1 in that it does not contain aluminum-silicon coated calcium-vanadium composite particles, nor does it contain Al-Ca master alloy powder or Al-V master alloy powder) This comparative example provides a die-cast aluminum alloy made from the following raw materials in parts by weight: 88 parts of industrial pure aluminum, 9 parts of metallic silicon, 3.5 parts of electrolytic copper, 4 parts of aluminum-manganese alloy, 1 part of aluminum-iron alloy, and 3 parts of aluminum-magnesium alloy. Among them, the Al content in industrial pure aluminum is 99.5 wt%, the Si content in metallic silicon is 98.8 wt%, the Cu content in electrolytic copper is 99.95 wt%, the manganese weight percentage in aluminum-manganese alloy is 15%, the iron weight percentage in aluminum-iron alloy is 15%, and the magnesium weight percentage in aluminum-magnesium alloy is 20%. The refining agent is composed of potassium chloride, sodium chloride and sodium hexafluoroaluminate in a weight ratio of 1:1:1. The preparation method of die-cast aluminum alloy is as follows: (1) Industrial pure aluminum, metallic silicon, electrolytic copper, aluminum-manganese alloy and aluminum-iron alloy are preheated at 220℃ for 2.5h and then put into a melting furnace, melted at 760℃ and held at the temperature to obtain the basic melt; (2) Adjust the temperature to 735℃, add aluminum-magnesium alloy for main alloying, and obtain composite melt; (3) Add 0.35% of the weight of the composite melt as a refining agent to purify the composite melt. After removing the slag, use argon-nitrogen mixed gas for rotary blowing degassing. The gas flow rate is 2L / min and the degassing time is 14min. Then, use ultrasonic homogenization for 13min. The frequency of ultrasonic homogenization is 21kHz and the power is 2.1kW. After standing for 25min, use high vacuum die casting to form the melt under vacuum of 50mbar and injection pressure of 90MPa. During the die casting process, the mold preheating temperature is 210℃, the low-speed injection speed is 0.3m / s, the high-speed injection speed is 4m / s, and the mold dwell time is 13s. After demolding, use low-temperature stabilization treatment at 160℃ for 4h to obtain die-cast aluminum alloy.

[0071] Comparative Example 2 (different from Example 1 in that it does not use aluminum-silicon coated calcium-vanadium composite particles, but directly adds Al-Ca master alloy powder and Al-V master alloy powder) This comparative example provides a die-cast aluminum alloy made from the following raw materials in parts by weight: 88 parts of industrial pure aluminum, 9 parts of metallic silicon, 3.5 parts of electrolytic copper, 4 parts of aluminum-manganese alloy, 1 part of aluminum-iron alloy, 3 parts of aluminum-magnesium alloy, 0.9 parts of Al-Ca master alloy powder, and 0.6 parts of Al-V master alloy powder. Among them, the Al content in industrial pure aluminum is 99.5 wt%, the Si content in metallic silicon is 98.8 wt%, the Cu content in electrolytic copper is 99.95 wt%, the manganese weight percentage in aluminum-manganese alloy is 15%, the iron weight percentage in aluminum-iron alloy is 15%, and the magnesium weight percentage in aluminum-magnesium alloy is 20%. The Al-Ca master alloy powder contains 12 wt% Ca, and the Al-V master alloy powder contains 10 wt% V. The refining agent is composed of potassium chloride, sodium chloride and sodium hexafluoroaluminate in a weight ratio of 1:1:1. The preparation method of die-cast aluminum alloy is as follows: (1) Industrial pure aluminum, metallic silicon, electrolytic copper, aluminum-manganese alloy and aluminum-iron alloy are preheated at 220℃ for 2.5h and then put into a melting furnace, melted at 760℃ and held at the temperature to obtain the basic melt; (2) Adjust the temperature to 735℃, add aluminum-magnesium alloy for main alloying; then adjust the temperature to 715℃, add Al-Ca master alloy powder and Al-V master alloy powder and keep warm for 6 minutes for micro alloying to obtain composite melt. (3) Add 0.35% of the weight of the composite melt as a refining agent to purify the composite melt. After removing the slag, use argon-nitrogen mixed gas for rotary blowing degassing. The gas flow rate is 2L / min and the degassing time is 14min. Then, use ultrasonic homogenization for 13min. The frequency of ultrasonic homogenization is 21kHz and the power is 2.1kW. After standing for 25min, use high vacuum die casting to form the melt under vacuum of 50mbar and injection pressure of 90MPa. During the die casting process, the mold preheating temperature is 210℃, the low-speed injection speed is 0.3m / s, the high-speed injection speed is 4m / s, and the mold dwell time is 13s. After demolding, use low-temperature stabilization treatment at 160℃ for 4h to obtain die-cast aluminum alloy.

[0072] Comparative Example 3 (different from Example 1 in that ultrasonic homogenization and high-vacuum die casting are omitted, and ordinary die casting process is used for molding). This comparative example provides a die-cast aluminum alloy made from the following raw materials in parts by weight: 88 parts of industrial pure aluminum, 9 parts of metallic silicon, 3.5 parts of electrolytic copper, 4 parts of aluminum-manganese alloy, 1 part of aluminum-iron alloy, 3 parts of aluminum-magnesium alloy, and 1.5 parts of aluminum-silicon coated calcium-vanadium composite particles. Among them, the Al content in industrial pure aluminum is 99.5 wt%, the Si content in metallic silicon is 98.8 wt%, the Cu content in electrolytic copper is 99.95 wt%, the manganese weight percentage in aluminum-manganese alloy is 15%, the iron weight percentage in aluminum-iron alloy is 15%, and the magnesium weight percentage in aluminum-magnesium alloy is 20%. Preparation of aluminum-silicon coated calcium-vanadium composite particles: Under an inert atmosphere, Al-Ca master alloy powder, Al-V master alloy powder, Al-Mg master alloy powder and 25wt% Al-Si master alloy powder were mixed and ball-milled for 2 hours, and then pressed into composite particle core materials with an average particle size of 10mm. The composite particle core materials were preheated to 460℃ and placed in a rolling coating device. The remaining Al-Si master alloy powder was added, and rolling coating was performed at a temperature of 500℃, a rotation speed of 30r / min, and a coating time of 20min, so that the surface of Al-Si master alloy powder was softened and continuously adhered to the surface of the composite particle core material. Subsequently, a secondary compaction was performed at a pressure of 50MPa, and a short-term heat preservation densification treatment was carried out at a temperature of 530℃ and under an inert atmosphere for 8min, so that an Al-Si coating layer with a thickness of 0.2-1mm was formed on the surface of the composite particle core material. After cooling, aluminum-silicon coated calcium-vanadium composite particles were obtained. The weight ratio of Al-Ca master alloy powder, Al-V master alloy powder, Al-Si master alloy powder and Al-Mg master alloy powder is 28:18:55:5. The Al-Ca master alloy powder contains 12 wt% Ca, the Al-V master alloy powder contains 10 wt% V, the Al-Si master alloy powder contains 15 wt% Si, and the Al-Mg master alloy powder contains 7 wt% Mg. The refining agent is composed of potassium chloride, sodium chloride and sodium hexafluoroaluminate in a weight ratio of 1:1:1. The preparation method of die-cast aluminum alloy is as follows: (1) Industrial pure aluminum, metallic silicon, electrolytic copper, aluminum-manganese alloy and aluminum-iron alloy are preheated at 220℃ for 2.5h and then put into a melting furnace, melted at 760℃ and held at the temperature to obtain the basic melt; (2) Adjust the temperature to 735℃, add aluminum-magnesium alloy for main alloying; then adjust the temperature to 715℃, add aluminum-silicon coated calcium-vanadium composite particles and keep warm for 6 minutes for micro alloying to obtain composite melt. (3) Add 0.35% of the weight of the composite melt as a refining agent to purify the composite melt. After removing the slag, use argon-nitrogen mixed gas for rotary blowing degassing. The gas flow rate is 2L / min and the degassing time is 14min. After standing for 25min, without vacuuming, the melt is die-cast under normal exhaust conditions. During the die-casting process, the mold preheating temperature is 210℃, the low-speed injection speed is 0.3m / s, the high-speed injection speed is 4m / s, the injection pressure is 90MPa, the mold dwell time is 13s, and after demolding, it is subjected to low-temperature stabilization treatment at 160℃ for 4h to obtain the die-cast aluminum alloy.

[0073] Comparative Example 4 (different from Example 1 in that it does not undergo low-temperature stabilization treatment) This comparative example provides a die-cast aluminum alloy made from the following raw materials in parts by weight: 88 parts of industrial pure aluminum, 9 parts of metallic silicon, 3.5 parts of electrolytic copper, 4 parts of aluminum-manganese alloy, 1 part of aluminum-iron alloy, 3 parts of aluminum-magnesium alloy, and 1.5 parts of aluminum-silicon coated calcium-vanadium composite particles. Among them, the Al content in industrial pure aluminum is 99.5 wt%, the Si content in metallic silicon is 98.8 wt%, the Cu content in electrolytic copper is 99.95 wt%, the manganese weight percentage in aluminum-manganese alloy is 15%, the iron weight percentage in aluminum-iron alloy is 15%, and the magnesium weight percentage in aluminum-magnesium alloy is 20%. Preparation of aluminum-silicon coated calcium-vanadium composite particles: Under an inert atmosphere, Al-Ca master alloy powder, Al-V master alloy powder, Al-Mg master alloy powder and 25wt% Al-Si master alloy powder were mixed and ball-milled for 2 hours, and then pressed into composite particle core materials with an average particle size of 10mm. The composite particle core materials were preheated to 460℃ and placed in a rolling coating device. The remaining Al-Si master alloy powder was added, and rolling coating was performed at a temperature of 500℃, a rotation speed of 30r / min, and a coating time of 20min, so that the surface of Al-Si master alloy powder was softened and continuously adhered to the surface of the composite particle core material. Subsequently, a secondary compaction was performed at a pressure of 50MPa, and a short-term heat preservation densification treatment was carried out at a temperature of 530℃ and under an inert atmosphere for 8min, so that an Al-Si coating layer with a thickness of 0.2-1mm was formed on the surface of the composite particle core material. After cooling, aluminum-silicon coated calcium-vanadium composite particles were obtained. The weight ratio of Al-Ca master alloy powder, Al-V master alloy powder, Al-Si master alloy powder and Al-Mg master alloy powder is 28:18:55:5. The Al-Ca master alloy powder contains 12 wt% Ca, the Al-V master alloy powder contains 10 wt% V, the Al-Si master alloy powder contains 15 wt% Si, and the Al-Mg master alloy powder contains 7 wt% Mg. The refining agent is composed of potassium chloride, sodium chloride and sodium hexafluoroaluminate in a weight ratio of 1:1:1. The preparation method of die-cast aluminum alloy is as follows: (1) Industrial pure aluminum, metallic silicon, electrolytic copper, aluminum-manganese alloy and aluminum-iron alloy are preheated at 220℃ for 2.5h and then put into a melting furnace, melted at 760℃ and held at the temperature to obtain the basic melt; (2) Adjust the temperature to 735℃, add aluminum-magnesium alloy for main alloying; then adjust the temperature to 715℃, add aluminum-silicon coated calcium-vanadium composite particles and keep warm for 6 minutes for micro alloying to obtain composite melt. (3) Add 0.35% of the weight of the composite melt as a refining agent to purify the composite melt. After removing the slag, use argon-nitrogen mixed gas for rotary blowing degassing. The gas flow rate is 2L / min and the degassing time is 14min. Then, use ultrasonic homogenization for 13min. The frequency of ultrasonic homogenization is 21kHz and the power is 2.1kW. After standing for 25min, use high vacuum die casting to form the melt under vacuum of 50mbar and injection pressure of 90MPa. During the die casting process, the mold preheating temperature is 210℃, the low-speed injection speed is 0.3m / s, the high-speed injection speed is 4m / s, and the mold dwell time is 13s. After demolding, die-cast aluminum alloy is obtained.

[0074] Experimental Example The die-cast aluminum alloys prepared in Examples 1-4 and Comparative Examples 1-4 were tested for tensile strength, yield strength, elongation after fracture, Brinell hardness, density, and thermal conductivity. The test methods are as follows: Tensile strength, yield strength and elongation after fracture were tested in accordance with GB / T 228.1-2021 "Metallic materials - Tensile testing - Part 1: Test method at room temperature"; The Brinell hardness was tested according to GB / T 231.1-2018 "Metallic materials - Brinell hardness test - Part 1: Test method"; Density was determined using Archimedes' method of water displacement. Determination of thermal conductivity: The die-cast aluminum alloys prepared in each embodiment and comparative example were made into circular specimens with a diameter of 12.7 mm and a thickness of 25.4 mm; a graphite coating was uniformly sprayed on both sides of the specimen to be tested; the treated specimens were placed in a laser thermal conductivity meter for testing, and the test was performed in accordance with the "ASTM E1461 standard method for determining thermal diffusivity by flash method".

[0075] The test data is shown in Table 1 below: Table 1. Performance Test Data of Die-cast Aluminum Alloys Test Project Tensile strength (MPa) Yield strength (MPa) Elongation after fracture (%) Brinell hardness (HB) Density (g / cm³) Thermal conductivity (W / (m·K)) Example 1 368 294 7.8 119 2.77 145 Example 2 362 288 7.4 113 2.75 142 Example 3 365 286 7.7 116 2.75 144 Example 4 367 292 7.6 117 2.76 143 Comparative Example 1 272 195 1.9 98 2.72 128 Comparative Example 2 302 223 2.7 104 2.74 134 Comparative Example 3 315 231 3.1 108 2.74 131 Comparative Example 4 342 256 4.6 114 2.73 143

[0076] Reference Figures 1-2 As can be seen from Table 1, the high-strength and tough lightweight die-cast aluminum alloys for motor end caps prepared in Examples 1 to 4 of this application have good tensile strength, yield strength, hardness, thermal conductivity and other properties.

[0077] The preparation method of Comparative Example 1 does not include aluminum-silicon coated calcium-vanadium composite particles, nor does it add Al-Ca master alloy powder or Al-V master alloy powder. All other aspects are the same as in Example 1. The tensile strength, yield strength, elongation after fracture, hardness, and thermal conductivity of the die-cast aluminum alloy prepared in Comparative Example 1 are significantly reduced. This indicates that this application utilizes the synergistic microalloying effect of Ca and V to regulate the solidification structure, which can refine the primary α-Al grains, improve the eutectic structure morphology, and to a certain extent reduce the destructive effect of brittleness on the matrix continuity, thereby improving the uniformity of the structure. This allows the material to maintain good die-casting formability while achieving a synergistic improvement in strength and toughness, and is beneficial for improving fatigue crack resistance and service reliability.

[0078] In Comparative Example 2, the preparation method did not use aluminum-silicon coated calcium-vanadium composite particles. Al-Ca master alloy powder and Al-V master alloy powder were directly added. The rest was the same as in Example 1. The tensile strength, yield strength, elongation after fracture, hardness, and thermal conductivity of the die-cast aluminum alloy prepared in Comparative Example 2 were significantly reduced. This indicates that the present application uses aluminum-silicon coated calcium-vanadium composite particles in the microalloying stage. By pre-compositing the Ca source and V source and implementing Al-Si coating treatment, the oxidation loss of Ca element under high temperature conditions can be reduced after adding aluminum liquid. At the same time, the dispersion and diffusion conditions of V element in the melt can be improved, thereby improving the stability, effective utilization rate and distribution uniformity of microalloying elements, and providing a basis for subsequent microstructure optimization.

[0079] In Comparative Example 3, ultrasonic homogenization and high-vacuum die casting were omitted, and ordinary die casting was used for molding. The rest was the same as in Example 1. The tensile strength, yield strength, elongation after fracture, hardness, and thermal conductivity of the die-cast aluminum alloy prepared in Comparative Example 3 were significantly reduced. This indicates that this application combines ultrasonic homogenization treatment with high-vacuum die casting. Ultrasonic homogenization helps to promote the homogenization of the internal structure and composition of the melt, disperse local agglomerates, and improve the distribution of inclusions. High-vacuum die casting helps to reduce air entrapment and porosity defects. The synergistic effect of the two can further improve the filling integrity, internal quality, and dimensional accuracy of complex thin-walled motor end caps.

[0080] In Comparative Example 4, the preparation method did not involve low-temperature stabilization treatment, and all other aspects were the same as in Example 1. The tensile strength, yield strength, and elongation after fracture of the die-cast aluminum alloy prepared in Comparative Example 4 decreased, indicating that the low-temperature stabilization treatment adopted after die casting in this application can release some of the residual stress in die casting while avoiding problems such as blistering and deformation that are easily caused by conventional high-temperature heat treatment. This improves the dimensional stability of the casting and the structural stability during subsequent use, making it more suitable for the mass production and engineering application of die-cast parts such as motor end caps.

[0081] Although embodiments of this application have been shown and described, those skilled in the art will understand that various changes, modifications, substitutions or alterations can be made to these embodiments without departing from the principles and spirit of this application, and the technical solutions resulting from such changes, modifications, substitutions or alterations will all fall within the protection scope of this application.

Claims

1. A method for preparing a high-strength, high-toughness, lightweight die-cast aluminum alloy for motor end caps, characterized in that, Includes the following steps: (1) Industrial pure aluminum, metallic silicon, electrolytic copper, aluminum-manganese alloy and aluminum-iron alloy are preheated and put into a melting furnace, melted at 740-780℃ and held at the temperature to obtain the basic melt; (2) Adjust the temperature to 720-750℃ and add aluminum-magnesium alloy for main alloying; then adjust the temperature to 700-725℃ and add aluminum-silicon coated calcium-vanadium composite particles for micro alloying to obtain composite melt. (3) Add refining agent to purify the composite melt, remove the slag, degas by rotary spraying, and then homogenize by ultrasonic treatment for 8 to 18 minutes; after standing for 15 to 35 minutes, the melt is die-cast under high vacuum conditions of vacuum degree not higher than 60 mbar and injection pressure of 75 to 110 MPa. After demolding, it is subjected to low temperature stabilization treatment at 140 to 175℃ for 2 to 6 hours to obtain high strength and toughness lightweight die-cast aluminum alloy for motor end cover. The raw materials for the aluminum-silicon coated calcium-vanadium composite particles are composed of Al-Ca master alloy powder, Al-V master alloy powder, Al-Si master alloy powder, and Al-Mg master alloy powder in a weight ratio of 20-35:10-25:45-65:2-8. The Al-Ca master alloy powder contains 8–15 wt% Ca. The V content in the Al-V master alloy powder is 5-15 wt%. The Si content in the Al-Si master alloy powder is 10-20 wt%. The Mg content in the Al-Mg master alloy powder is 3-10 wt%; The preparation method of the aluminum-silicon coated calcium-vanadium composite particles includes: under an inert atmosphere, mixing Al-Ca master alloy powder, Al-V master alloy powder, Al-Mg master alloy powder and 20-30 wt% Al-Si master alloy powder and ball milling for 1-3 hours, and pressing into composite particle core material; preheating the composite particle core material to 420-500℃ and placing it in a rolling coating device, adding the remaining Al-Si master alloy powder, and rolling coating at a temperature of 450-560℃ to soften the surface of the Al-Si master alloy powder and continuously adhere it to the surface of the composite particle core material; subsequently, through secondary compaction and short-time heat preservation densification treatment, forming an Al-Si coating layer on the surface of the composite particle core material, and obtaining aluminum-silicon coated calcium-vanadium composite particles after cooling.

2. The method for preparing a high-strength, high-toughness, lightweight die-cast aluminum alloy for motor end caps according to claim 1, characterized in that, The preheating temperature of the industrial pure aluminum, metallic silicon, electrolytic copper, aluminum-manganese alloy and aluminum-iron alloy in step (1) is 180-260℃ and the preheating time is 1.5-3h.

3. The method for preparing a high-strength, high-toughness, lightweight die-cast aluminum alloy for motor end caps according to claim 1, characterized in that, The weight percentage of manganese in the aluminum-manganese alloy is 10% to 20%. And / or, the weight percentage of iron in the aluminum-iron alloy is 10% to 20%; And / or, the magnesium weight percentage in the aluminum-magnesium alloy is 15% to 25%; And / or, by weight, the industrial pure aluminum is 85 to 90 parts; And / or, by weight, the metallic silicon is 8 to 10.5 parts; And / or, by weight, the electrolytic copper is 2.8 to 4.2 parts; And / or, by weight, the aluminum-manganese alloy is 2.3 to 5 parts; And / or, by weight, the aluminum-iron alloy is 0.4 to 1.6 parts; And / or, by weight, the aluminum-magnesium alloy is 1.8 to 4 parts; And / or, by weight, the aluminum-silicon coated calcium-vanadium composite particles are 0.8 to 2.5 parts.

4. The method for preparing a high-strength, high-toughness, lightweight die-cast aluminum alloy for motor end caps according to claim 1, characterized in that, After adding the aluminum-silicon coated calcium-vanadium composite particles in step (2), keep warm for 3 to 8 minutes.

5. The method for preparing a high-strength, high-toughness, lightweight die-cast aluminum alloy for motor end caps according to claim 1, characterized in that, The refining agent in step (3) is a chloride-fluorine composite aluminum alloy refining agent.

6. The method for preparing a high-strength, high-toughness, lightweight die-cast aluminum alloy for motor end caps according to claim 1, characterized in that, The rotary jet degassing step (3) uses high-purity argon or an argon-nitrogen mixture, with a gas flow rate of 1-3 L / min and a degassing time of 8-20 min.

7. A high-strength, high-toughness, lightweight die-cast aluminum alloy for motor end caps prepared by the method described in any one of claims 1 to 6.

Images