Weldable and recyclable al-cu series high-strength and high-toughness die-casting aluminum alloy integrated die-casting method and system

Abstract

The application belongs to the technical field of aluminum alloy preparation and relates to an integrated die-casting method and system of a weldable and recyclable Al-Cu series high-strength and high-toughness die-cast aluminum alloy, which comprises the following steps: preparing a die-cast aluminum alloy liquid; performing integrated high-pressure die casting by using the die-cast aluminum alloy liquid; performing slow injection at a first speed, transition injection at a second speed, and then accelerating to a third speed for filling injection until the pressure in a mold cavity rises to a pressurization trigger pressure and then performing pressurization treatment; and performing post-treatment after the high-pressure die casting is completed to obtain an Al-Cu series high-strength and high-toughness die-cast aluminum alloy casting. The application can fundamentally improve the flowability and oxidation problem of the Al-Cu alloy, and efficiently and stably produce large die-cast structural parts with high performance and high reliability in a heat treatment-free state.

Description

Technical Field

[0001] This application belongs to the field of aluminum alloy preparation technology, and more specifically, relates to an integrated die-casting method and system for weldable and recyclable Al-Cu high-strength and tough die-cast aluminum alloys. Background Technology

[0002] Al-Cu alloys have attracted much attention in recent years due to their excellent mechanical properties, high-temperature stability, and oxidation resistance; however, their poor casting performance presents a significant application bottleneck. These alloys have low fluidity, are prone to shrinkage defects, exhibit high linear shrinkage, and show a marked tendency for segregation during solidification. The addition of Cu increases melt viscosity, reduces surface tension, and increases its temperature sensitivity, leading to flow stream breakage and splashing during melt filling, thus compromising the integrity of the melt front. Simultaneously, Cu disrupts the density of the aluminum oxide film, making it more susceptible to cracking and repeated oxidation, forming a multi-layered structure that hinders melt fusion and successful mold filling.

[0003] Furthermore, Al-Cu alloys have poor weldability. During welding, the low-melting-point eutectic phase easily leads to grain boundary liquefaction, causing hot cracking. Welding heat input can also cause a strength loss of 40%–60%, a significant decrease in plasticity, and the complex oxide film behavior easily leads to porosity and inclusions. Therefore, they are only suitable for welding simple, thin-walled parts, and require strict control of preheating and post-heating processes before and after welding. If elements such as Si are mixed into the alloy, brittle phases will form, further impairing plasticity and corrosion resistance, which also limits the application of recycled materials to low-performance castings.

[0004] Integrated die casting technology eliminates the need for welding and riveting multiple independent components to form a complete part, allowing for the direct one-time molding of large and complex castings. Therefore, this process places extremely high demands on materials, requiring excellent fluidity, low susceptibility to hot cracking, sufficient mechanical properties, and the elimination of heat treatment. This ensures the material can fill complex cavities during die casting, guaranteeing surface quality and meeting the production needs of large, thin-walled parts (such as automotive shock absorber towers), reducing casting defects, and avoiding thermal deformation during heat treatment. Actual die casting production shows that Al-Cu alloy parts exhibit significant differences in mechanical properties across different parts, poor corrosion resistance, and unavoidable shrinkage porosity and hot cracking, severely limiting their application under gravity and pressure casting conditions. With increasing demands for lightweighting and collision safety in automobiles, there is still a need to significantly improve the material's strength, plasticity, and elongation. Currently, this is mainly achieved through the addition of trace elements and composition optimization to improve its overall performance.

[0005] In summary, although Al-Cu aluminum alloys possess advantages such as high strength and heat resistance, their casting, welding, and corrosion resistance deficiencies severely restrict their widespread application in integrated die casting. Current research focuses primarily on composition design, process improvement, and innovative preparation techniques; there is an urgent need to overcome these limitations and expand their application prospects in high-performance structures. Summary of the Invention

[0006] In view of the shortcomings of the prior art, the purpose of this application is to provide an integrated die casting method and system for weldable and recyclable Al-Cu high-strength and tough aluminum alloys, which aims to solve the problems of insufficient fluidity in the casting of Al-Cu alloys, as well as poor weldability and reduced remelting and recycling performance of die-cast products.

[0007] To achieve the above objectives, in a first aspect, this application provides an integrated die-casting method for weldable and recyclable Al-Cu-based high-strength and high-toughness die-cast aluminum alloys, comprising:

[0008] S1 prepares a die-casting aluminum alloy liquid, wherein the die-casting aluminum alloy liquid comprises: 4.0 wt.%~6.0 wt.% Cu, 0.31 wt.%~0.5 wt.% Ca, 0.4 wt.%~0.6 wt.% Mn, 0.45 wt.%~0.55 wt.% Ti, and a total amount of ≤0.8 wt.% Mg, Zn and Zr, and Mg / Zn≥2.0;

[0009] S2 utilizes the molten aluminum alloy for integrated high-pressure die casting: a first speed is used for slow injection to allow the molten aluminum alloy to enter the runner; then a second speed is used for transition injection to allow the molten aluminum alloy to enter the ingate through the runner; then the speed is accelerated to a third speed for filling injection to allow the molten aluminum alloy to fill the mold cavity from the ingate until the pressure in the mold cavity rises to the pressure boosting trigger pressure for pressurization; wherein, the third speed is greater than the first speed and the second speed.

[0010] After S3 high-pressure die casting is completed, post-processing is performed to obtain Al-Cu series high-strength and high-toughness die-cast aluminum alloy castings.

[0011] Furthermore, in step S1, the method for preparing the die-cast aluminum alloy liquid includes the following steps:

[0012] S101 According to the preset composition, weigh out pure aluminum ingot, intermediate alloy ingot containing Al and 50% Cu, intermediate alloy ingot containing Al and 10% Mn, intermediate alloy ingot containing Al and 5% Ti, and intermediate alloy ingot containing Al and 10% Ca.

[0013] S102 Bake all the metal weighed in step S101 to remove potential liquid;

[0014] S103 first melts pure aluminum ingots into molten aluminum at a preset furnace temperature. When the temperature of the molten aluminum reaches the preset temperature, an intermediate alloy ingot containing Al and 10% Mn is added to the molten aluminum for melting. After it is completely melted, an intermediate alloy ingot containing Al and 50% Cu is added for melting.

[0015] S104 After adjusting the temperature of the molten metal obtained in step S103 to 740℃~750℃, the intermediate alloy ingot containing Al and 10% Ca is added to the molten metal obtained in step S103 to continue melting.

[0016] S105 Refining and degassing the molten metal obtained in step S104.

[0017] S106 removes the slag from the molten metal liquid after refining and degassing, and lets it stand for a preset time. Then, an intermediate alloy ingot containing Al and 5% Ti is added, stirred evenly, and left to stand for the preset time to obtain the die-cast aluminum alloy liquid.

[0018] Furthermore, the preset furnace temperature is 850℃~870℃; the preset temperature is 720℃~750℃.

[0019] Furthermore, in step S105, a rotary jetting method is used for refining and degassing, with a rotation speed of 500 r / min. At the same time, a mixed gas composed of nitrogen and refining agent is sprayed out, and the refining and degassing process lasts for 15 min to 20 min.

[0020] Furthermore, in step S106, the preset time is 15 min to 30 min.

[0021] Furthermore, in step S2, the vacuum degree of the mold cavity is 30mbar~50mbar, and during the entire injection process: the injection pressure is 140bar~160bar, the injection flow rate is 50%~60%, and the injection time is 6.2s~6.8s.

[0022] Furthermore, in step S2, when filling and injecting at the third speed, the filling stroke is 62mm~63.2mm and the filling time is 53ms~59ms; after filling and injecting, the return hammer pressure of the injection punch is 125bar~135bar, the return hammer flow rate of the injection punch is 95%~100%, and the return hammer delay is 4.8s~5.2s; the boosting trigger pressure is 75bar~85bar, and the boosting pressure is 385bar~400bar.

[0023] Furthermore, in step S2, the first speed is 0.15m / s to 0.19m / s, the second speed is 0.15m / s to 0.19m / s, the third speed is 3m / s to 3.5m / s, and the time for the second speed to accelerate to the third speed is 18ms to 22ms.

[0024] Furthermore, in step S3, the post-processing is a cooling process, and the cooling time is 11s~15s.

[0025] According to a second aspect of this application, a system is provided for an integrated die-casting method for weldable and recyclable Al-Cu-based high-strength and high-toughness die-cast aluminum alloys, comprising:

[0026] A device for preparing liquid die-casting aluminum alloy;

[0027] An integrated high-pressure die-casting device includes an interconnected gating and sprue module and a die-casting mold. The gating and sprue module includes a sprue, a runner, an overflow unit, and a venting unit. The sprue has a hemispherical buffer cavity. The sprue and the runner are connected by a transition cone with a taper of 40°~50° and a length of 30mm~40mm. An ingate is provided at the outlet end of the runner, and the ingate is connected to the inlet of the die-casting mold. The die-casting mold is connected to an overflow unit, and the overflow unit is connected to a venting unit through an irregularly bent pipe. The cross-section of the irregularly bent pipe perpendicular to the airflow direction is trapezoidal.

[0028] The post-processing module is used to perform post-processing after high-pressure die casting to obtain Al-Cu series high-strength and high-toughness die-cast aluminum alloy castings.

[0029] Overall, the technical solutions conceived in this application have the following beneficial effects compared with the prior art:

[0030] (1) This application fundamentally improves the fluidity and oxidation problems of Al-Cu alloy through innovative alloy composition design. With the addition of a carefully designed multi-stage pressure die casting process, it solves the core pain points of traditional Al-Cu alloy in integrated die casting applications, such as poor fluidity, easy shrinkage porosity and hot cracking, and uneven performance. Finally, it realizes the efficient and stable production of high-performance and high-reliability large die casting structural parts in a heat-free state.

[0031] (2) The liquid composition of the die-cast aluminum alloy used in this application for integrated die casting is precisely designed. Based on the aluminum-copper alloy, the addition of trace amounts of Mg, Zn and Zr elements can improve the high-temperature performance and corrosion resistance of the alloy under certain environments, and further enhance the strength and hardness of the cast aluminum alloy, fundamentally changing the die-casting performance of the alloy. In addition, the mass fractions of Cu and Ca can vary in the range of 4.0wt.%~6.0wt.% and 0.31wt.%~0.5wt.%, respectively. The addition of Mn element reduces the sensitivity to hot cracking, Ti element refines the grains and enhances the feeding ability of the solidification front, Mg element refines the grains and inhibits the coarsening of the eutectic phase, reducing the impact of microstructure deterioration on performance during remelting. This solves the problem of significant decline in mechanical properties after remelting of traditional aluminum alloy scrap, and achieves high recyclability of the die-cast alloy product.

[0032] (3) The integrated die casting method of this application is suitable for the preparation of large castings. The molten metal is pushed smoothly through the gating system in the slow injection stage (first speed) to maximize the discharge of gas in the pressure chamber and avoid gas entrapment and the formation of pores. The transition stage (second speed) controls the molten metal to flow smoothly through the gating system to prepare for high-speed filling. In the high-speed filling stage (third speed), after the molten metal reaches the ingate, it fills the cavity at an extremely high speed, ensuring that the molten metal can instantly fill the entire complex cavity before solidification. It is particularly suitable for the molding of large, thin-walled parts and ensures clear outlines. At the moment the filling ends, an extremely high pressure is immediately applied and maintained for a period of time. This pressure can force the molten metal that has not yet solidified to be fed into the solidifying area, greatly reducing or eliminating internal shrinkage defects, improving the density and overall mechanical properties of the casting. The final casting has high strength, high toughness, high density and very few defects, which can meet the stringent safety and reliability requirements of automotive structural parts (such as shock absorber towers, battery pack housings, etc.).

[0033] (4) The integrated die-casting system of this application has been optimized to address various technical challenges in die-casting high-performance Al-Cu alloys. A hemispherical buffer cavity is set at the bottom of the sprue, which can effectively buffer the impact energy of the molten metal, changing it from turbulent to laminar flow. This significantly reduces the risk of gas entrainment in the molten metal and reduces porosity defects at the source. For Al-Cu alloys, reducing turbulence also reduces the chance of oxidation inclusions from contact with air. The design of the taper and length of the transition cone connecting the sprue and the runner ensures a smooth transition of the molten metal flow and uniform acceleration of the flow rate, avoiding sudden changes in cross-sectional area. This creates eddies or splashes, further ensuring a smooth filling process and reducing oxidation and air entrapment. Compared to traditional straight venting channels that allow molten metal to spray out directly, the irregularly bent pipe connecting the overflow channel and the venting channel in this application increases venting resistance, preventing molten metal from blocking the venting channel prematurely. Furthermore, its internal trapezoidal pipe creates a eddy effect, allowing the melt carrying oxide scale and cold metal to preferentially enter the overflow channel, while the gas is discharged through the venting system. This greatly improves the efficiency of venting and collecting the leading cold metal, ensuring the purity of the molten metal inside the cavity, and thus obtaining a dense, defect-free casting. Attached Figure Description

[0034] Figure 1 This is a schematic diagram of the integrated die-casting method for weldable and recyclable Al-Cu high-strength and tough die-cast aluminum alloys provided in Embodiment 1 of this application;

[0035] Figure 2 This is a schematic diagram of the sampling location of the die-casting part provided in Embodiment 1 of this application;

[0036] Figure 3 This is a schematic diagram of the surface quality of the die-cast sample provided in Embodiment 2 of this application;

[0037] Figure 4 This is a schematic diagram of a SEM tissue image provided in Embodiment 2 of this application;

[0038] Figure 5 This is a schematic diagram of the surface quality of the die-cast sample provided in Comparative Example 1 of this application;

[0039] Figure 6 This is a schematic diagram of the SEM tissue image provided in Comparative Example 1 of this application;

[0040] Figure 7 This is a schematic diagram illustrating the welding performance of the sample provided in this application;

[0041] Figure 8 These are schematic diagrams of sampling stress and strain provided in various embodiments and comparative examples of this application;

[0042] Figure 9 This is a schematic diagram of the planar structure of the gating module provided in Embodiment 4 of this application;

[0043] Figure 10 This is a three-dimensional structural schematic diagram of the gating and drainage module provided in Embodiment 4 of this application;

[0044] Figure 11 This is a schematic diagram of the gating module structure from a bottom view provided in Embodiment 4 of this application.

[0045] In all the accompanying drawings, the same reference numerals are used to denote the same elements or structures, wherein:

[0046] 1-Straight runner, 11-Hemispherical buffer cavity, 12-Transition cone, 2-Gateway, 21-Primary gateway, 22-Secondary gateway, 3-Overflow unit, 4-Exhaust unit, 5-Cavity, 6-Trapezoidal pipe. Detailed Implementation

[0047] To make the objectives, technical solutions, and advantages of this application clearer, the following detailed description is provided in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the scope of this application.

[0048] In this article, the term "and / or" describes the relationship between related objects, indicating that three relationships can exist. For example, A and / or B can represent: A existing alone, A and B existing simultaneously, or B existing alone. The symbol " / " in this article indicates that the related objects are in an "or" relationship; for example, A / B means A or B.

[0049] The terms "first" and "second," etc., used in the specification and claims herein are used to distinguish different objects, not to describe a specific order of objects. For example, "first response message" and "second response message," etc., are used to distinguish different response messages, not to describe a specific order of response messages.

[0050] In the embodiments of this application, the terms "exemplary" or "for example" are used to indicate that something is an example, illustration, or description. Any embodiment or design that is described as "exemplary" or "for example" in the embodiments of this application should not be construed as being more preferred or advantageous than other embodiments or design. Specifically, the use of the terms "exemplary" or "for example" is intended to present the relevant concepts in a specific manner.

[0051] In the description of the embodiments of this application, unless otherwise stated, "multiple" means two or more, for example, multiple processing units means two or more processing units, multiple elements means two or more elements, etc.

[0052] Example 1

[0053] This embodiment provides an integrated die-casting method for weldable and recyclable Al-Cu-based high-strength and high-toughness die-cast aluminum alloys, such as... Figure 1 As shown, the steps include:

[0054] S1 prepares a die-casting aluminum alloy liquid, which contains: 4.0 wt.%~6.0 wt.% Cu, 0.31 wt.%~0.5 wt.% Ca, 0.4 wt.%~0.6 wt.% Mn, 0.45 wt.%~0.55 wt.% Ti, and a total amount of ≤0.8 wt.% Mg, Zn and Zr, and Mg / Zn≥2.0, that is, the elemental content ratio of Mg and Zn is greater than or equal to 2;

[0055] For example, die-cast aluminum alloy liquid may contain: 4.1 wt.%, 4.2 wt.%, 4.3 wt.%, 4.4 wt.%, 4.5 wt.%, 4.6 wt.%, 4.7 wt.%, 4.8 wt.%, 4.9 wt.%, 5.0 wt.%, 5.1 wt.%, 5.2 wt.%, 5.3 wt.%, 5.4 wt.%, 5.5 wt.%, 5.6 wt.%, 5.7 wt.%, 5.8 wt.%, 5.9 wt.%, or 6.0 wt.%, or any Cu element content corresponding to any two of the aforementioned values; 0.31 wt.%, 0 0.33wt.%, 0.35wt.%, 0.37wt.%, 0.39wt.%, 0.4wt.%, 0.45wt.%, 0.47wt.%, or 0.5wt.% of Ca, or any value between any two of the aforementioned values; 0.4wt.%, 0.5wt.%, or 0.6wt.% of Mn, or any value between any two of the aforementioned values; 0.45wt.%, 0.50wt.%, or 0.55wt.% of Ti, or any value between any two of the aforementioned values;

[0056] S2 utilizes molten aluminum alloy for integrated high-pressure die casting: a first-speed slow injection is used to allow the molten aluminum alloy to enter the runner; then a second-speed transition injection is used to allow the molten aluminum alloy to enter the ingate through the runner; finally, the injection is accelerated to a third-speed filling injection, allowing the molten aluminum alloy to fill the mold cavity from the ingate until the pressure inside the mold cavity rises to the pressurization trigger pressure, after which pressurization is performed; wherein, the third speed is greater than the first and second speeds.

[0057] After the S3 booster treatment is completed, post-treatment is carried out to obtain Al-Cu series high strength and toughness die-cast aluminum alloy castings.

[0058] In step S1 above, the method for preparing the die-cast aluminum alloy liquid includes the following steps:

[0059] S101 According to the preset composition, weigh out pure aluminum ingots, intermediate alloy ingots containing Al and 50% Cu, intermediate alloy ingots containing Al and 10% Mn, intermediate alloy ingots containing Al and 5% Ti, and intermediate alloy ingots containing Al and 10% Ca; specifically, weigh out 219 kg of pure aluminum ingots with a purity of 99.99%, 33 kg of Al-50Cu intermediate alloy ingots, 15 kg of Al-10Mn intermediate alloy ingots, 18 kg of Al-5Ti-B intermediate alloy ingots, and 15 kg of Al-10Ca intermediate alloy ingots.

[0060] S102 Bake all the metal weighed in step S1 to remove potential liquid; specifically, bake all the metal ingots on the side of a 500kg aluminum alloy crucible holding melting furnace, open the furnace and set the furnace temperature to 300℃, hold the furnace temperature for 30 minutes after the furnace temperature reaches 300℃ to remove moisture in the furnace, after the holding temperature is completed, set the furnace temperature to 600℃, and put the baked 219kg pure aluminum ingots into a crucible holding melting furnace that can hold 500kg aluminum alloy;

[0061] In S103, at a preset furnace temperature, pure aluminum ingots are first melted into molten aluminum. Once the molten aluminum reaches the preset temperature, intermediate alloy ingots containing Al and 10% Mn are added to the molten aluminum for melting. After complete melting, intermediate alloy ingots containing Al and 50% Cu are added for further melting. Specifically, the furnace temperature is raised to 600℃ and held for 30 minutes. After holding, the furnace temperature is set to 870℃ for melting. After the pure aluminum ingots are melted into molten aluminum, the melt temperature is measured using a melting thermometer. When the melt temperature reaches 750℃, 33 kg of Al-10Mn intermediate alloy ingots are placed in a 500 kg aluminum alloy crucible holding melting furnace. Because of its highest melting point, it requires a longer time and higher temperature to completely dissolve and diffuse. After the Al-10Mn is basically melted, Al-50Cu intermediate alloy ingots are added. Each addition should be thoroughly stirred to promote homogenization.

[0062] After adjusting the temperature of the molten metal obtained in step S103 to 740℃~750℃, an intermediate alloy ingot containing Al and 10% Ca is added to the molten metal obtained in step S103 for further melting. Specifically, after all the aforementioned intermediate alloys have been added and confirmed to be completely melted, the furnace temperature is reset to 750℃. When the melt temperature is uniformly and stably maintained at approximately 740℃~750℃, the Al-10Ca intermediate alloy ingot is added, melted, and stirred evenly. Then, a rotary jet refining device is used to introduce a mixture of high-purity nitrogen and refining agent for 15 minutes. The main shaft of the rotary jet refining device rotates at a speed of 500 r / min to effectively remove hydrogen and inclusions from the melt.

[0063] S105 Refines and degasses the molten metal obtained in step S104; specifically, a rotary jet refining device is used to introduce a mixture of high-purity nitrogen and refining agent into the molten alloy while rotating, for 15 minutes. The main shaft of the rotary jet refining device rotates at a speed of 500 r / min to effectively remove hydrogen and inclusions from the melt.

[0064] S106 removes the slag from the molten metal after refining and degassing, and lets it stand for 15-30 minutes. Then, an intermediate alloy ingot containing Al and 5% Ti (which may also contain trace amounts of B) is added, stirred evenly, and let it stand for another 15-30 minutes to obtain a die-cast aluminum alloy liquid. The time for the two standing processes is as follows.

[0065] During the aforementioned preparation process, special attention must be paid to covering and protecting Al-10Ca when adding it, as it is easily oxidized and burned off. The refining temperature and time must be properly controlled during preparation; too low a temperature will result in poor results, while too high a temperature will increase the tendency for oxidation and gas absorption. Sufficient settling time is necessary to ensure the purity of the melt. The intermediate alloy ingot containing Al and 5% Ti (which may also contain trace amounts of B) must be added in the final stage. Throughout the process, the melt must be properly covered to reduce oxidation and gas absorption, and vigorous stirring is essential to ensure uniform composition.

[0066] In step S2 above, the composition of the molten aluminum alloy is first detected using an electrical discharge spectrometer to determine if it reaches the preset mass percentage. If it does, the gas content is then detected using the water displacement method, and the theoretical density needs to reach 2.8 g / cm³. 3 And when the density equivalent is ≤0.1%, vacuum high-pressure die casting is performed using a die casting machine.

[0067] Specifically, when using liquid aluminum alloy for integrated high-pressure die casting, the vacuum degree of the mold cavity is first adjusted to 30mbar~50mbar. During the entire injection process, the injection pressure is set to 140bar~160bar, the injection flow rate is 50%~60%, and the injection time is 6.2s~6.8s.

[0068] In this embodiment, the first speed is 0.15 m / s to 0.19 m / s, the second speed is 0.15 m / s to 0.19 m / s, and the third speed is 3 m / s to 3.5 m / s, with the acceleration time from the second speed to the third speed being 18 ms to 22 ms. More specifically, the first speed is set to 0.17 m / s, the second speed is set to 0.17 m / s, the third speed is set to 3.15 m / s, the acceleration time from the second speed to the third speed is 20 ms, the die-casting mold temperature is set to 220 ± 10℃, and the aluminum alloy liquid temperature is set to 680 ± 10℃.

[0069] When using the third-speed filling and injection, the filling stroke is 62mm~63.2mm, and the filling time is 53ms~59ms. After filling and injection, the return hammer pressure of the injection punch is 125bar~135bar, the return hammer flow rate is 95%~100%, and the return hammer delay is 4.8s~5.2s. The boost trigger pressure is 75bar~85bar, and the boost pressure is 385bar~400bar. Specifically, the filling stroke is 62.6mm, the filling time is 56ms, the boost pressure is 393.9bar, the boost time is set to 112ms, and the cycle time is set to 66s.

[0070] In step S3 above, the post-processing adopts the conventional die-casting cooling method, and the cooling time is 11s~15s.

[0071] Obtain as Figure 2 After the Al-Cu high-strength and high-toughness die-cast aluminum alloy casting shown is produced, samples are taken from specific locations, and multiple standard tests are performed on the obtained castings to evaluate the performance of the castings obtained by the integrated die-casting method of Al-Cu high-strength and high-toughness die-cast aluminum alloy in this embodiment.

[0072] The specific experimental steps are as follows:

[0073] 1) A total of 20 die-cast samples of Al-4Cu-0.5Mn-0.5Ti-0.31Ca were produced using the aforementioned die-casting method. Initially, due to the mold temperature not being fully stable and the casting parameters being in the debugging stage, the mechanical properties of the first few parts were generally low, exhibiting unstable elongation and yield strength. As the mold temperature control was gradually optimized, the microstructure density and mechanical properties of subsequent samples significantly improved, fully demonstrating the advantages of stable process parameters. To systematically evaluate the process stability and microstructure uniformity, samples numbered 5, 10, 15, and 20 were selected from this batch as representatives for collecting tensile test specimens. To ensure the reliability of the experimental results, the preparation of all specimens was strictly carried out in accordance with international standards. In the tensile test, GB / T 2975-2018 standard was adopted, which clearly specifies the sampling location, size, and processing method of tensile specimens. The strict implementation of these standards ensured the repeatability and accuracy of the experimental data. For mass-produced materials, comprehensive testing should be conducted from multiple locations. To ensure the required quantity, A20 samples were used for different areas of the die casting.

[0074] 2) Each sample is in a pre-set... Figure 2Samples were cut from the three key regions (A1, A2, and A3) shown. Five standard tensile specimens were cut from region A1, and four standard tensile specimens were cut from each of regions A2 and A3, resulting in a total of 52 sets of mechanical property data. This approach covers the cooling and stress distribution characteristics of different locations in the component—such as the area near the gate, the central main rib area, and the edge shrinkage area—and therefore has strong representativeness. This sampling strategy allows for analysis from multiple dimensions. By comparing the performance differences of the same region at different time periods (early, middle, and late passes), the stability of mold temperature and casting conditions can be reflected. By comparing the data from the three regions A1 to A3, the microstructure density and uniformity of strengthening phase precipitation in different structural areas can be evaluated. Based on the 52 sets of mechanical property data, key parameters such as average value, standard deviation, and maximum / minimum values ​​can be statistically analyzed, providing a quantitative basis for subsequent process optimization.

[0075] 3) After the tensile test, a recycling test is conducted for evaluation. 25% of the die-cast scrap (by mass) is added to the primary alloy melt to simulate a typical recycling scenario in actual industry. This scrap is initially cleaned and shredded to reduce the interference of coatings and impurities on the alloy quality. Subsequently, it is heated and melted in a medium-frequency furnace under controlled conditions, with the melting temperature maintained at 730℃~760℃ for approximately 50–60 minutes, while simultaneously supplemented with purge gas and flux refining to suppress oxidation, degassing, and slag inclusions.

[0076] 4) After the recovered alloy has been fully melted and purified, its chemical composition is determined using ICP-OES (Inductively Coupled Plasma Optical Emission Spectrometry), with particular attention paid to the content deviations of key elements such as Cu, Ca, and Fe. Based on the elemental content determination results, the alloy is supplemented in trace amounts to restore it to the target chemical composition. Subsequently, the recovered melt is cast into HPDC standard tensile test specimens for subsequent performance comparison and evaluation.

[0077] 5) Evaluate the mechanical properties of the recycled alloy using standard tensile tests (such as GB / T 228.1 or ASTM E8) and hardness tests. By comparing the yield strength, tensile strength, elongation, and hardness of the recycled alloy with those of the virgin alloy, the degree of performance retention during the recycling process can be analyzed.

[0078] 6) The recycling efficiency is quantitatively evaluated by measuring the recovery rate of Cu and Ca in the recycled alloy. If ≥95% of the total Cu / Ca content is retained in the alloy before the experiment, the alloy can be considered stable.

[0079] Example 2

[0080] The difference between this embodiment and Embodiment 1 is that the composition and weight percentage of the aluminum alloy are: Cu 5.0 wt.%, Mn 0.47 wt.%, Ti 0.48 wt.%, Ca 0.32 wt%, and trace elements are added. These trace elements are one or more of Mg, Zr, and Zn, with each individual impurity element having a maximum content of 0.05 wt.%. The remaining components are all Al. The method for preparing the die-casting aluminum alloy liquid and the steps of the integrated die-casting method in this embodiment are the same as in Embodiment 1. Figure 3 The diagram shown illustrates the surface quality of the die-cast sample obtained in this embodiment. It can be seen that the sample surface is smooth and free of obvious cracks. Figure 4 The image shown is an SEM image of the sample, revealing a significantly refined microstructure. The α-Al matrix exhibits fine equiaxed crystals, while the second phase (primarily Al₂Cu) is small, uniformly distributed, and lacks a distinct continuous network structure. This uniform and fine microstructure is attributed to the effective refinement of the grains and improvement of the second phase precipitation morphology by the addition of Ca.

[0081] Example 3

[0082] The difference between this embodiment and Embodiment 1 is that the composition and weight percentage of the aluminum alloy are: Cu 6.0 wt.%, Mn 0.49 wt.%, Ti 0.51 wt.%, Ca 0.38 wt.%, and auxiliary trace elements, which are one or more of Mg, Zr, and Zn, with a maximum of 0.05 wt.% for a single impurity element, and the remaining components are all Al. The method for preparing the die-casting aluminum alloy liquid and the steps of the integrated die-casting method in this embodiment are the same as in Embodiment 1.

[0083] Comparative Example 1

[0084] The difference between this comparative example and Example 1 is that the composition and weight percentage of the aluminum alloy are: Cu 5.0 wt.%, Mn 0.51 wt.%, Ti 0.49 wt.%, and auxiliary trace elements, which are one or more of Mg, Zr, and Zn. Each individual impurity element is at most 0.05 wt.%, the remainder is Al, and Ca is not added. The method for preparing the die-casting aluminum alloy liquid and the steps of the integrated die-casting method in this comparative example are the same as in Example 1. Figure 5 The diagram shown illustrates the surface quality of the die-cast sample obtained in this embodiment. Obvious cracks can be seen on the sample surface. Figure 6 The image shown is an SEM image of the sample. The microstructure of this alloy is relatively coarse. Its α-Al matrix grains are large, and the second phase (mainly Al2Cu phase) is also coarse and unevenly distributed, tending to aggregate at grain boundaries and form a partially continuous network structure.

[0085] Comparative Example 2

[0086] The difference between this comparative example and Example 1 is that the composition and weight percentage of the aluminum alloy are: Cu 5.0 wt.%, Mn 0.52 wt.%, Ti 0.51 wt.%, Ca 0.50 wt.%, and auxiliary trace elements, which are one or more of Mg, Zr, and Zn, with a maximum of 0.05 wt.% for a single impurity element, the remainder being Al, and the amount of Ca added is increased to 0.50 wt%. The method for preparing the die-casting aluminum alloy liquid and the steps of the integrated die-casting method in this comparative example are the same as in Example 1.

[0087] The mechanical property test results of the castings obtained in Examples 1-3, Comparative Examples 1 and 2 are shown in Table 1 below. According to the traditional recycling rate formula, the recycling process effectively converts 25% of the die-casting waste into a high-performance alloy, with properties consistent with industrial application requirements. The recycling test strategy not only verified the controllability of the chemical composition of the developed heat-treatable, weldable, and recyclable Al-Cu high-strength and tough die-cast aluminum alloy, but also ensured that the tensile and hardness properties meet the design targets of yield strength ≥160MPa and elongation ≥15%, providing data support for the mass application of this alloy in automotive structural parts.

[0088] Table 1 Mechanical property test results

[0089]

[0090] The extremely high cooling rate and turbulence effect in the integrated die-casting method mean that the nucleation sites provided by the Ti content in existing aluminum alloy compositions are insufficient to dominate and control the entire solidification process. This easily leads to the formation of inhomogeneous structures and the inclusion of defects, thus becoming stress concentration points and deteriorating plasticity. This application achieves the injection of more nucleation particles (such as Al3Ti) into the aluminum alloy melt by increasing the Ti content, resulting in a finer and more uniform equiaxed crystal structure during solidification. This microstructure not only simultaneously improves strength and plasticity but also significantly improves the melt's feeding ability and reduces internal defects, thereby fundamentally avoiding early cracking of die-cast parts, macroscopically manifested as an effective increase in elongation.

[0091] Furthermore, Mg and Zr can refine grains and suppress eutectic formation, while Mn can form stable intermetallic compounds with Cu, reducing the content of free copper and thus decreasing the precipitation of low-melting-point eutectic phases. Simultaneously, Mn can refine grains, resulting in more uniform grain boundary distribution and reducing crack formation. In practical applications, Al-Cu aluminum alloys containing 0.2%–1% Mn exhibit significantly better weldability than Mn-free aluminum alloys, with hot crack susceptibility reduced by more than 40% (not shown in the table).

[0092] The addition of Ti and Ca improves fluidity, and Ti also refines grain size. More importantly, Ti reduces incomplete fusion defects caused by viscous molten pool during welding, reduces the stability of the CuO oxide film, and decreases weld porosity, achieving extremely high weldability levels typical of Al-Cu alloys. Figure 7 As shown, the specimens obtained by the integrated die-casting method can be welded to plates with a thickness greater than 50 mm using argon arc welding. The weld in the red circle exhibits high hardness, good performance, and no weld porosity. Specifically, during the welding process, Ti and Zr react with Al in the molten pool to generate fine Al3Ti and Al3Zr particles. These particles can play a dispersion strengthening role, improving the microhardness and mechanical properties of the weld zone, thus having a beneficial effect on weldability. Mn can form the AlMnCu phase, which can improve the alloy's heat resistance. Mn can also reduce the tendency for hot cracking, thus improving the alloy's weldability. The addition of Zn significantly improves the alloy's fluidity and readily forms the MgZn phase with Mg, increasing the alloy's strength and mechanical properties, indirectly benefiting weldability. However, excessive Mg content reduces brazability, therefore its content needs to be controlled.

[0093] Ca can significantly reduce the surface tension of Al-Cu alloy melts, making the liquid metal easier to spread and fill the mold cavity. Lower surface tension reduces frictional resistance between the melt and the mold wall, especially in complex thin-walled structures, allowing the melt to flow more smoothly into narrow areas and avoiding cold shuts and incomplete filling defects. As a modifier, Ca refines the primary θ-Al₂Cu phase and eutectic structure through heterogeneous nucleation. Adding 0.31 wt.% to 0.5 wt.% Ca reduces the primary dendrite size of the primary θ-Al₂Cu phase from over 500 μm to below 150 μm, and secondary dendrites are reduced by 80%. The refined grain structure reduces the obstruction of the dendritic network to melt flow during solidification, enhancing the feeding ability of the liquid metal at the solidification front. By narrowing the effective crystallization temperature range of the alloy and expanding the proportion of the liquid zone, Ca can increase the melt flow time without increasing the pouring temperature. Especially under rapid solidification conditions such as high-pressure die casting, the extension of the liquid zone significantly improves the filling capacity. Ca reacts with oxides in the melt to form low-melting-point calcium aluminate. These compounds have a high density and easily settle to the bottom of the crucible. Adding Ca can reduce the inclusion content, reduce the mechanical obstruction of the inclusions to the flow of the melt, and improve the quality of the casting.

[0094] Through analysis Figure 8 middle aAs shown in the stress-strain diagrams of Examples 1-3 and Comparative Examples 1-2, Ca can reduce the surface tension of the Al-Cu alloy melt, decrease the frictional resistance between the melt and the mold wall, making the liquid metal easier to spread and fill the mold cavity. It can also smoothly flow into narrow areas in complex thin-walled structures, avoiding cold shuts and incomplete filling defects, effectively improving alloy fluidity and resulting in more complete casting. A comparison of the SEM microstructure images of Example 2 and Comparative Example 1 shows that after adding Ca, the α-Al matrix grains are refined, and the second phase is smaller and more uniformly distributed. For example, in Example 2, the primary dendrite size of the θ-Al2Cu phase is significantly reduced, improving the overall performance of the alloy. The tensile strength, yield strength, and elongation data of Examples 1-3 are better than those of Comparative Example 1 (without Ca). For example, the elongation in Example 2 reaches 21.2%, far exceeding the 15.9% of Comparative Example 1. This is due to grain refinement and microstructure optimization, which enhances the alloy's resistance to deformation and fracture. Figure 8 As shown in the stress-strain diagram of the recovered sample in Figure b, the Ca-containing alloy retains a high degree of performance after recovery, which can meet the requirements of industrial applications. In contrast, the performance of Comparative Example 1 deteriorates significantly after recovery, demonstrating the important role of Ca in maintaining the stability of the recovered alloy.

[0095] Example 4

[0096] This embodiment provides a system for implementing the aforementioned integrated die-casting method for weldable and recyclable Al-Cu high-strength and tough die-cast aluminum alloys. The system includes:

[0097] A device for preparing liquid die-casting aluminum alloy;

[0098] An integrated high-pressure die-casting device includes an interconnected gating and sprue module and a die-casting mold. The gating and sprue module includes a sprue and a runner. The sprue is equipped with a hemispherical buffer cavity. The sprue and runner are connected by a transition cone with a taper of 40°~50° and a length of 30mm~40mm. An ingate is provided at the outlet end of the runner, which is connected to the inlet of the die-casting mold. An overflow unit is connected to the die-casting mold. An exhaust unit is connected to the overflow unit through an irregularly bent pipe. The cross-section of the irregularly bent pipe perpendicular to the airflow direction is trapezoidal, that is, the airflow channel inside the irregularly bent pipe is a trapezoidal pipe.

[0099] The post-processing module is used to perform post-processing after high-pressure die casting to obtain Al-Cu series high-strength and high-toughness die-cast aluminum alloy castings.

[0100] Specifically, such as Figure 9-11As shown, the aforementioned gating module includes a sprue 1, a runner 2, an overflow unit 3, and a venting unit 4. The sprue 1 is the first section into which the molten metal enters after being pushed out of the pressure chamber (not shown in the figure). It is located at a position lower than the runner 2, and the distance between the sprue 1 and the runner 2 is not less than 2 / 3 of the sprue diameter. The sprue 1 is offset from the center of the die-casting mold by at least 200mm to avoid heat concentration and prevent the molten metal from prematurely entering the runner 2 and solidifying prematurely. The bottom of the sprue 1 has a hemispherical buffer cavity 11 with a diameter 1.8 times the sprue diameter. The sprue 1 and the runner 2 are connected by a transition cone 12 with a taper of 40°~50° and a cone length of 30mm~40mm.

[0101] In this embodiment, the diameter of the pressure chamber can be taken as 80mm, therefore the diameter of the sprue is also taken as 80mm, and the draft angle is set to 6°~10°. This design can reduce the amount of oxide scale generated in the sprue 1 by 35%, and reduce the porosity of the casting from 3%~6% to 0.6%~1%.

[0102] The sprue 2 is the channel connecting the sprue 1 and the ingate. The sprue 2 includes a primary sprue 21 and a secondary sprue 22. Its main function is to guide the molten metal smoothly into the ingate and provide some feeding during solidification. The primary sprue 21 is located 11mm from the parting line. The secondary sprue 22 is inclined upwards at 5° to utilize gravity to assist filling, avoiding the influence of gravity on the filling effect during die casting. The ingate is close to the thin-walled end of the cavity and away from the hot spot to achieve sequential solidification.

[0103] Overflow unit 3 consists of multiple overflow channels, with the maximum distance between each overflow channel and the hot spot area of ​​the casting controlled at 36mm to ensure feeding efficiency. The center of each overflow channel is aligned with the center of the hot spot, and the total volume is 2.5 times the volume of the hot spot, preventing the formation of hot spots between the overflow channel and the casting. Specific locations can be set at the cavity wall where the liquid metal first impacts, in the dead corners on both sides of the ingate, at the point where two streams of liquid metal impact each other, and around cavity 5. These locations effectively collect gas and cold, stagnant liquid metal, preventing defects.

[0104] The exhaust unit 4, serving as the connection between the overflow groove and the vacuum mechanical valve, effectively removes air and gases generated by coating evaporation from the mold cavity during the die-casting filling process. It is primarily located at the parting line and the final filling point of the liquid metal, guiding the gas out of the mold cavity. After the liquid metal filling is complete, it quickly removes any remaining gas, preventing gas from accumulating in the mold cavity and affecting product quality.

[0105] In this embodiment, the exhaust channel and the overflow channel are connected by a Z-shaped (or irregular S-shaped) trapezoidal pipe 6 with a length of 12mm~25mm and a turning angle of 135°. The interior of the trapezoidal pipe 6 is a pipe with a trapezoidal cross-section perpendicular to the airflow direction, and baffles are arranged in an array along the airflow direction inside the pipe. Each baffle is fixed to the small-sized bottom surface of the trapezoidal pipe perpendicular to the airflow direction, and the interval between adjacent baffles is 5mm~6.5mm. The height of the baffle is less than the height of the Z-shaped trapezoidal pipe. The Z-shaped appearance and the baffle design inside the pipe can improve the gas discharge efficiency by 20%-30%. The exhaust channel is arranged around the cavity contour, and an auxiliary exhaust blind channel (not shown in the figure) can also be added at the end of the ribs and other places where the molten metal is filled last.

[0106] It is understood that the detailed functional implementation of each of the above units / modules can be found in the description in the aforementioned method embodiments, and will not be repeated here.

[0107] It should be understood that expressions such as “comprising” and “may include” used in this application indicate the existence of the disclosed functions, operations, or constituent elements, and do not limit one or more additional functions, operations, and constituent elements. In this application, terms such as “comprising” and / or “having” are to be interpreted as indicating a particular characteristic, number, operation, constituent element, component, or combination thereof, but not to exclude the existence or possibility of adding one or more other characteristics, numbers, operations, constituent elements, components, or combinations thereof.

[0108] Furthermore, in this application, the expression "and / or" includes any and all combinations of the associated listed words. For example, the expression "A and / or B" may include A, may include B, or may include both A and B.

[0109] In the description of the embodiments of this application, it should be noted that, unless otherwise explicitly specified and limited, the term "connection" should be interpreted broadly. For example, "connection" can be a detachable connection or a non-detachable connection; it can be a direct connection or an indirect connection through an intermediate medium. "Fixed connection" refers to a connection where the relative positional relationship remains unchanged after connection. "Rotary connection" refers to a connection where the components can rotate relative to each other after connection. "Sliding connection" refers to a connection where the components can slide relative to each other after connection. The directional terms mentioned in the embodiments of this application, such as "top," "bottom," "inner," "outer," "left," and "right," are only for reference to the directions in the accompanying drawings. Therefore, the directional terms used are for better and clearer explanation and understanding of the embodiments of this application, and are not intended to indicate or imply that the device or component referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on the embodiments of this application.

[0110] Furthermore, the mathematical concepts mentioned in the embodiments of this application, such as symmetry, equality, parallelism, and perpendicularity, are limitations specific to the current technological level, rather than absolute and strict mathematical definitions. Slight deviations are permissible; approximations of symmetry, equality, parallelism, and perpendicularity are all acceptable. For example, "A and B are parallel" means that A and B are parallel or approximately parallel, and the angle between A and B can be between 0 and 10 degrees. "A and B are perpendicular" means that A and B are perpendicular or approximately perpendicular, and the angle between A and B can be between 80 and 100 degrees.

[0111] The above description is merely a specific embodiment of this application, but the scope of protection of this application is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in this application should be included within the scope of protection of this application. Therefore, the scope of protection of this application should be determined by the scope of the claims.

Claims

1. An integrated die casting method of a weldable and recyclable Al-Cu high-strength and high-toughness die casting aluminum alloy, characterized by, The application relates to a preparation method of an Al-Cu series high-strength and high-toughness die-casting aluminum alloy, which comprises the following steps: S1. Preparing a die-casting aluminum alloy liquid, wherein the die-casting aluminum alloy liquid comprises 4.0wt.%-6.0wt.% of Cu, 0.31wt.%-0.5wt.% of Ca, 0.4wt.%-0.6wt.% of Mn, 0.45wt.%-0.55wt.% of Ti, and a total amount of Mg, Zn and Zr being less than or equal to 0.8wt.% and Mg / Zn being greater than or equal to 2.0; and the preparation method comprises the following steps: S101. According to preset components, pure aluminum ingots, intermediate alloy ingots containing Al and 50% Cu, intermediate alloy ingots containing Al and 10% Mn, intermediate alloy ingots containing Al and 5% Ti, and intermediate alloy ingots containing Al and 10% Ca are weighed; S102. All the metals weighed in step S101 are baked to remove potential liquid; S103. At a preset furnace temperature, the pure aluminum ingots are first melted into an aluminum liquid, and when the temperature of the aluminum liquid reaches a preset temperature, the intermediate alloy ingots containing Al and 10% Mn are added into the aluminum liquid for melting; after complete melting, the intermediate alloy ingots containing Al and 50% Cu are added for melting; S104. After the temperature of the molten metal liquid obtained in step S103 is adjusted to 740 DEG C-750 DEG C, the intermediate alloy ingots containing Al and 10% Ca are added into the molten metal liquid obtained in step S103 for continuous melting; S105. The molten metal liquid obtained in step S104 is subjected to refining and degassing treatment; S106. The dross of the molten metal liquid after refining and degassing is removed, and the molten metal liquid is subjected to static treatment for a preset time; then the intermediate alloy ingots containing Al and 5% Ti are added and stirred uniformly, and the molten metal liquid is subjected to static treatment for the preset time again, so that the die-casting aluminum alloy liquid is obtained; S2. The die-casting aluminum alloy liquid is used for integrated high-pressure die casting; a first speed of 0.15 m / s-0.19 m / s is adopted for slow-speed injection, so that the die-casting aluminum alloy liquid enters a sprue; then a second speed of 0.15 m / s-0.19 m / s is adopted for transition injection, so that the die-casting aluminum alloy liquid enters an inner gate via the sprue; the speed is accelerated to a third speed of 3 m / s-3.5 m / s for filling injection, and the time for accelerating the second speed to the third speed is 18 ms-22 ms, so that the die-casting aluminum alloy liquid is filled into a mold cavity from the inner gate, and after the pressure in the mold cavity rises to a pressurization trigger pressure, pressurization treatment is carried out; wherein the third speed is greater than the first speed and the second speed; S3. After the pressurization treatment is completed, post-treatment is carried out, so that an Al-Cu series high-strength and high-toughness die-casting aluminum alloy casting is obtained.

2. The integrated die casting method according to claim 1, wherein The preset furnace temperature is 850 DEG C-870 DEG C; and the preset temperature is 720 DEG C-750 DEG C.

3. The integrated die casting method of claim 1, wherein In step S105, the refining and degassing treatment is carried out by adopting a rotary blowing mode, and the rotary speed is 500 r / min; meanwhile, a mixed gas composed of nitrogen and a refining agent is sprayed, and the refining and degassing process lasts for 15 min-20 min.

4. The integrated die casting method of claim 1, wherein In step S106, the preset time is 15 min-30 min.

5. The integrated die casting method of claim 1, wherein In step S2, the vacuum degree of the mold cavity is 30-50 mbar, and during the whole injection process, the injection pressure is 140-160 bar, the injection flow rate is 50-60%, and the injection time is 6.2-6.8 s.

6. The integrated die casting method of claim 1, wherein In step S2, when filling and injecting at the third speed, the filling stroke is 62-63.2 mm, and the filling time is 53-59 ms; after the filling and injecting is completed, the rebound pressure of the injection punch is 125-135 bar, the rebound flow rate of the injection punch is 95-100%, and the rebound delay time is 4.8-5.2 s; the pressurization trigger pressure is 75-85 bar, and the pressurization pressure is 385-400 bar.

7. The integrated die casting method of claim 1, wherein In step S3, the post-processing is cooling processing, and the cooling processing time is 11-15 s.

8. A system for implementing the integrated die casting method of the weldable and recyclable Al-Cu based high-strength and high-toughness die casting aluminum alloy according to any one of claims 1 to 7, characterized in that, The application further provides an Al-Cu high-strength and high-toughness die-cast aluminum alloy casting method comprising the steps of: A die-cast aluminum alloy liquid preparation device is used to prepare a die-cast aluminum alloy liquid. An integrated high-pressure die-casting device comprises a sprue module and a die-casting mold connected with each other, the sprue module comprises a straight sprue and a cross sprue, a semispherical buffer cavity is arranged on the straight sprue, the straight sprue is connected with the cross sprue through a transition cone, the taper of the transition cone is 40-50°, and the taper length of the transition cone is 30-40 mm, an inner gate is arranged at the outlet end of the cross sprue, the inner gate is connected with the inlet of the die-casting mold, an overflow unit is connected with the die-casting mold, an exhaust unit is connected with the overflow unit through an irregular bent pipeline, and the cross section of the irregular bent pipeline along the direction perpendicular to the airflow direction is trapezoidal. A post-processing module is used to perform post-processing after the high-pressure die casting is completed, so as to obtain an Al-Cu high-strength and high-toughness die-cast aluminum alloy casting.

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