Heat-Treated, Corrosion-Resistant Die-Cast Aluminum Alloys, Structural Components, and Preparation Methods

Abstract

This application belongs to the field of integrated die casting technology, and more specifically, relates to heat-treatable die-cast aluminum alloys, structural parts, and preparation methods that are resistant to hot cracking and corrosion. The heat-treatable die-cast aluminum alloy provided in this application is based on a Zr-Cr-Fe synergistic control system. By controlling its composition range and ratio, Cr preferentially forms a Chinese character-shaped Al-Si-Cr-Fe phase with Fe, replacing the harmful needle-like Fe-rich phase; simultaneously, Zr forms Al3Zr dispersed particles to refine the grains, synergistically reducing the tendency for hot cracking. By controlling the composition range of Cr, Mn, Zr, and Mg, and the Zn / Mg weight ratio, intergranular corrosion and exfoliation corrosion are effectively suppressed, and a MgZn2 and Mg2Si composite passivation layer is formed on the casting surface, further improving corrosion resistance. Through the synergistic effect of multiple alloying elements, high mechanical properties, low hot cracking tendency, and strong corrosion resistance can be achieved without heat treatment, making it suitable for integrated die castings with stringent comprehensive performance requirements.

Description

Technical Field

[0001] This application belongs to the field of aluminum alloy die casting technology, and more specifically, relates to heat-free die-cast aluminum alloys, structural parts, and preparation methods that are resistant to hot cracking and corrosion. Background Technology

[0002] With the rapid development of industries such as new energy vehicles and aerospace, higher demands are being placed on the performance of die-cast aluminum alloys. In the field of new energy vehicles, large integrated die-cast structural components, such as vehicle frames and battery trays, need to possess excellent resistance to thermal cracking under complex working conditions to avoid structural failure caused by thermal stress concentration. Simultaneously, since vehicles are exposed to outdoor environments for extended periods, the corrosion resistance of aluminum alloys directly affects the vehicle's service life and safety. In the aerospace field, components must not only withstand extreme conditions such as high temperatures and high pressures but also meet lightweight requirements, making heat-treatable die-cast aluminum alloys an ideal choice. However, existing technologies have many shortcomings in meeting these comprehensive performance requirements.

[0003] Some existing heat-free die-cast aluminum alloys, such as the alloy disclosed in patent application CN115505795A, achieve ultra-high strength by significantly increasing the Cu and Mg content. However, the alloy has low elongation and does not address hot cracking issues during manufacturing, as well as corrosion resistance and recyclability in application, making it difficult to meet the requirements of large structural components in new energy vehicles for material toughness and long-term reliability. Patent document CN116121605A involves a heat-free die-cast aluminum alloy for electric bicycles. While it meets product safety requirements in certain performance aspects and reduces production costs, its elongation is only 2%~5%, and its toughness is poor, making it unsuitable for applications requiring high toughness. Furthermore, this technical solution does not optimize the alloy's resistance to hot cracking under complex working conditions or its corrosion resistance during long-term use, limiting its practical application.

[0004] Regarding recyclability, when using recycled aluminum to produce high-performance aluminum alloys, the complex composition of the waste aluminum raw materials generally results in insufficient ductility and hardness in the aluminum materials processed by existing technologies. For example, the heat-free die-cast aluminum alloy material disclosed in patent document CN116752018A can improve strength to a certain extent, but it does not fully consider the impact of impurity elements in recycled aluminum on the overall performance of the alloy. During multiple recycling processes, the alloy's resistance to thermal cracking and corrosion may decline sharply, making it difficult to achieve efficient and stable recycling.

[0005] Therefore, there is an urgent need to develop a heat-free die-cast aluminum alloy with excellent mechanical properties, resistance to hot cracking and corrosion, and high recyclability. Summary of the Invention

[0006] In view of the shortcomings of the prior art, the purpose of this application is to provide heat-free die-cast aluminum alloys, structural parts and preparation methods that are resistant to hot cracking and corrosion. It aims to solve the problems of the mechanical properties of existing aluminum alloy die castings that need to be improved, especially the low elongation, as well as the obvious hot cracking tendency, poor corrosion resistance and low recyclability of aluminum alloy die castings. It is especially suitable for large integrated die castings.

[0007] To achieve the above objectives, in a first aspect, this application provides a heat-treatable die-cast aluminum alloy that is resistant to hot cracking and corrosion, comprising the following components by weight percentage: Si: 8%~10%, Cu: 0.2%~0.6%, Mn: 0.1%~0.5%, Mg: 0.2%~0.6%, Zn: 0.1%~0.5%, Ti: 0.05%~0.3%, Sr: 0.01%~0.1%, Fe: 0.3%~1%, Zr: 0.05%~0.2%, Cr: 0.05%~0.3%, V: 0.05%~0.2%, rare earth elements: 0.01%~0.1%, with the balance being Al; wherein the rare earth elements include Ce and La;

[0008] Furthermore, the weight ratio of Zr to Cr is no greater than 1:1, and the weight ratio of Cr to Fe is no greater than 1:3.

[0009] Preferably, the above-mentioned heat-crack-resistant and corrosion-resistant heat-treatable die-cast aluminum alloy comprises, by weight percentage, the following components: Si: 8%~9%, Cu: 0.3%~0.5%, Mn: 0.3%~0.5%, Mg: 0.3%~0.5%, Zn: 0.2%~0.4%, Ti: 0.1%~0.3%, Sr: 0.04%~0.1%, Fe: 0.4%~1%, Zr: 0.1%~0.2%, Cr: 0.1%~0.3%, V: 0.05%~0.1%, rare earth elements: 0.03%~0.05%, with the balance being Al; wherein the rare earth elements include Ce and La;

[0010] Furthermore, the weight ratio of Zr to Cr is no greater than 1:1, and the weight ratio of Cr to Fe is no greater than 1:3.

[0011] Preferably, in the above-mentioned heat-free die-cast aluminum alloy, the weight ratio of Zr to Cr is 1:(1~3), and the weight ratio of Cr to Fe is 1:(3~4).

[0012] Preferably, in the above-mentioned heat-free die-cast aluminum alloy, the weight ratio of Zn to Mg is 1:(1~1.5).

[0013] Preferably, in the above-mentioned heat-free die-cast aluminum alloy, the weight ratio of Sr to rare earth elements is (1~2):1.

[0014] Preferably, in the above-mentioned heat-free die-cast aluminum alloy, the weight percentage of Ce is 0.02%~0.06%; and / or,

[0015] Preferably, the weight percentage of La is 0.01% to 0.03%.

[0016] Secondly, this application provides a method for preparing the above-mentioned heat-free die-cast aluminum alloy, which includes the following steps:

[0017] S1. Prepare the raw materials according to the above-mentioned composition of heat-free die-cast aluminum alloy, and then treat the prepared raw materials by melting, alloying, modification and refining to obtain aluminum alloy melt.

[0018] S2. The above-mentioned aluminum alloy melt is poured into the pressure chamber of the injection system. First, the pouring temperature of the above-mentioned aluminum alloy melt is detected by the first control system, and the high-speed injection speed is adjusted according to the temperature. Then, the real-time temperature of the aluminum alloy melt in the pressure chamber is detected by the second control system, and the casting pressure and holding time are adjusted according to the real-time temperature to obtain the above-mentioned heat-free die-cast aluminum alloy.

[0019] Preferably, in step S2, the first control system includes a temperature measuring device and a speed regulating device; wherein, the temperature measuring device is used to detect the pouring temperature of the aluminum alloy melt, and the speed regulating device automatically adjusts the high-speed injection speed according to the pouring temperature.

[0020] Preferably, in step S2, the second control system includes a contact temperature measuring device and a pressure regulating device; wherein, the contact temperature measuring device is used to detect the real-time temperature of the aluminum alloy melt in the pressure chamber, and the pressure regulating device automatically adjusts the casting pressure and holding time according to the real-time temperature.

[0021] Preferably, in step S2, when the casting temperature is 700℃~720℃, the high-speed injection speed is 3.5m / s~4.5m / s; when the casting temperature is higher than 720℃, the high-speed injection speed decreases by 0.01m / s~0.05m / s for every 1℃ increase.

[0022] Preferably, in step S2, when the real-time temperature is 680℃~700℃, the casting pressure is 50MPa~60MPa; when the real-time temperature is higher than 700℃, for every 10℃ increase, the casting pressure is reduced by 5MPa~10MPa and held for 1s~3s.

[0023] Thirdly, this application provides a structural component that is resistant to hot cracking and corrosion, at least a portion of which is the above-mentioned heat-free die-cast aluminum alloy, or a heat-free die-cast aluminum alloy prepared by the above-mentioned preparation method.

[0024] In summary, the technical solutions conceived in this application have the following main technical advantages compared with the prior art:

[0025] (1) The heat-free die-cast aluminum alloy with hot crack resistance and corrosion resistance provided in this application achieves high mechanical properties, low hot cracking tendency and strong corrosion resistance without heat treatment by designing the types and contents of elements in the die-cast aluminum alloy and through the synergistic ratio and interaction of multiple alloying elements. Through the synergistic effect of specific components in phase composition regulation, grain refinement and surface passivation, the as-cast aluminum alloy has excellent comprehensive properties and is suitable for die-cast structural parts with strict requirements for mechanical properties, hot crack resistance and corrosion resistance.

[0026] (2) Regarding the resistance to hot cracking, this application uses Zr-Cr-Fe as the core control system. By controlling the content of the three elements and the mass ratio of Zr to Cr and the mass ratio of Cr to Fe, Cr is preferentially combined with Fe to form the Chinese character-shaped Al-Si-Cr-Fe phase, effectively replacing the harmful needle-like Fe-rich phase. At the same time, Zr precipitates in the form of Al3Zr dispersed particles, playing a role in refining the grains. The two work together to significantly reduce the hot cracking tendency of aluminum alloy die castings, making the hot cracking rate no more than 1%. In addition, it can also improve the tolerance of Fe, which helps to improve the mechanical properties of aluminum alloy die castings. It also has good recyclability, enabling efficient and stable recycling.

[0027] (3) In terms of corrosion resistance, this application effectively suppresses the tendency of intergranular corrosion and exfoliation corrosion by reasonably limiting the composition range of Cr, Mn, Zr and Mg elements; further, by controlling the weight ratio of Zn to Mg, a continuous and dense passivation layer composed of MgZn2 and Mg2Si is generated in situ on the surface of the die casting during the forming process, thereby significantly improving the stability of aluminum alloy die castings in corrosive environments.

[0028] (4) Regarding fatigue resistance, the die-cast aluminum alloy provided in this application, through the control of the proportion of key precipitating elements in the alloy and the synergistic effect of precipitation, especially the weight ratio of Zn to Mg of 1:(1~1.5) and the weight ratio of Zr to Cr of 1:(1~3), can endow the die-cast aluminum alloy with excellent mechanical properties and fatigue resistance even after short-term heat treatment. The elemental composition of this die-cast aluminum alloy is suitable for use in automotive structural parts, and after electrophoretic coating and drying curing, it can achieve synergistic strengthening of artificial aging and natural aging, giving full play to the precipitation strengthening effect inside the alloy. It not only has high strength and plasticity, but also exhibits excellent fatigue resistance and structural stability under long-term dynamic load, which can meet the comprehensive requirements of automotive structural parts for high strength, high toughness and durability.

[0029] (5) This application optimizes the die-casting process of aluminum alloy die-castings by using a first control system including a temperature measuring device and a speed regulating device. The high-speed injection speed is automatically adjusted according to the pouring temperature of the aluminum alloy melt, so that the aluminum alloy melt has suitable fluidity and filling speed when filling the mold cavity, avoiding air entrapment due to excessive speed or cold shut due to excessive speed, and ensuring complete mold filling. Furthermore, a second control system including a contact temperature measuring device and a pressure regulating device is used to adjust the casting pressure and holding time according to the real-time temperature of the aluminum alloy melt in the pressure chamber. This can compensate for the shrinkage of the aluminum alloy melt, effectively reduce shrinkage porosity and shrinkage cavities inside the casting, improve its density, reduce the tendency of hot cracking, and thus improve the yield of castings. Attached Figure Description

[0030] Figure 1 This is a schematic flowchart of the preparation method of the heat-free die-cast aluminum alloy that is resistant to hot cracking and corrosion, as provided in this application.

[0031] Figure 2 This is a schematic diagram of the structure of the large integrated die-cast floor casting obtained according to the embodiments of this application;

[0032] Figure 3 The metallographic structure of the hot crack and corrosion resistant aluminum alloy die casting produced for the first time in Example 1 of this application is shown at different scales; wherein the scale of content (a) is 100 μm and the scale of content (b) is 10 μm.

[0033] Figure 4 The metallographic structures of the hot-crack-resistant and corrosion-resistant aluminum alloy die castings recycled through five rounds of recycling in Example 1 of this application are shown on different scales; the scale of content (a) is 100 μm and the scale of content (b) is 10 μm. Detailed Implementation

[0034] 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.

[0035] In the description of this application, it should be understood that the term "and / or" describes a 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 document indicates that the related objects are in an "or" relationship; for example, A / B means A or B.

[0036] In the specification and claims of this application, the terms “first,” “second,” and “third,” etc., are used to distinguish different objects, rather than to describe a specific order of objects, and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated.

[0037] In the description of the embodiments in this application, the words "exemplary" or "for example" are used to indicate that they are examples, illustrations, or descriptions. 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 options. Specifically, the use of the words "exemplary" or "for example" is intended to present the relevant concepts in a specific manner.

[0038] In the description of the embodiments of this application, unless otherwise stated, "multiple" means two or more.

[0039] This application provides a heat-treatable die-cast aluminum alloy that is resistant to hot cracking and corrosion, comprising the following components and their weight percentages: Si: 8%~10%, Cu: 0.2%~0.6%, Mn: 0.1%~0.5%, Mg: 0.2%~0.6%, Zn: 0.1%~0.5%, Ti: 0.05%~0.3%, Sr: 0.01%~0.1%, Fe: 0.3%~1%, Zr: 0.05%~0.2%, Cr: 0.05%~0.3%, V: 0.05%~0.2%, rare earth elements: 0.01%~0.1%, with the balance being Al; wherein the rare earth elements include Ce and La;

[0040] Furthermore, the weight ratio of Zr to Cr is no greater than 1:1, and the weight ratio of Cr to Fe is no greater than 1:3.

[0041] In some embodiments, the above-mentioned heat-free die-cast aluminum alloy comprises the following components and their weight percentages: Si: 8%~9%, Cu: 0.3%~0.5%, Mn: 0.3%~0.5%, Mg: 0.3%~0.5%, Zn: 0.2%~0.4%, Ti: 0.1%~0.3%, Sr: 0.04%~0.1%, Fe: 0.4%~1%, Zr: 0.1%~0.2%, Cr: 0.1%~0.3%, V: 0.05%~0.1%, rare earth elements: 0.03%~0.05%, with the balance being Al; wherein the rare earth elements include Ce and La;

[0042] Furthermore, the weight ratio of Zr to Cr is no greater than 1:1, and the weight ratio of Cr to Fe is no greater than 1:3.

[0043] In some embodiments, the weight percentage of Si in the above-mentioned heat-free die-cast aluminum alloy may be 8%, 8.1%, 8.2%, 8.3%, 8.4%, 8.5%, 8.6%, 8.7%, 8.8%, 8.9% or 9%.

[0044] In some embodiments, the weight percentage of Cu in the above-mentioned heat-free die-cast aluminum alloy may be 0.3%, 0.35%, 0.4%, 0.45% or 0.5%.

[0045] In some embodiments, the weight percentage of Mn in the above-mentioned heat-free die-cast aluminum alloy may be 0.3%, 0.35%, 0.4%, 0.45% or 0.5%.

[0046] In some embodiments, the weight percentage of Mg in the above-mentioned heat-free die-cast aluminum alloy may be 0.3%, 0.35%, 0.4%, 0.45% or 0.5%.

[0047] In some embodiments, the weight percentage of Zn in the above-mentioned heat-free die-cast aluminum alloy may be 0.2%, 0.25%, 0.3%, 0.35%, or 0.4%.

[0048] In some embodiments, the weight percentage of Ti in the above-mentioned heat-free die-cast aluminum alloy may be 0.1%, 0.15%, 0.2%, 0.25% or 0.3%.

[0049] In some embodiments, the weight percentage of Sr in the above-mentioned heat-free die-cast aluminum alloy may be 0.04%, 0.05%, 0.06%, 0.07%, 0.08%, 0.09%, or 0.1%.

[0050] In some embodiments, the weight percentage of Fe in the above-mentioned heat-free die-cast aluminum alloy may be 0.4%, 0.5%, 0.6%, 0.7%, 0.8%, 0.9% or 1%.

[0051] In some embodiments, the weight percentage of Zr in the above-mentioned heat-free die-cast aluminum alloy may be 0.1%, 0.12%, 0.15%, 0.18% or 0.2%.

[0052] In some embodiments, the weight percentage of Cr in the above-mentioned heat-free die-cast aluminum alloy may be 0.1%, 0.12%, 0.15%, 0.18%, 0.2%, 0.25%, 0.28%, or 0.3%.

[0053] In some embodiments, the weight percentage of V in the above-mentioned heat-free die-cast aluminum alloy may be 0.05%, 0.06%, 0.07%, 0.08%, 0.09%, or 0.1%.

[0054] In some embodiments, the weight percentage of rare earth elements in the above-mentioned heat-free die-cast aluminum alloy may be 0.03%, 0.035%, 0.04%, 0.045%, or 0.05%. In some embodiments, the weight percentage of Ce in the above-mentioned heat-free die-cast aluminum alloy is 0.02% to 0.06% (specifically, 0.02%, 0.025%, 0.03%, 0.035%, 0.04%, 0.05%, 0.06%, etc.); and the weight percentage of La is 0.01% to 0.03% (specifically, 0.01%, 0.012%, 0.015%, 0.018%, 0.02%, 0.025%, 0.03%, etc.).

[0055] In some embodiments, in the above-mentioned heat-free die-cast aluminum alloy, the weight ratio of Zr to Cr is 1:(1~3), and the weight ratio of Cr to Fe is 1:(3~4). Specifically, the weight ratio of Zr to Cr can be 1:1, 1:2, or 1:3. Specifically, the weight ratio of Cr to Fe can be 1:3, 1:3.5, or 1:4.

[0056] In some embodiments, the weight ratio of Zn to Mg in the above-mentioned heat-free die-cast aluminum alloy is 1:(1~1.5), which can be 1:1, 1:1.17, 1:1.33 or 1:1.5.

[0057] In some embodiments, the weight ratio of Sr to rare earth elements in the above-mentioned heat-free die-cast aluminum alloy is (1~2):1, which can be 1:1, 1.25:1, 1.33:1, 1.5:1 or 2:1.

[0058] The heat-treatable, corrosion-resistant, and heat-free die-cast aluminum alloy provided in this application controls the mechanical properties, hot-cracking resistance, and corrosion resistance of the die-cast aluminum alloy by designing the types and contents of its elemental composition. By employing a synergistic control system of Zr-Cr-Fe elements, and simultaneously controlling the weight ratio of Zr to Cr and the mass ratio of Cr to Fe, Cr preferentially forms a Chinese character-shaped Al-Si-Cr-Fe phase with Fe, replacing the traditional needle-like Fe-rich phase. This results in a Fe tolerance greater than 0.3%, while Zr forms Al3Zr dispersed particles to refine the grain structure. This synergistic effect significantly reduces the hot-cracking tendency of the die-cast aluminum alloy, with a hot-cracking rate not exceeding 3%. Furthermore, by controlling the content range of Cr, Mn, Zr, and Mg elements, intergranular corrosion and exfoliation corrosion are suppressed, thereby improving the corrosion resistance of the die-cast aluminum alloy. Simultaneously, by controlling the weight ratio of Zn to Mg, a MgZn2 passivation layer and a Mg2Si passivation layer spontaneously form on the surface of the aluminum alloy melt after die casting, further enhancing the corrosion resistance of the die-cast aluminum alloy. Through the synergistic effect of the various elements in the composition, a heat-free die-cast aluminum alloy with superior mechanical properties, resistance to hot cracking, and corrosion resistance is obtained.

[0059] In some embodiments, the heat-free die-cast aluminum alloy provided in this application, which is resistant to hot cracking and corrosion, has a hot cracking rate of ≤1%, a corrosion rate of <0.1mm / a, a room temperature ultimate tensile strength of ≥330MPa (up to 360MPa), a room temperature yield strength of ≥220MPa (up to 250MPa), and a room temperature elongation of ≥13% (up to 16%). It has excellent mechanical properties and is resistant to hot cracking and corrosion, making it suitable for manufacturing various structural components.

[0060] Considering that the die-cast aluminum alloy provided in this application needs to undergo electrophoretic coating after being used in automotive body structures, and requires drying and curing at 150℃~200℃ followed by cooling after electrophoresis, this application also tested the room temperature mechanical properties and fatigue resistance of the aforementioned die-cast aluminum alloy after short-time heat treatment. In some embodiments, the heat treatment temperature was 100℃~200℃, and the heat treatment time was 0.5h~1h. Experiments showed that the die-cast aluminum alloy provided in this application still exhibits good room temperature mechanical properties and excellent fatigue resistance after short-time heat treatment. The reason for this may be that after the above heat treatment, the die-cast aluminum alloy provided in this application can promote the precipitation of β″, Q′ and η′ phases in the die-cast aluminum alloy, and transform the GP zone into a metastable transition phase. During the subsequent cooling process, a small number of incompletely precipitated supersaturated solute atoms remain in the matrix. These residual solute atoms will slowly diffuse and agglomerate, forming new and finer GP zones around the existing transition phases (β″, Q′) or other defects in the matrix. These newly formed GP zones produce additional precipitation strengthening effects during the subsequent natural aging process, thus enabling the die-cast aluminum alloy to still have excellent properties after short-term heat treatment.

[0061] In some embodiments, the die-cast aluminum alloy provided in this application, after short-time heat treatment, has a room temperature ultimate tensile strength ≥340MPa, a room temperature yield strength ≥230MPa, a room temperature elongation ≥13%, and a fatigue cycle count exceeding ten million times, making it suitable for manufacturing automotive structural components, especially body structural components.

[0062] On the other hand, such as Figure 1 As shown, this application also provides a method for preparing the above-mentioned heat-free die-cast aluminum alloy, comprising the following steps:

[0063] S1. Prepare the raw materials according to the above-mentioned composition of heat-free die-cast aluminum alloy, and then treat the prepared raw materials by melting, alloying, modification and refining to obtain aluminum alloy melt.

[0064] S2. The above-mentioned aluminum alloy melt is poured into the pressure chamber of the injection system for die casting. First, the pouring temperature of the above-mentioned aluminum alloy melt is detected by the first control system, and the high-speed injection speed is adjusted according to the temperature. Then, the real-time temperature of the aluminum alloy melt in the pressure chamber is detected by the second control system, and the casting pressure and holding time are adjusted according to the real-time temperature to obtain the above-mentioned heat-free die-cast aluminum alloy.

[0065] In some embodiments, the raw materials prepared above include aluminum-containing raw materials, silicon-containing raw materials, copper-containing raw materials, manganese-containing raw materials, magnesium-containing raw materials, zinc-containing raw materials, titanium-containing raw materials, strontium-containing raw materials, iron-containing raw materials, zirconium-containing raw materials, chromium-containing raw materials, vanadium-containing raw materials, cerium-containing raw materials, and lanthanum-containing raw materials. It is understood that this application does not limit the form of the above raw materials; they can be alloys or pure metals containing the above elements, as long as the composition of the die-cast aluminum alloy obtained after melting the added raw materials is within the range defined in this application. In some embodiments, the above raw materials may include pure Al or Al alloys, pure Si or Si alloys, pure Cu or Cu alloys, pure Mn or Mn alloys, pure Mg or Mg alloys, pure Zn or Zn alloys, pure Ti or Ti alloys, pure Sr or Sr alloys, pure Fe or Fe alloys, pure Zr or Zr alloys, pure Cr or Cr alloys, pure V or V alloys, pure Ce or Ce alloys, and pure La or La alloys. In some specific embodiments of this application, the raw materials include pure Al, pure Mg, pure Zn, pure copper, aluminum-silicon alloy, aluminum-manganese alloy, aluminum-strontium alloy, aluminum-cerium alloy, aluminum-lanthanum alloy, aluminum-titanium alloy, aluminum-iron alloy, aluminum-zirconium alloy, aluminum-chromium alloy, and aluminum-vanadium alloy.

[0066] In some embodiments, the order in which the above-mentioned raw materials are added can be selected according to actual needs. In some embodiments, in step S1, the order of adding the raw materials is as follows:

[0067] S1-1. Heat pure Al and aluminum-silicon alloy to 780℃~820℃ (specifically 780℃, 790℃, 800℃, 810℃, 820℃, etc.) until the raw materials are completely melted to obtain the first melt;

[0068] S1-2. After the first melt is cooled to 720℃~760℃ (specifically 720℃, 730℃, 740℃, 750℃, 760℃, etc.), aluminum manganese alloy, aluminum titanium alloy, and aluminum zirconium alloy are added for alloying treatment. After complete melting, the mixture is stirred evenly at the first speed to obtain the second melt.

[0069] S1-3. The second melt is heated to 780℃~820℃ (specifically 780℃, 790℃, 800℃, 810℃, 820℃, etc.), and pure Cu, pure Zn, and aluminum-iron alloy are added for further melting. After complete melting, the temperature is lowered to 720℃~760℃, and aluminum-chromium alloy and aluminum-vanadium alloy are added for melting. After stirring and mixing at the second speed, a protective gas is applied for refining and degassing. At the same time, aluminum-strontium alloy, aluminum-cerium alloy, aluminum-lanthanum alloy, and pure Mg are added for modification treatment. After complete melting, the mixture is stirred and mixed at the third speed, and then the surface slag is removed to obtain the third melt, which is the aluminum alloy melt with the target composition.

[0070] In some embodiments, the first rotation speed is 300 r / min to 350 r / min, the second rotation speed is 400 r / min to 450 r / min, and the third rotation speed is 500 r / min to 550 r / min, with each stirring and mixing time being 3 min to 10 min independently. Adding aluminum-zirconium alloy at the initial stage of smelting and performing multi-stage stirring can promote Al3Zr nucleation. Simultaneously, aluminum-chromium alloy, aluminum-cerium alloy, and aluminum-lanthanum alloy are added, allowing Cr, Ce, and La elements to synergistically adsorb onto the surface of inclusions (including impurities and slag), achieving a triple effect of degassing, slag removal, and Fe-rich phase regulation.

[0071] In some embodiments, the protective gas applied during refining and slag removal is one or more of high-purity argon and high-purity nitrogen.

[0072] In some embodiments, in step S2, the first control system includes a temperature measuring device and a speed regulating device. The temperature measuring device detects the pouring temperature of the molten aluminum alloy, and the speed regulating device automatically adjusts the high-speed injection speed based on the pouring temperature. This ensures that the molten aluminum alloy has suitable fluidity and filling speed when filling the mold cavity, preventing air entrapment due to excessive speed or cold shut due to insufficient speed, thus guaranteeing complete mold filling. As a specific implementation, when the pouring temperature of the molten aluminum alloy is between 700℃ and 720℃, the high-speed injection speed is 3.5 m / s to 4.5 m / s. If the temperature measuring device in the first control system detects that the pouring temperature of the molten aluminum alloy is higher than the upper limit of the pouring temperature (720℃), the speed regulating device will automatically reduce the speed. In some embodiments, for every 1℃ increase in the pouring temperature of the aluminum alloy, the high-speed injection speed decreases by 0.01 m / s to 0.05 m / s.

[0073] In some embodiments, in step S2, the second control system includes a contact temperature measuring device and a pressure regulating device. The contact temperature measuring device detects the real-time temperature of the molten aluminum alloy in the pressure chamber, and the pressure regulating device adjusts the casting pressure and holding time based on the real-time temperature. This allows for feeding of the molten aluminum alloy, effectively reducing shrinkage porosity and voids inside the casting, improving its density, reducing the tendency for hot cracking, and thus increasing the casting yield. As a specific implementation, when the real-time temperature of the molten aluminum alloy in the pressure chamber is between 680°C and 700°C, a casting pressure of 50MPa to 60MPa is used for die casting. If the contact temperature measuring device in the second control system detects that the temperature of the molten aluminum alloy in the pressure chamber is higher than the upper limit of the real-time temperature (700°C), the pressure regulating device will automatically reduce the pressure and delay the time. In some embodiments, for every 10°C increase in the real-time temperature of the molten aluminum alloy in the pressure chamber, the casting pressure is reduced by 5MPa to 10MPa while holding the pressure for 1 to 3 seconds.

[0074] In some embodiments, before pouring the aluminum alloy melt into the injection system chamber in step S2, the injection system chamber and mold are preheated. The preheating temperature of the chamber is 200°C to 250°C, and the preheating temperature of the mold is 200°C to 250°C. This can effectively reduce the temperature difference between the melt and the mold, prevent defects such as hot spots and cold shuts caused by rapid cooling, and help to achieve high-quality aluminum alloy die castings.

[0075] On the other hand, this application also provides a method for recycling the above-mentioned die-cast aluminum alloy based on the above preparation method, comprising the following steps:

[0076] The above-mentioned die-cast aluminum alloy is used as recycled aluminum material. After roasting and crushing, it is mixed with new alloy raw materials, and then subjected to the above-mentioned melting, alloying and modification treatment to obtain a composite aluminum alloy melt. B2O3 particles are added, stirred and mixed evenly, and then ultrasonically vibrated. Finally, it is die-cast, so as to realize the recycling of die-cast aluminum alloy.

[0077] In some embodiments, the amount of B2O3 particles is 0.1% to 0.5% of the total weight of the composite aluminum alloy melt. In some embodiments, the stirring and mixing method can be, but is not limited to, electromagnetic stirring, with a stirring speed of 300 r / min to 500 r / min and a stirring time of 5 min to 10 min. In some embodiments, the ultrasonic vibration power is 2 kW to 2.5 kW, and the ultrasonic vibration time is 40 s to 60 s.

[0078] The recycling method provided in this application uses B2O3 to regulate the impurity Fe to form a FeB2 phase with a higher density, and utilizes the synergistic effect of ultrasonic vibration to effectively settle the FeB2 phase without the need for a degassing step.

[0079] On the other hand, this application also provides a structural component resistant to hot cracking and corrosion, at least a portion of which is the aforementioned heat-free die-cast aluminum alloy, or a heat-free die-cast aluminum alloy prepared by the aforementioned method. This structural component possesses excellent mechanical properties, resistance to hot cracking and corrosion, and can be manufactured by die casting, making it suitable for manufacturing thin-walled structural components. It is understood that this structural component can be entirely manufactured from the aforementioned heat-free die-cast aluminum alloy; alternatively, it can be partially manufactured from the aforementioned heat-free die-cast aluminum alloy, with the remaining portion made from other materials (such as plastics, other metals, etc.), and the specific choice can be flexibly made according to actual application needs.

[0080] It is understood that this application does not impose any particular limitation on the specific types of the aforementioned structural components, and they can be any structural components suitable for aluminum alloy manufacturing. Furthermore, the structure and properties of this structural component can be referenced from conventional technologies, and will not be elaborated further here. This structural component can be applied in new energy vehicles as an automotive structural component, such as the entire vehicle body, rear wheel arch inner panel, rear longitudinal beam, floor connecting plate, rear floor plate, beam internal reinforcing plate, hood, mudguards, doors, rear cargo box, and roof, etc. This structural component can also be used in other fields, such as aerospace, high-speed rail, shipbuilding, mobile devices, home appliances, chemical industry, and construction.

[0081] It should be understood that materials of the same or similar type, model, quality, properties, or function as the reagents and instruments used in the following embodiments can be used to implement this application. Unless otherwise specified, the experimental methods used in the following embodiments are conventional methods. Unless otherwise specified, the materials and reagents used in the following embodiments are commercially available.

[0082] The following are examples and comparative examples:

[0083] Example 1

[0084] The heat-treatable, corrosion-resistant, and heat-free die-cast aluminum alloy provided in this embodiment has the following composition and weight percentages: Si: 8.5wt%, Cu: 0.4wt%, Mn: 0.4wt%, Mg: 0.3wt%, Zn: 0.3wt%, Ti: 0.15wt%, Sr: 0.04wt%, rare earth element Ce: 0.02wt%, rare earth element La: 0.01wt%, Fe: 0.8wt%, Zr: 0.1wt%, Cr: 0.2wt%, V: 0.08wt%, with the balance being Al. The weight ratio of Zn / Mg is 1:1, the weight ratio of Cr / Fe is 1:4, the weight ratio of Zr / Cr is 1:2, and the weight ratio of Sr / rare earth element is 1.3:1.

[0085] The preparation method of the heat-treatable, corrosion-resistant, and heat-free die-cast aluminum alloy based on the above composition includes the following steps:

[0086] S1, Ingredients

[0087] Raw materials were weighed according to the above design, including Al-20Si, Al-10Mn, Al-10Sr, Al-10Ce, Al-10La, Al-10Ti, Al-10Fe, Al-5Zr, Al-10Cr, Al-10V master alloy, industrial pure Cu ingot, industrial pure Zn ingot, industrial pure Mg ingot, and industrial pure aluminum. The surface oxide layer was removed by grinding.

[0088] S2, Smelting

[0089] Melting: Industrial pure aluminum and Al-20Si master alloy are added to a graphite crucible preheated to 400°C and melted in a melting furnace at 800°C under argon protection (flow rate 0.8 L / min) to obtain the first melt;

[0090] Alloying treatment: After the first melt is cooled to 750℃, Al-10Mn, Al-10Ti and Al-5Zr master alloys are added for smelting. After complete melting, low-frequency electromagnetic stirring (magnetic field strength of 0.2mT and frequency of 10Hz) is turned on and stirred at 300r / min for 10min. After standing to remove slag, the second melt is obtained.

[0091] Modification and Refining: The second melt is heated to 800℃, and industrial pure Cu ingot, industrial pure Zn ingot, and Al-10Fe master alloy are added for further melting. After complete melting, the temperature is lowered to 750℃, and Al-10Cr and Al-10V are added. Medium-frequency electromagnetic stirring (magnetic field strength of 0.2mT, frequency of 30Hz) is turned on and stirred at 400r / min for 5min. Then, argon gas is introduced and rotated to remove gas for 15min (rotation speed of 250r / min). At the same time, Al-10Sr, Al-10Ce, Al-10La and industrial pure Mg ingot preheated to 200℃ are added. High-frequency electromagnetic stirring (magnetic field strength of 0.2mT, frequency of 50Hz) is performed at 500r / min for 3min. Slag is removed to obtain the third melt, namely aluminum alloy melt.

[0092] S3, Die Casting Production

[0093] The die-casting mold is preheated and evacuated to 200°C and a vacuum level of 80 mbar. Then, the third molten material is poured into the pressure chamber of the die-casting mold. The high-speed injection speed of the molten material is automatically adjusted by the first control system, which includes an infrared temperature measuring device and a speed adjustment device. The infrared temperature measuring device measures the temperature of the molten material when it is poured into the pressure chamber. When the pouring temperature of the molten material fluctuates within the range of 700°C to 720°C, the high-speed injection speed is 4 m / s. When the pouring temperature of the molten material is greater than 720°C, the speed adjustment device automatically matches the high-speed injection speed. For every 1°C increase, the high-speed injection speed decreases by 0.05 m / s (i.e., the adjustment step is 0.05 m / s), and the low-speed injection speed is 0.2 m / s (not involved in speed adjustment). Then, the casting pressure and holding time of each casting are dynamically adjusted through a second control system. This second control system includes a contact temperature measuring device and a pressure regulating system. The contact temperature measuring device, consisting of a telescopic robotic arm and a thermocouple, measures the temperature of the molten material in the pressure chamber when it is stable. Before the molten material is poured into the pressure chamber, the robotic arm extends the thermocouple into the chamber. After the molten material is poured in and stabilizes, the temperature is read, and then the thermocouple is retracted. When the temperature of the molten material in the pressure chamber fluctuates within the range of 680℃ to 700℃, the casting pressure is 50MPa, and die casting is performed directly to obtain an aluminum alloy die casting, denoted as D. When the temperature of the molten material in the pressure chamber exceeds 700℃, the pressure regulating system automatically matches the casting pressure and holding time. For every 10℃ increase, the casting pressure is reduced by 5MPa and held for 1 second before die casting.

[0094] Specifically, the structure obtained by die casting the above-mentioned aluminum alloy melt is as follows: Figure 2 The integrated die-cast rear floor casting for vehicles shown is denoted as D, and its dimensions (length × width × height) are approximately 1.5m × 1.5m × 0.5m.

[0095] The metallographic structure of the floor casting was observed, and its room temperature mechanical properties, hot crack resistance, and corrosion resistance were tested. The test methods are as follows:

[0096] 1) Mechanical properties: The room temperature ultimate tensile strength, room temperature yield strength and room temperature elongation of aluminum alloy die castings were tested in accordance with GB / T228.1-2021. Ten specimens were used for each test, and the average value was taken.

[0097] 2) Resistance to hot cracking: The number of hot cracking defects in every 100 castings is counted. Hot cracking rate = (number of castings with hot cracking defects / total number of castings) × 100%.

[0098] 3) Corrosion resistance: Using the weight loss corrosion method, 10 castings were suspended in a 3.5% NaCl solution. After 7 days, the weight loss of the castings in the corrosive environment was measured, and the corrosion rate was calculated.

[0099] Considering that the rear floor casting obtained in this application requires electrophoretic coating in practical applications, and after electrophoresis, it needs to be dried and cured at a temperature of 150℃~200℃ and then cooled, this application also tested the room temperature mechanical properties and fatigue resistance of the above-mentioned die-cast aluminum alloy after short-time heat treatment. The test methods are as follows:

[0100] The casting samples were heated to 100℃~200℃ and held for 0.5~1h for short-term heat treatment. Then, the heat-treated castings were placed in an air box for air cooling. After cooling to room temperature, the castings were removed and samples were taken from the casting body. The room temperature ultimate tensile strength, room temperature yield strength and room temperature elongation of aluminum alloy die castings were tested according to GB / T228.1-2021. Ten samples were taken for each test, and the average value was taken. The number of fatigue cycles of the samples was tested according to GB / T 3075-2021 Axial force control method for fatigue testing of metallic materials. The stress ratio was 0.1 and the frequency was 20kHz.

[0101] The metallographic structure of the first production casting is as follows Figure 3 As shown, the properties of the castings are shown in Tables 1 and 3.

[0102] This application also provides a method for recycling and regenerating the above-mentioned aluminum alloy die castings, including the following steps:

[0103] The produced casting blanks (including aluminum alloy die castings and gating systems) are used as recycled aluminum material and calcined at 480℃ for 3 hours to remove the organic coating. Afterward, they are broken into 50-100mm blocks and mixed with new alloy raw materials (recycled aluminum material accounting for 60% of the weight). The mixture is then fed into a furnace and processed through steps S1 and S2 to obtain a third melt (no argon degassing is required). B2O3 particles are then added, at a weight of 0.2% of the total melt weight. Electromagnetic stirring (magnetic field strength 0.2mT, frequency 50Hz) is initiated at 500r / min for 5 minutes to mix thoroughly. Ultrasonic vibration at 2kW power is then performed for 60 seconds to further mix the mixture. Step S3, die casting, is then performed, completing one round of recycling and regeneration, resulting in an aluminum alloy die casting, denoted as D1. The recycling and regeneration steps are repeated five times to obtain an aluminum alloy die casting, denoted as D5, after five rounds of recycling and regeneration.

[0104] The metallographic structure of the aluminum alloy die casting D5 after five rounds of recycling was observed, and the room temperature mechanical properties, hot crack resistance and corrosion resistance of the die casting D5 after five rounds of recycling were tested according to the above method. Ten samples were used for each sample, and the average value was taken.

[0105] The metallographic structure of aluminum alloy die castings recycled through five rounds of recycling is as follows: Figure 4 As shown in Table 2, the properties of the castings are as follows.

[0106] Depend on Figure 3Content (a), Figure 3 Content (b) Figure 4 Content (a), Figure 4 Content (b) shows that, compared to the first production of aluminum alloy die castings D ( Figure 3 Microstructure of D5 aluminum alloy die-cast parts recycled and regenerated through five rounds at different scales ( Figure 4 The absence of significant coarsening indicates that the microstructure of the recycled aluminum alloy die-casting is stable.

[0107] Example 2

[0108] The heat-treatable, corrosion-resistant, and heat-free die-cast aluminum alloy provided in this embodiment has the following composition and weight percentages: Si: 9wt%, Cu: 0.45wt%, Mn: 0.4wt%, Mg: 0.35wt%, Zn: 0.3wt%, Ti: 0.15wt%, Sr: 0.04wt%, rare earth element Ce: 0.025wt%, rare earth element La: 0.012wt%, Fe: 0.6wt%, Zr: 0.1wt%, Cr: 0.2wt%, V: 0.08wt%, with the balance being Al. The weight ratios of Zn / Mg are 1:1.17, Cr / Fe: 1:3, Zr / Cr: 1:2, and Sr / rare earth element: 1.08:1.

[0109] The preparation method of the heat-treatable, corrosion-resistant, and heat-free die-cast aluminum alloy based on the above composition includes the following steps:

[0110] S1, Ingredients

[0111] Raw materials were weighed according to the above design, including Al-20Si, Al-10Mn, Al-10Sr, Al-10Ce, Al-10La, Al-10Ti, Al-10Fe, Al-5Zr, Al-10Cr, Al-10V master alloy, industrial pure Cu ingot, industrial pure Zn ingot, industrial pure Mg ingot, and industrial pure aluminum. The surface oxide layer was removed by grinding.

[0112] S2, Smelting

[0113] Melting: Industrial pure aluminum and Al-20Si master alloy are added to a graphite crucible preheated to 400°C and melted in a melting furnace at 800°C under argon protection (flow rate 0.8 L / min) to obtain the first melt;

[0114] Alloying treatment: After the first melt is cooled to 750℃, Al-10Mn, Al-10Ti and Al-5Zr master alloys are added for smelting. After complete melting, low-frequency electromagnetic stirring (magnetic field strength of 0.2mT and frequency of 10Hz) is turned on and stirred at 350r / min for 8min. After standing to remove slag, the second melt is obtained.

[0115] Modification and refining: The second melt is heated to 800℃, and industrial pure Cu ingot, industrial pure Zn ingot, and Al-10Fe master alloy are added for further melting. After complete melting, the temperature is lowered to 750℃, and Al-10Cr and Al-10V are added. Medium-frequency electromagnetic stirring (magnetic field strength of 0.2mT, frequency of 30Hz) is turned on and stirred at 450r / min for 5min. Then, argon gas is introduced and rotated to remove gas for 15min (rotation speed of 250r / min). At the same time, Al-10Sr, Al-10Ce, Al-10La and industrial pure Mg ingot preheated to 200℃ are added and stirred at 550r / min for 5min using high-frequency electromagnetic stirring (magnetic field strength of 0.2mT, frequency of 50Hz). Slag is removed to obtain the third melt.

[0116] S3, Die Casting Production

[0117] The die-casting mold undergoes hot molding, spraying, and vacuuming treatment, preheating to 250℃ and a vacuum degree of 120mbar. Then, the third molten material is poured into the pressure chamber of the die-casting mold. The high-speed injection speed of the molten material is automatically adjusted by the first control system, which includes an infrared temperature measuring device and a speed adjustment device. The infrared temperature measuring device measures the temperature of the molten material when it is poured into the pressure chamber. When the molten material temperature fluctuates within the range of 700℃ to 720℃, the high-speed injection speed is 3.5m / s. When the molten material temperature is greater than 720℃, the speed adjustment device automatically matches the high-speed injection speed, reducing the high-speed injection speed by 0.05m / s for every 1℃ increase (i.e., the adjustment step is 0.05m / s). The low-speed injection speed is 0.3m / s (not involved in speed adjustment). Then, the casting pressure and holding time of each casting are dynamically adjusted through a second control system. This second control system includes a contact temperature measuring device and a pressure regulating system. The contact temperature measuring device, consisting of a telescopic robotic arm and a thermocouple, measures the temperature of the molten material in the pressure chamber when it is stable. Before the molten material is poured into the pressure chamber, the robotic arm extends the thermocouple into the chamber. After the molten material is poured in and stabilizes, the temperature is read, and then the thermocouple is retracted. When the temperature of the molten material in the pressure chamber fluctuates within the range of 680℃ to 700℃, the casting pressure is 60MPa, and die casting is performed directly to obtain an aluminum alloy die casting. When the temperature of the molten material in the pressure chamber exceeds 700℃, the pressure regulating system automatically matches the casting pressure and holding time. For every 10℃ increase, the casting pressure is reduced by 10MPa and held for 3 seconds before die casting.

[0118] This application also provides a method for recycling and regenerating the above-mentioned aluminum alloy die castings, including the following steps:

[0119] The produced casting blanks (including aluminum alloy die castings and gating systems) are used as recycled aluminum material and calcined at 500℃ for 3 hours to remove the oil coating. Afterward, they are broken into 50-100mm blocks and mixed with new alloy raw materials (recycled aluminum material accounting for 60% by weight). The mixture is then fed into a furnace and processed through steps S1 and S2 to obtain a third melt (no argon gas degassing is required). B2O3 particles (0.3% of the total melt weight) are then added, and electromagnetic stirring (magnetic field strength 0.2mT, frequency 50Hz) is initiated at 550r / min for 5 minutes. Ultrasonic vibration at 2.5kW power for 40 seconds is then performed to mix the mixture before step S3, die casting production, thus completing one round of recycling. This recycling process is repeated five times to obtain aluminum alloy die castings that have undergone five rounds of recycling, denoted as D5.

[0120] The mechanical properties, hot crack resistance, and corrosion resistance of the casting were tested using the test method provided in Example 1. The room temperature mechanical properties and fatigue resistance of the first-production aluminum alloy die casting D after short-time heat treatment were also tested. The results are shown in Tables 1, 2, and 3.

[0121] Example 3

[0122] The heat-resistant and corrosion-resistant die-cast aluminum alloy provided in this embodiment has the following composition and weight percentages: Si: 9wt%, Cu: 0.4wt%, Mn: 0.4wt%, Mg: 0.4wt%, Zn: 0.3wt%, Ti: 0.15wt%, Sr: 0.05wt%, rare earth element Ce: 0.025wt%, rare earth element La: 0.015wt%, Fe: 0.4wt%, Zr: 0.1wt%, Cr: 0.1wt%, V: 0.1wt%, with the balance being Al. The weight ratios of Zn / Mg are 1:1.13, Cr / Fe: 1:4, Zr / Cr: 1:1, and Sr / rare earth element: 1.25:1. The first-production aluminum alloy die-casting D and the aluminum alloy die-casting D5, which underwent five rounds of recycling, were prepared according to the preparation method and recycling method provided in Example 1.

[0123] The mechanical properties, hot crack resistance, and corrosion resistance of the casting were tested using the test method provided in Example 1. The room temperature mechanical properties and fatigue resistance of the first-production aluminum alloy die casting D after short-time heat treatment were also tested. The results are shown in Tables 1, 2, and 3.

[0124] Comparative Example 1

[0125] The heat-free die-cast aluminum alloy provided in this comparative example has a Zr weight percentage of 0.2 wt% and a Cr weight percentage of 0.1 wt% (Zr / Cr weight ratio of 2:1). Other components and their weight percentages are the same as those provided in Example 1, with the balance being Al. Aluminum alloy die castings D and D5, which have undergone five rounds of recycling, were prepared according to the preparation and recycling methods provided in Example 1.

[0126] The mechanical properties, hot crack resistance, and corrosion resistance of the casting were tested using the test method provided in Example 1. The room temperature mechanical properties and fatigue resistance of the first-production aluminum alloy die casting D after short-time heat treatment were also tested. The results are shown in Tables 1, 2, and 3.

[0127] Comparative Example 2

[0128] The die-cast aluminum alloy provided in this comparative example has a Zr weight percentage of 0.05 wt% and a Cr weight percentage of 0.2 wt% (Zr / Cr weight ratio of 1:4). Other components and their weight percentages are the same as those provided in Example 1, with the balance being Al. An initial aluminum alloy die-casting D and an aluminum alloy die-casting D5, after five rounds of recycling, were prepared according to the preparation and recycling methods provided in Example 1.

[0129] The mechanical properties, hot crack resistance, and corrosion resistance of the casting were tested using the test method provided in Example 1. The room temperature mechanical properties and fatigue resistance of the first-production aluminum alloy die casting D after short-time heat treatment were also tested. The results are shown in Tables 1, 2, and 3.

[0130] Comparative Example 3

[0131] The die-cast aluminum alloy provided in this comparative example has a Cr weight percentage of 0.3 wt% and an Fe weight percentage of 0.6 wt% (Cr / Fe weight ratio of 1:2). Other components and their weight percentages are the same as those provided in Example 1, with the balance being Al. An initial aluminum alloy die-casting D and an aluminum alloy die-casting D5, which underwent five rounds of recycling, were prepared according to the preparation and recycling methods provided in Example 1.

[0132] The mechanical properties, hot crack resistance, and corrosion resistance of the casting were tested using the test method provided in Example 1. The room temperature mechanical properties and fatigue resistance of the first-production aluminum alloy die casting D after short-time heat treatment were also tested. The results are shown in Tables 1, 2, and 3.

[0133] Comparative Example 4

[0134] The die-cast aluminum alloy used in this comparative example is A356. The alloy was prepared according to its composition, and an A356 melt was obtained. The parameters of the A356 melt were then adjusted according to the method provided in Example 1, and the first batch of A356 die-cast parts was produced. These first batches of A356 die-cast parts were then recycled and remelted to obtain aluminum alloy die-cast parts that underwent five rounds of recycling.

[0135] The room temperature mechanical properties, hot crack resistance, and corrosion resistance of newly produced aluminum alloy A356 die castings and aluminum alloy A356 die castings recycled through five rounds of processing were tested using the test method provided in Example 1. The room temperature mechanical properties and fatigue resistance of newly produced aluminum alloy A356 die castings after short-time heat treatment were also tested. The results are shown in Tables 1, 2, and 3.

[0136] Comparative Example 5

[0137] The die-casting aluminum alloy used in this comparative example is AlSi10MnMg. The alloy was prepared according to its composition, and an AlSi10MnMg melt was obtained. The melt parameters were then adjusted according to the method provided in Example 1, and the first AlSi10MnMg die-casting was produced. This first AlSi10MnMg die-casting was then recycled and remelted to obtain a five-round recycled aluminum alloy die-casting.

[0138] The room temperature mechanical properties, hot crack resistance, and corrosion resistance of newly produced AlSi10MnMg die castings and AlSi10MnMg die castings recycled through five rounds of processing were tested using the testing method provided in Example 1. The room temperature mechanical properties and fatigue resistance of newly produced AlSi10MnMg die castings after short-time heat treatment were also tested. The results are shown in Tables 1, 2, and 3.

[0139]

[0140]

[0141]

[0142] Test results (Table 1) show that compared to commercially available mature A356 die-cast aluminum alloys and AlSi10MnMg die-cast aluminum alloys, the heat-free die-cast aluminum alloy provided in this application, through the design of its element types and composition ranges, and the synergistic ratio and interaction of multiple alloying elements, can achieve high mechanical properties, low hot cracking tendency, and strong corrosion resistance without heat treatment. Specifically, the room temperature ultimate tensile strength of the heat-free aluminum alloy die-cast parts produced for the first time in the embodiments of this application is greater than 330 MPa and can reach 360 MPa, the room temperature yield strength is greater than 220 MPa and can reach 250 MPa, and the room temperature elongation is greater than 13% and can reach 16%, exhibiting excellent mechanical properties. In addition, compared to commercially available mature die-cast aluminum alloys, the heat-free die-cast aluminum alloy prepared in the embodiments of this application has no hot cracking defects, the hot cracking rate is not greater than 1%, and the corrosion rate is less than 0.1 mm / a, exhibiting excellent hot cracking resistance and corrosion resistance.

[0143] Furthermore, the aluminum alloy die-castings produced in the first embodiment were recycled and remelted. The resulting aluminum alloy die-castings, after five rounds of recycling, still exhibited superior mechanical properties, a lower hot cracking rate, and a smaller corrosion rate (Table 2). This demonstrates that the die-cast aluminum alloy provided in this application has good recyclability, enabling efficient and stable recycling. On the other hand, it also demonstrates the high stability and reliability of the production process provided in this application. In practical applications, these characteristics give aluminum alloy die-castings significant advantages in sustainable development and industrial production. Through multiple recycling processes, resource waste and environmental pollution can be reduced, production costs can be lowered, and the economic efficiency of materials can be improved, resulting in significant economic and environmental benefits.

[0144] Furthermore, the aluminum alloy die castings produced for the first time in this application still exhibit excellent room temperature mechanical properties and fatigue resistance after short-time heat treatment (Table 3, heat treatment temperature is 200℃, heat treatment time is 1h). The reason for this may be that after short-time heat treatment, the die casting aluminum alloy provided in this application can promote the precipitation of β″, Q′ and η′ phases in the die casting aluminum alloy, transforming the GP zone into a metastable transition phase. During the subsequent cooling process, a small amount of incompletely precipitated supersaturated solute atoms remain in the matrix. These residual solute atoms will slowly diffuse and agglomerate, forming new and finer GP zones around the existing transition phases (β″, Q′) or at other defects in the matrix. These newly formed GP zones produce additional precipitation strengthening effects during the subsequent natural aging process, thus enabling the die casting aluminum alloy to still have excellent performance after short-time heat treatment. In practical production applications, when the die-cast aluminum alloy provided in this application is used to prepare automotive structural parts, the manufactured vehicle body structural parts are dried and cured after electrophoretic coating treatment, which can achieve synergistic strengthening of artificial aging and natural aging, so that the automotive structural parts have excellent mechanical properties and fatigue resistance.

[0145] By comparing Example 1 and Comparative Example 1, it can be seen that the mechanical properties of the aluminum alloy die castings produced for the first time in Comparative Example 1 and the aluminum alloy die castings recycled after five rounds of recycling decreased. The reason may be that when the Zr / Cr weight ratio is too high (the Zr / Cr weight ratio in Comparative Example 1 is 2:1), the primary Al3Zr phase precipitates in the microstructure. This phase is coarse rod-shaped or radial needle-shaped, which is detrimental to the mechanical properties of the matrix, thus leading to a significant decrease in the strength of the aluminum alloy die castings.

[0146] Those skilled in the art will readily understand that the above description is merely a preferred embodiment of this application and is not intended to limit this application. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of this application should be included within the protection scope of this application.

Claims

1. A heat-treatable, non-heat-treated aluminum alloy resistant to hot cracking and corrosion, characterized in that, By weight percentage, it comprises the following components: Si: 8%~10%, Cu: 0.2%~0.6%, Mn: 0.1%~0.5%, Mg: 0.2%~0.6%, Zn: 0.1%~0.5%, Ti: 0.05%~0.3%, Sr: 0.01%~0.1%, Fe: 0.3%~1%, Zr: 0.05%~0.2%, Cr: 0.05%~0.3%, V: 0.05%~0.2%, rare earth elements: 0.01%~0.1%, with the balance being Al; wherein the rare earth elements include Ce and La; Furthermore, the weight ratio of Zr to Cr is 1:(1~3), and the weight ratio of Cr to Fe is no greater than 1:

3.

2. The heat-free die-cast aluminum alloy according to claim 1, characterized in that, By weight percentage, it comprises the following components: Si: 8%~9%, Cu: 0.3%~0.5%, Mn: 0.3%~0.5%, Mg: 0.3%~0.5%, Zn: 0.2%~0.4%, Ti: 0.1%~0.3%, Sr: 0.04%~0.1%, Fe: 0.4%~1%, Zr: 0.1%~0.2%, Cr: 0.1%~0.3%, V: 0.05%~0.1%, rare earth elements: 0.03%~0.05%, with the balance being Al; wherein the rare earth elements include Ce and La; Furthermore, the weight ratio of Zr to Cr is no greater than 1:1, and the weight ratio of Cr to Fe is no greater than 1:

3.

3. The heat-free die-cast aluminum alloy according to claim 2, characterized in that, In the heat-free die-cast aluminum alloy, the weight ratio of Cr to Fe is 1:(3~4).

4. The heat-free die-cast aluminum alloy according to claim 3, characterized in that, In the heat-free die-cast aluminum alloy, the weight ratio of Zn to Mg is 1:(1~1.5); and / or, The weight ratio of Sr to rare earth elements is (1~2):

1.

5. The heat-free die-cast aluminum alloy according to claim 4, characterized in that, In the heat-free die-cast aluminum alloy, the weight percentage of Ce is 0.02%~0.06%; and / or, The weight percentage of La is 0.01% to 0.03%.

6. The heat-free die-cast aluminum alloy according to claim 1, characterized in that, The heat-free die-cast aluminum alloy, after being immersed in a 3.5% sodium chloride solution for 7 days, exhibited a corrosion rate of less than 0.1 mm / a.

7. A method for preparing a heat-free die-cast aluminum alloy as described in any one of claims 1 to 6, characterized in that, Includes the following steps: S1. Prepare the raw materials according to the composition of the heat-free die-cast aluminum alloy, and then treat the prepared raw materials by melting, alloying, modification and refining to obtain aluminum alloy melt. S2. The aluminum alloy melt is poured into the pressure chamber of the injection system. First, the pouring temperature of the aluminum alloy melt is detected by the first control system, and the high-speed injection speed is adjusted according to the temperature. Then, the real-time temperature of the aluminum alloy melt in the pressure chamber is detected by the second control system, and the casting pressure and holding time are adjusted according to the real-time temperature to obtain the heat-free die-cast aluminum alloy.

8. The preparation method according to claim 7, characterized in that, In step S2, the first control system includes a temperature measuring device and a speed regulating device; wherein, the temperature measuring device is used to detect the pouring temperature of the aluminum alloy melt, and the speed regulating device automatically adjusts the high-speed injection speed according to the pouring temperature; The second control system includes a contact temperature measuring device and a pressure regulating device; wherein, the contact temperature measuring device is used to detect the real-time temperature of the aluminum alloy melt in the pressure chamber, and the pressure regulating device automatically adjusts the casting pressure and holding time according to the real-time temperature.

9. The preparation method according to claim 8, characterized in that, When the casting temperature is 700℃~720℃, the high-speed injection speed is 3.5m / s~4.5m / s; when the casting temperature is higher than 720℃, the high-speed injection speed decreases by 0.01m / s~0.05m / s for every 1℃ increase. When the real-time temperature is 680℃~700℃, the casting pressure is 50MPa~60MPa; when the real-time temperature is higher than 700℃, for every 10℃ increase, the casting pressure decreases by 5MPa~10MPa and is held for 1s~3s.

10. A structural component resistant to thermal cracking and corrosion, characterized in that, At least a portion of the structural component is a heat-free die-cast aluminum alloy as described in any one of claims 1 to 6, or a heat-free die-cast aluminum alloy prepared by the preparation method described in any one of claims 7 to 9.

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