High-strength corrosion-resistant heat-treatment-free die-casting aluminum alloy and preparation method thereof

Abstract

The invention belongs to the technical field of metal materials, and particularly relates to a high-strength corrosion-resistant heat-treatment-free die-casting aluminum alloy and a preparation method thereof. The aluminum alloy comprises, by mass, 5.5%-7.1% of Mg, 2.5%-3.5% of Si, 0.5%-0.75% of Mn, 0.11%-0.7% of Cu, 0.08%-0.15% of Fe, 0.05%-0.1% of Mo, 0.02%-0.05% of V, 0.01%-0.05% of Zr, 0.03%-0.09% of Y and the balance Al and inevitable impurity elements, the content of a single impurity element is smaller than or equal to 0.02%, and the total content of the impurity elements is smaller than or equal to 0.2%. And the mass ratio of the Mg element to the Cu element in the aluminum alloy components is in the range of (10: 1)-(50: 1). The heat-treatment-free die-casting aluminum alloy provided by the invention is high in yield strength and obvious in weight reduction effect.

Description

Technical Field

[0001] This invention belongs to the field of metal materials technology, and particularly relates to a high-strength, corrosion-resistant, heat-treatable die-cast aluminum alloy and its preparation method. Background Technology

[0002] To improve driving range and handling performance, new energy vehicles are facing increasing demands for lightweighting. The car body accounts for approximately 30% of the total vehicle weight, representing the largest weight percentage and the area with the greatest potential for lightweighting. Die casting offers advantages such as high production efficiency, high dimensional accuracy, excellent mechanical properties, and the ability to form complex shapes and clearly defined thin-walled, deep-cavity castings. Therefore, integrated die casting has become a key focus of the automotive industry's lightweighting technology strategy. However, the integration of multiple parts leads to the large size of die castings, significantly increasing the difficulty of subsequent straightening after heat treatment and raising the scrap rate. Therefore, the development of heat-treatable die-casting aluminum alloys suitable for large, thin-walled die castings has become an inevitable choice for integrated die casting. However, the yield strength of steel parts or wrought aluminum alloys is above 200 MPa, while the yield strength of existing heat-treatable die-casting aluminum alloys generally does not exceed 130 MPa. This results in the actual weight reduction effect of parts being far lower than expected. Therefore, improving the yield strength of materials is an inevitable trend for the future development of integrated die castings.

[0003] Currently, the widely used heat-free high-strength and high-toughness aluminum alloys mainly employ two major technical routes: Al-Si and Al-Mg. Al-Si alloys have high formability and yield, and are relatively easy to prepare, making them the mainstream heat-free aluminum alloys for industrial production. However, the yield strength of this series of alloys generally does not exceed 125 MPa, making it difficult to achieve good weight reduction. Al-Mg alloys have excessively high yield strength. While extensive research has been conducted domestically, they have not yet been formally industrialized, mainly due to insufficient alloy properties, especially elongation, and high production costs. CN118326213A discloses an Al-Mg-Si-Mn-Cu-Zr series high-strength and high-toughness die-cast aluminum alloy, its preparation method, and its applications. The die-cast aluminum alloy comprises the following components in the indicated mass percentages: 6.0–12.0 wt.% Mg, 0.5–3.0 wt.% Si, 0.2–1.5 wt.% Mn, 0.5–3.0 wt.% Cu, 0.05–0.5 wt.% Zr, and 0.01–0.4 wt.% metallic X, wherein metallic X is selected from Sb and / or Ti. The alloy exhibits excellent corrosion resistance and superior impact resistance. After heat treatment at 450℃ for 20 hours, its yield strength is approximately 250 MPa, tensile strength is approximately 345 MPa, and elongation is approximately 7.5%. However, the excessively high Mg content in this patent results in poor fluidity, making it prone to burn-off during casting, and the elongation is less than 10%, failing to meet the minimum requirement of 10–16% for structural components. CN112522557A discloses a high-strength and high-toughness die-cast aluminum alloy and its production process. The high-strength and high-toughness die-cast aluminum alloy is composed of the following components by mass percentage: Mg: 4%~7%; Si: 1.6%~2.8%; Mn: 0.4%~0.9%; Ti: 0.1%~0.3%; Be: 0.002%~0.010%; aluminum-titanium-carbon-boron seed material: 0.3%~2%; Fe: ≤0.2%, wherein the ratio of Mg to Si should satisfy: Mg / Si≥2.5. This patent improves the casting performance by adding rare earth lanthanum, which changes the morphology of the hard and brittle second-phase particles from needle-like to short rod-like. However, in this patent, the yield strength is below 200 MPa when the elongation is higher than 10%, and the elongation is below 10% when the yield strength exceeds 200 MPa. Furthermore, it contains Be, a harmful and easily burnable element, increasing the difficulty and cost of smelting. Summary of the Invention

[0004] In view of this, the purpose of this invention is to provide a high-strength, corrosion-resistant, heat-treatable die-cast aluminum alloy and its preparation method, so as to solve the problems of low yield strength and insignificant weight reduction effect of existing heat-treatable aluminum alloys.

[0005] This invention provides a high-strength, corrosion-resistant, heat-treatable die-cast aluminum alloy. The aluminum alloy composition, by mass percentage, is as follows: Mg 5.5~7.1%, Si 2.5~3.5%, Mn 0.5~0.75%, Cu 0.11~0.7%, Fe 0.08~0.15%, Mo 0.05~0.1%, V 0.02~0.05%, Zr 0.01~0.05%, Y 0.03~0.09%, with the remainder being Al and unavoidable impurity elements. The content of a single impurity element is ≤0.02%, and the total content of impurity elements is ≤0.2%. Furthermore, the mass ratio of Mg to Cu in the aluminum alloy composition is within the range of (10:1) to (50:1).

[0006] Preferably, the aluminum alloy composition by mass percentage is as follows: Mg 5.5~7.1%, Si 2.5~3.5%, Mn 0.5~0.5%, Cu 0.11~0.5%, Fe 0.08~0.15%, Mo 0.05~0.1%, V 0.02~0.05%, Zr 0.02~0.05%, Y 0.03~0.09%, with the remainder being Al and unavoidable impurity elements, the total amount of unavoidable impurity elements being ≤0.2%.

[0007] Preferably, the unavoidable impurity elements include one or more of Pb, Sn, Cd and Zn.

[0008] Preferably, the heat-free die-cast aluminum alloy has an ultimate tensile strength of 310~380MPa, a yield strength of 215~270MPa, and an elongation after fracture of 10~20%.

[0009] This invention provides a method for preparing the high-strength, corrosion-resistant, heat-treatable die-cast aluminum alloy described in the above technical solution, comprising the following steps:

[0010] a) Calculate the amount of different raw materials to be added according to the alloy composition, and then add aluminum raw materials, manganese raw materials, copper raw materials, vanadium raw materials, zirconium raw materials, yttrium raw materials and silicon raw materials to melt in a melting furnace, with the temperature controlled at 750~790℃, to obtain the first alloy melt;

[0011] b) Cool the first alloy melt to 740~760℃ to obtain the second alloy melt;

[0012] c) Add magnesium raw material to the second alloy melt and stir until completely melted, with the temperature controlled at 730~750℃, to obtain the third alloy melt;

[0013] d) Add a slag remover to the third alloy melt, control the temperature of the alloy melt at 730~740℃, stir for a period of time and then remove the slag to obtain the fourth alloy melt.

[0014] e) The fourth alloy melt is subjected to degassing and slag removal treatment to obtain the fifth alloy melt;

[0015] f) The fifth alloy melt is subjected to composition testing, density testing and slag content testing. After passing the tests, it is allowed to stand and cool down to 690~710℃ to obtain a pre-die-cast aluminum alloy melt.

[0016] g) The pre-die-cast aluminum alloy melt is die-cast to obtain a high-strength, corrosion-resistant, heat-free die-cast aluminum alloy.

[0017] Preferably, the aluminum raw material is pure aluminum and / or electrolytic aluminum; the silicon raw material is one or more of aluminum-silicon master alloy, industrial silicon, and readily soluble silicon; the manganese raw material is aluminum-manganese master alloy and / or manganese agent; the copper raw material is pure copper and / or aluminum-copper master alloy; the magnesium raw material is pure magnesium; the vanadium raw material is pure vanadium and / or aluminum-vanadium master alloy; the zirconium raw material is pure zirconium and / or aluminum-zirconium master alloy; the molybdenum raw material is pure molybdenum and / or aluminum-molybdenum master alloy; and the yttrium raw material is aluminum-yttrium master alloy.

[0018] Preferably, in step d), the slag remover is a sodium-free refining agent; the amount of the slag remover added accounts for 0.1~0.3 wt.% of the total alloy melt; and the stirring time is 10~15 min.

[0019] Preferably, in step e), the specific process of degassing and slag removal includes: adding a covering agent to the fourth alloy melt, and then using a rotary degasser to introduce inert gas into the melt.

[0020] Preferably, in step e), the covering agent is a sodium-free covering agent; the covering agent is added within 2 minutes; the amount of the covering agent added accounts for 0.05~0.1 wt.% of the total alloy melt; the inert gas is nitrogen and / or argon; the inert gas is introduced at a pressure of 0.18~0.25 MPa; the rotor speed of the rotary degasser is 300~500 rad / min; the degassing and slag removal treatment time is 15~30 minutes; and the melt temperature during the degassing and slag removal treatment is controlled at 720~730℃.

[0021] Preferably, in step g), the temperature of the pre-cast aluminum alloy melt injected into the die-casting mold is 695~715℃; the die-casting pressure is 1200~1700 bar; the slow injection speed of the die-casting is 0.20~0.35 m / s; the fast injection speed of the die-casting is 3.5~7.0 m / s; the preheating temperature of the die and the barrel used for die-casting is 150~250℃; and the vacuum degree of the die cavity is 80~95 Pa.

[0022] Compared with the prior art, the present invention provides a high-strength, corrosion-resistant, heat-treatable die-cast aluminum alloy and its preparation method. The composition of the high-strength, corrosion-resistant, heat-treatable die-cast aluminum alloy provided by the present invention, by mass percentage, is as follows: Mg 5.5~7.1%, Si 2.5~3.5%, Mn 0.5~0.75%, Cu 0.11~0.7%, Fe 0.08~0.15%, Mo 0.05~0.1%, V 0.02~0.05%, Zr 0.01~0.05%, Y 0.03~0.09%, with the remainder being Al and unavoidable impurity elements. The content of a single impurity element is ≤0.02%, and the total content of impurity elements is ≤0.2%. Furthermore, the mass ratio of Mg to Cu in the aluminum alloy composition is in the range of (10:1) to (50:1). This invention refines and homogenizes the microstructure of aluminum alloys through trace alloying elements, reduces magnesium burn-off and oxidation by the harmless element γ, and ensures the comprehensive performance of the aluminum alloy through precise control of other alloying components. Based on this, combined with an optimized die-casting process, a die-cast aluminum alloy that balances mechanical and corrosion resistance can be prepared without heat treatment. Experimental results show that the aluminum alloy provided by this invention has an ultimate tensile strength of 310~380MPa, a yield strength of 215~270MPa, and an elongation after fracture of 10~20%, which can greatly improve the weight reduction effect of castings and can be applied to integrated thin-walled die-casting parts with high requirements for corrosion resistance and weight reduction.

[0023] More specifically, the present invention has at least the following beneficial effects:

[0024] 1. The strength, especially the yield strength, of the alloy of the present invention is increased by more than 80% compared with the existing heat-free die-cast aluminum alloys, and its performance is comparable to that of ordinary steel parts. The weight reduction effect is significant, which can significantly improve the driving range and handling performance of automobiles.

[0025] 2. The alloy of this invention has excellent corrosion resistance and is suitable for automotive chassis structural components with high corrosion resistance requirements, which can significantly reduce corrosion protection costs.

[0026] 3. The alloy of this invention uses an Al-Mg eutectic alloy as the basic alloy system, taking into account both the strength and casting performance of the alloy. Adding Si reduces the alloy's susceptibility to hot cracking while further improving its casting performance; adding Cu significantly increases the alloy's tensile strength; adding Mo, Zr, and V refines the grain size, improves microstructure uniformity and thermal stability; adding Y to replace Be reduces the oxidation loss of Mg, thereby ensuring melt quality.

[0027] 4. Other component design aspects: Based on the material performance requirements, process characteristics, and processing requirements, the range of each element is reasonably controlled. Copper and magnesium are the main strengthening elements of the alloy of this invention. The optimal copper-magnesium ratio is not only crucial for the strength-toughness balance of the alloy, but also directly affects the corrosion resistance of the alloy. Through extensive experiments, this invention has optimally controlled the elemental mass ratio of Mg to Cu within the range of (10~50):1. Silicon is the main alloying element in the alloy of this invention, controlled at 2.5~3.5%, ensuring good mold filling ability and resistance to hot cracking. When the silicon content is below 2.5%, the total latent heat of crystallization of the alloying elements is relatively small, and it has little impact on the casting performance of the alloy; when the silicon content is above 3.5%, the casting performance of the alloy increases, but the formation of excessive Si phase leads to a deterioration in the toughness of the alloy.

[0028] 5. By controlling the range of iron and manganese content and strictly controlling the mass fraction of Mn and Fe, this invention achieves effective control over the precipitation of primary iron-rich phases, and effectively regulates the morphology, size, and distribution of iron-rich phases, thereby reducing their harm to alloy toughness.

[0029] 6. The high-strength, corrosion-resistant, heat-treatable die-cast aluminum alloy material provided by this invention is suitable for the production of large structural parts with high strength and toughness requirements and difficult heat treatment. Without heat treatment, it can meet the production requirements of thin-walled automotive structural parts with tensile strength of 310~380MPa, yield strength of 215~270MPa, and elongation of 10~20%, which has significant weight reduction significance and broad application prospects. Detailed Implementation

[0030] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0031] This invention provides a high-strength, corrosion-resistant, heat-treatable die-cast aluminum alloy. The aluminum alloy composition, by mass percentage, is as follows: Mg 5.5~7.1%, Si 2.5~3.5%, Mn 0.5~0.75%, Cu 0.11~0.7%, Fe 0.08~0.15%, Mo 0.05~0.1%, V 0.02~0.05%, Zr 0.01~0.05%, Y 0.03~0.09%, with the remainder being Al and unavoidable impurity elements. The content of a single impurity element is ≤0.02%, and the total content of impurity elements is ≤0.2%. Furthermore, the mass ratio of Mg to Cu in the aluminum alloy composition is in the range of (10:1) to (50:1).

[0032] In the heat-free die-cast aluminum alloy provided by the present invention, the content of Mg can specifically be 5.5 wt.%, 5.6 wt.%, 5.7 wt.%, 5.8 wt.%, 5.9 wt.%, 6.0 wt.%, 6.1 wt.%, 6.2 wt.%, 6.3 wt.%, 6.4 wt.%, 6.5 wt.%, 6.6 wt.%, 6.7 wt.%, 6.8 wt.%, 6.9 wt.%, 7.0 wt.%, or 7.1 wt.%.

[0033] In the heat-free die-cast aluminum alloy provided by the present invention, the Si content can specifically be 2.5wt.%, 2.6wt.%, 2.7wt.%, 2.8wt.%, 2.9wt.%, 3.0wt.%, 3.1wt.%, 3.2wt.%, 3.3wt.%, 3.4wt.%, or 3.5wt.%.

[0034] In the heat-free die-cast aluminum alloy provided by the present invention, the Mn content can specifically be 0.5 wt.%, 0.51 wt.%, 0.52 wt.%, 0.53 wt.%, 0.54 wt.%, 0.55 wt.%, 0.56 wt.%, 0.57 wt.%, 0.58 wt.%, 0.59 wt.%, 0.6 wt.%, 0.61 wt.%, 0.62 wt.%, 0.63 wt.%, 0.64 wt.%, 0.65 wt.%, 0.66 wt.%, 0.67 wt.%, 0.68 wt.%, 0.69 wt.%, 0.7 wt.%, 0.71 wt.%, 0.72 wt.%, 0.73 wt.%, 0.74 wt.%, or 0.75 wt.%.

[0035] In the heat-free die-cast aluminum alloy provided by the present invention, the Cu content can specifically be 0.11 wt.%, 0.12 wt.%, 0.15 wt.%, 0.2 wt.%, 0.21 wt.%, 0.25 wt.%, 0.3 wt.%, 0.4 wt.%, 0.5 wt.%, 0.55 wt.%, 0.6 wt.%, 0.62 wt.%, or 0.7 wt.%.

[0036] In the heat-free die-cast aluminum alloy provided by the present invention, the Fe content can specifically be 0.08wt.%, 0.09wt.%, 0.10wt.%, 0.11wt.%, 0.12wt.%, 0.13wt.%, 0.14wt.%, or 0.15wt.%.

[0037] In the heat-free die-cast aluminum alloy provided by the present invention, the content of Mo can specifically be 0.05wt.%, 0.055wt.%, 0.06wt.%, 0.065wt.%, 0.07wt.%, 0.075wt.%, 0.08wt.%, 0.085wt.%, 0.09wt.%, 0.095wt.%, or 0.1wt.%.

[0038] In the heat-free die-cast aluminum alloy provided by the present invention, the content of V can specifically be 0.02wt.%, 0.025wt.%, 0.03wt.%, 0.035wt.%, 0.04wt.%, 0.045wt.% or 0.05wt.%.

[0039] In the heat-free die-cast aluminum alloy provided by the present invention, the Zr content can specifically be 0.01wt.%, 0.015wt.%, 0.02wt.%, 0.025wt.%, 0.03wt.%, 0.035wt.%, 0.04wt.%, 0.045wt.% or 0.05wt.%.

[0040] In the heat-free die-cast aluminum alloy provided by the present invention, the content of Y can specifically be 0.03wt.%, 0.035wt.%, 0.04wt.%, 0.045wt.%, 0.05wt.%, 0.055wt.%, 0.06wt.%, 0.065wt.%, 0.07wt.%, 0.075wt.%, 0.08wt.%, 0.085wt.%, or 0.09wt.%.

[0041] In the heat-free die-cast aluminum alloy provided by this invention, the mass ratio of Mg to Cu in the aluminum alloy composition can be 10:1, 11:1, 12:1, 13:1, 14:1, 15:1, 16:1, 17:1, 18:1, 19:1, 20:1, 21:1, 22:1, 23:1, 24:1, 25:1, 26:1, 27:1, 28:1, 29:1, 30:1, 31:1, 32:1, 33:1, 34:1, 35:1, 36:1, 37:1, 38:1, 39:1, 40:1, 41:1, 42:1, 43:1, 44:1, 45:1, 46:1, 47:1, 48:1, 49:1, or 50:1.

[0042] In the heat-free die-cast aluminum alloy provided by the present invention, the unavoidable impurity elements include, but are not limited to, one or more of Pb, Sn, Cd and Zn.

[0043] In the heat-free die-cast aluminum alloy provided by the present invention, the ultimate tensile strength of the heat-free die-cast aluminum alloy is preferably 310~380MPa; the yield strength of the heat-free die-cast aluminum alloy is preferably 215~270MPa; and the elongation after fracture of the heat-free die-cast aluminum alloy is preferably 10~20%.

[0044] This invention also provides a method for preparing the high-strength, corrosion-resistant, heat-treatable die-cast aluminum alloy described in the above technical solution, comprising the following steps:

[0045] a) Calculate the amount of different raw materials to be added according to the alloy composition, and then add aluminum raw materials, manganese raw materials, copper raw materials, vanadium raw materials, zirconium raw materials, yttrium raw materials, molybdenum raw materials and silicon raw materials to melt in a melting furnace, with the temperature controlled at 750~790℃, to obtain the first alloy melt;

[0046] b) Cool the first alloy melt to 740~760℃ to obtain the second alloy melt;

[0047] c) Add magnesium raw material to the second alloy melt and stir until completely melted, with the temperature controlled at 730~750℃, to obtain the third alloy melt;

[0048] d) Add a slag remover to the third alloy melt, control the temperature of the alloy melt at 730~740℃, stir for a period of time and then remove the slag to obtain the fourth alloy melt.

[0049] e) The fourth alloy melt is subjected to degassing and slag removal treatment to obtain the fifth alloy melt;

[0050] f) The fifth alloy melt is subjected to composition testing, density testing and slag content testing. After passing the tests, it is allowed to stand and cool down to 690~710℃ to obtain a pre-die-cast aluminum alloy melt.

[0051] g) The pre-die-cast aluminum alloy melt is die-cast to obtain a high-strength, corrosion-resistant, heat-free die-cast aluminum alloy.

[0052] In the preparation method provided by this invention, the aluminum raw material is preferably pure aluminum and / or electrolytic aluminum; the silicon raw material is preferably one or more of aluminum-silicon master alloy, industrial silicon, and readily soluble silicon; the manganese raw material is preferably aluminum-manganese master alloy and / or manganese agent; the copper raw material is preferably pure copper and / or aluminum-copper master alloy; the magnesium raw material is preferably pure magnesium; the vanadium raw material is preferably pure vanadium and / or aluminum-vanadium intermetallic alloy; the zirconium raw material is preferably pure zirconium and / or aluminum-zirconium master alloy; the molybdenum raw material is preferably pure molybdenum and / or aluminum-molybdenum master alloy; and the yttrium raw material is preferably aluminum-yttrium master alloy. In this invention, the aluminum raw material contains trace amounts of Fe, which enters the alloy melt along with the aluminum raw material, thus eliminating the need to add iron raw material separately.

[0053] In the preparation method provided by the present invention, in step a), the temperature can be specifically controlled to be 750℃, 755℃, 760℃, 765℃, 770℃, 775℃, 780℃, 785℃ or 790℃.

[0054] In the preparation method provided by the present invention, in step b), the first alloy melt can be cooled to 740°C, 745°C, 750°C, 755°C or 760°C.

[0055] In the preparation method provided by the present invention, in step c), the temperature can be specifically controlled to be 730℃, 735℃, 740℃, 745℃ or 750℃.

[0056] In the preparation method provided by the present invention, in step d), the slag remover is preferably a sodium-free refining agent; the amount of the slag remover added is preferably 0.1~0.3 wt.% of the total alloy melt, specifically 0.1 wt.%, 0.12 wt.%, 0.15 wt.%, 0.17 wt.%, 0.2 wt.%, 0.23 wt.%, 0.25 wt.%, 0.27 wt.%, or 0.3 wt.% of the total alloy melt.

[0057] In the preparation method provided by the present invention, in step d), the temperature of the alloy melt can be specifically controlled to be 730℃, 731℃, 732℃, 733℃, 734℃, 735℃, 736℃, 737℃, 738℃, 739℃ or 740℃.

[0058] In the preparation method provided by the present invention, in step d), the stirring time is preferably 10-15 min, specifically 10 min, 10.5 min, 11 min, 11.5 min, 12 min, 12.5 min, 13 min, 13.5 min, 14 min, 14.5 min or 15 min.

[0059] In the preparation method provided by this invention, step e) preferably includes the following specific process: adding a covering agent to the fourth alloy melt, followed by introducing inert gas into the melt using a rotary degasser. In this invention, the rotary degasser uses a high-speed rotating rotor that sprays inert gas to break large inert gas bubbles into very fine bubbles, dispersing them evenly throughout the aluminum alloy melt. After contacting hydrogen and oxide inclusions in the melt, the inert bubbles carry these impurities to the melt surface and are discharged, thereby achieving degassing and slag removal from the aluminum alloy melt.

[0060] In the preparation method provided by the present invention, in step e), the covering agent is preferably a sodium-free covering agent; the covering agent is preferably added within 2 minutes; the amount of the covering agent added is preferably 0.05~0.1 wt.% of the total alloy melt, specifically it can be 0.05 wt.%, 0.055 wt.%, 0.06 wt.%, 0.065 wt.%, 0.07 wt.%, 0.075 wt.%, 0.08 wt.%, 0.085 wt.%, 0.09 wt.%, 0.095 wt.%, or 0.1 wt.% of the total alloy melt.

[0061] In the preparation method provided by the present invention, in step e), the inert gas is preferably nitrogen and / or argon; the inlet pressure of the inert gas is preferably 0.18~0.25MPa, specifically 0.18MPa, 0.19MPa, 0.2MPa, 0.21MPa, 0.22MPa, 0.23MPa, 0.24MPa or 0.25MPa.

[0062] In the preparation method provided by the present invention, in step e), the rotor speed of the rotary degasser is preferably 300~500 rad / min, specifically 300 rad / min, 320 rad / min, 350 rad / min, 370 rad / min, 400 rad / min, 420 rad / min, 450 rad / min, 470 rad / min or 500 rad / min.

[0063] In the preparation method provided by the present invention, in step e), the degassing and slag removal treatment time is preferably 15-30 min, specifically 15 min, 16 min, 17 min, 18 min, 19 min, 20 min, 21 min, 22 min, 23 min, 24 min, 25 min, 26 min, 27 min, 28 min, 29 min or 30 min.

[0064] In the preparation method provided by the present invention, in step e), the melt temperature of the degassing and slag removal treatment is preferably controlled at 720~730℃, specifically 720℃, 721℃, 722℃, 723℃, 724℃, 725℃, 726℃, 727℃, 728℃, 729℃ or 730℃.

[0065] In the preparation method provided by this invention, in step f), the acceptable requirement for the composition detection is that it is within the designed alloy composition range; the acceptable requirement for the density detection is that the reduced pressure solidification density value is ≥2.61 g / cm³. 3 The qualification requirement for slag content detection is that the K-modulus value of the slag content is ≤1 / 20.

[0066] In the preparation method provided by the present invention, in step f), the endpoint temperature of the cooling can specifically be 690℃, 691℃, 692℃, 693℃, 694℃, 695℃, 696℃, 697℃, 698℃, 699℃, 700℃, 701℃, 702℃, 703℃, 704℃, 705℃, 706℃, 707℃, 708℃, 709℃, or 710℃.

[0067] In the preparation method provided by the present invention, in step g), the temperature at which the pre-cast aluminum alloy melt is injected into the die-casting mold is preferably 695~715℃, specifically 695℃, 696℃, 697℃, 698℃, 699℃, 700℃, 701℃, 702℃, 703℃, 704℃, 705℃, 706℃, 707℃, 708℃, 709℃, 710℃, 711℃, 712℃, 713℃, 714℃ or 715℃.

[0068] In the preparation method provided by the present invention, in step g), the pressure of die casting is preferably 1200~1700 bar, specifically 1200 bar, 1250 bar, 1300 bar, 1350 bar, 1400 bar, 1450 bar, 1500 bar, 1550 bar, 1600 bar, 1650 bar or 1700 bar.

[0069] In the preparation method provided by the present invention, in step g), the slow injection speed of the die casting is preferably 0.20~0.35 m / s, specifically 0.20 m / s, 0.22 m / s, 0.25 m / s, 0.27 m / s, 0.30 m / s, 0.32 m / s, or 0.35 m / s; the fast injection speed of the die casting is preferably 3.5~7.0 m / s, specifically 3.5 m / s, 3.7 m / s, 4.0 m / s, 4.2 m / s, 4.5 m / s, 4.7 m / s, 5.0 m / s, 5.2 m / s, 5.5 m / s, 5.7 m / s, 6.0 m / s, 6.2 m / s, 6.5 m / s, 6.7 m / s, or 7.0 m / s. In this invention, injection speed refers to the speed at which the injection punch in the pressure chamber moves the molten aluminum during the die casting process; wherein, slow injection speed refers to the speed at which the injection punch moves when it moves the molten aluminum to the gate position in the cavity, and fast injection speed refers to the speed at which the injection punch moves when it moves the molten aluminum from the gate in the cavity to quickly atomize and fill the entire mold cavity.

[0070] In the preparation method provided by the present invention, in step g), the preheating temperature of the die and cylinder used for die casting is preferably 150~250℃, specifically 150℃, 160℃, 170℃, 180℃, 190℃, 200℃, 210℃, 220℃, 230℃, 240℃ or 250℃.

[0071] In the preparation method provided by the present invention, in step g), the vacuum degree of the die-casting mold cavity is preferably 80~95 Pa, specifically 80 Pa, 81 Pa, 82 Pa, 83 Pa, 84 Pa, 85 Pa, 86 Pa, 87 Pa, 88 Pa, 89 Pa, 90 Pa, 91 Pa, 92 Pa, 93 Pa, 94 Pa or 95 Pa.

[0072] For clarity, the following examples and comparative models will be used to provide a detailed description.

[0073] Example 1

[0074] The high-strength, corrosion-resistant, heat-treatable die-cast aluminum alloy provided in this embodiment comprises the following components by mass percentage: Mg 5.9%, Si 2.8%, Mn 0.58%, Cu 0.21%, Fe 0.11%, Mo 0.07%, V 0.04%, Zr 0.02%, Y 0.07%, with the remainder being Al and unavoidable impurity elements. The content of a single impurity element is ≤0.02%, and the total content of impurity elements is ≤0.2%.

[0075] The method for preparing this die-cast part includes the following steps:

[0076] (1) Calculate the amount of different raw materials to be added according to the alloy composition, and then add aluminum, manganese, copper, vanadium, zirconium, yttrium, molybdenum and silicon raw materials to melt in a melting furnace, and control the temperature at 770℃ to obtain the first alloy melt;

[0077] (2) The first alloy melt is cooled to 750°C to obtain the second alloy melt;

[0078] (3) Add magnesium raw material to the second alloy melt and stir until completely melted, with the temperature controlled at 740℃ to obtain the third alloy melt;

[0079] (4) Add 0.2 wt.% of the total weight of the alloy melt to the third alloy melt. The added slag remover is a sodium-free refining agent. The temperature of the alloy melt is controlled at 730℃. After stirring for 15 minutes, the slag is removed to obtain the fourth alloy melt.

[0080] (5) The fourth alloy melt is subjected to degassing and slag removal treatment, the process of which includes: adding a covering agent to the fourth alloy melt, and then using a rotary degasser to introduce an inert gas into the melt; wherein, the covering agent used is a sodium-free covering agent, which is added within 2 minutes, and the amount added accounts for 0.1 wt.% of the total alloy melt; the inert gas introduced is high-purity nitrogen, the pressure of which is 0.20 MPa, and the rotor speed of the rotary degasser is 400 rad / min; the degassing and slag removal treatment time is 20 minutes, and the melt temperature is controlled at 730℃; after the degassing and slag removal treatment is completed, the fifth alloy melt is obtained;

[0081] (6) The fifth alloy melt was subjected to composition analysis, density analysis, and slag content analysis. The composition was within the required range, and the reduced pressure solidification density was ≥2.61 g / cm³. 3 If the K-modulus value of the slag is ≤1 / 20, the quality of the melt is deemed to be qualified. Then, the melt is allowed to stand and cool down to 700℃ to obtain the pre-cast aluminum alloy melt.

[0082] (7) The aluminum alloy melt obtained above is put into the aluminum melting furnace of the die casting machine and vacuum high pressure casting is carried out using the die casting machine; wherein, the temperature of the pre-die casting aluminum alloy melt when injected into the die casting mold is 705℃, the casting pressure is 1400 bar, the slow injection speed is 0.25 m / s, the fast injection speed is 5.0 m / s, the preheating temperature of the mold and the barrel is 190℃, and the vacuum degree of the mold cavity is 88 Pa.

[0083] Examples 2-6

[0084] The only difference from Example 1 is the composition of the final die-cast aluminum alloy, as shown in Table 1.

[0085] Example 7

[0086] A method for preparing a high-strength, corrosion-resistant, heat-treatable die-cast aluminum alloy:

[0087] The difference between this embodiment and embodiment 1 is only in step (7). Specifically, in step (7), the temperature of the pre-cast aluminum alloy melt injected into the die-casting mold is 695°C, the casting pressure is 1700 bar, the slow injection speed is 0.2 m / s, the fast injection speed is 3.5 m / s, the preheating temperature of the mold and the barrel is 250°C, and the vacuum degree of the mold cavity is 80 Pa.

[0088] Example 8

[0089] A method for preparing a high-strength, corrosion-resistant, heat-treatable die-cast aluminum alloy:

[0090] The difference between this embodiment and embodiment 1 is only in step (7). Specifically, in step (7), the temperature of the pre-cast aluminum alloy melt injected into the die-casting mold is 715°C, the casting pressure is 1400 bar, the slow injection speed is 0.35 m / s, the fast injection speed is 7.0 m / s, the preheating temperature of the mold and the barrel is 150°C, and the vacuum degree of the mold cavity is 95 Pa.

[0091] Comparative Examples 1-3

[0092] The only difference from Example 1 is the composition of the final die-cast aluminum alloy, as detailed in Table 1.

[0093] Comparative Example 4

[0094] A method for preparing a high-strength, corrosion-resistant, heat-treatable die-cast aluminum alloy:

[0095] The only difference between this comparative example and Example 1 is step (7). Specifically, in step (7), the temperature of the pre-cast aluminum alloy melt injected into the die-casting mold is 680°C, the casting pressure is 1200 bar, the slow injection speed is 0.15 m / s, the fast injection speed is 3.9 m / s, the preheating temperature of the mold and the barrel is 280°C, and the vacuum degree of the mold cavity is 95 Pa.

[0096] Comparative Example 5

[0097] A method for preparing a high-strength, corrosion-resistant, heat-treatable die-cast aluminum alloy:

[0098] The only difference between this comparative example and Example 1 is step (7). Specifically, in step (7), the temperature of the pre-cast aluminum alloy melt injected into the die-casting mold is 720°C, the casting pressure is 1800 bar, the slow injection speed is 0.37 m / s, the fast injection speed is 7.5 m / s, the preheating temperature of the mold and the barrel is 130°C, and the vacuum degree of the mold cavity is 108 Pa.

[0099] Table 1. Composition of heat-free aluminum alloys prepared in Examples 1-6 and Comparative Examples 1-3

[0100]

[0101] Performance Evaluation

[0102] Mechanical property testing of die-cast aluminum alloys: Samples were taken from 3.0 mm die-cast specimens, including tensile strength, yield strength, and elongation, all according to GB / T228.1-2021. Ten samples were used for each mechanical property test, and the average value was taken.

[0103] Corrosion performance test of die-cast aluminum alloy: The sample is a 3.0 mm die-cast specimen. The corrosion conditions are in accordance with GB / T10125-2021. The corrosion time is 720 hours. The test value is the mass loss per unit area.

[0104] The test results are shown in Table 2.

[0105] Table 2. Test results of mechanical and corrosion properties

[0106]

[0107] As can be seen from the above description, the above embodiments of the present invention achieve the following technical effects: The heat-free die-casting alloy provided in this application, through alloy composition design, produces a die-casting aluminum alloy that not only has high tensile strength, high yield strength and high elongation, but also effectively meets the weight reduction requirements of OEMs, and has significant technical significance and broad application prospects.

[0108] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A high-strength, corrosion-resistant, heat-treatable die-cast aluminum alloy, characterized in that, The aluminum alloy composition by mass percentage is as follows: Mg 5.5~7.1%, Si 2.5~3.5%, Mn 0.5~0.75%, Cu 0.11~0.7%, Fe 0.08~0.15%, Mo 0.05~0.1%, V 0.02~0.05%, Zr 0.01~0.05%, Y 0.03~0.09%, with the remainder being Al and unavoidable impurity elements. The content of a single impurity element is ≤0.02%, and the total content of impurity elements is ≤0.2%. Furthermore, the mass ratio of Mg to Cu in the aluminum alloy composition is in the range of (10:1) to (50:1).

2. The heat-free die-cast aluminum alloy according to claim 1, characterized in that, The aluminum alloy composition by mass percentage is as follows: Mg 5.5~7.1%, Si 2.5~3.5%, Mn 0.5~0.5%, Cu 0.11~0.5%, Fe 0.08~0.15%, Mo 0.05~0.1%, V 0.02~0.05%, Zr 0.02~0.05%, Y 0.03~0.09%, with the remainder being Al and unavoidable impurity elements, the total amount of unavoidable impurity elements being ≤0.2%.

3. The heat-free die-cast aluminum alloy according to claim 1, characterized in that, The unavoidable impurity elements include one or more of Pb, Sn, Cd, and Zn.

4. The heat-free die-cast aluminum alloy according to claim 1, characterized in that, The heat-free die-cast aluminum alloy has an ultimate tensile strength of 310~380MPa, a yield strength of 215~270MPa, and an elongation after fracture of 10~20%.

5. A method for preparing a high-strength, corrosion-resistant, heat-treatable die-cast aluminum alloy as described in any one of claims 1 to 4, characterized in that, Includes the following steps: a) Calculate the amount of different raw materials to be added according to the alloy composition, and then add aluminum raw materials, manganese raw materials, copper raw materials, vanadium raw materials, zirconium raw materials, yttrium raw materials, molybdenum raw materials and silicon raw materials to melt in a melting furnace, with the temperature controlled at 750~790℃, to obtain the first alloy melt; b) Cool the first alloy melt to 740~760℃ to obtain the second alloy melt; c) Add magnesium raw material to the second alloy melt and stir until completely melted, with the temperature controlled at 730~750℃, to obtain the third alloy melt; d) Add a slag remover to the third alloy melt, control the temperature of the alloy melt at 730~740℃, stir for a period of time and then remove the slag to obtain the fourth alloy melt. e) The fourth alloy melt is subjected to degassing and slag removal treatment to obtain the fifth alloy melt; f) The fifth alloy melt is subjected to composition testing, density testing and slag content testing. After passing the tests, it is allowed to stand and cool down to 690~710℃ to obtain a pre-die-cast aluminum alloy melt. g) The pre-die-cast aluminum alloy melt is die-cast to obtain a high-strength, corrosion-resistant, heat-free die-cast aluminum alloy.

6. The preparation method according to claim 5, characterized in that, The aluminum raw material is pure aluminum and / or electrolytic aluminum; the silicon raw material is one or more of aluminum-silicon master alloy, industrial silicon, and readily soluble silicon; the manganese raw material is aluminum-manganese master alloy and / or manganese agent; the copper raw material is pure copper and / or aluminum-copper master alloy; the magnesium raw material is pure magnesium; the vanadium raw material is pure vanadium and / or aluminum-vanadium master alloy; the zirconium raw material is pure zirconium and / or aluminum-zirconium master alloy; the molybdenum raw material is pure molybdenum and / or aluminum-molybdenum master alloy; and the yttrium raw material is aluminum-yttrium master alloy.

7. The preparation method according to claim 5, characterized in that, In step d), the slag remover is a sodium-free refining agent; the amount of the slag remover added accounts for 0.1~0.3 wt.% of the total alloy melt; and the stirring time is 10~15 min.

8. The preparation method according to claim 5, characterized in that, In step e), the specific process of degassing and slag removal includes: adding a covering agent to the fourth alloy melt, and then using a rotary degasser to introduce inert gas into the melt.

9. The preparation method according to claim 8, characterized in that, In step e), the covering agent is a sodium-free covering agent; the covering agent is added within 2 minutes; the amount of the covering agent added accounts for 0.05~0.1 wt.% of the total alloy melt; the inert gas is nitrogen and / or argon; the inert gas is introduced at a pressure of 0.18~0.25 MPa; the rotor speed of the rotary degasser is 300~500 rad / min; the degassing and slag removal treatment time is 15~30 minutes; and the melt temperature during the degassing and slag removal treatment is controlled at 720~730℃.

10. The preparation method according to claim 5, characterized in that, In step g), the temperature of the pre-cast aluminum alloy melt injected into the die-casting mold is 695~715℃; the die-casting pressure is 1200~1700 bar; the slow injection speed of the die-casting is 0.20~0.35 m / s; the fast injection speed of the die-casting is 3.5~7.0 m / s; the preheating temperature of the die and the barrel used for die-casting is 150~250℃; and the vacuum degree of the die cavity is 80~95 Pa.

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