Corrosion-resistant die-casting magnesium alloy, preparation method and vehicle part

Abstract

The invention relates to a corrosion-resistant die-casting magnesium alloy, a preparation method and a vehicle part, in particular to the technical field of metal alloy preparation, development and application, and the corrosion-resistant die-casting magnesium alloy comprises the following components in percentage by mass: 6-8% of aluminum, 0.5-1% of zinc, 0.1-0.5% of manganese, 0.5-1% of yttrium, 3-3.5% of lanthanum, 0.5-0.6% of cerium, 0.2-0.7% of neodymium, 0.2-0.5% of zirconium, 0.2-0.7% of calcium and the balance of magnesium and inevitable impurities. According to the corrosion-resistant die-casting magnesium alloy provided by the invention, the composition of the magnesium alloy is optimally designed, the corrosion resistance of the magnesium alloy can be remarkably improved by virtue of the synergistic effect of all the elements and by virtue of mechanisms such as solution strengthening, fine grain strengthening and microalloying design, so that the surface corrosion weight loss rate is less than or equal to 0.028; and meanwhile, it can be guaranteed that the corrosion-resistant die-casting magnesium alloy still has the good mechanical property.

Description

Technical Field

[0001] This invention relates to the field of metal alloy preparation and development and application technology, specifically to a corrosion-resistant die-cast magnesium alloy and its preparation method, and automotive parts, and more particularly to a corrosion-resistant die-cast magnesium alloy containing rare earth elements and its preparation method, and automotive parts. Background Technology

[0002] Cast magnesium alloys are magnesium-based alloys. By adding alloying elements, grain refinement and suppression of discontinuous phase precipitation can be achieved, resulting in higher mechanical properties. Furthermore, the addition of rare earth elements (such as Ce, Y, and La) can further enhance mechanical and other properties.

[0003] In industries such as aerospace and automotive, magnesium alloys are used due to their low density (approximately 1.8-1.9 g / cm³). 3 It is only 2 / 3 the weight of aluminum alloy and 1 / 4 the weight of cast iron, which has a good lightweight effect. At the same time, it has excellent damping performance and good electromagnetic shielding performance, and is often used as a material for some shell and bracket parts.

[0004] Magnesium alloys possess good fluidity and low shrinkage, making them suitable for use in the automotive die-casting industry. Die casting offers advantages such as high productivity, high casting precision, and dimensional stability. However, due to the inherent corrosion susceptibility of conventionally cast magnesium alloys, corrosion prevention becomes the biggest challenge when using magnesium alloys in automotive parts.

[0005] With technological advancements, the current mature corrosion protection technology for cast magnesium alloy parts is surface coating (passivation + electrophoresis or micro-arc oxidation + electrophoresis, etc.). This process can ensure that parts withstand corrosion for ≥240 hours in a standard salt spray environment. However, compared to aluminum alloy castings and steel parts, surface coating incurs additional costs. A comprehensive assessment shows that coating costs significantly increase the total cost of most parts, forcing automakers to pause their magnesium alloy technology initiatives, particularly for parts with a large surface area to weight ratio, such as door panels.

[0006] Based on the need for further lightweighting and cost reduction of automotive parts, while ensuring strength and plasticity, the corrosion resistance of die-cast magnesium alloys needs to be further improved, at least to the level of die-cast aluminum alloys (YL112).

[0007] However, while the strength of existing magnesium alloys such as AZ91D and AS41B, which are mature materials in the automotive industry, meets product requirements, their corrosion resistance is far from satisfactory. Therefore, developing new corrosion-resistant die-cast magnesium alloys, enabling magnesium alloy parts to be free from surface coating or to use low-cost coating processes, is of great significance for further reducing the cost of magnesium alloy parts and expanding their application in the automotive industry. Summary of the Invention

[0008] In view of the problems existing in the prior art, the purpose of the present invention is to provide a corrosion-resistant die-cast magnesium alloy and its preparation method, as well as automotive parts, to solve the defects of the current die-cast magnesium alloys used in automotive parts, which have poor corrosion resistance and cannot match mechanical properties.

[0009] To achieve this objective, the present invention adopts the following technical solution:

[0010] In a first aspect, the present invention provides a corrosion-resistant die-cast magnesium alloy, wherein the corrosion-resistant die-cast magnesium alloy comprises, by weight percentage:

[0011] Aluminum 6-8%, Zinc 0.5-1%, Manganese 0.1-0.5%, Yttrium 0.5-1%, Lanthanum 3-3.5%, Cerium 0.5-0.6%, Neodymium 0.2-0.7%, Zirconium 0.2-0.5%, Calcium 0.2-0.7%, with the balance being magnesium and unavoidable impurities.

[0012] The corrosion-resistant die-cast magnesium alloy provided by this invention significantly improves the corrosion resistance of magnesium alloys by optimizing the composition of the alloy and utilizing the synergistic effects between elements through mechanisms such as solid solution strengthening, grain refinement strengthening, and microalloying design, resulting in a surface corrosion weight loss rate ≤0.028. At the same time, it can ensure that the corrosion-resistant die-cast magnesium alloy still has good mechanical properties.

[0013] As a preferred embodiment of the present invention, the unavoidable impurities are ≤0.01% by mass.

[0014] In a second aspect, the present invention provides a method for preparing a corrosion-resistant die-cast magnesium alloy as described in the first aspect, the method comprising:

[0015] The raw materials are prepared according to the formula, and then melted, refined and die-cast in sequence to obtain a corrosion-resistant die-cast magnesium alloy.

[0016] As a preferred technical solution of the present invention, the melting includes: pure metal melting, slag removal by stirring and intermediate alloy melting in sequence.

[0017] Preferably, mixed salt is added during the stirring and slag removal process.

[0018] Preferably, the amount of the mixed salt added is 0.8-1.2% of the melt mass.

[0019] Preferably, the mixed salt comprises NaCl, KCl, MgCl2 and CaF2 in a mass ratio of (1.8-2.2):(3.5-4.2):(2.8-3.2):1.

[0020] As a preferred technical solution of the present invention, the refining includes: refining with argon gas.

[0021] As a preferred technical solution of the present invention, the refining temperature is 710-730℃.

[0022] As a preferred embodiment of the present invention, the refining time is 5-10 minutes.

[0023] As a preferred technical solution of the present invention, after refining, the mixture is left to stand for 20-25 minutes before die casting.

[0024] As a preferred embodiment of the present invention, the die-casting temperature is 680-690℃.

[0025] Thirdly, the present invention provides an automotive part, which is made of a corrosion-resistant die-cast magnesium alloy as described in the first aspect.

[0026] Compared with existing technical solutions, the present invention has the following beneficial effects:

[0027] (1) The corrosion-resistant die-cast magnesium alloy provided by this invention has excellent mechanical properties and corrosion resistance, with a yield strength of ≥160MPa, a tensile strength of ≥250MPa, an elongation of ≥6.5%, and a surface corrosion weight loss rate of ≤0.028. .

[0028] (2) The corrosion-resistant die-cast magnesium alloy provided by this invention improves the mechanical properties and corrosion resistance of aluminum-based alloys by adding alloying elements such as Al, Zn, Mn, Ca, Zr, Y, La, Ce, and Nd through mechanisms such as solid solution strengthening, grain refinement strengthening, and microalloying design. The combined addition of Al and Zn improves the tensile strength and elongation of the magnesium alloy. In addition, Mn reduces the effect of impurities such as Fe on mechanical properties. The addition of Mn, Zr, and rare earth elements (La, Ce, Y) helps to refine the eutectic structure, further enhancing the strength and elongation of the alloy. The synergistic effect of Ca with rare earth elements (La, Ce, Y) and the synergistic effect of Mn with Zr can both improve the corrosion resistance of the alloy.

[0029] The present invention will now be described in further detail. However, the examples described below are merely simplified examples of the present invention and do not represent or limit the scope of protection of the present invention. The scope of protection of the present invention is determined by the claims. Detailed Implementation

[0030] To better illustrate the present invention and facilitate understanding of its technical solutions, typical but non-limiting embodiments of the present invention are as follows:

[0031] Currently, driven by the need for further lightweighting and cost reduction in automotive parts, the corrosion resistance of die-cast magnesium alloys needs to be further improved, at least to the level of die-cast aluminum alloys (YL112), while ensuring strength and ductility. However, while mature magnesium alloy materials such as AZ91D and AS41B in the automotive industry meet product strength requirements, their corrosion resistance is far from adequate. Therefore, this invention optimizes the magnesium alloy formulation, improving its corrosion resistance while maintaining good mechanical properties. This allows magnesium alloy parts to be free from surface coating or to utilize low-cost coating processes, which is of great significance for further cost reduction and expanded application in the automotive industry. Specifically:

[0032] I. This embodiment provides a corrosion-resistant die-cast magnesium alloy, wherein the corrosion-resistant die-cast magnesium alloy comprises, by weight percentage:

[0033] Aluminum 6-8%, Zinc 0.5-1%, Manganese 0.1-0.5%, Yttrium 0.5-1%, Lanthanum 3-3.5%, Cerium 0.5-0.6%, Neodymium 0.2-0.7%, Zirconium 0.2-0.5%, Calcium 0.2-0.7%, with the balance being magnesium and unavoidable impurities.

[0034] In this invention, the aluminum content in the corrosion-resistant die-cast magnesium alloy is 6-8% by mass percentage, for example, it can be 6%, 6.2%, 6.4%, 6.6%, 6.8%, 7%, 7.2%, 7.4%, 7.6%, 7.8% or 8%, etc., but is not limited to the listed values. Other unlisted values ​​within this range are also acceptable.

[0035] In this invention, the zinc content in the corrosion-resistant die-cast magnesium alloy is 0.5-1% by mass, for example, it can be 0.5%, 0.55%, 0.6%, 0.65%, 0.7%, 0.75%, 0.8%, 0.85%, 0.9%, 0.95% or 1%, etc., but is not limited to the listed values. Other unlisted values ​​within this range are also acceptable.

[0036] In this invention, the manganese content in the corrosion-resistant die-cast magnesium alloy is 0.1-0.5% by mass, for example, it can be 0.1%, 0.14%, 0.18%, 0.22%, 0.26%, 0.3%, 0.34%, 0.38%, 0.42%, 0.46% or 0.5%, etc., but is not limited to the listed values. Other unlisted values ​​within this range are also acceptable.

[0037] In this invention, the yttrium content in the corrosion-resistant die-cast magnesium alloy is 0.5-1% by mass, for example, it can be 0.5%, 0.55%, 0.6%, 0.65%, 0.7%, 0.75%, 0.8%, 0.85%, 0.9%, 0.95% or 1%, etc., but is not limited to the listed values. Other unlisted values ​​within this range are also acceptable.

[0038] In this invention, the lanthanum content in the corrosion-resistant die-cast magnesium alloy is 3-3.5% by mass, for example, it can be 3%, 3.05%, 3.1%, 3.15%, 3.2%, 3.25%, 3.3%, 3.35%, 3.4%, 3.45%, or 3.5%, but is not limited to the listed values. Other unlisted values ​​within this range are also acceptable.

[0039] In this invention, the cerium content in the corrosion-resistant die-cast magnesium alloy is 0.5-0.6% by mass, for example, it can be 0.5%, 0.51%, 0.52%, 0.53%, 0.54%, 0.55%, 0.56%, 0.57%, 0.58%, 0.59%, or 0.6%, etc., but is not limited to the listed values. Other unlisted values ​​within this range are also acceptable.

[0040] In this invention, the neodymium content in the corrosion-resistant die-cast magnesium alloy is 0.2-0.7% by mass, for example, it can be 0.2%, 0.25%, 0.3%, 0.35%, 0.4%, 0.45%, 0.5%, 0.55%, 0.6%, 0.65%, or 0.7%, but is not limited to the listed values. Other unlisted values ​​within this range are also acceptable.

[0041] In this invention, the zirconium content in the corrosion-resistant die-cast magnesium alloy is 0.2-0.5% by mass, for example, it can be 0.2%, 0.23%, 0.26%, 0.29%, 0.32%, 0.35%, 0.38%, 0.41%, 0.44%, 0.47% or 0.5%, etc., but is not limited to the listed values. Other unlisted values ​​within this range are also acceptable.

[0042] In this invention, the calcium content in the corrosion-resistant die-cast magnesium alloy is 0.2-0.7% by mass, for example, it can be 0.2%, 0.25%, 0.3%, 0.35%, 0.4%, 0.45%, 0.5%, 0.55%, 0.6%, 0.65%, or 0.7%, but is not limited to the listed values. Other unlisted values ​​within this range are also acceptable.

[0043] The unavoidable impurities are ≤0.01% by mass.

[0044] II. This embodiment provides a method for preparing a corrosion-resistant die-cast magnesium alloy, the method comprising:

[0045] The raw materials are prepared according to the formula, and then melted, refined and die-cast in sequence to obtain a corrosion-resistant die-cast magnesium alloy.

[0046] In this invention, the raw materials used in the formulation include: pure Mg (purity ≥ 99.9%), pure Al (purity ≥ 99.9%), pure Zn (purity ≥ 99.9%), and master alloys such as magnesium-manganese master alloys like MgMn10 master alloy, magnesium-yttrium master alloys like MgY20 master alloy, magnesium-lanthanum master alloys like MgLa30 master alloy, magnesium-cerium master alloys like MgCe20 master alloy, magnesium-neodymium master alloys like MgNd30 master alloy, magnesium-zirconium master alloys like MgZr30 master alloy, and magnesium-calcium master alloys like MgCa30 master alloy.

[0047] In this invention, since the master alloy often contains impurity element Fe, as well as trace amounts of Ni, Cu and B, the Fe content should be strictly tested and controlled when selecting the master alloy. There are no strict requirements on the proportion of the main elements of the master alloy, as long as they can be proportioned to the desired alloy composition.

[0048] In this invention, the alloy is prepared according to the designed alloy composition, and large alloy ingots can be cut into small pieces to facilitate subsequent melting and feeding.

[0049] The melting process includes: sequential pure metal melting, slag removal by stirring, and intermediate alloy melting.

[0050] Preferably, mixed salt is added during the stirring and slag removal process.

[0051] Preferably, the amount of the mixed salt added is 0.8-1.2% of the melt mass, for example, it can be 0.8%, 0.84%, 0.88%, 0.92%, 0.96%, 1%, 1.04%, 1.08%, 1.12%, 1.16% or 1.2%, etc., but is not limited to the listed values, and other unlisted values ​​within this range are also acceptable.

[0052] Preferably, the mixed salt comprises NaCl, KCl, MgCl2, and CaF2 in a mass ratio of (1.8-2.2):(3.5-4.2):(2.8-3.2):1, for example, 1.8:3.5:2.8:1, 1.84:3.57:2.9:1, 1.88:3.64:3:1, 1.92:3.71:3.1:1, 1.96:3.78:3.2:1, 2:3.85:3:1, 2.04:3.92:3:1, 2.08:3.99:3:1, 2.12:4.06:3:1, 2.16:4.13:3:1, 2.2:4.2:3:1, or 2:4:3:1, etc., but is not limited to the listed values; other unlisted values ​​within this range are also acceptable.

[0053] In this invention, the order of adding various materials during the melting process can be designed according to conventional requirements in the field, avoiding burn-off and other situations that may prevent the formulation from meeting the requirements. For example, pure Mg, pure Al, and pure Zn are added to a crucible preheated to 250-350°C, and a protective gas of SF6:CO2 with a volume ratio of 1:(150-170) is introduced throughout the process. The crucible is then baked and heated to 720-750°C to completely melt the metal. Afterward, the temperature is lowered to 700-720°C, a refining agent is added, and the mixture is stirred and slag is removed. Then, the temperature is raised to 750-780°C, and MgMn10 master alloy and MgNd30 master alloy preheated to 200-250°C are added. After the master alloys have completely melted, the mixture is stirred steadily in one direction for 5-10 minutes. Then, heat to 780-800℃, add MgZr30 master alloy preheated at 250-300℃, and use a bell jar to press it below the liquid surface. After it is completely melted, stir steadily in one direction for 5-10 minutes. Then, cool to 720-750℃, add MgCa30 master alloy, MgY20 master alloy, and MgCe20 master alloy preheated at 200-260℃, and use a bell jar to press it below the liquid surface. After it is completely melted, stir steadily in one direction for 5-10 minutes. Then, cool to 720-730℃, add MgLa30 master alloy preheated at 250-300℃, and use a bell jar to press it below the liquid surface. After it is completely melted, stir steadily in one direction for 5-10 minutes. Then, refining can be carried out.

[0054] The refining process includes: argon refining.

[0055] The refining temperature is 710-730℃, for example, it can be 710℃, 712℃, 714℃, 716℃, 718℃, 720℃, 722℃, 724℃, 726℃, 728℃ or 730℃, but is not limited to the listed values. Other unlisted values ​​within this range are also acceptable.

[0056] The refining time is 5-10 minutes, for example, it can be 5 minutes, 5.5 minutes, 6 minutes, 6.5 minutes, 7 minutes, 7.5 minutes, 8 minutes, 8.5 minutes, 9 minutes, 9.5 minutes or 10 minutes, but is not limited to the listed values. Other unlisted values ​​within this range are also acceptable.

[0057] After refining, the mixture is allowed to stand for 20-25 minutes before die casting. For example, the time can be 20 minutes, 20.5 minutes, 21 minutes, 21.5 minutes, 22 minutes, 22.5 minutes, 23 minutes, 23.5 minutes, 24 minutes, 24.5 minutes, or 25 minutes, but it is not limited to the listed values. Other unlisted values ​​within this range are also acceptable.

[0058] The die-casting temperature is 680-690℃, for example, it can be 680℃, 681℃, 682℃, 683℃, 684℃, 685℃, 686℃, 687℃, 688℃, 689℃ or 690℃, but is not limited to the listed values. Other unlisted values ​​within this range also meet the requirements.

[0059] III. This embodiment provides an automotive part, which is made of corrosion-resistant die-cast magnesium alloy.

[0060] In this invention, the automotive parts can be selected as housing-type parts or bracket-type parts, such as transmission housing, flywheel housing, motor housing, instrument panel beam, etc.

[0061] IV. To illustrate the performance achievable by the corrosion-resistant die-cast magnesium alloy provided by this invention, the following practical examples are used for explanation:

[0062] The melting principle of the raw materials in the following examples is as follows:

[0063] Pure Mg, pure Al, and pure Zn were added to a crucible preheated to 300°C, and a protective gas mixture of SF6:CO2 (volume ratio 1:160) was continuously introduced. The mixture was baked and heated to 735°C until the metal was completely melted. The temperature was then lowered to 710°C, a refining agent was added, and the mixture was stirred and the slag was skimmed off. The temperature was then raised to 760°C, and preheated MgMn10 and MgNd30 master alloys (preheated to 225°C) were added. After the master alloys were completely melted, the mixture was stirred steadily in one direction for 8 minutes. The temperature was then raised to 790°C, and preheated MgZr30 master alloy (preheated to 280°C) was added. The mixture is then pressed below the liquid surface using a bell jar and completely melted. After that, it is stirred steadily in one direction for 8 minutes. Then, the temperature is lowered to 735°C, and MgCa30 master alloy, MgY20 master alloy, and MgCe20 master alloy preheated at 250°C are added. The mixture is then pressed below the liquid surface using a bell jar and completely melted. After that, it is stirred steadily in one direction for 8 minutes. After that, the temperature is lowered to 725°C, and MgLa30 master alloy preheated at 280°C is added. The mixture is then pressed below the liquid surface using a bell jar and completely melted. After that, it is stirred steadily in one direction for 8 minutes. After that, it can be refined.

[0064] Example 1

[0065] This embodiment provides a corrosion-resistant die-cast magnesium alloy, wherein the corrosion-resistant die-cast magnesium alloy comprises, by weight percentage:

[0066] Aluminum 6%, Zinc 0.5%, Manganese 0.2%, Yttrium 0.5%, Lanthanum 3%, Cerium 0.5%, Neodymium 0.2%, Zirconium 0.2%, Calcium 0.2%, with the balance being magnesium and unavoidable impurities;

[0067] The unavoidable impurities are 0.01% by mass.

[0068] The preparation process is as follows:

[0069] The ingredients are prepared according to the formula, and then melted, refined and die-cast in sequence to obtain a corrosion-resistant die-cast magnesium alloy.

[0070] The melting process includes: pure metal melting, slag removal by stirring, and intermediate alloy melting in sequence; a mixed salt is added during the slag removal by stirring; the amount of the mixed salt added is 1% of the melt mass; the mixed salt includes NaCl, KCl, MgCl2, and CaF2 in a mass ratio of 2:4:3:1.

[0071] The refining process includes: argon gas refining; the refining temperature is 720℃; and the refining time is 8 minutes.

[0072] After refining, the mixture is left to stand for 22 minutes before die casting; the die casting temperature is 685℃.

[0073] Example 2

[0074] This embodiment provides a corrosion-resistant die-cast magnesium alloy, wherein the corrosion-resistant die-cast magnesium alloy comprises, by weight percentage:

[0075] Aluminum 8%, Zinc 0.6%, Manganese 0.5%, Yttrium 0.6%, Lanthanum 3.5%, Cerium 0.6%, Neodymium 0.5%, Zirconium 0.3%, Calcium 0.3%, with the balance being magnesium and unavoidable impurities;

[0076] The unavoidable impurities are 0.005% by mass.

[0077] The preparation process is as follows:

[0078] The ingredients are prepared according to the formula, and then melted, refined and die-cast in sequence to obtain a corrosion-resistant die-cast magnesium alloy.

[0079] The melting process includes: sequential pure metal melting, slag removal by stirring, and intermediate alloy melting; a mixed salt is added during the slag removal by stirring; the amount of the mixed salt added is 0.8% of the melt mass; the mixed salt includes NaCl, KCl, MgCl2, and CaF2 in a mass ratio of 2.2:3.5:2.8:1.

[0080] The refining process includes: argon gas refining; the refining temperature is 710℃; and the refining time is 10 minutes.

[0081] After refining, the mixture is left to stand for 25 minutes before die casting; the die casting temperature is 690℃.

[0082] Example 3

[0083] This embodiment provides a corrosion-resistant die-cast magnesium alloy, wherein the corrosion-resistant die-cast magnesium alloy comprises, by weight percentage:

[0084] Aluminum 6.5%, Zinc 0.8%, Manganese 0.2%, Yttrium 0.8%, Lanthanum 3.3%, Cerium 0.55%, Neodymium 0.7%, Zirconium 0.5%, Calcium 0.2%, with the balance being magnesium and unavoidable impurities;

[0085] The unavoidable impurities are 0.006% by mass.

[0086] The preparation process is as follows:

[0087] The ingredients are prepared according to the formula, and then melted, refined and die-cast in sequence to obtain a corrosion-resistant die-cast magnesium alloy.

[0088] The melting process includes: sequential pure metal melting, slag removal by stirring, and intermediate alloy melting; a mixed salt is added during the slag removal by stirring; the amount of the mixed salt added is 1.2% of the melt mass; the mixed salt includes NaCl, KCl, MgCl2, and CaF2 in a mass ratio of 1.8:4.2:2.8:1.

[0089] The refining process includes: argon gas refining; the refining temperature is 730℃; and the refining time is 5 minutes.

[0090] After refining, the mixture is left to stand for 20 minutes before die casting; the die casting temperature is 680℃.

[0091] Example 4

[0092] This embodiment provides a corrosion-resistant die-cast magnesium alloy, wherein the corrosion-resistant die-cast magnesium alloy comprises, by weight percentage:

[0093] Aluminum 6.6%, Zinc 0.75%, Manganese 0.3%, Yttrium 1%, Lanthanum 3.1%, Cerium 0.52%, Neodymium 0.25%, Zirconium 0.23%, Calcium 0.22%, with the balance being magnesium and unavoidable impurities;

[0094] The unavoidable impurities are 0.009% by mass.

[0095] The preparation process is as follows:

[0096] The ingredients are prepared according to the formula, and then melted, refined and die-cast in sequence to obtain a corrosion-resistant die-cast magnesium alloy.

[0097] The melting process includes: sequential pure metal melting, slag removal by stirring, and intermediate alloy melting; a mixed salt is added during the slag removal by stirring; the amount of the mixed salt added is 1% of the melt mass; the mixed salt includes NaCl, KCl, MgCl2, and CaF2 in a mass ratio of 1.8:4:3.2:1.

[0098] The refining process includes: argon gas refining; the refining temperature is 715℃; and the refining time is 8 minutes.

[0099] After refining, the mixture is left to stand for 23 minutes before die casting; the die casting temperature is 688℃.

[0100] Example 5

[0101] This embodiment provides a corrosion-resistant die-cast magnesium alloy, wherein the corrosion-resistant die-cast magnesium alloy comprises, by weight percentage:

[0102] Aluminum 6.9%, Zinc 0.58%, Manganese 0.4%, Yttrium 0.5%, Lanthanum 3.4%, Cerium 0.57%, Neodymium 0.45%, Zirconium 0.25%, Calcium 0.4%, with the balance being magnesium and unavoidable impurities;

[0103] The unavoidable impurities are 0.008% by mass.

[0104] The preparation process is as follows:

[0105] The ingredients are prepared according to the formula, and then melted, refined and die-cast in sequence to obtain a corrosion-resistant die-cast magnesium alloy.

[0106] The melting process includes: sequential pure metal melting, slag removal by stirring, and intermediate alloy melting; a mixed salt is added during the slag removal process; the amount of the mixed salt added is 1% of the melt mass; the mixed salt includes NaCl, KCl, MgCl2, and CaF2 in a mass ratio of 2.2:4:2.8:1.

[0107] The refining process includes: argon gas refining; the refining temperature is 725℃; and the refining time is 6 minutes.

[0108] After refining, the mixture is left to stand for 21 minutes before die casting; the die casting temperature is 682℃.

[0109] Comparative Example 1

[0110] The only difference from Example 1 is that the aluminum content in the corrosion-resistant die-cast magnesium alloy is 5% by mass.

[0111] Comparative Example 2

[0112] The only difference from Example 1 is that the aluminum content in the corrosion-resistant die-cast magnesium alloy is 9% by mass.

[0113] Comparative Example 3

[0114] The only difference from Example 1 is that the zinc content in the corrosion-resistant die-cast magnesium alloy is 0.3% by mass.

[0115] Comparative Example 4

[0116] The only difference from Example 1 is that the zinc content in the corrosion-resistant die-cast magnesium alloy is 1.3% by mass.

[0117] Comparative Example 5

[0118] The only difference from Example 1 is that the manganese content in the corrosion-resistant die-cast magnesium alloy is 0.05% by mass.

[0119] Comparative Example 6

[0120] The only difference from Example 1 is that the manganese content in the corrosion-resistant die-cast magnesium alloy is 1% by mass.

[0121] Comparative Example 7

[0122] The only difference from Example 1 is that the yttrium content in the corrosion-resistant die-cast magnesium alloy is 0.3% by mass.

[0123] Comparative Example 8

[0124] The only difference from Example 1 is that the yttrium content in the corrosion-resistant die-cast magnesium alloy is 1.3% by mass.

[0125] Comparative Example 9

[0126] The only difference from Example 1 is that the lanthanum content in the corrosion-resistant die-cast magnesium alloy is 2% by mass.

[0127] Comparative Example 10

[0128] The only difference from Example 1 is that the lanthanum content in the corrosion-resistant die-cast magnesium alloy is 4% by mass.

[0129] Comparative Example 11

[0130] The only difference from Example 1 is that the cerium content in the corrosion-resistant die-cast magnesium alloy is 0.2% by mass.

[0131] Comparative Example 12

[0132] The only difference from Example 1 is that the cerium content in the corrosion-resistant die-cast magnesium alloy is 1% by mass.

[0133] Comparative Example 13

[0134] The only difference from Example 1 is that the neodymium content in the corrosion-resistant die-cast magnesium alloy is 0.1% by mass.

[0135] Comparative Example 14

[0136] The only difference from Example 1 is that the neodymium content in the corrosion-resistant die-cast magnesium alloy is 1% by mass.

[0137] Comparative Example 15

[0138] The only difference from Example 1 is that the zirconium content in the corrosion-resistant die-cast magnesium alloy is 0.1% by mass.

[0139] Comparative Example 16

[0140] The only difference from Example 1 is that the zirconium content in the corrosion-resistant die-cast magnesium alloy is 1.5% by mass.

[0141] Comparative Example 17

[0142] The only difference from Example 1 is that the calcium content in the corrosion-resistant die-cast magnesium alloy is 0.1% by mass.

[0143] Comparative Example 18

[0144] The only difference from Example 1 is that the calcium content in the corrosion-resistant die-cast magnesium alloy is 1.2% by mass.

[0145] Comparative Example 19

[0146] The only difference from Example 1 is that the yttrium in the corrosion-resistant die-cast magnesium alloy is replaced with an equal amount of neodymium.

[0147] Comparative Example 20

[0148] The only difference from Example 1 is that neodymium is not added to the corrosion-resistant die-cast magnesium alloy.

[0149] Comparative Example 21

[0150] The only difference from Example 1 is that zirconium is not added to the corrosion-resistant die-cast magnesium alloy.

[0151] The corrosion-resistant die-cast magnesium alloys obtained in the above examples and comparative examples were subjected to mechanical property tests (GB / T 228.1 Metallic materials, tensile testing—Part 1: Test method at room temperature) and corrosion resistance tests: At room temperature (25°C), material specimens embedded in epoxy resin with the upper surface exposed were immersed in a 3.5% NaCl solution for immersion, with only the upper surface in contact with the NaCl solution during immersion. The weight loss rate of the specimens was measured after the test, and the results are shown in Table 1 below.

[0152] Table 1

[0153]

[0154] As shown in Table 1, the solution provided by this invention improves the mechanical properties and corrosion resistance of aluminum-based alloys by adding alloying elements such as Al, Zn, Mn, Ca, Zr, Y, La, Ce, and Nd through mechanisms such as solid solution strengthening, grain refinement strengthening, and microalloying design. The combined addition of Al and Zn improves the tensile strength and elongation of magnesium alloys. Furthermore, Mn reduces the effect of impurities such as Fe on mechanical properties. The addition of Mn, Zr, and rare earth elements (La, Ce, Y) helps refine the eutectic structure, further enhancing the strength and elongation of the alloy. The synergistic effect of Ca with rare earth elements (La, Ce, Y) and the synergistic effect of Mn with Zr both improve the corrosion resistance of the alloy.

[0155] In this invention, Al is strengthened through solid solution to form Mg. 17 Al 12The second phase of the Mn alloy strengthens the alloy and improves its strength. In this invention, an appropriate amount of Zn (0.5-1.0%) can comprehensively improve mechanical properties through solid solution strengthening, the formation of multi-component strengthening phases with Al and rare earth elements, and synergistic grain refinement with La. Furthermore, an appropriate amount of Zn helps form a uniform corrosion product film, reducing localized corrosion and pitting. A small amount of Zn (0.3%) will result in insufficient contribution to performance, while excessive Zn will form a Zn-rich phase, reducing corrosion resistance. In this invention, the formation of Al8Mn5 with Al by Mn can reduce the harmful effects of impurity elements (such as Fe, Ni, Cu, etc.). An appropriate amount of Mn (0.1-0.5%) can significantly refine the magnesium alloy microstructure, improving the alloy's mechanical properties and corrosion resistance. Too much Mn (≥1%) will lead to Mn segregation, forming a coarse Al-Mn phase and reducing elongation; too little Mn (<0.1%) will result in insufficient contribution to performance.

[0156] In this invention, Y forms a diffusely distributed Mg matrix with the Mg matrix and Al. 24 Y5 and Al2Y phases can significantly refine grains and pin grain boundaries, hindering dislocation movement and significantly improving alloy strength. Furthermore, an appropriate amount of Y (0.5-1.0%) can reduce the potential difference with the matrix, promoting the formation of a dense protective oxide film (containing Y2O3) on the alloy surface and improving corrosion resistance. When Y is added together with Zn, it can form an LPSO phase, further enhancing corrosion resistance. Excessive Y (>1.2%) easily forms coarse Al2Y phases, reducing plasticity. La can effectively refine grains and simultaneously form Al with Al. 11 The La3 phase significantly improves the alloy properties. However, in this invention, excessive La elements (≥4%) will form segregation, leading to a decrease in the tensile strength and elongation of the alloy.

[0157] Element Ce can significantly refine grains and weaken texture, thus improving elongation. Simultaneously, Ce preferentially forms complex phases with elements such as Al and Mn (e.g., Al...). 11 Ce3, Al 10 Ce2Mn7), coarse-grained Mg 17 Al 12 This process transforms the second phase at grain boundaries from a network structure to a dispersed granular structure, thereby improving mechanical properties. In this invention, the optimal addition amount is controlled within the range of 0.5-0.6%. Excessive Ce (≥1.0%) will lead to the formation of a second phase (such as CeMg). 12 Mg 17 Ce2 forms a continuous network structure along the grain boundaries, coarsens the grains, and reduces the load-bearing capacity.

[0158] In this invention, Nd forms a second phase (Mg) with Mg and Al. 12 Nd, Al 11 Nd3, etc., will also break down coarse Mg. 17 Al 12The Nd phase refines the grains, pins dislocations, weakens the texture, and improves the tensile strength and elongation of the alloy. Furthermore, during corrosion, Nd accumulates in the corrosion product film, forming Nd₂O₃. This oxide improves the density and protective properties of the corrosion film, reduces the corrosion rate, and effectively hinders the diffusion of chloride ions, thus suppressing localized corrosion (such as pitting). Excess Nd (≥1.0%) leads to the formation of Mg. 41 The Nd5 second phase has a large potential difference with the magnesium matrix, which greatly reduces corrosion resistance.

[0159] In this invention, Zr precipitates as fine particles during solidification, significantly increasing the nucleation rate, refining grains, and comprehensively improving strength and plasticity. Furthermore, during corrosion, Zr accumulates in the corrosion product film, forming ZrO2. This oxide can adsorb calcium and phosphate ions, promoting the formation of a denser and more stable corrosion product layer, thereby improving corrosion resistance. Ca reacts with Al to form the Al2Ca phase, significantly improving strength at both room temperature and high temperature. Appropriate amounts of Ca (0.2-0.7%) can purify the melt and promote the formation of Ca-containing phosphate or carbonate films on the surface, improving the protective properties of the film and thus reducing the corrosion rate. Excessive Ca (>1.1%) leads to uneven Ca distribution, forming coarse, brittle phases (Mg2Ca) at grain boundaries, significantly reducing the alloy's elongation and impact toughness. Simultaneously, the potential difference between the Mg2Ca phase and the magnesium matrix can act as a cathode or anode for micro-galvanic corrosion, accelerating localized corrosion and reducing corrosion resistance.

[0160] The preferred embodiments of the present invention have been described in detail above. However, the present invention is not limited to the specific details in the above embodiments. Within the scope of the technical concept of the present invention, various simple modifications can be made to the technical solution of the present invention, and these simple modifications all fall within the protection scope of the present invention.

[0161] It should also be noted that the various specific technical features described in the above specific embodiments can be combined in any suitable manner without contradiction. In order to avoid unnecessary repetition, the present invention will not describe the various possible combinations separately.

[0162] Furthermore, various different embodiments of the present invention can be combined in any way, as long as they do not violate the spirit of the present invention, they should also be regarded as the content disclosed by the present invention.

Claims

1. A corrosion-resistant die-cast magnesium alloy, characterized in that, The corrosion-resistant die-cast magnesium alloy comprises, by weight percentage: Aluminum 6-8%, Zinc 0.5-1%, Manganese 0.1-0.5%, Yttrium 0.5-1%, Lanthanum 3-3.5%, Cerium 0.5-0.6%, Neodymium 0.2-0.7%, Zirconium 0.2-0.5%, Calcium 0.2-0.7%, with the balance being magnesium and unavoidable impurities.

2. The corrosion-resistant die-cast magnesium alloy as described in claim 1, characterized in that, The unavoidable impurities are ≤0.01% by mass.

3. A method for preparing a corrosion-resistant die-cast magnesium alloy as described in claim 1 or 2, characterized in that, The preparation method includes: The raw materials are prepared according to the formula, and then melted, refined and die-cast in sequence to obtain a corrosion-resistant die-cast magnesium alloy.

4. The preparation method according to claim 3, characterized in that, The melting process includes: sequential pure metal melting, stirring and slag removal, and intermediate alloy melting; Preferably, mixed salt is added during the stirring and slag removal process; Preferably, the amount of the mixed salt added is 0.8-1.2% of the melt mass; Preferably, the mixed salt comprises NaCl, KCl, MgCl2 and CaF2 in a mass ratio of (1.8-2.2):(3.5-4.2):(2.8-3.2):

1.

5. The preparation method according to claim 3, characterized in that, The refining process includes: argon refining.

6. The preparation method according to claim 3, characterized in that, The refining temperature is 710-730℃.

7. The preparation method according to claim 3, characterized in that, The refining time is 5-10 minutes.

8. The preparation method according to claim 3, characterized in that, After refining, the mixture is left to stand for 20-25 minutes before die casting.

9. The preparation method according to claim 3, characterized in that, The die-casting temperature is 680-690℃.

10. A vehicle part, characterized in that, The automotive parts are made from the corrosion-resistant die-cast magnesium alloy as described in claim 1 or 2.

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