Extruded aluminum alloy material for light-weight drive motor liquid cooling shell of new energy vehicle and preparation method thereof

Abstract

The application belongs to the technical field of liquid cooling shell aluminum alloy materials, and particularly relates to an extruded aluminum alloy material for a liquid cooling shell of a light-weight driving motor of a new energy vehicle and a preparation method thereof.The extruded aluminum alloy material for the liquid cooling shell of the light-weight driving motor of the new energy vehicle comprises the following elements in percentage by mass: Si: 7.0%-8.5%, Mg: 0.3%-0.45%, Fe: <=0.10%, Ti: 0.16%-0.22%, Sr: 0.045%-0.06%, Cu: <=0.1%, Mn: <=0.1%, La: 0.05%-0.07%, Ce: 0.03%-0.05%, total amount of impurities: <=0.10%, and the balance is Al.The aluminum alloy material and the preparation method thereof have high strength and toughness, high heat conduction and corrosion resistance.The preparation method is scientific and reasonable.

Description

Technical Field

[0001] This invention belongs to the technical field of liquid-cooled housing aluminum alloy materials, specifically relating to extruded aluminum alloy materials for lightweight drive motor liquid-cooled housings in new energy vehicles and their preparation methods. Background Technology

[0002] With the rapid development of the new energy vehicle industry, vehicle lightweighting has become one of the key technological paths to reduce energy consumption and improve driving range. Among lightweight components, the liquid-cooled housing of the drive motor, as an important structural-functional integrated component, not only needs to have good heat dissipation performance, but also needs to achieve weight reduction while ensuring safety. Currently, most lightweight housing components commonly found on the market are produced using casting processes, which have problems such as high energy consumption, high cost, and difficulty in avoiding internal defects. Although some progress has been made in automotive lightweighting, the mechanical properties (such as tensile strength, yield strength, elongation, and toughness) of cast aluminum alloys are generally low, making it difficult to meet the high strength and high reliability requirements of key components in new energy vehicles under high-speed, high-load, and long-life conditions, posing certain safety hazards. At the same time, the high price of products on the market and the high cost of repair and replacement seriously restrict the development of the new energy vehicle industry.

[0003] Currently, research on aluminum alloy materials largely focuses on adjusting and optimizing the proportions of alloying elements. For example, existing technologies disclosed in patents CN112159916A and CN113025855A improve the strength, thermal conductivity, and corrosion resistance of aluminum-silicon alloys by adding certain amounts of Cu, Mg, Mn, Fe, and rare earth elements (such as Ce, La, and Sr). Furthermore, CN117947319A also explores the introduction of trace elements such as V and Nb to refine grains and suppress the formation of harmful phases, thereby improving the alloy's ductility, toughness, and corrosion resistance. However, most of these studies remain at the level of single or composite element regulation, with insufficient attention paid to the systematic design and control of the material's microstructure. In reality, the comprehensive performance of aluminum alloys depends not only on their chemical composition but also closely on their microstructure under the extrusion process (such as grain size, second-phase distribution, and texture characteristics). However, the aluminum alloy materials currently developed are difficult to improve in terms of strength, toughness, elongation and formability in a coordinated manner, and cannot fully meet the multiple requirements of new energy vehicle drive motor housings for high strength, high toughness, good thermal conductivity and corrosion resistance. Summary of the Invention

[0004] The technical problem to be solved by this invention is to overcome the above-mentioned defects in the existing technology, and to provide an extruded aluminum alloy material for a lightweight liquid-cooled housing of a drive motor for new energy vehicles and its preparation method. The prepared aluminum alloy material meets the requirements of a liquid-cooled housing for a drive motor of new energy vehicles, exhibiting high strength and toughness, high thermal conductivity, and corrosion resistance. The preparation method of this invention is scientifically and rationally designed.

[0005] The extruded aluminum alloy material for the liquid-cooled housing of the lightweight drive motor for new energy vehicles described in this invention comprises, by mass percentage, the following elements: Si: 7.0%~8.5%, Mg: 0.3%~0.45%, Fe: ≤0.10%, Ti: 0.16%~0.22%, Sr: 0.045%~0.06%, Cu: ≤0.1%, Mn: ≤0.1%, La: 0.05%~0.07%, Ce: 0.03%~0.05%, total impurities ≤0.10%, and the balance being Al;

[0006] In this formulation, the mass ratio of La to Ce is controlled at (1.2~2.4):1. La has a stronger ability to refine grains, while Ce is more effective in purifying the melt and neutralizing the influence of harmful impurities such as Fe. When the two are combined in this ratio, La-dominant Al... 11 The La3 phase and the Ce-dominated Al4Ce phase can form a composite nucleation core, which can not only refine the α-Al matrix grains more effectively, but also make the eutectic silicon phase better spheroidized and fibrous, while more fully purifying the grain boundaries and reducing the formation of low-melting-point harmful phases.

[0007] The mass ratio of Sr to Ti is controlled at (0.21~0.35):1. In traditional Al-Si alloys, Sr is often used for modification treatment, while Ti is used for grain refinement. The two are usually considered independently. This invention has found that controlling the Sr content within this ratio range can produce a synergistic effect with the heterogeneous nucleation particles such as TiB2 and TiAl3 introduced by Ti. An appropriate amount of Sr can optimize the melt environment and promote the full utilization of the Ti-based grain refiner. At the same time, it avoids the problems of increased melt gas absorption tendency and decreased toughness caused by excessive grain refinement due to excessive Sr. This precise control of the Sr and Ti ratio is the guarantee for achieving a stable, fine, and uniform as-cast structure.

[0008] This invention strictly controls the Fe content to ≤0.10% and limits the Cu and Mn contents to ≤0.1%, minimizing the formation of coarse, needle-like Fe-rich phases (such as β-Al5FeSi) and complex intermetallic compounds. These hard and brittle phases are the main factors that fracture the matrix and deteriorate toughness and thermal conductivity in traditional cast aluminum alloys. The composition system of this invention, through low Fe and low impurities supplemented by the purification effect of rare earth elements, fundamentally reduces the number and size of harmful phases, creating the preconditions for obtaining a clean and uniform microstructure in subsequent extrusion processing.

[0009] The method for preparing the extruded aluminum alloy material for the liquid-cooled housing of the lightweight drive motor of new energy vehicles includes the following steps:

[0010] (1) Smelting: Melt A356 aluminum ingots, heat to 740~750℃, add aluminum-silicon master alloy, adjust silicon content to the target range, and obtain a uniform aluminum alloy melt;

[0011] (2) Composite refining and modification treatment: The aluminum alloy melt obtained in step (1) is heated to 760~770℃ and degassed; then preheated aluminum-titanium-boron is added, the titanium content is controlled at 0.16~0.22%, active titanium refiner is added, and after reacting for 5~8 minutes, preheated aluminum-strontium intermediate alloy is added for treatment, the strontium content is controlled at 0.045%~0.06%, and the mixture is refined, degassed, and slag is removed to obtain aluminum alloy melt;

[0012] (3) Casting and forming: The aluminum alloy molten liquid obtained in step (2) is injected into the mold through a gravity tilting casting system to obtain an aluminum alloy ingot blank;

[0013] (4) Ingot pretreatment: Remove the gating gates and risers, mill the surface or turn the surface of the ingot blank obtained in step (3) to obtain the extrusion ingot;

[0014] (5) Extrusion molding and heat treatment.

[0015] Preferably, in step (2), the active titanium refining agent is a refining agent containing TiAl3 phase, and the amount added is 0.05%~0.07% of the total mass of aluminum liquid.

[0016] Preferably, in step (2), the aluminum-titanium-boron alloy is AlTi5B1. The sequence used in step (2), which involves first adding AlTi5B1 master alloy for basic refinement, then adding an active titanium refiner (containing TiAl3 phase) for enhanced nucleation, and finally adding AlSr10 master alloy for modification treatment, is carefully designed. This sequence ensures the full activation and stability of the nucleation core, avoids the potential poisoning effect of premature Sr addition on nucleation particles such as TiB2, and thus maximizes the refinement effect and stability of the as-cast microstructure.

[0017] Preferably, in step (3), the specific process parameters after injection into the mold are: the tilting speed is 95-100 degrees in 5-6s, the pressure is maintained and cooled for 6-8 minutes after casting, and then the mold is reset and opened to obtain aluminum alloy ingot blank.

[0018] Preferably, in step (4), the average grain size of the as-cast ingot is ≤80μm. In step (5), the average size of the non-aluminum matrix particles in the extruded microstructure after extrusion forming and heat treatment is ≤7μm, and they are dispersed. The fine as-cast grains lay the foundation for uniform plastic deformation during the extrusion process and can effectively prevent cracking. Through compositional design (low Fe, Cu, Mn, with added La and Ce) and subsequent composite refining processes, it is ensured that after extrusion, the reinforcing phase (such as Mg2Si, AlFeSi rare earth compounds, etc.) is uniformly distributed in the aluminum matrix in a fine and dispersed form, rather than continuously distributed along the grain boundaries. This microstructure of fine-grained matrix and dispersed reinforcing phase is the key to achieving high strength, high toughness, and high thermal conductivity simultaneously.

[0019] Preferably, in step (5), the specific steps of extrusion molding and heat treatment are as follows:

[0020] a. Place the pretreated ingot into a heating furnace and heat it at 440~460℃ for 2~4 hours;

[0021] b. Transfer the heated ingot to an extrusion press and extrude the ingot into a profile with the shape of a liquid-cooled housing for a drive motor;

[0022] c. Perform online quenching on the extruded shell profile;

[0023] d. Perform T6 heat treatment on the quenched profile.

[0024] Preferably, the extrusion parameters for step b are: extrusion cylinder temperature set to 340~360℃, extrusion ratio to 15~25, and extrusion speed to 1.0~3.0m / min.

[0025] Preferably, step d specifically involves: first, solution treatment at 530~550℃ for 2~4 hours, followed by water quenching; then, artificial aging treatment at 160~180℃ for 4~8 hours.

[0026] The high thermal conductivity of this invention is mainly attributed to three aspects: 1) Low Fe, Cu, and Mn content and rare earth purification effect, which greatly reduces impurity phases and solid solution atoms that severely hinder electron (phonon) transport; 2) Fine, spherical eutectic silicon and dispersed second phase, which reduce heat scattering at the phase interface; 3) Uniform and fine recrystallized grain structure with fewer grain boundary defects. This allows the material to efficiently conduct heat generated by the motor to the coolant while serving as a structural component, with significantly better heat dissipation performance than traditional shell materials.

[0027] Compared with the prior art, the beneficial effects of the present invention are:

[0028] (1) The preparation method of the present invention has a “double refinement” step in the composite refining process, which first adds AiTi5B1 and then adds active titanium refiner, to ensure the full refinement of the as-cast structure; gravity tilting casting reduces air entrapment and oxide inclusions, resulting in a dense billet; specific extrusion temperature, speed and extrusion ratio, combined with online quenching and T6 treatment, ultimately transform the optimized as-cast structure into an ideal extruded structure.

[0029] (2) The aluminum alloy prepared by the present invention has a tensile strength ≥326.5MPa, a yield strength ≥281.6MPa, an elongation ≥13.2%, and a thermal conductivity ≥170W / (m·K), forming a performance envelope that achieves an excellent balance between high strength and toughness and high thermal conductivity, which is a breakthrough in the application of liquid cooling shells in new energy vehicles. Attached Figure Description

[0030] Figure 1 Metallographic image of the product prepared in Example 1.

[0031] Figure 2 Metallographic image of the product prepared for Comparative Example 1.

[0032] Figure 3 Metallographic image of the product prepared for Comparative Example 2.

[0033] Figure 4 Metallographic image of the product prepared for Comparative Example 3.

[0034] Figure 5 Metallographic image of the product prepared for Comparative Example 4. Detailed Implementation

[0035] The present invention will be further described below with reference to specific embodiments.

[0036] The raw materials and additives used in this invention are all commercially available.

[0037] The method for preparing the extruded aluminum alloy material for the liquid-cooled housing of the lightweight drive motor of new energy vehicles according to the present invention includes the following steps:

[0038] (1) Smelting: Melt A356 aluminum ingots, heat to 740~750℃, add aluminum-silicon master alloy, adjust silicon content to the target range, and obtain a uniform aluminum alloy melt;

[0039] (2) Composite refining and modification treatment: The aluminum alloy melt obtained in step (1) is heated to 760~770℃ and high-purity argon is introduced for degassing; then preheated AlTi5B1 is added, and the titanium content is controlled at 0.16~0.22%. After reacting for 3~5 minutes, 0.05%~0.07% of active titanium refiner by mass of aluminum melt is added to strengthen nucleation; after reacting for another 5~8 minutes, preheated aluminum-strontium master alloy is added for modification treatment, and the strontium content is controlled at 0.045%~0.06%; the total refining and degassing time is 18~25 minutes; after refining, slag is removed to obtain pure aluminum alloy melt;

[0040] (3) Casting: The pure aluminum alloy melt obtained in step (2) is injected into the mold through a gravity tilting casting system. The specific process parameters are: the tilting speed is 95-100 degrees in 5-6s, the pressure is maintained and cooled for 6-8 minutes after casting, and then the mold is reset and opened to obtain the aluminum alloy ingot blank.

[0041] (4) Ingot pretreatment: Remove the gating gates and risers, mill the surface or turn the surface of the ingot blank obtained in step (3) to obtain a clean extrusion ingot;

[0042] (5) Extrusion molding and heat treatment:

[0043] a. Place the pretreated ingot into a heating furnace and heat it at 440~460℃ for 2~4 hours;

[0044] b. Transfer the heated ingot to the extrusion press, set the extrusion cylinder temperature to 340~360℃, the extrusion ratio to 15~25, and the extrusion speed to 1.0~3.0m / min, and extrude the ingot into a profile with the shape of a liquid-cooled housing for a drive motor;

[0045] c. The extruded shell profile is subjected to online quenching, and the quenching medium is forced air cooling or water mist cooling;

[0046] d. Perform T6 heat treatment on the quenched profiles: first, perform solution treatment at a temperature of 530~550℃ and hold for 2~4 hours, followed by water quenching; then perform artificial aging treatment at a temperature of 160~180℃ and hold for 4~8 hours.

[0047] Example 1

[0048] The extruded aluminum alloy material for the lightweight drive motor liquid-cooled housing of new energy vehicles described in this invention comprises, by mass percentage, the following elements: Si: 7.5%, Mg: 0.35%, Fe: 0.08%, Ti: 0.19%, Sr: 0.052%, Cu: 0.05%, Mn: 0.05%, La: 0.06%, Ce: 0.04%, total impurities: 0.08%, with the balance being Al. The mass ratio of La to Ce is 1.5:1, and the mass ratio of Sr to Ti is 0.274:1.

[0049] The method for preparing the extruded aluminum alloy material for the liquid-cooled housing of the lightweight drive motor of new energy vehicles according to the present invention includes the following steps:

[0050] (1) Smelting: Melt A356 aluminum ingots, heat to 745℃, add silicon-aluminum master alloy, adjust silicon content, and obtain uniform aluminum alloy melt;

[0051] (2) Composite refining and modification treatment: The aluminum alloy melt obtained in step (1) is heated to 765°C and high-purity argon is introduced for degassing; then AlTi5B1 preheated to 250°C is added, and the titanium content is controlled at 0.19%. After reacting for 4 minutes, 0.05% of active titanium refining agent 1587 based on the total mass of the aluminum melt is added; after reacting for another 7 minutes, the preheated aluminum-strontium intermediate alloy is added for modification treatment, and the strontium content is controlled at 0.052%; the total refining and degassing time is 18 minutes; after refining, the slag is removed to obtain pure aluminum alloy melt;

[0052] (3) Casting: The pure aluminum alloy melt obtained in step (2) is injected into the mold through a gravity tilting casting system. The specific process parameters are: the tilting speed completes 98-degree rotation within 5s, and after casting, the pressure is held and cooled for 7 minutes. Then the mold is reset and opened to obtain an aluminum alloy ingot blank.

[0053] (4) Ingot pretreatment: Remove the gating gates and risers, mill the surface or turn the surface of the ingot blank obtained in step (3) to obtain a clean extrusion ingot;

[0054] (5) Extrusion molding and heat treatment:

[0055] a. Place the pretreated ingot into a heating furnace and heat it at 450℃ for 3 hours;

[0056] b. Transfer the heated ingot to the extrusion press, set the extrusion cylinder temperature to 350℃, the extrusion ratio to 20, and the extrusion speed to 2.0m / min, and extrude the ingot into a profile with the shape of a liquid-cooled housing for a drive motor;

[0057] c. The extruded shell profile is subjected to online quenching. The quenching medium is forced air cooling, and the cooling rate is >50℃ / s.

[0058] d. Perform T6 heat treatment on the quenched profile: first, perform solution treatment at 540℃ for 3 hours, followed by water quenching; then perform artificial aging treatment at 170℃ for 6 hours.

[0059] Samples of the ingots and final profiles were taken for testing. Metallographic images of the products are shown below. Figure 1 As shown, the average grain size in the as-cast state is 68 μm. After T6 extrusion treatment, the average size of the second-phase particles in the matrix is ​​3.1 μm, exhibiting a dispersed and uniform distribution. Room temperature mechanical properties: tensile strength is 334.6 MPa, yield strength is 281.6 MPa, elongation is 13.2%, and hardness HBW109.1. Thermal conductivity is 172 W / (m·K).

[0060] Example 2

[0061] The extruded aluminum alloy material for the lightweight drive motor liquid-cooled housing of new energy vehicles described in this invention, by mass percentage, comprises the following elements: Si: 8.0%, Mg: 0.30%, Fe: 0.06%, Ti: 0.17%, Sr: 0.058%, Cu: 0.04%, Mn: 0.04%, La: 0.055%, Ce: 0.046%, total impurities: 0.07%, with the balance being Al. The mass ratio of La to Ce is 1.2:1, and the mass ratio of Sr to Ti is 0.341:1.

[0062] The method for preparing the extruded aluminum alloy material for the liquid-cooled housing of the lightweight drive motor of new energy vehicles according to the present invention includes the following steps:

[0063] (1) Smelting: Melt A356 aluminum ingots, heat to 740°C, add silicon-aluminum master alloy, adjust silicon content to the target range, and obtain a uniform aluminum alloy melt;

[0064] (2) Composite refining and modification treatment: The aluminum alloy melt obtained in step (1) is heated to 760°C and high-purity argon is introduced for degassing; then preheated AlTi5B1 is added, and the titanium content is controlled at 0.17%. After reacting for 5 minutes, 0.06% of active titanium refining agent 1587 based on the total mass of the aluminum melt is added; after reacting for another 8 minutes, preheated aluminum-strontium intermediate alloy is added for modification treatment, and the strontium content is controlled at 0.058%; the total refining and degassing time is 19 minutes; after refining, slag is removed to obtain pure aluminum alloy melt;

[0065] (3) Casting: The pure aluminum alloy melt obtained in step (2) is injected into the mold through a gravity tilting casting system. The specific process parameters are: the tilting speed completes the 95-degree rotation within 5s, and the pressure is maintained and cooled for 6 minutes after casting. Then the mold is reset and opened to obtain the aluminum alloy ingot blank.

[0066] (4) Ingot pretreatment: Remove the gating gates and risers, mill the surface or turn the surface of the ingot blank obtained in step (3) to obtain a clean extrusion ingot;

[0067] (5) Extrusion molding and heat treatment:

[0068] a. Place the pretreated ingot into a heating furnace and heat it at 440℃ for 4 hours;

[0069] b. Transfer the heated ingot to the extrusion press, set the extrusion cylinder temperature to 340℃, the extrusion ratio to 25, and the extrusion speed to 1.2m / min, and extrude the ingot into a profile with the shape of a liquid-cooled housing for a drive motor;

[0070] c. The extruded shell profile is subjected to online quenching with water mist cooling medium at a rate >50℃ / s;

[0071] d. Perform T6 heat treatment on the quenched profile: first, perform solution treatment at 535℃ and hold for 3.5h, then water quench; then perform artificial aging treatment at 175℃ and hold for 5h.

[0072] Samples were taken from the ingot and the final profile for testing. The average grain size in the as-cast state was 72 μm. After T6 treatment in the extruded state, the average size of the second-phase particles in the matrix was 3.5 μm, exhibiting a dispersed and uniform distribution. Room temperature mechanical properties: tensile strength was 326.5 MPa, yield strength was 286.3 MPa, elongation was 13.6%, and hardness was HBW 103.4. Thermal conductivity was 174 W / (m·K).

[0073] Example 3

[0074] The extruded aluminum alloy material for the lightweight drive motor liquid-cooled housing of new energy vehicles described in this invention, by mass percentage, comprises the following elements: Si: 7.2%, Mg: 0.40%, Fe: 0.10%, Ti: 0.21%, Sr: 0.046%, Cu: 0.06%, Mn: 0.06%, La: 0.068%, Ce: 0.038%, total impurities: 0.09%, with the balance being Al. The mass ratio of La to Ce is 1.8:1, and the mass ratio of Sr to Ti is 0.219:1.

[0075] The method for preparing the extruded aluminum alloy material for the liquid-cooled housing of the lightweight drive motor of new energy vehicles according to the present invention includes the following steps:

[0076] (1) Smelting: Melt A356 aluminum ingots, heat to 750°C, add silicon-aluminum master alloy, adjust silicon content to the target range, and obtain a uniform aluminum alloy melt;

[0077] (2) Composite refining and modification treatment: The aluminum alloy melt obtained in step (1) is heated to 770°C and degassed by passing high-purity argon gas; then preheated AlTi5B1 is added, and the titanium content is controlled at 0.21%. After reacting for 5 minutes, 0.05% of active titanium refining agent 1587 based on the total mass of the aluminum melt is added; after reacting for another 5 minutes, preheated aluminum-strontium intermediate alloy is added for modification treatment, and the strontium content is controlled at 0.046%; the total refining and degassing time is 18 minutes; after refining, the slag is removed to obtain pure aluminum alloy melt.

[0078] (3) Casting: The pure aluminum alloy melt obtained in step (2) is injected into the mold through a gravity tilting casting system. The specific process parameters are: the tilting speed completes 100-degree rotation within 6s, and after casting, the pressure is maintained and cooled for 8 minutes. Then the mold is reset and opened to obtain an aluminum alloy ingot blank.

[0079] (4) Ingot pretreatment: Remove the gating gates and risers, mill the surface or turn the surface of the ingot blank obtained in step (3) to obtain a clean extrusion ingot;

[0080] (5) Extrusion molding and heat treatment:

[0081] a. Place the pretreated ingot into a heating furnace and heat it at 460℃ for 2 hours;

[0082] b. Transfer the heated ingot to the extrusion press, set the extrusion cylinder temperature to 360℃, the extrusion ratio to 15, and the extrusion speed to 2.8m / min, and extrude the ingot into a profile with the shape of a liquid-cooled housing for a drive motor;

[0083] c. The extruded shell profile is subjected to online quenching with water mist cooling medium at a rate >50℃ / s;

[0084] d. Perform T6 heat treatment on the quenched profile: first, perform solution treatment at 545℃ for 2.5h, followed by water quenching; then perform artificial aging treatment at 165℃ for 7h.

[0085] Samples were taken from the ingot and the final profile for testing. The average grain size in the as-cast state was 63 μm. After T6 extrusion treatment, the average size of the second-phase particles in the matrix was 2.8 μm, exhibiting a dispersed and uniform distribution. Room temperature mechanical properties: tensile strength was 342.1 MPa, yield strength was 287.5 MPa, elongation was 13.4%, and hardness was HBW 103.8. Thermal conductivity was 170 W / (m·K).

[0086] Example 4

[0087] The extruded aluminum alloy material for the lightweight drive motor liquid-cooled housing of new energy vehicles described in this invention comprises, by mass percentage, the following elements: Si: 8.4%, Mg: 0.43%, Fe: 0.05%, Ti: 0.22%, Sr: 0.060%, Cu: 0.08%, Mn: 0.08%, La: 0.07%, Ce: 0.03%, total impurities: 0.10%, with the balance being Al. The mass ratio of La to Ce is 2.33:1, and the mass ratio of Sr to Ti is 0.273:1.

[0088] The method for preparing the extruded aluminum alloy material for the liquid-cooled housing of the lightweight drive motor of new energy vehicles according to the present invention includes the following steps:

[0089] (1) Smelting: Melt A356 aluminum ingots, heat to 745℃, add silicon-aluminum master alloy, adjust silicon content to the target range, and obtain uniform aluminum alloy melt;

[0090] (2) Composite refining and modification treatment: The aluminum alloy melt obtained in step (1) is heated to 765°C and high-purity argon is introduced for degassing; then preheated AlTi5B1 is added, and the titanium content is controlled at 0.22%. After reacting for 5 minutes, 0.06% of active titanium refining agent 1587 based on the total mass of the aluminum melt is added; after reacting for another 8 minutes, preheated aluminum-strontium intermediate alloy is added for modification treatment, and the strontium content is controlled at 0.06%; the total refining and degassing time is 20 minutes; after refining, slag is removed to obtain pure aluminum alloy melt;

[0091] (3) Casting: The pure aluminum alloy melt obtained in step (2) is injected into the mold through a gravity tilting casting system. The specific process parameters are: the tilting speed completes the 95-degree rotation within 6s, the pressure is held and cooled for 6min after casting, and then the mold is reset and opened to obtain the aluminum alloy ingot blank.

[0092] (4) Ingot pretreatment: Remove the gating gates and risers, mill the surface or turn the surface of the ingot blank obtained in step (3) to obtain a clean extrusion ingot;

[0093] (5) Extrusion molding and heat treatment:

[0094] a. Place the pretreated ingot into a heating furnace and heat it at 450℃ for 3 hours;

[0095] b. Transfer the heated ingot to the extrusion press, set the extrusion cylinder temperature to 350℃, the extrusion ratio to 20, and the extrusion speed to 2.0m / min, and extrude the ingot into a profile with the shape of a liquid-cooled housing for a drive motor;

[0096] c. The extruded shell profile is subjected to online quenching, with water mist cooling as the quenching medium and a cooling rate > 50℃ / s;

[0097] d. Perform T6 heat treatment on the quenched profile: first, perform solution treatment at 540℃ for 3 hours, followed by water quenching; then perform artificial aging treatment at 170℃ for 5 hours.

[0098] Samples were taken from the ingot and the final profile for testing. The average grain size in the as-cast state was 70 μm. After T6 treatment in the extruded state, the average size of the second-phase particles in the matrix was 4.1 μm, exhibiting a dispersed and uniform distribution. Room temperature mechanical properties: tensile strength was 337.2 MPa, yield strength was 282.1 MPa, elongation was 14.3%, and hardness was HBW 99.6. Thermal conductivity was 172 W / (m·K).

[0099] Comparative Example 1

[0100] The difference between the comparative example and Example 1 is that La is not added, only Ce is added, and the Ce content is controlled at 0.10% and the La content at 0%. The contents of other elements are the same as in Example 1. The preparation process is the same as in Example 1, and the content control corresponds to the raw material ratio control.

[0101] Samples of the ingots and final profiles were taken for testing. Metallographic images of the products are shown below. Figure 2 As shown, the average grain size in the as-cast state is 115 μm, indicating a coarsened microstructure. The average size of the extruded second-phase particles is 8.5 μm, and their distribution is uneven, with localized segregation visible. Room temperature mechanical properties: tensile strength is 255 MPa, yield strength is 165 MPa, elongation is 8.2%, and hardness is HBW99.2. Thermal conductivity is 162 W / (m·K). Due to the lack of La / Ce synergistic refining effect, the microstructure is coarse, and all properties are significantly reduced.

[0102] Comparative Example 2

[0103] The difference between the comparative example and Example 1 is that Ce is not added, only La is added, and the La content is controlled at 0.10%, while the Ce content is 0%. The contents of other elements are the same as in Example 1. The preparation process is the same as in Example 1, and the content control corresponds to the raw material ratio.

[0104] The as-cast microstructure shows clearly coarse, lamellar eutectic silicon. Metallographic image of the product is shown below. Figure 3 As shown, the extruded second-phase particles are uneven in size, with some iron-rich phases appearing as short needles. Room temperature mechanical properties: tensile strength is 270 MPa, yield strength is 178 MPa, elongation is only 7.5% (due to coarse silicon phases interfering with the matrix), hardness HBW 88.1. Thermal conductivity is 165 W / (m·K). Due to the lack of Sr modification, both plasticity and thermal conductivity are impaired.

[0105] Comparative Example 3

[0106] The chemical elements in this comparative example are the same as those in Example 1. Step (2) in this comparative example is replaced with the following steps, while other processes remain the same:

[0107] (2) Refining treatment: The molten liquid is heated to 760°C, and AlTi5B1 master alloy and Al-10Sr master alloy are added at one time. After refining and degassing for 10 minutes, the slag is removed. The total processing time is much shorter than that of the process of this invention.

[0108] Samples of the ingots and final profiles were taken for testing. Metallographic images of the products are shown below. Figure 4 As shown, the average grain size in the as-cast state is 102 μm, indicating insufficient grain refinement. The second phase exhibits a wide size distribution with an average size of 7.2 μm. Room temperature mechanical properties include a tensile strength of 265 MPa, a yield strength of 170 MPa, an elongation of 9.0%, and a hardness of HBW 88.9. The thermal conductivity is 160 W / (m·K).

[0109] Comparative Example 4

[0110] The chemical elements in this comparative example are the same as those in Example 1. Step (5) in this comparative example is replaced with the following steps, while other processes remain the same:

[0111] (5) Extrusion molding and heat treatment:

[0112] a. The soaking temperature of the ingot is 500℃.

[0113] b. The extrusion cylinder temperature is 400℃, the extrusion ratio is 10, and the extrusion speed is 0.5 m / min.

[0114] c. Online quenching is performed using natural air cooling.

[0115] d. T6 treatment: Solution treatment temperature is 500℃, and the holding time is 5h; aging temperature is 120℃, and the holding time is 12h.

[0116] Samples of the ingots and final profiles were taken for testing. Metallographic images of the products are shown below. Figure 5 As shown, the extruded microstructure exhibits recrystallization and grain growth, with coarsened second-phase particles distributed along grain boundaries, reaching an average size of 9.8 μm. Room temperature mechanical properties include a tensile strength of 245 MPa, a yield strength of 155 MPa, an elongation of 10.5%, and a hardness of HBW 88.2. Thermal conductivity is 155 W / (m·K). Inappropriate thermomechanical treatment leads to insufficient precipitation of the strengthening phase and microstructural deterioration, resulting in a significant decrease in strength and thermal conductivity.

Claims

1. An extruded aluminum alloy material for a lightweight liquid-cooled housing of a drive motor for new energy vehicles, characterized in that, The aluminum alloy, by weight percentage, consists of the following elements Composition: Si: 7.0%~8.5%, Mg: 0.3%~0.45%, Fe: ≤0.10%, Ti: 0.16%~0.22%, Sr: 0.045%~0.06%, Cu: ≤0.1%, Mn: ≤0.1%, La: 0.05%~0.07%, Ce: 0.03%~0.05%, total impurities ≤0.10%, balance Al; The mass ratio of La to Ce was controlled at 1.2 to 2.4:1, and the mass ratio of Sr to Ti was controlled at 0.21 to 0.35:

1. The method for preparing the extruded aluminum alloy material for the liquid-cooled housing of the lightweight drive motor of new energy vehicles includes the following steps: (1) Smelting: Melt A356 aluminum ingots, heat to 740~750℃, add aluminum-silicon master alloy, adjust silicon content to the target range, and obtain a uniform aluminum alloy melt; (2) Composite refining and modification treatment: The aluminum alloy melt obtained in step (1) is heated to 760~770℃ and degassed; then preheated aluminum-titanium-boron alloy is added, the titanium content is controlled at 0.16~0.22%, active titanium refiner is added, and after reacting for 5~8 minutes, preheated aluminum-strontium intermediate alloy is added for treatment, the strontium content is controlled at 0.045%~0.06%, and the alloy is refined, degassed, and slag is removed to obtain aluminum alloy melt; the active titanium refiner is a refiner containing TiAl3 phase, and the amount added is 0.05%~0.07% of the total mass of aluminum melt; (3) Casting and forming: The aluminum alloy molten liquid obtained in step (2) is injected into the mold through a gravity tilting casting system to obtain an aluminum alloy ingot blank; (4) Ingot pretreatment: Remove the gating gates and risers, mill the surface or turn the surface of the ingot blank obtained in step (3) to obtain the extrusion ingot; (5) Extrusion molding and heat treatment: a. Place the pretreated ingot into a heating furnace and heat it at 440~460℃ for 2~4 hours; b. Transfer the heated ingot to an extrusion press and extrude the ingot into a profile with the shape of a liquid-cooled housing for a drive motor; the extrusion parameters are: extrusion cylinder temperature set at 340~360℃, extrusion ratio at 15~25, and extrusion speed at 1.0~3.0m / min; c. Perform online quenching on the extruded shell profile; d. The quenched profiles are subjected to T6 heat treatment. First, solution treatment is performed at a temperature of 530~550℃ for 2~4 hours, followed by water quenching; then artificial aging treatment is performed at a temperature of 160~180℃ for 4~8 hours.

2. The extruded aluminum alloy material for the liquid-cooled housing of the lightweight drive motor for new energy vehicles according to claim 1, characterized in that: In step (2), the aluminum titanium boron is AlTi5B1.

3. The extruded aluminum alloy material for the liquid-cooled housing of the lightweight drive motor for new energy vehicles according to claim 2, characterized in that: In step (3), the specific process parameters after injection into the mold are: the tilting speed is 95-100 degrees in 5-6 seconds, the pressure is maintained and cooled for 6-8 minutes after casting, and then the mold is reset and opened to obtain aluminum alloy ingot blank.

4. The extruded aluminum alloy material for the liquid-cooled housing of the lightweight drive motor for new energy vehicles according to claim 3, characterized in that: In step (4), the obtained extrusion ingot has an average grain size of ≤80μm in the as-cast structure.

5. The extruded aluminum alloy material for the liquid-cooled housing of the lightweight drive motor for new energy vehicles according to claim 4, characterized in that: In step (5), the average size of the non-aluminum matrix grains in the extruded microstructure after extrusion forming and heat treatment is ≤7μm and they are diffusely distributed.

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