High-strength high-thermal-conductivity cast rare earth aluminum alloy suitable for brazing and preparation method thereof

Abstract

The application belongs to cast aluminum alloy, and discloses a high-strength and high-thermal-conductivity cast rare earth aluminum alloy suitable for brazing and a preparation method thereof. The cast rare earth aluminum alloy is composed of the following components in percentage by weight: RE: 9.0-11.0 %, RE being La and / or Ce; Fe: 1.8-3.5 %; Mg: 0.4-0.6 %; impurities: ≤0.20 %; and the balance being Al. The application further discloses a preparation method of the high-strength and high-thermal-conductivity cast rare earth aluminum alloy suitable for brazing. In the aluminum alloy of the application, a ternary eutectic structure in the form of nanoscale particles is formed, and the solid solution strengthening effect of Mg atoms is synergistic, so that the alloy has high thermal conductivity, high room-temperature tensile strength and high eutectic temperature, and fully meets the requirements of hard brazing process. The application has simple process and low cost, and is suitable for manufacturing of parts with strict requirements on heat dissipation, strength and weldability, such as liquid cooling plates of new energy vehicles.

Description

Technical Field

[0001] This invention belongs to the field of cast aluminum alloy technology, specifically relating to a high-strength, high-thermal-conductivity cast rare-earth aluminum alloy suitable for brazing and its preparation method. Background Technology

[0002] Lightweighting, as a crucial approach to energy conservation and emission reduction, has led to the increasingly widespread application of lightweight, high-strength aluminum alloys in automotive components. In the thermal management systems of new energy vehicles, key components such as liquid cooling plates not only require high strength to ensure structural reliability and durability but also excellent thermal conductivity for effective thermal control and management of the powertrain. Currently, these components are typically assembled from 6000 series (Al-Mg-Si) aluminum alloys (which have good thermal conductivity) through forging and machining, followed by brazing with 3000 series (Al-Mn) aluminum alloys. However, the production process for wrought aluminum alloys is lengthy, involves high energy consumption during heat treatment, and is difficult to manufacture structurally complex components, resulting in low material utilization and high product costs.

[0003] Casting, as a near-net-shape forming technology, enables the rapid forming of thin-walled, complex, and high-precision workpieces, requiring only minimal or no subsequent machining to complete the workpiece preparation, offering significant advantages. However, in practical applications, it has been found that the mainstream aluminum alloy brazing filler metals currently on the market are Al-Si alloys. To ensure the wettability and spreadability of the solder, the brazing temperature typically needs to be maintained at 590~610 ℃. This temperature range is close to or even exceeds the solidus temperature of many commercially available cast aluminum alloys (e.g., Al-Si system approximately 577 ℃, Al-Cu system approximately 548 ℃, Al-Mg system approximately 450 ℃). During the brazing holding process, the strengthening phase in the alloy is prone to coarsening or localized ablation, which severely deteriorates the mechanical properties of the workpiece.

[0004] To address the above problems, existing technologies have proposed several solutions, but they still have significant limitations.

[0005] Chinese patent application CN202311337159.8 discloses a brazable cast aluminum alloy, which adds Fe, Cu, M1, and M2 elements (M1 being Ti and / or Zr, and M2 being at least one selected from V, Mo, and Cr) to an Al-Mn alloy system. This forms a high-temperature stable eutectic structure and dispersed precipitates, ensuring the alloy's melting point is above 620 °C and improving the thermal stability of its microstructure. However, this alloy has a complex composition, a room temperature tensile strength below 180 MPa, and Mn is an element that deteriorates the thermal conductivity of aluminum alloys. Furthermore, the multi-component alloy design leads to poor thermal conductivity. Patent application CN202411151355.0 discloses a high thermal conductivity, brazable high-pressure cast aluminum alloy. By adding transition metal elements with high eutectic temperatures, the alloy's solidus temperature is above 620 °C, and its room temperature tensile strength is greater than 150 MPa. However, a high content of transition metal elements negatively impacts the alloy's thermal conductivity. Patent application CN202311216296.6 discloses a brazable high thermal conductivity cast aluminum alloy system. It adds Mg, Fe, Si, Mn, Cr, and Zr to the Al-RE eutectic composition, resulting in an alloy melting point above 625 ℃ and a room temperature tensile strength greater than 200 MPa. However, the high content of transition metal elements can also negatively impact the alloy's thermal conductivity. Patent application CN202510072487.2 discloses a TiB2-reinforced brazable high thermal conductivity cast rare earth aluminum alloy. Adding trace amounts of nano-TiB2 particles to the hypoeutectic Al-Ce-Ni-Fe alloy effectively refines the eutectic structure and maintains a melting point above 630 ℃ and a room temperature thermal conductivity of approximately 200 W / (m·K), but its room temperature tensile strength is less than 150 MPa.

[0006] In summary, existing technologies struggle to ensure both high eutectic temperatures to meet brazing requirements and excellent strength and thermal conductivity. Summary of the Invention

[0007] To overcome the shortcomings and deficiencies of existing technologies, the present invention aims to provide a high-strength, high-thermal-conductivity cast rare-earth aluminum alloy suitable for brazing and its preparation method. The alloy of this invention uses La and / or Ce as the main rare-earth elements. This alloy system possesses good casting performance, excellent mechanical properties, high thermal conductivity, simple preparation process, relatively low cost, and a high eutectic temperature. Its typical performance parameters are: thermal conductivity of 145 W / (m·K) – 170 W / (m·K), room temperature tensile strength of 200 MPa – 226.5 MPa, and eutectic temperature of 637.4 ℃ – 638.1 ℃. This alloy can meet the comprehensive requirements of high strength, high thermal conductivity, and brazing capability for aluminum alloy materials in the heat dissipation field, and has broad application prospects and promotion potential in heat dissipation components such as liquid cooling plates in new energy vehicles.

[0008] The objective of this invention is achieved through the following technical solution:

[0009] A high-strength, high-thermal-conductivity cast rare-earth aluminum alloy suitable for brazing, comprising the following components by weight percentage:

[0010] RE: 9.0 ~ 11.0 wt.%, where RE is La and / or Ce;

[0011] Fe: 1.8 ~ 3.5 wt.%;

[0012] Mg: 0.4 ~ 0.6 wt.%;

[0013] Impurities: ≤ 0.20 wt.%;

[0014] The balance is Al.

[0015] The method for preparing the high-strength, high-thermal-conductivity cast rare-earth aluminum alloy suitable for brazing includes the following steps:

[0016] 1) Melt pure aluminum, Al-RE master alloy and Al-Fe master alloy. After the melt cools to the casting temperature, add Al-Mg master alloy. After it is completely melted, mix it well and purify the melt.

[0017] 2) The melt is cast and annealed to obtain a high-strength, high-thermal-conductivity cast rare-earth aluminum alloy suitable for brazing.

[0018] The melting temperature in step 1) is 800~900℃; the casting temperature is 750~770℃.

[0019] The Al-RE master alloy mentioned in step 1) is Al-20La and / or Al-20Ce, the Al-Fe master alloy is Al-20Fe, and the Al-Mg master alloy is Al-10Mg.

[0020] The mixing mentioned in step 1) refers to stirring until uniform; the purification of the melt refers to adding a slag remover, stirring, and removing slag and floating slag.

[0021] The slagging agent is a mixture of commercially available YT-J-1 refining agent and YT-D-4 refining agent at a mass ratio of 1:1. The amount added is 0.1~1.5% of the melt mass.

[0022] The annealing conditions described in step 2) are: heat treatment at 390~410℃ for 5.5~6.5h.

[0023] The casting mentioned in step 2) refers to pouring the molten material into a preheated (180~220℃) metal mold to form an ingot.

[0024] The principle of this invention:

[0025] This invention is based on a near-eutectic Al-RE alloy system (RE being La and / or Ce) with a relatively high eutectic temperature (approximately 640 °C). This system has the following advantages: First, the diffusion coefficient of RE atoms in the Al matrix is ​​extremely low, imparting good high-temperature stability to the alloy microstructure, making it less prone to ablation or thermal softening during brazing and heat treatment. Second, the equilibrium solid solubility of RE atoms in the Al matrix is ​​extremely low, with a solubility abrupt change near the eutectic point, tending towards nanoscale Al... 11 The RE3 eutectic phase is dispersed and precipitated, and the low lattice distortion is conducive to obtaining high thermal conductivity, while the hard Al 11 The load transfer effect between the RE3 phase and the α-Al phase effectively enhances the mechanical properties of the alloy. Furthermore, this alloy system has a narrow solidification range, and the eutectic reaction releases a large amount of latent heat, significantly improving melt fluidity and resulting in excellent casting performance. Finally, La or Ce, as byproducts of heavy rare earth mining, are abundant and inexpensive, which is conducive to large-scale production.

[0026] Adding Fe to near-eutectic Al-RE alloys can significantly improve their strength without noticeably lowering the eutectic temperature or compromising thermal conductivity, but the Fe content is strictly limited. In the Al-RE-Fe alloy system of this invention, an Al-RE-La ternary eutectic reaction occurs during melt solidification, generating (Al + Al) 11 RE3 + Al 13 The Fe4+ ternary eutectic structure is formed, rather than the Al-Fe binary eutectic reaction that first occurs to form (Al + Al). 13 The Fe4) binary eutectic structure subsequently undergoes an Al-RE binary eutectic reaction to form (Al + Al) 11 RE3) Binary eutectic structure. During the solidification process of ternary eutectic structure, Al... 13 Fe4 phase and Al11 The precipitation of the RE3 phase continuously pushes La and Fe atoms towards the solid / liquid interface front, and this solute redistribution phenomenon induces localized compositional supercooling. This provides a continuous driving force for the alternating nucleation of each eutectic phase, while also limiting the growth size of each eutectic phase, ultimately coupling to form an alternating nanoscale granular ternary eutectic structure. Adding an appropriate amount of Mg to the near-eutectic Al-RE-Fe alloy system can further improve the alloy's strength through the solid solution strengthening effect of Mg atoms in the α-Al phase. However, since excessive Mg in the alloy will deteriorate the alloy's conductivity and lower the eutectic temperature, the Mg content in the alloy must be strictly limited.

[0027] Appropriate annealing of as-cast near-eutectic Al-RE-Fe-Mg alloys can improve their electrical conductivity. Since the intermediate alloys used in the smelting process inevitably contain impurity elements such as Fe and Si, these impurities can dissolve in the Al matrix during solidification, causing severe lattice distortion and thus deteriorating the alloy's electrical conductivity. A suitable annealing process can promote the diffusion of Si atoms dissolved in the Al matrix into the Al matrix. 11 The RE3 phase interface forms a stable Al-RE-Si ternary phase precipitation, which ultimately improves the conductivity of the alloy.

[0028] The present invention has the following advantages and beneficial effects:

[0029] (1) The rare earth aluminum alloy of the present invention has high strength: The present invention significantly refines the eutectic structure of the alloy by alloying Fe element and controlling the solidification process, and obtains excellent tensile strength through solid solution strengthening effect of Mg element.

[0030] (2) The rare earth aluminum alloy of the present invention has brazing properties: the alloy system has a very high eutectic temperature (greater than 635 °C), and Fe and RE atoms have low solid solubility and slow diffusion in the Al matrix, resulting in good microstructure thermal stability, which is suitable for hard brazing.

[0031] (3) The aluminum alloy of the present invention has high thermal conductivity: RE and Fe atoms are mainly present in the second phase, with low solid solubility in the Al matrix, resulting in weak lattice distortion and small scattering effect on free electrons. Therefore, the alloy has excellent thermal conductivity. Furthermore, the annealing process can promote the precipitation of Si atoms, which are dissolved in the Al matrix, and further improve the thermal conductivity of the alloy.

[0032] (4) The process of this invention is simple and the cost is controllable: the preparation process is simple, the raw materials, energy consumption and production costs are low, and there is no need to change the existing mature production line. The high tolerance of the alloy to Fe element makes it possible to use recycled aluminum raw materials with high Fe content, further reducing costs. Attached Figure Description

[0033] Figure 1 Here is a SEM microstructure of the annealed Al-10La alloy in Comparative Example 1;

[0034] Figure 2 The image shows the SEM microstructure of the annealed Al-10La-1Fe alloy in Comparative Example 2.

[0035] Figure 3 This is a SEM microstructure of the annealed Al-10La-2Fe-0.5Mg alloy in Example 1;

[0036] Figure 4 This is a SEM microstructure of the annealed Al-10La-3Fe-0.5Mg alloy in Example 2;

[0037] Figure 5 The image shows the SEM microstructure of the annealed Al-4La-6Ce-2Fe-0.5Mg alloy in Example 4.

[0038] Figure 6 The image shows the SEM microstructure of the annealed Al-10La-2Fe alloy in Comparative Example 3.

[0039] Figure 7 The image shows the SEM microstructure of the annealed Al-10La-2Fe-1Mg alloy in Comparative Example 4. Detailed Implementation

[0040] The present invention will be described in further detail below with reference to specific embodiments, but the implementation of the present invention is not limited thereto.

[0041] Comparative Example 1

[0042] To better illustrate the effects of this invention, a cast binary near-eutectic Al-La alloy without additional Fe element was used as Comparative Example 1. The composition and content of the aluminum alloy in this comparative example were: La 10wt%, balance Al.

[0043] The preparation method of the aluminum alloy in this comparative example includes the following steps:

[0044] 1) Preheating: Place the metal mold in a 200 ℃ constant temperature oven for preheating;

[0045] 2) Based on the composition and content of the aluminum alloy, weigh out industrial pure aluminum and Al-20La master alloy, place them in a crucible, and melt them at high temperature in an electric resistance furnace (melting temperature is 900℃); after melting, stir for 2 minutes to promote homogenization (stirring speed is 500 rpm), and after the melt cools to the casting temperature (760℃), add slag remover to purify and stir to remove slag.

[0046] 3) After the alloy melt temperature stabilizes (maintained at 760℃), pour the alloy melt into a preheated metal mold at a casting temperature of 760℃ to obtain an alloy ingot.

[0047] 4) Anneal the alloy ingot at 400 °C for 6 h to obtain the final product.

[0048] Comparative Example 2

[0049] To better illustrate the effects of this invention, a cast ternary Al-La-Fe alloy with a small amount of Fe was used as Comparative Example 2. The composition and content of the aluminum alloy in this comparative example were: La 10wt%, Fe 1.0wt%, with the balance being Al.

[0050] The preparation method of the aluminum alloy in this comparative example includes the following steps:

[0051] 1) Preheating: Place the metal mold in a 200 ℃ constant temperature oven for preheating;

[0052] 2) Based on the composition and content of the aluminum alloy, weigh industrial pure aluminum, Al-20La and Al-20Fe master alloy and place them in a crucible. Melt them at high temperature in a resistance furnace (melting temperature is 900℃). After melting, stir for 2 minutes to promote homogenization. After the melt cools to the casting temperature (760℃), add slag remover to purify and stir to remove slag.

[0053] 3) After the alloy melt temperature stabilizes (maintained at 760℃), pour the alloy melt into a preheated metal mold at a casting temperature of 760℃ to obtain an alloy ingot.

[0054] 4) Anneal the alloy ingot at 400 °C for 6 h to obtain the final product.

[0055] Figure 1 and Figure 2 The images show the SEM microstructures of Comparative Example 1 and Comparative Example 2, respectively. Comparative Example 1 consists only of the primary α-Al phase and (α-Al + Al) phase. 11 The alloy exhibited a binary eutectic structure (La3), and although the total volume fraction of the eutectic structure decreased with the addition of 1.0 wt.% Fe (Comparative Example 2), the eutectic Al... 13 The volume fraction of the Fe4 phase gradually increases, exhibiting a similar appearance to Al. 11 A fishbone-like eutectic structure with interconnected La3 eutectic structures.

[0056] Example 1

[0057] To better illustrate the effects of this invention, rare earth element La is used as the main alloying element to form nanoscale (Al + Al) alloys. 11 La3 + Al13 Example 1 describes an Al-La-Fe-Mg based alloy with a ternary eutectic structure and synergistic solid solution reinforcement of Mg atoms. This example discloses a method for controlling the solidification process of the alloy melt by designing the alloy composition to obtain a nanoscale ternary granular eutectic reinforced alloy that possesses both high thermal conductivity and high strength, suitable for brazing and casting as a near-eutectic rare earth aluminum alloy. The composition and content of the rare earth aluminum alloy in this example are: La 10wt%, Fe 2.0wt%, Mg 0.5wt%, balance Al.

[0058] The method for preparing rare earth aluminum alloy in this embodiment includes the following steps:

[0059] 1) Preheating: Place the metal mold in a 200 ℃ constant temperature oven for preheating;

[0060] 2) According to the composition and content of the aluminum alloy, weighed industrial pure aluminum, Al-20La and Al-20Fe master alloy are placed into a crucible and melted at high temperature in an electric resistance furnace (melting temperature is 900℃). After melting, stir for 2 minutes to promote homogenization. After the melt cools to the casting temperature (760℃), add Al-10Mg master alloy, melt and stir evenly. Add slag remover to purify the melt and stir to remove slag and floating dross.

[0061] 3) After the alloy melt temperature stabilizes (maintained at 760℃), pour the alloy melt into a preheated metal mold at a casting temperature of 760℃ to obtain an alloy ingot.

[0062] 4) Anneal the alloy ingot at 400 °C for 6 h to obtain the final product.

[0063] Example 2

[0064] To better illustrate the effects of this invention, rare earth element La is used as the main alloying element to form nanoscale (Al + Al) alloys. 11 La3 + Al 13 Example 2 describes an Al-La-Fe-Mg based alloy with a ternary eutectic structure and synergistic solid solution reinforcement of Mg atoms. This example discloses a method for controlling the solidification process of the alloy melt by designing the alloy composition to obtain a nanoscale ternary granular eutectic reinforced alloy that possesses both high thermal conductivity and high strength, suitable for brazing and casting as a near-eutectic rare earth aluminum alloy. The composition and content of the rare earth aluminum alloy in this example are: La 10wt%, Fe 3.0wt%, Mg 0.5wt%, balance Al.

[0065] The method for preparing rare earth aluminum alloy in this embodiment includes the following steps:

[0066] 1) Preheating: Place the metal mold in a 200 ℃ constant temperature oven for preheating;

[0067] 2) According to the composition and content of the aluminum alloy, weighed industrial pure aluminum, Al-20La and Al-20Fe master alloy are placed into a crucible and melted at high temperature in an electric resistance furnace (melting temperature is 900℃). After melting, stir for 2 minutes to promote homogenization. After the melt cools to the casting temperature (760℃), add Al-10Mg master alloy, melt and stir evenly. Add slag remover to purify the melt and stir to remove slag and floating dross.

[0068] 3) After the alloy melt temperature stabilizes (maintained at 760℃), pour the alloy melt into a preheated metal mold at a casting temperature of 760℃ to obtain an alloy ingot.

[0069] 4) Anneal the alloy ingot at 400 °C for 6 h to obtain the final product.

[0070] Example 3

[0071] To better illustrate the implementation effect of the present invention, rare earth Ce is used as the main alloying element, and nanoscale (Al + Al) is formed. 11 Ce3 + Al 13 Example 3 describes an Al-Ce-Fe-Mg based alloy with a ternary eutectic structure and synergistic solid solution reinforcement of Mg atoms. This example discloses a method for controlling the solidification process of the alloy melt by designing the alloy composition to obtain a nanoscale ternary granular eutectic reinforced alloy that possesses both high thermal conductivity and high strength, suitable for brazing and casting as a near-eutectic rare earth aluminum alloy. The composition and content of the rare earth aluminum alloy in this example are: Ce 10wt%, Fe 2.0wt%, Mg 0.5wt%, balance Al.

[0072] The method for preparing rare earth aluminum alloy in this embodiment includes the following steps:

[0073] 1) Preheating: Place the metal mold in a 200 ℃ constant temperature oven for preheating;

[0074] 2) Based on the composition and content of the aluminum alloy, weighed industrial pure aluminum, Al-20Ce and Al-20Fe master alloy are placed into a crucible and melted at high temperature in an electric resistance furnace (melting temperature is 900℃). After melting, stir for 2 minutes to promote homogenization. After the melt cools to the casting temperature (760℃), add Al-10Mg master alloy, melt and stir evenly. Add slag remover to purify the melt and stir to remove slag and floating dross.

[0075] 3) After the alloy melt temperature stabilizes (maintained at 760℃), pour the alloy melt into a preheated metal mold at a casting temperature of 760℃ to obtain an alloy ingot.

[0076] 4) Anneal the alloy ingot at 400 °C for 6 h to obtain the final product.

[0077] Example 4

[0078] To better illustrate the implementation effect of the present invention, La-Ce mixed rare earth (MM) alloying elements are used as the main alloying elements, and nanoscale (Al + Al) alloys are formed. 11 MM3 + Al 13 Example 4 describes an Al-MM-Fe-Mg based alloy with a ternary eutectic structure and synergistic Mg atom solid solution reinforcement. This example discloses a method for controlling the solidification process of the alloy melt by designing the alloy composition to obtain a nanoscale ternary granular eutectic reinforced alloy that possesses both high thermal conductivity and high strength, suitable for brazing and casting as a near-eutectic rare earth aluminum alloy. The composition and content of the rare earth aluminum alloy in this example are: La 4wt%, Ce 6wt%, Fe 2.0wt%, Mg 0.5wt%, balance Al.

[0079] The method for preparing rare earth aluminum alloy in this embodiment includes the following steps:

[0080] 1) Preheating: Place the metal mold in a 200 ℃ constant temperature oven for preheating;

[0081] 2) Based on the composition and content of the aluminum alloy, weighed industrial pure aluminum, Al-20Ce, Al-20La and Al-20Fe master alloy are placed into a crucible and melted at high temperature in an electric resistance furnace (melting temperature is 900℃). After melting, stir for 2 minutes to promote homogenization. After the melt cools to the casting temperature (760℃), add Al-10Mg master alloy, melt and stir evenly. Add slag remover to purify the melt and stir to remove slag and floating dross.

[0082] 3) After the alloy melt temperature stabilizes (maintained at 760℃), pour the alloy melt into a preheated metal mold at a casting temperature of 760℃ to obtain an alloy ingot.

[0083] 4) Anneal the alloy ingot at 400 °C for 6 h to obtain the final product.

[0084] Figure 3 This is a SEM microstructure of the annealed Al-10La-2Fe-0.5Mg alloy in Example 1.

[0085] Figure 4 This is a SEM microstructure of the annealed Al-10La-3Fe-0.5Mg alloy in Example 2.

[0086] Figure 5This is a SEM micrograph of the annealed Al-4La-6Ce-2Fe-0.5Mg alloy from Example 4. The image shows that the eutectic phase in the eutectic region is extremely fine, transforming from the previously dispersed, coarse binary lamellar (α-Al + Al) structure. 11 La3) eutectic and fishbone-like (α-Al + Al) 13 Fe4) eutectic, transforming into nanoscale ternary particles (Al + Al) 11 RE3 +Al 13 The Fe4+ eutectic exists, while Mg atoms are completely dissolved in the α-Al phase. It is important to emphasize that only by precisely controlling the Fe content in the alloy and reducing the (Al+Al) content can this alloy be successfully constructed. 13 The eutectic precipitation temperature of Fe4) is close to that of (Al + Al) 11 The eutectic temperature of RE3) is determined by the eutectic Al during solidification. 13 Fe4 phase and eutectic Al 11 The precipitation of the RE3 phase ejects RE and Fe atoms to the solid / liquid interface front, inducing compositional supercooling. This provides a driving force for the alternating nucleation of the two phases and also limits their growth size, ultimately coupling to form alternating nanoscale particle morphologies.

[0087] Comparative Example 3

[0088] To better illustrate the effects of this invention, in order to form nanoscale (Al + Al) 11 RE3 + Al 13 Comparative Example 3 is an Al-La-Fe based alloy with a ternary eutectic structure but without Mg atom solid solution reinforcement. The composition and content of the aluminum alloy in this comparative example are: La 10wt%, Fe 2.0wt%, balance Al.

[0089] The preparation method of the aluminum alloy in this comparative example includes the following steps:

[0090] 1) Preheating: Place the metal mold in a 200 ℃ constant temperature oven for preheating;

[0091] 2) Based on the composition and content of the aluminum alloy, weigh industrial pure aluminum, Al-20La and Al-20Fe master alloy and place them in a crucible. Melt them at high temperature in a resistance furnace (melting temperature is 900℃). After melting, stir for 2 minutes to promote homogenization. After the melt cools to the casting temperature (760℃), add slag remover to purify and stir to remove slag.

[0092] 3) After the alloy melt temperature stabilizes (maintained at 760℃), pour the alloy melt into a preheated metal mold at a casting temperature of 760℃ to obtain an alloy ingot.

[0093] 4) Anneal the alloy ingot at 400 °C for 6 h to obtain the final product.

[0094] Comparative Example 4

[0095] To better illustrate the effects of this invention, in order to form nanoscale (Al + Al) 11 RE3 + Al 13 Comparative Example 4 is an Al-La-Fe-Mg based alloy with a ternary eutectic structure but reinforced by solid solution of excess Mg atoms. The composition and content of the aluminum alloy in this comparative example are: La 10wt%, Fe 2.0wt%, Mg 1wt%, balance Al.

[0096] The preparation method of the aluminum alloy in this comparative example includes the following steps:

[0097] 1) Preheating: Place the metal mold in a 200 ℃ constant temperature oven for preheating;

[0098] 2) Based on the composition and content of the aluminum alloy, weigh industrial pure aluminum, Al-20La and Al-20Fe master alloy and place them in a crucible. Melt them at high temperature in a resistance furnace (melting temperature is 900℃). After melting, stir for 2 minutes to promote homogenization. After the melt cools to the casting temperature (760℃), add Al-10Mg master alloy. After melting, stir evenly, add slag remover to purify the melt, stir and remove slag and floating dross.

[0099] 3) After the alloy melt temperature stabilizes (maintained at 760℃), pour the alloy melt into a preheated metal mold at a casting temperature of 760℃ to obtain an alloy ingot.

[0100] 4) Anneal the alloy ingot at 400 °C for 6 h to obtain the final product.

[0101] Figure 6 and Figure 7 SEM micrographs of Comparative Examples 3 and 4 are shown. Comparative Examples 3 and 4 exhibit ternary eutectic morphologies similar to those of the examples, with the only difference being the content of dissolved Mg atoms in the α-Al phase.

[0102] The aluminum alloy composition and content of Comparative Examples 1-4 and Examples 1-4 are shown in Table 1.

[0103] Table 1. Composition and content (wt.%) of each alloy in Comparative Examples 1-4 and Examples 1-4

[0104]

[0105] The thermal conductivity, mechanical properties, and solidification process of the nanoscale ternary granular eutectic synergistic Mg atom solid solution reinforced, brazable castable near-eutectic rare earth aluminum alloy with both high thermal conductivity and high strength, as well as the comparative example aluminum alloy, were tested respectively. The test results are shown in Table 2:

[0106] Table 2 Thermal conductivity, mechanical properties, and eutectic temperature of each alloy in the comparative examples and embodiments.

[0107]

[0108] As shown in Table 2, alloying with only a small amount of Fe (Comparative Example 2) not only resulted in little change in the alloy's strength but also a significant decrease in its plasticity. Furthermore, the room temperature thermal conductivity of the alloy decreased from 187.4 W / (m·K) to 174.4 W / (m·K). However, by designing the Fe content in the alloy and altering the solidification process of the alloy melt, nano-sized ternary particles (Al + Al) were directly precipitated from the melt during solidification. 11 La3 + Al 13 The Fe4) eutectic process, combined with the solid solution strengthening effect of Mg atoms in the α-Al phase, significantly improves the tensile strength of the alloy to 216.8 MPa and 226.5 MPa (corresponding to Examples 1 and 2, respectively). Furthermore, because the particulate second phase scatters free electrons less strongly than the lamellar second phase, the thermal conductivity of the alloy remains at a high level, at 156.3 W / (m·K) and 149.1 W / (m·K), respectively (corresponding to Examples 1 and 2, respectively). Examples 3 and 4 exhibit similar overall performance to Example 1, indicating that using La and / or Ce as the main alloying elements is feasible. Finally, the eutectic temperature of all alloys in the examples is above 635 °C, meeting current brazing temperature requirements. For Comparative Example 3, the tensile strength of the alloy is low, only 209.0 MPa, due to the solid solution strengthening effect of the lack of Mg atoms. For Comparative Example 4, although the tensile strength of the alloy is high, at 239.3 MPa, the thermal conductivity of the alloy is low, only 142.8 W / (m·K), due to the strong lattice distortion of the α-Al phase caused by the high solid solution content of Mg atoms. In addition, the eutectic temperature of the alloy system is low (632.3 ℃), which is not suitable for brazing.

[0109] The above embodiments only use La and Ce as examples to describe the present invention in detail, but the present invention is not limited thereto. Those skilled in the art should understand that, based on the same inventive concept, using other light rare earth elements or combinations thereof with properties similar to La and Ce, and obtaining a nanoscale ternary granular eutectic structure by controlling the Fe content, also falls within the protection scope of the present invention.

Claims

1. A high-strength, high-thermal-conductivity cast rare-earth aluminum alloy suitable for brazing, characterized in that: It consists of the following components by weight percentage: RE: 9.0 ~ 11.0%, where RE is La and / or Ce; Fe: 1.8 ~ 3.5%; Mg: 0.4 ~ 0.6%; Impurities: ≤ 0.20%; The margin is Al.

2. The high-strength, high-thermal-conductivity cast rare-earth aluminum alloy suitable for brazing according to claim 1, characterized in that: It consists of the following components by weight percentage: RE: 9.5 ~ 10.5%; Fe: 2 ~ 3.2%; Mg: 0.4 ~ 0.6%; Impurities: ≤ 0.20%; The margin is Al.

3. The method for preparing the high-strength, high-thermal-conductivity cast rare-earth aluminum alloy suitable for brazing according to claim 1 or 2, characterized in that: Includes the following steps: 1) Melt pure aluminum, Al-RE master alloy and Al-Fe master alloy. After the melt cools to the casting temperature, add Al-Mg master alloy. After it is completely melted, mix it well and purify the melt. 2) The melt is cast and annealed to obtain a high-strength, high-thermal-conductivity cast rare-earth aluminum alloy suitable for brazing.

4. The method for preparing the high-strength, high-thermal-conductivity cast rare-earth aluminum alloy suitable for brazing according to claim 3, characterized in that: The melting temperature in step 1) is 800~900℃; the casting temperature is 750~770℃; The Al-RE master alloy mentioned in step 1) is Al-20La and / or Al-20Ce, the Al-Fe master alloy is Al-20Fe, and the Al-Mg master alloy is Al-10Mg; The annealing conditions described in step 2) are: heat treatment at 390~410℃ for 5.5~6.5h.

5. The method for preparing the high-strength, high-thermal-conductivity cast rare-earth aluminum alloy suitable for brazing according to claim 3, characterized in that: The mixing mentioned in step 1) refers to stirring until uniform; the purification of the melt refers to adding a slag remover, stirring, and removing slag and floating slag.

6. The method for preparing the high-strength, high-thermal-conductivity cast rare-earth aluminum alloy suitable for brazing according to claim 5, characterized in that: The slag remover is a mixture of commercially available YT-J-1 refining agent and YT-D-4 refining agent in a mass ratio of 1:1; the amount of slag remover added is 0.1~1.5% of the melt mass.

7. The method for preparing the high-strength, high-thermal-conductivity cast rare-earth aluminum alloy suitable for brazing according to claim 3, characterized in that: The casting mentioned in step 2) refers to pouring the molten material into a preheated metal mold to form an ingot; the preheating temperature is 180~220℃. In step 1), smelting refers to melting and then mixing.

8. The application of the high-strength, high-thermal-conductivity cast rare-earth aluminum alloy suitable for brazing as described in claim 1 or 2, characterized in that: The high-strength, high-thermal-conductivity cast rare-earth aluminum alloy is used in heat dissipation components of new energy vehicles and is suitable for brazing processes.

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