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

Abstract

This invention belongs to the technical field of cast aluminum alloys, and discloses a high-strength, low-thermal-conductivity cast rare-earth aluminum alloy suitable for brazing and its preparation method. The rare-earth aluminum alloy is composed of the following components by weight percentage: RE: 9~11%, RE being La and / or Ce; Mn: 0.8~1.2%; Mg: 0.4~1%; impurities: ≤0.20%; balance being Al. This invention also discloses a method for preparing the rare-earth aluminum alloy. The synergistic effect of the elements in the rare-earth aluminum alloy of this invention results in a high eutectic temperature, high tensile strength, and low thermal conductivity, meeting the requirements of hard brazing processes. The method of this invention is simple and low-cost. The aluminum alloy of this invention is suitable for manufacturing components in new energy vehicles, such as refrigerant manifolds and refrigerant storage tanks, which have stringent requirements for low heat dissipation, high strength, and weldability.

Description

Technical Field

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

[0002] Lightweighting, as an important means of achieving energy conservation and emission reduction, has led to the increasingly widespread application of aluminum alloys, which possess lightweight and high specific strength properties, in automotive parts. In the thermal management system of new energy vehicles, key components such as refrigerant storage tanks and refrigerant manifolds not only need high strength to ensure structural reliability and long-term durability, but also must have low thermal conductivity. This is because hot and cold circuits are often arranged adjacent to each other, and excessively high thermal conductivity will cause parasitic heat loss, resulting in unnecessary heat exchange between the refrigerant and the external environment.

[0003] Currently, these components are typically assembled from 6000 series (Al-Mg-Si) aluminum alloys through forging and machining, followed by brazing with 3000 series (Al-Mn) aluminum alloys. However, wrought aluminum alloys suffer from long production processes, high energy consumption during heat treatment, difficulty in fabricating complex structures, and low material utilization, resulting in high product costs. Furthermore, existing wrought aluminum alloys generally have high thermal conductivity, which is insufficient for applications requiring low thermal conductivity.

[0004] In contrast, casting 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 cost and time advantages. However, in practical applications, the mainstream aluminum alloy brazing filler metals are currently Al-Si alloys. To ensure the wettability and spreadability of the solder, the brazing temperature typically needs to be maintained at 590–610°C. This temperature range is close to or even exceeds the solidus temperature of many commercially available cast aluminum alloys (e.g., approximately 577°C for Al-Si, approximately 548°C for Al-Cu, and approximately 450°C for Al-Mg). During the heat treatment process in brazing, the strengthening phase in the alloy is prone to coarsening or localized ablation, which severely deteriorates the mechanical properties of the workpiece. Therefore, to utilize the efficient forming advantages of casting while meeting the high-temperature resistance requirements of brazing and taking into account the stringent requirements of the thermal management system for low thermal conductivity, it is urgent to develop a cast aluminum alloy that combines high solidus temperature, high strength, and low thermal conductivity.

[0005] However, most current scientific research focuses on the development of high-strength, high-thermal-conductivity cast aluminum alloys, while systematic exploration of high-strength, low-thermal-conductivity cast aluminum alloys remains relatively lacking. Based on the inverse relationship between thermal conductivity and mechanical properties, it seems that adding large amounts of strengthening elements can naturally yield high-strength, low-thermal-conductivity aluminum alloys. However, it should be noted that excessive addition of alloying elements with low eutectic temperatures (such as Mg) will significantly lower the alloy's melting point, leading to localized melting during high-temperature brazing; while excessive addition of alloying elements with high eutectic temperatures (such as Fe) easily generates coarse primary phases, which are neither effective in reducing thermal conductivity nor beneficial to the alloy's formability and mechanical properties.

[0006] Existing research on brazable, low-thermal-conductivity, high-strength cast aluminum alloys still has significant limitations in terms of alloy composition design, microstructure control, and process window, failing to fundamentally meet the comprehensive requirements of brazing processability, high strength, low thermal conductivity, and low cost of cast aluminum alloys.

[0007] Patent application CN202280051491.5 discloses a method for preparing a brazable high-pressure die-cast aluminum alloy. This method involves adding a high content of transition elements with high eutectic temperatures, such as Mn, Fe, and Ni, to achieve a solidus temperature above 610℃. Furthermore, the room temperature tensile strength remains at 170 MPa after brazing. However, the high Ni content significantly increases raw material costs.

[0008] Chinese patent application CN202311831797.5 discloses a brazing aluminum alloy material and its preparation method. The material mainly contains 3.0–12.0% rare earth metal element RE, aiming to construct a brazable aluminum alloy material system with a solidus temperature exceeding 625 °C by forming a eutectic structure with a high eutectic temperature and a high volume fraction of high-temperature stable phase. Small amounts of Fe, Mn, and Cr are added to improve anti-sticking properties. However, the tensile strength of this alloy system after brazing is relatively low, making it difficult to meet the requirements of applications with high load-bearing capacity.

[0009] Chinese patent application CN 202410815545.1 discloses a low thermal conductivity Al-Fe-Mn die-cast aluminum alloy that can be brazed at high temperatures. This alloy contains, by mass percentage: Fe 1.2-1.8 wt%, Mn 2.2-2.7 wt%, and trace amounts of Si, Cr, Ti, and Sm. The alloy has a solidus temperature above 625 ℃, a cast tensile strength exceeding 200 MPa, and maintains a tensile strength above 150 MPa after brazing. Its thermal conductivity is 80-100 W / (m·K). However, its elongation at break is low, only 3.5-6%, posing certain safety risks.

[0010] In summary, existing technologies struggle to simultaneously achieve high eutectic temperatures to meet brazing requirements while also ensuring excellent mechanical properties, low thermal conductivity, and low cost. Summary of the Invention

[0011] To overcome the shortcomings and deficiencies of existing technologies, the present invention aims to provide a high-strength, low-thermal-conductivity castable rare-earth aluminum alloy suitable for brazing and its preparation method. The alloy of the present invention uses La and / or Ce as the main rare-earth elements. This alloy system possesses good casting performance, excellent mechanical properties, low thermal conductivity, simple preparation process, relatively low cost, and a high eutectic temperature. The aluminum alloy of the present invention has a thermal conductivity of 95 W / (m·K)-98.3 W / (m·K), a room temperature tensile strength of 220 MPa-240.3 MPa, and a eutectic temperature of 636.38 ℃-638.68 ℃. This alloy can meet the comprehensive requirements of high strength, low thermal conductivity, and brazing capability for aluminum alloy materials in thermal management systems, and has broad application prospects and promotion potential in key components requiring low thermal conductivity, such as refrigerant storage tanks and refrigerant manifolds in new energy vehicles.

[0012] This invention is achieved through the following technical solution:

[0013] A high-strength, low-thermal-conductivity cast rare-earth aluminum alloy suitable for brazing is composed of the following components by weight percentage;

[0014] RE: 9~11%, where RE is La and / or Ce;

[0015] Mn: 0.8~1.2%;

[0016] Mg: 0.4~1%

[0017] Impurities: ≤ 0.20%;

[0018] The balance is Al.

[0019] The method for preparing the high-strength, low-thermal-conductivity cast rare-earth aluminum alloy suitable for brazing includes the following steps:

[0020] 1) Melt pure aluminum, Al-RE master alloy and Al-Mn 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.

[0021] 2) The melt is cast to obtain a high-strength, low-thermal-conductivity cast rare-earth aluminum alloy suitable for brazing.

[0022] The melting temperature in step 1) is 750-800 ℃; the casting temperature is 720-730 ℃.

[0023] The Al-RE master alloy mentioned in step 1) is Al-20La and / or Al-20Ce, the Al-Mn master alloy is Al-10Mn, and the Al-Mg master alloy is Al-10Mg.

[0024] 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.

[0025] The slag-removing 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.

[0026] The casting mentioned in step 2) refers to pouring the molten material into a preheated (180-220 ℃) ​​metal mold to form an ingot.

[0027] The principle of this invention:

[0028] 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). First, the extremely low diffusion coefficient of RE atoms in the Al matrix endows the alloy with excellent high-temperature stability, making it less prone to ablation or thermal softening during brazing and heat treatment. Second, the extremely low equilibrium solid solubility of RE atoms in the Al matrix, with a solubility abrupt change near the eutectic point, tends to form nanoscale Al atoms. 11 The RE3 eutectic phase was dispersed and precipitated using 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.

[0029] Adding manganese (Mn) to near-eutectic Al-RE alloys can significantly improve alloy strength and reduce thermal conductivity without substantially lowering the eutectic temperature. This is because Mn has high solid solubility in the α-Al matrix and tends to form a substitutional solid solution after addition. Simultaneously, Mn atoms differ significantly from Al atoms in atomic size, valence, and electron configuration, causing significant lattice distortion in the matrix after solid solution, enhancing the scattering of free electrons and thus significantly reducing the alloy's thermal conductivity. Further adding an appropriate amount of magnesium (Mg) with a high eutectic composition to near-eutectic Al-RE-Mn alloys compensates for the low limiting solid solution content of Mn in the α-Al matrix. Utilizing the solid solution strengthening effect of Mg in the α-Al phase, strength is further improved and thermal conductivity reduced. However, it is important to note that excessive addition of Mg will lower the eutectic temperature of the alloy; therefore, its content must be strictly controlled.

[0030] The aluminum alloy of the present invention has the characteristics of high strength, low thermal conductivity and good brazingability due to the combined effect of various elements.

[0031] The present invention has the following advantages and beneficial effects:

[0032] (1) High strength: This invention utilizes high volume fraction eutectic Al 11 The synergistic effect of the second-phase strengthening of the RE3 phase and the solid solution strengthening of Mn and Mg elements endows the alloy with excellent mechanical properties.

[0033] (2) Good brazing properties: The alloy system has a very high eutectic temperature (greater than 635℃), and thanks to the low solid solubility and slow diffusion rate of RE atoms in the α-Al matrix, its microstructure has excellent thermal stability and can be well adapted to the hard brazing process.

[0034] (3) Low thermal conductivity: Mn atoms can be dissolved in a large amount in the α-Al matrix, and its intrinsic parameters such as atomic size and valence are significantly different from those of Al atoms, which can effectively enhance the scattering effect on free electrons, thereby significantly reducing the thermal conductivity of the alloy.

[0035] (4) Simple process and controllable cost: The preparation process is simple, and the raw materials, energy consumption and production costs are low. There is no need to change the existing mature production line. In addition, the alloy's high tolerance to Mn element makes it possible to use recycled aluminum raw materials with high Mn content, which can further reduce costs. Attached Figure Description

[0036] Figure 1 The image shows the SEM microstructure of the as-cast Al-10Ce alloy in Comparative Example 1.

[0037] Figure 2The image shows the SEM microstructure of the as-cast Al-10Ce-0.5Mn alloy in Comparative Example 2.

[0038] Figure 3 The image shows the SEM microstructure of the as-cast Al-10Ce-1.0Mn-0.5Mg alloy in Example 1.

[0039] Figure 4 The image shows the SEM microstructure of the as-cast Al-10Ce-1.0Mn-1.0Mg alloy in Example 2.

[0040] Figure 5 The image shows the SEM microstructure of the as-cast Al-4La-6Ce-1.0Mn-1.0Mg alloy in Example 4.

[0041] Figure 6 The image shows the SEM microstructure of the as-cast Al-10Ce-1.0Mn alloy in Comparative Example 3. Detailed Implementation

[0042] 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.

[0043] Comparative Example 1

[0044] To better illustrate the effects of this invention, a cast binary near-eutectic Al-Ce alloy without additional Mn was used as Comparative Example 1. The composition and content of the aluminum alloy in this comparative example are: Ce: 10 wt%, balance Al.

[0045] The preparation method of the aluminum alloy in this comparative example includes the following steps:

[0046] 1) Preheating: Place the metal mold in a 200 ℃ constant temperature oven for preheating;

[0047] 2) Based on the composition and content of the aluminum alloy, weigh industrial pure aluminum and Al-20Ce master alloy, place them in a crucible, and melt them at high temperature in a resistance furnace (melting temperature is 750 ℃); after melting, stir for 2 minutes to promote homogenization. After the melt cools to the casting temperature (720 ℃), add a slag remover (commercially available YT-J-1 refining agent and YT-D-4 refining agent mixed in a mass ratio of 1:1; the amount added is 1% of the melt mass) for purification, and stir to remove slag (stir for 5 minutes).

[0048] 3) After the alloy melt temperature stabilizes (maintained at 720 ℃), the alloy melt is poured into a preheated metal mold at a casting temperature of 720 ℃ to obtain an alloy ingot.

[0049] Comparative Example 2

[0050] To better illustrate the implementation effect of the present invention, a cast ternary Al-Ce-Mn alloy with a small amount of Mn added is used as Comparative Example 2. The composition and content of the aluminum alloy in this comparative example are: Ce: 10 wt%, Mn: 0.5 wt%, balance Al.

[0051] The preparation method of the aluminum alloy in this comparative example includes the following steps:

[0052] 1) Preheating: Place the metal mold in a 200 ℃ constant temperature oven for preheating;

[0053] 2) Based on the composition and content of the aluminum alloy, weigh industrial pure aluminum, Al-20Ce and Al-10Mn master alloy and place them in a crucible. Melt them at high temperature in an electric resistance furnace (melting temperature is 750 ℃). After melting, stir for 2 minutes to promote homogenization. After the melt cools to the casting temperature (720 ℃), add slag remover to purify and stir to remove slag.

[0054] 3) After the alloy melt temperature stabilizes (maintained at 720 ℃), the alloy melt is poured into a preheated metal mold at a casting temperature of 720 ℃ to obtain an alloy ingot.

[0055] Figure 1 and Figure 2 SEM micrographs of alloys from Comparative Example 1 and Comparative Example 2 are shown. Comparative Example 1 contains only primary α-Al phase and (α-Al + Al) phase. 11 The alloy has a binary eutectic structure (Ce3), but when 0.5 wt.% of Mn was added to the alloy (Comparative Example 2), no new Mn-containing second phase appeared. Instead, the Mn-containing second phase tended to be completely dissolved in the α-Al matrix.

[0056] Example 1

[0057] To better illustrate the effects of this invention, Example 1 is an Al-Ce-Mn-Mg based alloy with rare earth element Ce as the main alloying element and a relatively high amount of Mn element, synergistically reinforced by Mg atom solid solution. This example provides a brazable castable near-eutectic rare earth aluminum alloy with both low thermal conductivity and high strength obtained through alloying. The composition and content of the rare earth aluminum alloy in this example are: Ce: 10 wt%, Mn: 1.0 wt%, Mg: 0.5 wt%, balance Al.

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

[0059] 1) Preheat the metal mold in a 200 ℃ constant temperature oven (preheat to 200 ℃);

[0060] 2) Based on the composition and content of the aluminum alloy, weighed industrial pure aluminum, Al-20Ce and Al-10Mn master alloy are placed into a crucible and melted at high temperature in an electric resistance furnace (melting temperature is 750 ℃). After melting, stir for 2 minutes to promote homogenization. After the melt cools to the casting temperature (720 ℃), add Al-10Mg master alloy, melt and stir evenly (stir for 2 minutes). 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 720 ℃), the alloy melt is poured into a preheated metal mold at a casting temperature of 720 ℃ to obtain an alloy ingot.

[0062] Example 2

[0063] To better illustrate the implementation effect of the present invention, Example 2 is an Al-Ce-Mn-Mg based alloy with rare earth Ce as the main alloying element and a relatively high amount of Mn element, synergistically reinforced by Mg atom solid solution. This example provides a brazable castable near-eutectic rare earth aluminum alloy with both low thermal conductivity and high strength obtained through alloying. The composition and content of the rare earth aluminum alloy in this example are: Ce: 10 wt%, Mn: 1.0 wt%, Mg: 1.0 wt%, balance Al.

[0064] The method for preparing rare earth aluminum alloy in this embodiment includes the following steps:

[0065] 1) Preheating: Place the metal mold in a 200 ℃ constant temperature oven for preheating;

[0066] 2) Based on the composition and content of the aluminum alloy, weighed industrial pure aluminum, Al-20Ce and Al-10Mn master alloy are placed into a crucible and melted at high temperature in an electric resistance furnace (melting temperature is 750 ℃). After melting, stir for 2 minutes to promote homogenization. After the melt cools to the casting temperature (720 ℃), add Al-10Mg master alloy, melt and stir evenly (stir for 2 minutes). Add slag remover to purify the melt and stir to remove slag and floating dross.

[0067] 3) After the alloy melt temperature stabilizes (maintained at 720 ℃), pour the alloy melt into a preheated metal mold at a casting temperature of 720 ℃ to obtain an alloy ingot.

[0068] Example 3

[0069] To better illustrate the effects of this invention, Example 3 uses an Al-La-Mn-Mg-based alloy with rare earth element La as the main alloying element and a relatively high amount of Mn element, synergistically reinforced by Mg atom solid solution. This example provides a brazable castable near-eutectic rare earth aluminum alloy with both low thermal conductivity and high strength obtained through alloying. The composition and content of the rare earth aluminum alloy in this example are: La: 10 wt%, Mn: 1.0 wt%, Mg: 1.0 wt%, balance Al.

[0070] The method for preparing rare earth aluminum alloy in this embodiment includes the following steps:

[0071] 1) Preheating: Place the metal mold in a 200 ℃ constant temperature oven for preheating;

[0072] 2) Based on the composition and content of the aluminum alloy, weighed industrial pure aluminum, Al-20La and Al-10Mn master alloy are placed into a crucible and melted at high temperature in an electric resistance furnace (melting temperature is 750 ℃). After melting, stir for 2 minutes to promote homogenization. After the melt cools to the casting temperature (720 ℃), add Al-10Mg master alloy, melt and stir evenly. Add slag remover to purify the melt and stir to remove slag and floating dross.

[0073] 3) After the alloy melt temperature stabilizes (maintained at 720 ℃), the alloy melt is poured into a preheated metal mold at a casting temperature of 720 ℃ to obtain an alloy ingot.

[0074] Example 4

[0075] To better illustrate the implementation effects of the present invention, Example 4 uses an Al-La-Mn-Mg-based alloy with La-Ce mixed rare earth (MM) as the main alloying element and a relatively high amount of Mn element, synergistically reinforced by Mg atom solid solution. This example provides a brazable castable near-eutectic rare earth aluminum alloy with both low thermal conductivity and high strength obtained through alloying. The composition and content of the rare earth aluminum alloy in this example are: La: 4 wt%, Ce: 6 wt%, Mn: 1.0 wt%, Mg: 1.0 wt%, balance Al.

[0076] The method for preparing rare earth aluminum alloy in this embodiment includes the following steps:

[0077] 1) Preheating: Place the metal mold in a 200 ℃ constant temperature oven for preheating;

[0078] 2) Based on the composition and content of the aluminum alloy, weighed industrial pure aluminum, Al-20La, Al-20Ce and Al-10Mn master alloy are placed into a crucible and melted at high temperature in an electric resistance furnace (melting temperature is 750 ℃). After melting, stir for 2 minutes to promote homogenization. After the melt cools to the casting temperature (720 ℃), add Al-10Mg master alloy, melt and stir evenly. Add slag remover to purify the melt and stir to remove slag and floating dross.

[0079] 3) After the alloy melt temperature stabilizes (maintained at 720 ℃), the alloy melt is poured into a preheated metal mold at a casting temperature of 720 ℃ to obtain an alloy ingot.

[0080] Figure 3 This is a SEM microstructure image of the as-cast Al-10Ce-1Mn-0.5Mg alloy in Example 1.

[0081] Figure 4 This is a SEM microstructure of the as-cast Al-10Ce-1Mn-1.0Mg alloy in Example 2.

[0082] Figure 5 The image shows the SEM microstructure of the as-cast Al-4La-6Ce-1Mn-1.0Mg alloy in Example 4.

[0083] from Figures 3-5 As can be seen from the data, increasing the Mn content and adding Mg resulted in the precipitation of primary Al in the alloy's microstructure. 20 The REMn2 phase, and the volume fraction of this phase gradually increases with increasing Mg content; the eutectic structure remains (α-Al + Al). 11 RE3) binary eutectic, in addition, all Mg elements are in solid solution and Mn elements are partially in solid solution inside the α-Al matrix.

[0084] Comparative Example 3

[0085] To better illustrate the effects of this invention, an Al-Ce-Mn based alloy strengthened with a single element Mn but without Mg atom solid solution reinforcement was used as Comparative Example 3. The composition and content of the aluminum alloy in this comparative example are: Ce: 10wt%, Mn: 1.0wt%, with the balance being Al.

[0086] The preparation method of the aluminum alloy in this comparative example includes the following steps:

[0087] 1) Preheating: Place the metal mold in a 200 ℃ constant temperature oven for preheating;

[0088] 2) Based on the composition and content of the aluminum alloy, weigh industrial pure aluminum, Al-20Ce and Al-10Mn 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 alloy melt temperature stabilizes (maintained at 760℃), pour the alloy melt into a preheated metal mold. The casting temperature is 760℃ to obtain an alloy ingot.

[0089] Figure 6 The image shows the SEM microstructure of Comparative Example 3. The microstructure of this alloy still consists of (α-Al + Al) 11 The structure consists of a binary eutectic of Ce3, but since no Mg element was added, no primary Al precipitates in the microstructure. 20 In the REMn2 phase, all Mn atoms are completely dissolved in the α-Al matrix.

[0090] The aluminum alloy composition and content of Comparative Examples 1-3 and Example-4 are shown in Table 1.

[0091] Table 1. Composition and content (wt.%) of each alloy in Comparative Examples 1-3 and Examples 1-4

[0092]

[0093] The thermal conductivity, mechanical properties, and solidification process of the aluminum alloys in Examples 1-4 and Comparative Examples 1-3 were tested respectively, and the test results are shown in Table 2.

[0094] Table 2 Thermal conductivity, mechanical properties, and eutectic temperature of each alloy in Comparative Examples 1-3 and Examples 1-4

[0095]

[0096] As shown in Table 2, alloying with only a small amount of Mn (Comparative Example 2) only slightly improves the strength of the alloy, and the thermal conductivity of the alloy remains at a high level. However, by adding a higher content of Mn and Mg to the alloy, not only does the Mn element precipitate primary Al, but the Mg element also contributes to the overall improvement. 20The REMn2 phase acts as a second-phase strengthening agent. Furthermore, due to the synergistic solid solution strengthening effect of Mn and Mg atoms, the alloy strength is significantly improved, reaching 220.8 MPa and 235.7 MPa, respectively. Moreover, because solid solution atoms cause significant lattice distortion and a high degree of scattering of free electrons, the thermal conductivity of the Mn-Mg synergistically strengthened alloy is correspondingly lower. However, since Mg atom alloying leads to the precipitation of solid solution Mn atoms as a primary phase, the thermal conductivity of Example 2 is slightly higher than that of Example 1. Examples 3 and 4 exhibit similar overall performance to Example 2, 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, due to the lack of solid solution Mg atom strengthening effect, the tensile strength of the alloy is low, only 195.8 MPa.

[0097] 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 by adding appropriate amounts of Mn and Mg elements, while ensuring the eutectic temperature of the alloy, improving the strength of the alloy and reducing the thermal conductivity of the alloy, also falls within the protection scope of the present invention.

Claims

1. A high-strength, low-thermal-conductivity cast rare-earth aluminum alloy suitable for brazing, characterized in that: Composed of the following components by weight percentage composition: RE: 9~11%, wherein the RE is La and / or Ce; Mn: 0.8~1.2%; Mg: 0.4~1% Impurities: ≤ 0.20%; The balance is Al.

2. The high-strength, low-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%, wherein the RE is La and / or Ce; Mn: 0.9~1.1%; Mg: 0.5~1% Impurities: ≤ 0.20%; The balance is Al.

3. The method for preparing a high-strength, low-thermal-conductivity cast rare-earth aluminum alloy suitable for brazing according to any one of claims 1 to 2, characterized in that: Includes the following steps: 1) Melt pure aluminum, Al-RE master alloy and Al-Mn 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 to obtain a high-strength, low-thermal-conductivity cast rare-earth aluminum alloy suitable for brazing.

4. The method for preparing a high-strength, low-thermal-conductivity cast rare-earth aluminum alloy suitable for brazing according to claim 3, characterized in that: The melting temperature in step 1) is 750-800 ℃; the casting temperature is 720-730 ℃. The Al-RE master alloy mentioned in step 1) is Al-20La and / or Al-20Ce, the Al-Mn master alloy is Al-10Mn, and the Al-Mg master alloy is Al-10Mg.

5. The method for preparing a high-strength, low-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. The casting mentioned in step 2) refers to pouring the molten material into a metal mold with a preheated temperature of 180-220 ℃, forming it, and obtaining an ingot.

6. The method for preparing a high-strength, low-thermal-conductivity cast rare-earth aluminum alloy suitable for brazing according to claim 3, 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 application of the high-strength, low-thermal-conductivity cast rare-earth aluminum alloy suitable for brazing according to any one of claims 1 to 2, characterized in that: The high-strength, low-thermal-conductivity cast rare-earth aluminum alloy suitable for brazing is used in refrigerant storage tanks and refrigerant manifolds for new energy vehicles.

8. The application of the high-strength, low-thermal-conductivity cast rare-earth aluminum alloy suitable for brazing according to any one of claims 1 to 2, characterized in that: The high-strength, low-thermal-conductivity cast rare-earth aluminum alloy is used in refrigerant storage tanks and / or refrigerant manifolds by brazing.

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