A brazable high thermal conductivity high pressure die cast aluminium alloy

Abstract

The application discloses a brazable high-thermal-conductivity high-pressure die-casting aluminum alloy and belongs to the technical field of aluminum alloy casting. The aluminum alloy contains the following elements in percentage by weight: RE 5-15%, Fe 0.3-0.6%, Mn 0.2-1.0%, Hf 0.05-0.5%, Ta 0.3-0.8%, Si≤0.5%, ≤0.05% of single impurity, <0.15% of total amount, and the rest is Al. The brazable high-thermal-conductivity high-pressure die-casting aluminum alloy obtained by the application has a high thermal conductivity coefficient, meanwhile, the alloy has a high melting point and can meet the temperature of high-temperature brazing.

Description

Technical Field

[0001] This invention belongs to the field of high-pressure die-casting technology of aluminum alloys, and specifically relates to a brazable high thermal conductivity high-pressure die-cast aluminum alloy. Background Technology

[0002] Aluminum alloys are widely used in the automotive industry due to their low density, excellent thermal conductivity, good machinability, and excellent corrosion resistance. High-pressure die casting technology, with its advantages of high production efficiency and low production cost, has become the main processing technology for manufacturing aluminum alloy parts. With the rapid development of the new energy vehicle industry, the requirements for lightweighting and thermal conductivity are increasing. The hot runner system, as a crucial system in new energy vehicles, has numerous branching channels, a complex structure, and many holes requiring sealing, making the processing and assembly process cumbersome. To avoid the drawbacks of drilling, the integral hot runner plate is divided into multiple plates and then connected as a whole by brazing. However, the melting point of high-pressure cast aluminum alloys is low, which cannot reach the high-temperature brazing temperature. Alternatively, alloys with high melting points have poor casting fluidity and high shrinkage, making them unsuitable for current high-pressure casting processes. This problem limits the application of brazing technology and affects the development of the automotive industry. Therefore, there is an urgent need for a brazable, high-thermal-conductivity high-pressure die-cast aluminum alloy to address the shortcomings of existing technologies. Summary of the Invention

[0003] In view of the above-mentioned defects or deficiencies in the prior art, it is desirable to provide a brazable high thermal conductivity high pressure die-cast aluminum alloy that has both a high thermal conductivity and a high melting point, which can meet the temperature requirements for high-temperature brazing.

[0004] The present invention discloses a brazable high thermal conductivity high pressure die-cast aluminum alloy, the elements contained therein by weight percentage are as follows: RE 5~15%, Fe 0.3-0.6%, Mn 0.2-1.0%, Hf 0.05-0.5%, Ta 0.3-0.8%, Sr 0.01-0.08%, Si≤0.5%, other individual impurities≤0.05%, total <0.15%, and the remainder is Al.

[0005] Preferably, the unavoidable impurities contain ≤0.02% Ti and ≤0.01% other impurity elements by mass percentage; the other impurity elements include Cr and Zr.

[0006] Compared with the prior art, the beneficial effects of the present invention are: The present invention provides a brazable high thermal conductivity high pressure die-cast aluminum alloy based on alloying concept and composition calculation, incorporating RE, Fe, Mn, Hf, Ta, Sr and Si to design a brazable high thermal conductivity high pressure die-cast aluminum alloy; The RE element is La / Yb.

[0007] The addition of La / Yb elements can purify the matrix, reduce defects, and increase thermal conductivity; at the same time, the addition of La / Yb elements ensures a high eutectic temperature, ensuring that the material has good high-temperature stability.

[0008] The addition of Fe can reduce the adhesion of aluminum alloy to steel mold during die casting, reduce sticking, improve the demolding effect of aluminum alloy, and thus improve the die casting effect.

[0009] The addition of Mn can improve the morphology of iron-containing intermetallic compounds and enhance their thermal conductivity.

[0010] Hf elements can form Al3Hf particles with Al, which can serve as an effective heterogeneous nucleation substrate for α-Al, significantly refining the α-Al grains in the high-pressure casting structure. This improves the fluidity and feeding ability of the melt, effectively suppressing hot cracking and shrinkage porosity. At the same time, the dispersed Al3Hf can effectively pin grain boundaries during the subsequent brazing heating process, inhibiting grain boundary slip and micro-hot cracking, thus ensuring the dimensional stability of thin-walled high-pressure castings at the high temperature of brazing.

[0011] The addition of Ta helps improve the fluidity of molten aluminum, making it easier to fill the complex cavities of the mold; at the same time, Ta can absorb the hydrogen content in the molten aluminum, reduce defects, and increase thermal conductivity.

[0012] Sr forms a small amount of Al4Sr in Al liquid, providing a certain volume fraction of "quasi-eutectic" liquid film under low Si conditions, which prolongs the fluidity length of the alloy; at the same time, Sr has a higher eutectic temperature, ensuring the reliability of brazing.

[0013] The addition of silicon can improve the flowability of the alloy, but excessive silicon will lower the solidus temperature of the material, affecting brazing. Furthermore, silicon reacts with iron to form the AlFeSi phase, which reduces the elongation of the material, hinders electron movement, and reduces thermal conductivity. It is preferable that the silicon content is at most 0.5%.

[0014] The brazable high thermal conductivity high-pressure die-cast aluminum alloy obtained by this invention has a high thermal conductivity and a high melting point, which can meet the temperature requirements for high-temperature brazing.

[0015] It should be understood that the description in the Summary of the Invention is not intended to limit the key or essential features of the embodiments of the present invention, nor is it intended to restrict the scope of the invention. Other features of the invention will become readily apparent from the following description. Attached Figure Description

[0016] Other features, objects, and advantages of the invention will become more apparent from the following detailed description of non-limiting embodiments with reference to the accompanying drawings: Figure 1The figure shows the temperature versus solid fraction curve of the brazable high thermal conductivity high-pressure die-cast aluminum alloy in this embodiment of the invention. Detailed Implementation

[0017] The present invention will now be described in further detail with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and not intended to limit it. Furthermore, it should be noted that, for ease of description, only the parts relevant to the invention are shown in the accompanying drawings.

[0018] It should be noted that, unless otherwise specified, the embodiments and features described in the present invention can be combined with each other. The present invention will now be described in detail with reference to the accompanying drawings and embodiments.

[0019] Embodiments of the present invention provide a brazable high thermal conductivity high-pressure die-cast aluminum alloy, comprising the following components by mass percentage: RE 5~15%, Fe 0.3-0.6%, Mn 0.2-1.0%, Hf 0.05-0.5%, Ta 0.3-0.8%, Sr 0.01-0.08%, Si≤0.5%, other individual impurities ≤0.05%, total <0.15%, and the remainder being Al.

[0020] In this embodiment, RE, Fe, Mn, Hf, Ta, Sr and Si were added to the aluminum alloy, and the RE element was La / Yb.

[0021] The addition of La / Yb elements can purify the matrix, reduce defects, and increase thermal conductivity; at the same time, the addition of La / Yb elements ensures a high eutectic temperature, ensuring that the material has good high-temperature stability.

[0022] The addition of Fe can reduce the adhesion of aluminum alloy to steel mold during die casting, reduce sticking, improve the demolding effect of aluminum alloy, and thus improve the die casting effect.

[0023] The addition of Mn can improve the morphology of iron-containing intermetallic compounds and enhance their thermal conductivity.

[0024] Hf elements can form Al3Hf particles with Al, which can serve as an effective heterogeneous nucleation substrate for α-Al, significantly refining the α-Al grains in the high-pressure casting structure. This improves the fluidity and feeding ability of the melt, effectively suppressing hot cracking and shrinkage porosity. At the same time, the dispersed Al3Hf can effectively pin grain boundaries during the subsequent brazing heating process, inhibiting grain boundary slip and micro-hot cracking, thus ensuring the dimensional stability of thin-walled high-pressure castings at the high temperature of brazing.

[0025] The addition of Ta helps improve the fluidity of molten aluminum, making it easier to fill the complex cavities of the mold; at the same time, Ta can absorb the hydrogen content in the molten aluminum, reduce defects, and increase thermal conductivity.

[0026] Sr forms a small amount of Al4Sr in Al liquid, providing a certain volume fraction of "quasi-eutectic" liquid film under low Si conditions, which prolongs the fluidity length of the alloy; at the same time, Sr has a higher eutectic temperature, ensuring the reliability of brazing.

[0027] The addition of silicon can improve the flowability of the alloy, but excessive silicon will lower the solidus temperature of the material, affecting brazing. Furthermore, silicon reacts with iron to form the AlFeSi phase, reducing the material's elongation, hindering electron movement, and decreasing thermal conductivity. Therefore, a silicon content of no more than 0.5% is preferred. The brazable high thermal conductivity high-pressure die-cast aluminum alloy prepared in this application has a high thermal conductivity and a high melting point, which can meet the temperature requirements for high-temperature brazing. Example

[0028] The raw materials used are commercially available pure Al ingots, Al-La master alloys, Al-Yb master alloys, Al-Fe master alloys, Al-Mn master alloys, Al-Hf master alloys, Al-Ta master alloys, Al-Sr master alloys, and Al-Si master alloys. The purity of the pure Al ingots is 99.99%. The Al-La master alloy is Al-5La master alloy, the Al-Yb master alloy is Al-5Yb master alloy, the Al-Fe master alloy is Al-10Fe master alloy, the Al-Mn master alloy is Al-5Mn master alloy, the Al-Hf master alloy is Al-5Hf master alloy, the Al-Ta master alloy is Al-5Ta master alloy, and the Al-Si master alloy is Al-30Si master alloy.

[0029] Weigh each component raw material according to its mass fraction; unavoidable impurities contain ≤0.02% Ti and ≤0.01% other impurity elements by mass fraction; other impurity elements include Cr and Zr; The high-pressure cast aluminum alloys described in the examples were prepared using the above-described preparation process. Their chemical composition was analyzed, as shown in Table 1. Then, their thermal conductivity was tested, as shown in Table 2. The temperature versus solid fraction curves of the prepared brazable, high thermal conductivity high-pressure cast aluminum alloys are shown below. Figure 1 This indicates that the high thermal conductivity high-pressure die-cast aluminum alloy that can be brazed has a melting point ≥630℃, which meets the temperature requirements for high-temperature brazing, and also has a high thermal conductivity of 160.67 W / (m·K).

[0030] Example 6.5 0.5 0.3 0.4 0.6 0.06 0.3 ≤0.01% margin

[0031] Example 1 67.5±0.3 2.66±0.01 0.89±0.01 160.67±0.57 In the description of this specification, the terms "one embodiment," "some embodiments," etc., refer to specific features, structures, materials, or characteristics described in connection with that embodiment or example, which are included in at least one embodiment or example of this application. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples.

[0032] The above are merely preferred embodiments of this application and are not intended to limit this application. Various modifications and variations can be made to this application by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this application should be included within the protection scope of this application.

Claims

1. A brazable, high thermal conductivity, high-pressure die-cast aluminum alloy, characterized in that, The elements contained, by weight percentage, are as follows: RE 5~15%, Fe 0.3-0.6%, Mn 0.2-1.0%, Hf 0.05-0.5%, Ta 0.3-0.8%, Sr 0.01-0.08%, Si≤0.5%, other individual impurities≤0.05%, total <0.15%, and the remainder is Al.

2. The method for preparing a brazable, high thermal conductivity, high-pressure die-cast aluminum alloy according to claim 1, characterized in that, The alloy is a self-developed, brazable, high thermal conductivity, high-pressure die-cast aluminum alloy.

3. The brazable high thermal conductivity high-pressure die-cast aluminum alloy according to claim 1, characterized in that, The RE element is La / Yb.

4. The brazable high thermal conductivity high-pressure die-cast aluminum alloy according to claim 1, characterized in that... In step (1), the addition of La / Yb elements can purify the matrix, reduce defects, and increase thermal conductivity; at the same time, the addition of La / Yb elements ensures a high eutectic temperature and ensures that the material has good high-temperature stability.

5. The brazable high thermal conductivity high-pressure die-cast aluminum alloy according to claim 1, characterized in that, The addition of Fe can reduce the adhesion of aluminum alloy to steel mold during die casting, reduce sticking, improve the demolding effect of aluminum alloy, and thus improve the die casting effect.

6. The brazable high thermal conductivity high-pressure die-cast aluminum alloy according to claim 1, characterized in that, The addition of Mn can improve the morphology of iron-containing intermetallic compounds and enhance their thermal conductivity.

7. The brazable high thermal conductivity high-pressure die-cast aluminum alloy according to claim 1, characterized in that, Hf elements can form Al3Hf particles with Al, which can serve as an effective heterogeneous nucleation substrate for α-Al, significantly refining the α-Al grains in the high-pressure casting structure. This improves the fluidity and feeding ability of the melt, effectively suppressing hot cracking and shrinkage porosity. At the same time, the dispersed Al3Hf can effectively pin grain boundaries during the subsequent brazing heating process, inhibiting grain boundary slip and micro-hot cracking, thus ensuring the dimensional stability of thin-walled high-pressure castings at the high temperature of brazing.

8. The brazable high thermal conductivity high-pressure die-cast aluminum alloy according to claim 1, characterized in that, The addition of Ta helps improve the fluidity of molten aluminum, making it easier to fill the complex cavities of the mold; at the same time, Ta can absorb the hydrogen content in the molten aluminum, reduce defects, and increase thermal conductivity.

9. The brazable high thermal conductivity high-pressure die-cast aluminum alloy according to claim 1, characterized in that, Sr forms a small amount of Al4Sr in Al liquid, providing a certain volume fraction of "quasi-eutectic" liquid film under low Si conditions, which extends the fluidity length of the alloy; at the same time, Sr has a higher eutectic temperature, ensuring the reliability of brazing.

10. A brazable, high thermal conductivity, high-pressure die-cast aluminum alloy according to claim 1, characterized in that, The addition of silicon can improve the flowability of the alloy, but excessive silicon will lower the solidus temperature of the material, affecting brazing. In addition, silicon reacts with iron to form the AlFeSi phase, which reduces the elongation of the material, hinders electron movement, and reduces thermal conductivity. It is preferable that the silicon content is no more than 0.5% by weight.

11. The brazable high thermal conductivity high-pressure die-cast aluminum alloy according to claim 1, characterized in that, The thermal conductivity of brazable, high-thermal-conductivity, high-pressure die-cast aluminum alloys is >160 W / (m·K).

12. The brazable high thermal conductivity high-pressure die-cast aluminum alloy according to claim 1, characterized in that, The brazable, high thermal conductivity, high-pressure die-cast aluminum alloy has a melting point ≥625℃.

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