Transition layer material for copper-aluminum dissimilar material connection and preparation method thereof

Abstract

The present application relates to a transition layer material for copper-aluminum dissimilar material connection and a preparation method thereof, and belongs to the technical field of welding.The transition layer material for copper-aluminum dissimilar material connection comprises a copper-zinc alloy and a zinc-aluminum alloy; the mass ratio of the copper-zinc alloy and the zinc-aluminum alloy is (2.8-3.2):(1.8-2.2); the copper-zinc alloy is adjacent to a copper base material, and the zinc-aluminum alloy is adjacent to an aluminum base material; the zinc content in the copper-zinc alloy is 15%-36%, and the aluminum content in the zinc-aluminum alloy is 6%-10%. By arranging the copper-zinc alloy and the zinc-aluminum alloy with a specific ratio between copper-aluminum dissimilar materials, effective metallurgical transition between copper-aluminum dissimilar materials is realized, the technical problem that brittle Al-Cu intermetallic compounds are generated due to large thermal physical property differences of copper-aluminum dissimilar materials is solved, the comprehensive performance of a copper-aluminum welded joint is significantly improved, and the application requirements of high-end equipment welding manufacturing are met.

Description

Technical Field

[0001] This invention belongs to the field of welding technology, and particularly relates to transition layer materials for joining dissimilar copper and aluminum materials and their preparation methods. Background Technology

[0002] Aluminum and copper, as common structural materials in industry, are widely used in electronic equipment, power transmission, automotive lightweighting, and aerospace industries due to their excellent electrical and thermal conductivity and lightweight properties. However, direct welding of aluminum and copper presents several technical challenges, mainly in the following aspects: First, differences in physical and chemical properties. Aluminum and copper have significantly different melting points and coefficients of thermal expansion. Aluminum's melting point is approximately 660℃, while copper's is as high as 1085℃. Aluminum's coefficient of thermal expansion is about 40% higher than copper's. This difference leads to defects such as uneven melting and cracking during welding, making it difficult to form a stable weld joint. Second, the formation of intermetallic compounds. Under high-temperature conditions, direct contact between aluminum and copper will cause a reaction to form brittle intermetallic compounds such as CuAl2 and Cu9Al4. These compounds have high hardness and brittleness, severely affecting the mechanical properties and reliability of the weld joint.

[0003] Existing technologies typically employ transition layer materials to mitigate the differences in physical and chemical properties between aluminum and copper. Typical transition layer materials include zinc and nickel. Invention patent CN 112975204 A discloses a self-fluxing filler metal and welding method for welding dissimilar aluminum-copper materials. Adding a self-fluxing filler metal and pre-placed nickel transition layer to the aluminum-copper dissimilar materials effectively prevents the formation of brittle alloys and synergistically enhances the uniformity of the weld seam phases. Patent CN 214395739 U discloses a pre-formed structure beneficial for aluminum-copper welding, where a pre-placed nickel transition layer in the aluminum-copper dissimilar materials improves the joint bonding strength. The transition layer can act as an intermediary during welding, reducing the reaction between aluminum and copper and minimizing the brittle phases generated by direct contact. However, the selection of the transition layer material, its composition design, and the choice of welding process significantly affect the performance of the final weld joint. Existing transition layer materials cannot yet solve the problems of brittle phase formation and low joint strength in aluminum-copper welding. Summary of the Invention

[0004] To address the aforementioned technical problems, this invention provides a transition layer material for joining dissimilar copper and aluminum materials and its preparation method. By setting a specific ratio of copper-zinc alloy and zinc-aluminum alloy between the dissimilar copper and aluminum materials, an effective metallurgical transition between the two materials is achieved. This solves the technical problem of the formation of brittle Al-Cu intermetallic compounds due to the large difference in thermal properties between the dissimilar copper and aluminum materials, significantly improving the overall performance of the copper-aluminum welded joint and meeting the application requirements of high-end equipment welding manufacturing.

[0005] The first objective of this invention is to provide a transition layer material for connecting dissimilar copper and aluminum materials, comprising a copper-zinc alloy and a zinc-aluminum alloy; wherein the mass ratio of the copper-zinc alloy to the zinc-aluminum alloy is (2.8-3.2):(1.8-2.2). The zinc content in the copper-zinc alloy is 15%-36%, and the aluminum content in the zinc-aluminum alloy is 6%-10%.

[0006] In one embodiment of the present invention, the elemental composition and mass percentage of the copper-zinc alloy are: Zn 15%-36%, Sn 8%-12%, Al 10%-18%, with the balance being Cu and other unavoidable impurities.

[0007] In one embodiment of the present invention, the elemental composition and mass percentage of the zinc-aluminum alloy are: Al 6%-10%, Cu 0.1%-1.0%, Mg 0.5%-2%, Mn 0.05%-0.5%, Si 0.1%-10%, with the balance being Zn and other unavoidable impurities.

[0008] In one embodiment of the present invention, the form of the transition layer material for connecting copper-aluminum dissimilar materials is selected from one or more of powder, foil, bulk and wire.

[0009] In one embodiment of the present invention, the particle size of the powder is 10μm-250μm; And / or, the thickness of the foil or block is independently 1mm-2mm; And / or, the diameter of the filament is 0.5mm-3.2mm.

[0010] In one embodiment of the present invention, the copper base material is selected from copper alloys or pure copper.

[0011] In one embodiment of the present invention, the aluminum base material is selected from aluminum alloy or pure aluminum.

[0012] In one embodiment of the present invention, the transition layer material is connected to the copper-aluminum dissimilar material by one or more of laser welding, explosive welding, and friction stir welding.

[0013] In one embodiment of the present invention, the process parameters of the laser welding are as follows: laser tilt angle is 10°-15°, defocusing amount is -1mm to 1mm, laser power is 2000W-2500W, welding speed is 10mm / s-15mm / s, the shielding gas is argon and its flow rate is 20L / min-25L / min, and the laser is biased to the base material side by 0.3mm-0.8mm. And / or, the process parameters for the explosive welding are: detonation velocity 1500m / s-2000m / s, charge gap 1.5mm-2mm, and collision angle 5°-10°; And / or, the process parameters for friction stir welding are: stirring head rotation speed of 600rpm-800rpm, welding speed of 80mm / min-100mm / min, and stirring head offset to the aluminum side of 0.2mm-0.3mm.

[0014] A second objective of this invention is to provide a method for preparing the transition layer material for joining copper-aluminum dissimilar materials, comprising the following steps: S1. Prepare metal or intermediate alloy ingots according to the target composition; S2. Melt and cast the metal or intermediate alloy ingot described in S1 to obtain alloy material; And / or, the metal or intermediate alloy ingot described in S1 is smelted and vacuum atomized to obtain alloy material; S3. Perform surface treatment and post-treatment on the alloy material described in S2 to obtain the transition layer material for connecting copper-aluminum dissimilar materials.

[0015] The technical solution of the present invention has the following advantages compared with the prior art: The transition layer material for joining copper-aluminum dissimilar materials described in this invention exhibits good compatibility and interoperability among its various metal elements. Zn enhances the wettability of the molten alloy to copper and aluminum substrates, strengthens the interfacial affinity with Al and Cu, promotes the spread of liquid metal at the interface and the formation of a dense bond, while simultaneously lowering the alloy's melting point and improving its plasticity. As a welding transition layer, it can effectively alleviate welding stress. Among these, the copper-zinc alloy exhibits excellent compatibility with the copper substrate, and Zn reacts with Cu to form a Cu-Zn phase (such as β-brass), which can prevent direct reaction at the copper-aluminum interface. The zinc-aluminum alloy has good compatibility with the aluminum substrate, and Zn reacts with Al to form an Al-Zn solid solution or eutectoid structure, achieving a stable metallurgical bond. This significantly improves the overall performance of the copper-aluminum dissimilar material welded joint and extends its service life.

[0016] The copper-zinc alloy (such as brass) in the transition layer material for joining dissimilar copper and aluminum materials described in this invention has a melting point between that of aluminum and copper (approximately 900°C), which can lower the welding temperature and reduce the heat-affected zone. The zinc-aluminum alloy has an even lower melting point (approximately 380°C), and as a filler material, it can achieve low-temperature bonding through liquid-phase diffusion, reducing residual stress. By using a transition layer material with a specific ratio of copper, zinc, and aluminum content to effectively join dissimilar copper and aluminum materials, the problem of significant differences in physicochemical properties between copper and aluminum in direct bonding is solved, as well as the problem of poor welding performance caused by large differences in thermophysical properties.

[0017] During welding, the transition layer material for joining dissimilar copper and aluminum materials described in this invention allows the Zn, Al, or Cu elements in the copper-zinc alloy or zinc-aluminum alloy to preferentially react with the base material, forming a more flexible intermediate phase (such as an Al-Zn solid solution or a Cu-Zn phase), reducing direct Al-Cu contact and thus inhibiting the formation of brittle Al-Cu intermetallic compounds.

[0018] The transition layer material for connecting copper-aluminum dissimilar materials described in this invention utilizes the good compatibility between copper and high-copper-content copper-zinc alloys, and between high-zinc-content zinc-aluminum alloys and aluminum, to achieve a good metallurgical bond between the transition layer and the copper-aluminum dissimilar material. This results in a high-strength, low-stress, and corrosion-resistant welded joint, suitable for applications requiring lightweight and high strength, such as in the automotive and aerospace industries. This expands the application range of copper-aluminum dissimilar materials in high-performance structural components. Attached Figure Description

[0019] To make the content of this invention easier to understand, the invention will be further described in detail below with reference to specific embodiments and accompanying drawings, wherein: Figure 1 This is a schematic diagram of the welding positions of the copper base material, transition material, and aluminum base material in Embodiment 1 of the present invention; Figure 2 This is a SEM image of the welded joint in Embodiment 1 of the present invention; Figure 3 This is a SEM image of the welded joint of Comparative Example 1 of the present invention; Figure 4 Here is a SEM image of the welded joint of Comparative Example 2 of the present invention; Figure 5 This is a SEM image of the welded joint of Comparative Example 3 of the present invention; Figure 6 The stress-strain curves are for the welded joints of Embodiment 1 and Comparative Example 1 of the present invention. Detailed Implementation

[0020] The present invention will be further described below with reference to the accompanying drawings and specific embodiments, so that those skilled in the art can better understand and implement the present invention. However, the embodiments described are not intended to limit the present invention.

[0021] In this invention, unless otherwise specified, the copper base material used in the embodiments of this invention is a 1.5mm thick brass plate; the aluminum base material is a 1.5mm thick 6061-T6 aluminum alloy plate; before welding, the surface is cleaned with anhydrous ethanol to remove oil, oxides and other contaminants, ensuring the cleanliness of the welding interface to obtain good welding quality.

[0022] Example 1

[0023] The transition layer material for copper-aluminum dissimilar material bonding in this embodiment, its preparation method, and welding process specifically include the following steps: S1. Preparation of copper-zinc alloys: S11. Prepare metals with a purity higher than 99.9% according to the composition ratio of the target copper-zinc alloy; the elemental composition and mass percentage of the copper-zinc alloy are: Zn 20.0%, Sn 10.0%, Al 15%, with the balance being Cu and other unavoidable impurities; S12. Add the corresponding proportions of each metal element to the induction melting furnace for melting at a melting temperature of 1050℃. Keep stirring evenly for 10 minutes, and then cast into a block copper-zinc alloy with a thickness of 3cm. S13. The cast block copper-zinc alloy is rapidly cooled to room temperature, cut into 10cm×6cm×1.5mm pieces, the oxide on the surface of the plate is removed by a belt sander, and then cleaned with alcohol to obtain the copper-zinc alloy. S2, Preparation of zinc-aluminum alloy: S21. Prepare metals with a purity higher than 99.9% according to the composition ratio of the target zinc-aluminum alloy; the elemental composition and mass percentage of the zinc-aluminum alloy are: Al 8%, Cu 0.5%, Mg 2%, Mn 0.1%, Si 1%, with the balance being Zn and other unavoidable impurities; S22, same as S12; S23, same as S13; S3. Welding of dissimilar copper and aluminum materials: Refer to... Figure 1 As shown, four materials (copper-zinc alloy and zinc-aluminum alloy in a mass ratio of 3:2) are fixed on the welding pads, and laser welding is performed on the copper base material and the aluminum base material. The self-fusion laser welding process is as follows: laser tilt angle is 10°, defocusing amount is 0mm, laser power is 2000W, welding speed is 15mm / s, and the shielding gas is pure argon (flow rate is 25L / min) to ensure that the energy of the laser beam is concentrated in the welding area. When laser welding copper base material and copper-zinc alloy, the laser is biased 0.5mm to the copper base material side; when laser welding copper-zinc alloy and zinc-aluminum alloy, the laser is biased 0.5mm to the copper-zinc alloy side; and when laser welding zinc-aluminum alloy and aluminum base material, the laser is biased 0.5mm to the aluminum base material side.

[0024] Comparative Example 1

[0025] It is basically the same as Example 1, except that copper-zinc alloy is not used for fusion welding.

[0026] Comparative Example 2

[0027] It is basically the same as Example 1, except that zinc-aluminum alloy is not used for fusion welding.

[0028] Comparative Example 3

[0029] The process is basically the same as in Example 1, except that a transition layer material is not used for direct fusion welding.

[0030] Test Example 1

[0031] Metallographic analysis was performed on the welded joints of the embodiments and comparative examples, and the results are as follows: Figures 2-5 As shown.

[0032] from Figure 2 As can be seen, in Example 1, a transition layer made of copper-zinc alloy and zinc-aluminum alloy in a mass ratio of 3:2 was used for copper-aluminum laser welding. The weld interface structure was uniform and the transition was smooth. The copper-zinc alloy side showed a uniform simple solid solution structure, while the zinc-aluminum alloy side showed a stable solid solution / eutectoid structure. No brittle Cu-Al intermetallic compounds appeared on either side of the interface. The interface was dense and without obvious defects, achieving good metallurgical bonding and continuous gradient transition.

[0033] from Figure 3 It can be seen that in Comparative Example 1, which did not use copper-zinc alloy, a large number of continuous and coarse Cu-Al brittle intermetallic compounds were generated at the interface where the copper base material and the zinc-aluminum alloy directly contacted each other. These compounds were mainly Al2Cu and Al3Cu4, resulting in a loose structure, deteriorated interfacial bonding, and a significant decrease in joint performance.

[0034] from Figure 4 It can be seen that in Comparative Example 2, which did not use zinc-aluminum alloy, a large number of brittle Al-Cu intermetallic compounds were also generated at the interface where the copper-zinc alloy directly contacted the aluminum base material. The microstructure was unevenly distributed and the interfacial bonding strength was low, making it impossible to form a stable and reliable joint.

[0035] from Figure 5 As can be seen, in Comparative Example 3, the copper-aluminum base material was directly welded without any transition layer. The interface formed the thickest and most continuous brittle Cu-Al intermetallic compound layer, which had many interface defects, the worst bonding, and the joint was extremely prone to embrittlement and failure.

[0036] The above results indicate that when copper and aluminum are in direct contact, the free energy for the formation of brittle phases such as Al2Cu is low and the thermodynamic driving force is high, making it difficult to suppress their nucleation and growth under conventional welding conditions. However, the copper-zinc-zinc-aluminum composite transition layer of the embodiment can preferentially form α-Cu(Zn) solid solution on the copper side and Al-Zn solid solution / eutectoid structure on the aluminum side through the interfacial regulation and barrier effect of Zn element, thus blocking the direct contact reaction between copper and aluminum from the source. At the same time, the moderate melting point of copper-zinc alloy and the low melting point of zinc-aluminum alloy reduce the welding temperature and thermal stress. Combined with element gradient diffusion, a smooth interface transition is achieved, effectively suppressing the generation and growth of brittle Cu-Al intermetallic compounds during welding. Finally, a copper-aluminum welded joint with uniform structure, strong interfacial bonding, no brittle phases, and excellent mechanical properties is obtained, which fully demonstrates that the composite transition layer has outstanding effects in solving welding defects of dissimilar copper-aluminum materials and improving the quality and reliability of joints.

[0037] Test Example 2

[0038] The tensile mechanical properties of the welded joints of Example 1 and Comparative Example 1 were tested according to the standard GB / T2651-2023, and the results are as follows: Figure 6 As shown. From Figure 6 It can be seen that the strength of the welded joint in Example 1 can reach about 240 MPa, while the strength of the welded joint in Comparative Example 1 is only about 13 MPa. The strength of the joint in Example 1 is significantly improved compared with that in Comparative Example 1. This is because Example 1 uses a composite transition layer made of copper-zinc alloy and zinc-aluminum alloy in a 3:2 mass ratio. During the laser welding process, the copper-zinc alloy side forms an α-Cu(Zn) solid solution with the copper base material, and the zinc-aluminum alloy side forms an Al-Zn solid solution / eutectoid structure with the aluminum base material. By utilizing the interfacial barrier and gradient diffusion effect of Zn, the direct contact reaction between copper and aluminum is blocked at the source. Simultaneously, the moderate melting point of the copper-zinc alloy and the low melting point of the zinc-aluminum alloy reduce welding temperature and thermal stress, achieving a smooth metallurgical transition at the interface. This effectively inhibits the formation and growth of brittle Cu-Al intermetallic compounds such as Al2Cu and Cu9Al4, resulting in a uniform and dense weld interface structure without significant defects, thus obtaining a stable and reliable high-strength joint. In contrast, Comparative Example 1 did not use a copper-zinc alloy; the copper base material and the zinc-aluminum alloy were in direct contact, leading to the formation of a large number of continuous and coarse brittle Cu-Al intermetallic compounds at the interface. This resulted in a loose structure, deteriorated interfacial bonding, a significant decrease in the joint's load-bearing capacity, and extremely poor mechanical properties. This demonstrates that the composite transition layer material of this embodiment can effectively solve the technical problems of brittle phase formation and low joint strength in direct welding of dissimilar copper and aluminum materials, significantly improving the mechanical properties and structural reliability of the welded joint.

[0039] Obviously, the above embodiments are merely illustrative examples for clear explanation and are not intended to limit the implementation. Those skilled in the art will recognize that other variations or modifications can be made based on the above description. It is neither necessary nor possible to exhaustively list all possible implementations here. However, obvious variations or modifications derived therefrom are still within the scope of protection of this invention.

Claims

1. A transition layer material for joining copper and aluminum dissimilar materials, characterized in that, It includes copper-zinc alloy and zinc-aluminum alloy; the mass ratio of the copper-zinc alloy to the zinc-aluminum alloy is (2.8-3.2):(1.8-2.2); the copper-zinc alloy is adjacent to the copper base material, and the zinc-aluminum alloy is adjacent to the aluminum base material; The zinc content in the copper-zinc alloy is 15%-36%, and the aluminum content in the zinc-aluminum alloy is 6%-10%.

2. The transition layer material for connecting copper-aluminum dissimilar materials according to claim 1, characterized in that, The elemental composition and mass percentage of the copper-zinc alloy are: Zn 15%-36%, Sn 8%-12%, Al 10%-18%, with the balance being Cu and other unavoidable impurities.

3. The transition layer material for connecting copper-aluminum dissimilar materials according to claim 1, characterized in that, The elemental composition and mass percentage of the zinc-aluminum alloy are as follows: Al 6%-10%, Cu 0.1%-1.0%, Mg 0.5%-2%, Mn 0.05%-0.5%, Si 0.1%-10%, with the balance being Zn and other unavoidable impurities.

4. The transition layer material for connecting copper-aluminum dissimilar materials according to claim 1, characterized in that, The transition layer material for connecting copper-aluminum dissimilar materials is selected from one or more of the following forms: powder, foil, bulk material, and wire.

5. The transition layer material for connecting copper-aluminum dissimilar materials according to claim 4, characterized in that, The particle size of the powder is 10μm-250μm; And / or, the thickness of the foil or block is independently 1mm-2mm; And / or, the diameter of the filament is 0.5mm-3.2mm.

6. The transition layer material for connecting copper-aluminum dissimilar materials according to claim 1, characterized in that, The copper base material is selected from copper alloys or pure copper.

7. The transition layer material for connecting copper-aluminum dissimilar materials according to claim 1, characterized in that, The aluminum base material is selected from aluminum alloy or pure aluminum.

8. The transition layer material for connecting copper-aluminum dissimilar materials according to claim 1, characterized in that, The transition layer material is connected to the copper-aluminum dissimilar material by one or more of laser welding, explosive welding, and friction stir welding.

9. The transition layer material for connecting copper-aluminum dissimilar materials according to claim 8, characterized in that, The laser welding process parameters are as follows: laser tilt angle is 10°-15°, defocusing amount is -1mm to 1mm, laser power is 2000W-2500W, welding speed is 10mm / s-15mm / s, shielding gas is argon with a flow rate of 20L / min-25L / min, and laser offset to the base material side is 0.3mm-0.8mm. And / or, the process parameters for the explosive welding are: detonation velocity 1500m / s-2000m / s, charge gap 1.5mm-2mm, and collision angle 5°-10°; And / or, the process parameters for friction stir welding are: stirring head rotation speed of 600rpm-800rpm, welding speed of 80mm / min-100mm / min, and stirring head offset to the aluminum side of 0.2mm-0.3mm.

10. The method for preparing the transition layer material for copper-aluminum dissimilar material bonding as described in any one of claims 1-9, characterized in that, Includes the following steps: S1. Prepare metal or intermediate alloy ingots according to the target composition; S2. Melt and cast the metal or intermediate alloy ingot described in S1 to obtain alloy material; And / or, the metal or intermediate alloy ingot described in S1 is smelted and vacuum atomized to obtain alloy material; S3. Perform surface treatment and post-treatment on the alloy material described in S2 to obtain the transition layer material for connecting copper-aluminum dissimilar materials.

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