A diffusion bonding method based on diffusion first and membrane breaking later suitable for preparing aluminum alloy laminated structure

Abstract

The application relates to a diffusion connection method based on pre-diffusion and post-membrane breaking, which is suitable for preparing an aluminum alloy laminated structure and relates to the field of welding. The application aims to solve the problems existing in the existing aluminum alloy diffusion connection technology and aluminum alloy laminated composite structure manufacturing technology, simplifies a process, and obtains aluminum alloy laminated composite structures of different scales under low-temperature and low-pressure welding conditions. The method comprises the following steps: 1, pretreating aluminum alloy base materials and a Zn intermediate layer; 2, heating, pressurizing and heat-insulating after assembling the aluminum alloy and the intermediate layer, so as to realize solid-phase diffusion connection; 3, applying ultrasonic waves after temperature rising to a liquid phase, so as to break the oxide film in the joint; and 4, continuing heat-insulating after temperature falling to joint solidification, so as to realize joint homogenization. The application breaks through the limitation of the aluminum alloy laminated composite material preparation process, is especially suitable for the preparation of aluminum laminated structures, such as micro-channel radiators, lithium battery tabs and aluminum honeycomb structures, and has great application prospects.

Description

Technical Field

[0001] This invention belongs to the field of welding, specifically relating to a diffusion bonding method based on diffusion followed by film breaking, suitable for preparing aluminum alloy laminated structures. Background Technology

[0002] Modern engineering applications demand a wide variety of metal-metal layered composite structures. Among these, aluminum and aluminum alloy laminated composites, due to their designable layered structures, can meet multiple performance and structural requirements, and currently have representative applications such as microfluidic heat sinks, radar antennas, lithium battery tabs, and fiber optic encapsulation. Based on the unique multilayer structure of aluminum laminated composites, dense connections between layers are required. Commonly used connection methods include rolling bonding, ultrasonic welding, ultrasonic additive manufacturing, and diffusion bonding.

[0003] Rolling technology utilizes the alternating stacking of multiple layers of plates, followed by preliminary mechanical bonding through pressing or hot pressing, and then plastic processing methods such as rolling to produce metal-metal layered composite sheets. This method is highly suitable for metal materials with good plasticity. However, this method also brings many problems. For example, severe plastic deformation can cause localized deformation of the harder material in the composite material, leading to necking or even fracture and separation. Stress concentration can easily form at the fracture and separation points, resulting in premature material failure. In addition, this method is generally suitable for bonding large-size panels, but not for bonding small-size or thin metal foils in multiple layers. Therefore, it cannot be applied to the precision manufacturing of small components (e.g., patent publication number CN114054773A, invention title: "Preparation Method of Laminated Heterogeneous Aluminum Alloy Sheets with Non-uniformly Distributed Precipitated Phases").

[0004] Ultrasonic metal welding utilizes the high-frequency vibration of ultrasound. Under a positive load, the ultrasonic vibration energy is converted into frictional work and deformation energy between the metal components being welded. Friction cleans the interface between the metal components, achieving a clean surface. Then, through a limited temperature rise and plastic deformation, the cleaned surfaces become infinitely close, leading to bonding and diffusion between the metal components, thus forming a reliable solid-state bond. Its advantages include: short welding time and low processing energy consumption; a wide range of weldable materials, suitable for metals that are difficult to weld using traditional methods; and low welding temperature, with the temperature during the welding process only 30%-50% of the melting point of the metal being welded. However, its application to welding multilayer structures still presents several challenges. First, the weld size is limited, making it unsuitable for the preparation of large-sized samples. Second, the weldable metals are limited to thin sheets with relatively small thicknesses, making it unsuitable for thick plates or multilayer structures (e.g., patent publication CN205666258U, entitled "A Lithium-ion Battery Cover Plate with a Soft-Connection Terminal").

[0005] Based on the relatively rudimentary ultrasonic metal welding technology, ultrasonic additive manufacturing technology has been developed. This technology has achieved a breakthrough in the continuous manufacturing of large-size laminated materials and possesses rapid and precise manufacturing capabilities lacking in other traditional manufacturing methods. However, similar to ultrasonic metal welding, the welding of thick plates and the manufacturing of thick laminated structures remain unresolved (e.g., patents CN110744184A, entitled "A Method for Preparing Micro-Layered Composite Materials Using Ultrasonic Additive Manufacturing and Hot Isostatic Pressing and Its Application"; CN207386797U, entitled "A Laser-Assisted Ultrasonic Additive Manufacturing Device for Metal Foil Strips"; and CN107591337A, entitled "An Electronic Component Packaging Method Based on Ultrasonic Consolidation Technology").

[0006] Diffusion bonding involves applying significant pressure at temperatures below the material's melting point (approximately 0.5Tm-0.8Tm, where Tm is the melting point) to bring metal sheets into close contact, achieving bonding through atomic diffusion at the interface. This method offers advantages such as the ability to bond multilayer metals and metals of various sizes, high cost-effectiveness, and ease of operation. In diffusion bonding of aluminum alloys, high temperature and pressure are essential for effective interdiffusion and oxide film removal. However, these harsh conditions present numerous challenges, including temperatures typically exceeding 500°C leading to softening of the base material and welding pressures exceeding 5 MPa causing joint deformation. Furthermore, diffusion bonding must be performed in a vacuum or Ar gas environment to avoid secondary oxidation affecting the joint, further complicating the process. Secondly, the metal stack structure prepared by diffusion bonding requires a long diffusion time to achieve a strong interfacial bonding strength, so its process cycle is long (e.g., patent CN109396638A, invention title "A diffusion welding method for aluminum alloy", patent CN109175660A, invention title "A diffusion welding device and diffusion welding method for aluminum alloy", and patent CN112548303A, invention title "A surface activation non-vacuum diffusion welding method for aluminum alloy and subsequent heat treatment method").

[0007] Ultrasonic-assisted diffusion bonding technology can rapidly fabricate high-strength joints of lightweight metals in air and has been applied to the bonding of Al or Mg alloys (e.g., patent publication CN112059397A, entitled "A Method for Ultrasonic-Assisted Welding of High-Temperature Materials under Atmosphere Protection"). Currently, ultrasonic-assisted diffusion bonding technology is limited to the fabrication of joints between two bulk materials and cannot be used for multilayer metal bonding. The main reason is that it requires the pressure and friction applied by the acoustic electrode to remove the oxide film, but the removal area is limited to a localized region directly below the acoustic electrode. For multilayer structures, oxide film removal is concentrated only at the upper metal layer interface near the acoustic electrode and cannot extend to the lower metal layer interface. Therefore, it has limitations due to the requirement for a certain number of metal layers.

[0008] Furthermore, ultrasonic-assisted instantaneous liquid phase diffusion bonding is prone to squeezing out the generated eutectic liquid phase from the joint during the ultrasonic process, resulting in inconsistent weld thickness (e.g., publication number CN109365989A, invention title "A method for obtaining a full solid solution joint in low temperature ultrasonic-assisted aluminum alloy welding"). Summary of the Invention

[0009] The purpose of this invention is to address the problem that aluminum alloy laminated structure joining processes cannot completely remove the multi-layered oxide film of the laminated structure, making them only applicable to the manufacture of bulk material joints and not suitable for the preparation of laminated structures. To overcome the aforementioned shortcomings of existing technologies, this invention provides a simple, easy-to-implement, and highly applicable method for low-temperature, low-pressure diffusion joining of aluminum alloys. This invention utilizes a Zn-based metal as an intermediate layer for diffusion welding of aluminum alloys, achieving diffusion joining of multi-layered aluminum alloys based on the principle of "diffusion first, film removal later."

[0010] This invention provides a diffusion bonding method for preparing aluminum alloy laminated structures based on a pre-diffusion followed by film rupture. The diffusion bonding method is performed according to the following steps:

[0011] 1. The surfaces of the aluminum alloy and Zn foil are mechanically ground and polished, and then placed in an acetone solution to remove and dry them, thus obtaining a pretreated aluminum alloy and Zn intermediate layer.

[0012] 2. Lay out aluminum alloy and Zn interlayer in the manner of placing Zn interlayer between two adjacent aluminum alloys, as a pre-welded part, pressurize the pre-welded part to 2-5 MPa, heat it to 350-370℃ and keep it at that temperature; the number of aluminum alloys is greater than 2.

[0013] 3. Heat to 390-410℃ and apply ultrasonic vibration to the upper side of the base material for 0.1-5s to remove the oxide film;

[0014] 4. After the ultrasonic treatment, the temperature is lowered to 350-370℃ and held; then cooled to room temperature to complete the low-temperature diffusion welding of the aluminum alloy and obtain a high-strength welded joint.

[0015] The quantity of the aluminum alloy is 2 to 7.

[0016] Further, the aluminum alloy mentioned in step one is a 1-series aluminum alloy, a 2-series aluminum alloy, a 3-series aluminum alloy, a 5-series aluminum alloy, a 6-series aluminum alloy, or a 7-series aluminum alloy; or, the aluminum alloy is a fine-grained strengthened ultrafine-grained aluminum alloy.

[0017] Furthermore, the thickness of the aluminum alloy described in step two is 0.1-10 mm.

[0018] Furthermore, the intermediate layer described in step two is a pure Zn or a Zn-based alloy with Zn-Al as the main component, in the form of metal foil, mixed solder paste, or metal powder.

[0019] Furthermore, the thickness of the intermediate layer described in step two is 10-300 μm.

[0020] Furthermore, the pressure applied in step two is 3-4 MPa, and the heat preservation time is 10-30 min.

[0021] Furthermore, the ultrasonic vibration time in step three is 0.1-1s, and the ultrasonic electrode output amplitude is 1-20μm.

[0022] Furthermore, the ultrasonic application location described in step three is either the lower or upper substrate.

[0023] Furthermore, the heat preservation time described in step four is 30-60 minutes.

[0024] Furthermore, the heating and temperature rise methods described in steps two and three are all resistance heating, high-frequency induction coil heating, infrared heating, or hot gas heating.

[0025] This invention differs from the traditional aluminum alloy diffusion bonding process of breaking the oxide film before diffusion; instead, it is based on the principle of diffusion followed by oxide film breaking. Compared to ultrasonic-assisted diffusion bonding, which relies on pressure and friction to remove the oxide film, ultrasonic liquid-phase cavitation for oxide film removal is simpler and easier to extend to the simultaneous removal of multiple oxide films. Immersing the continuous oxide film in liquid metal during diffusion bonding is a significant challenge. In this invention, when using a Zn intermediate layer for solid-phase diffusion bonding of Al alloys, the oxide film can completely detach from the base material and migrate towards the joint center, providing conditions for the oxide film to suspend within the diffusion alloy layer. When the diffusion layer transforms into a eutectic liquid phase, the impact of cavitation bubbles induced by ultrasound can simultaneously rupture multiple oxide films. Therefore, based on the principle of "diffusion followed by oxide film removal," diffusion bonding of multiple Al layers and Al alloys can be achieved, enabling additive manufacturing of laminated metals.

[0026] The key technology of this invention lies in the initial low-pressure bonding process, where Zn diffuses through oxide film cracks to Al, achieving a low-temperature solid-phase connection and lifting the oxide film. Then, at the Zn-Al eutectic temperature, ultrasonic waves in the liquid metal break down the oxide film. Finally, further heat preservation diffusion homogenizes the joint, improving its strength. This technology achieves low-temperature, low-pressure diffusion bonding of aluminum alloys under atmospheric conditions, eliminating the need for the high-temperature, high-pressure conditions of traditional diffusion welding. It can obtain a high-strength joint with the same strength as the base material while protecting it from excessive welding heat. This technology overcomes the limitations of aluminum alloy laminated composite material preparation processes (including rolling bonding, ultrasonic metal welding, and diffusion bonding), and is particularly suitable for the preparation of aluminum laminated structures, such as microchannel heat sinks, lithium battery tabs, and aluminum honeycomb structures, showing great application potential.

[0027] The beneficial effects of this invention are:

[0028] I. Compared with rolling connection, the present invention can greatly simplify the process, does not require the base material itself to undergo large plastic deformation, can be used to manufacture small-sized laminated structures, and is more suitable for precision manufacturing in the electronics field;

[0029] Second, compared with ultrasonic metal welding and ultrasonic additive manufacturing, their application in large components is limited because their film breaking mechanism is limited to thin metal foil stacked structures, and large-sized component welding cannot be realized. This invention can overcome the limitations of the number of metal layers (the welded aluminum alloy can be multi-layered) and size (suitable for large or small-sized stacked structures), and can be applied to the preparation of joints or stacked structures of thin metal foil and thick metal plates at the same time.

[0030] Third, compared to traditional diffusion bonding, this invention enables diffusion welding of aluminum alloys and fabrication of laminated structures in an atmospheric environment, simplifying the process. The low welding temperature and pressure used protect the aluminum alloy from heat softening and prevent joint deformation under pressure.

[0031] Fourth, the ultrasonic waves applied in the third stage can be transmitted to the multi-layer metal interface through the sample, and the cavitation effect of the ultrasonic waves in the liquid metal can be used to quickly break the multi-layer oxide film. Compared with ultrasonic-assisted diffusion connection, the ultrasonic time required by the present invention is extremely short and will not cause the liquid metal in the joint to be squeezed out.

[0032] V. This invention can be used for low-temperature diffusion bonding of various aluminum alloys. The intermediate layer can be selected from Zn and Zn-based alloys, and the joint strength is higher than that of the base material itself. Attached Figure Description

[0033] Figure 1 Schematic diagram of diffusion-bonded aluminum alloy in Example 1: where 1 is a pressurizing device, 2 is a clamp, 3 is a heating device, 4 is 6063Al, 5 is a Zn intermediate layer, and 6 is an ultrasonic electrode;

[0034] Figure 2 Microstructure diagram of the 6063 aluminum alloy connector using Zn intermediate layer diffusion connection in Example 1;

[0035] Figure 3 The tensile strength and photograph of the failed joint of the 6063 aluminum alloy joint using Zn intermediate layer diffusion connection in Example 1;

[0036] Figure 4 Microstructures and elemental energy spectra of aluminum alloy laminated composite materials of different scales manufactured using Zn intermediate layers in Examples 2, 3 and 4; (a1-a4) Example 2, (b1-b4) Example 3, (c1-c4) Example 4. Detailed Implementation

[0037] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the spirit of the contents disclosed in the present invention will be described in detail below. After understanding the embodiments of the present invention, any person skilled in the art can make changes and modifications based on the technology taught in the present invention without departing from the spirit and scope of the present invention.

[0038] The illustrative embodiments and descriptions of the present invention are used to explain the present invention, but are not intended to limit the present invention.

[0039] Example 1:

[0040] This embodiment presents a diffusion bonding method for preparing aluminum alloy laminated structures based on diffusion followed by film breaking, which is carried out according to the following steps:

[0041] First, use 180-grit and 400-grit sandpaper to mechanically grind and polish the 10mm thick 6063 aluminum alloy surface, then clean the surface with acetone and dry it.

[0042] 2. A 50μm thick pure Zn interlayer is prefabricated directly between two aluminum alloys to be welded, and a pressure of 3MPa is applied to the top. The mixture is then heated to 360℃ and held for 10 minutes. (See below) Figure 1 a;

[0043] Third, the temperature is then raised to 390℃, and ultrasonic vibration is applied to the upper side of the base material with an amplitude of 3.5 μm and a duration of 0.5 s to remove the oxide film from the base material and the intermediate metal layer. (See attached diagram.) Figure 1 b;

[0044] IV. After ultrasonic treatment, the temperature is lowered to 360℃ and held for 10 minutes; then cooled to room temperature to complete the low-temperature diffusion bonding of the aluminum alloy, resulting in a high-strength welded joint. See [link to documentation]. Figure 1 c.

[0045] Microstructure of 6063 aluminum alloy joints subjected to Zn diffusion welding at different stages is shown in the figure. Figure 2 . Figure 2 a represents the joint obtained after solid-phase diffusion at 360℃ for 10 min in step two. The continuous oxide film migrates towards the center of the joint and remains between the Zn-Al diffusion layer and the residual Zn. Figure 2 b is the joint obtained by heating to 390℃ in step three. It can be seen that the oxide film that has migrated away from the parent material is suspended in the Zn-Al eutectic phase. Figure 2 c represents the joint obtained after applying ultrasound for 0.1s in step three. The oxide film is broken by ultrasonic cavitation, resulting in gaps in the continuous oxide film. Figure 2 d represents the joint obtained after applying ultrasound for 0.5s in step three. The oxide film is broken up by ultrasonic cavitation and distributed in the joint in the form of fragments. Figure 2 e represents the joint obtained after diffusion for 5 minutes in step four. The joint microstructure consists of Zn-Al eutectoid and Zn-Al eutectic. Figure 2 f represents the joint obtained after diffusion for 10 minutes in step four. Zn and Al diffused sufficiently at this temperature, ultimately yielding a fully Zn-Al co-depositional joint.

[0046] Figure 3 To measure the tensile strength of the joint at different stages, the final fully Zn-Al eutectoid joint fractured within the base material during the tensile test, with a strength of 132 MPa, indicating that the joint strength is greater than 132 MPa. This proves that the invention can obtain a high-strength diffusion-welded joint through a diffusion-first, film-breaking welding method.

[0047] Example 2:

[0048] This embodiment presents a diffusion bonding method for preparing aluminum alloy laminated structures based on diffusion followed by film breaking, which is carried out according to the following steps:

[0049] First, use 180-grit and 400-grit sandpaper to mechanically grind and polish the 1mm thick 6063 aluminum alloy surface, then clean the surface with acetone and dry it.

[0050] 2. A 50μm thick pure Zn intermediate layer is directly prefabricated between 4 layers of aluminum alloy to be welded, and a pressure of 3MPa is applied on the top side. The temperature is then heated to 360℃ and held for 10 minutes.

[0051] Third, the temperature is then raised to 390℃, and ultrasonic vibration is applied to the upper side of the base material with an amplitude of 3.5μm and a duration of 0.5s to remove the oxide film from the base material and the intermediate metal layer.

[0052] IV. After the ultrasound is completed, the temperature is lowered to 360℃ and kept at that temperature for 10 minutes; then cooled to room temperature to complete the low-temperature diffusion connection of the aluminum alloy laminate structure, thus obtaining the aluminum alloy laminate structure.

[0053] The obtained interface morphology and elemental energy spectrum of the stacked structure are as follows: Figure 4 As shown in a1-4a4. Compared to Example 1, this embodiment replaces the 10mm thick aluminum alloy block with a 1mm thick aluminum alloy sheet, and the number of aluminum alloy sheets is 4, achieving the preparation of a multi-layer aluminum alloy laminate structure under the same process conditions.

[0054] Example 3:

[0055] This embodiment presents a diffusion bonding method for preparing aluminum alloy laminated structures based on diffusion followed by film breaking, which is carried out according to the following steps:

[0056] First, use 180-grit and 400-grit sandpaper to mechanically grind and polish the 0.3mm thick 6063 aluminum alloy surface, then clean the surface with acetone and dry it.

[0057] 2. A 50μm thick pure Zn intermediate layer is directly prefabricated between 7 layers of aluminum alloy to be welded, and a pressure of 3MPa is applied on the top side. The temperature is then heated to 360℃ and held for 10 minutes.

[0058] Third, the temperature is then raised to 390℃, and ultrasonic vibration is applied to the upper side of the base material with an amplitude of 3.5μm and a duration of 0.5s to remove the oxide film from the base material and the intermediate metal layer.

[0059] IV. After the ultrasound is completed, the temperature is lowered to 360℃ and kept at that temperature for 10 minutes; then cooled to room temperature to complete the low-temperature diffusion connection of the aluminum alloy laminate structure, thus obtaining the aluminum alloy laminate structure.

[0060] The obtained interface morphology and elemental energy spectrum of the stacked structure are as follows: Figure 4 As shown in b1-4b4. Compared to Example 2, this embodiment replaces the 1mm thick aluminum alloy sheet with a 0.3mm thick aluminum alloy foil, and the number of aluminum alloy foil layers is 7, achieving the preparation of a multi-layer thin aluminum alloy foil stacked structure under the same process conditions.

[0061] Example 4:

[0062] This embodiment presents a diffusion bonding method for preparing aluminum alloy laminated structures based on diffusion followed by film breaking, which is carried out according to the following steps:

[0063] First, use 180-grit and 400-grit sandpaper to mechanically grind and polish the 0.3mm thick 6063 aluminum alloy surface, then clean the surface with acetone and dry it.

[0064] 2. A 10μm thick pure Zn intermediate layer is directly prefabricated between 7 layers of aluminum alloy to be welded, and a pressure of 3MPa is applied on the top side. The temperature is then heated to 360℃ and held for 1 minute.

[0065] Third, the temperature is then raised to 390℃, and ultrasonic vibration is applied to the upper side of the base material with an amplitude of 3.5μm and a duration of 0.5s to remove the oxide film from the base material and the intermediate metal layer.

[0066] IV. After the ultrasound is completed, the temperature is lowered to 360℃ and kept at that temperature for 1 minute; then cooled to room temperature to complete the low-temperature diffusion connection of the aluminum alloy stacked structure, thus obtaining the aluminum alloy stacked structure.

[0067] The obtained interface morphology and elemental energy spectrum of the stacked structure are as follows: Figure 4 As shown in c1-4c4. Compared to Example 3, this implementation changes the 50μm thick Zn interlayer to a 10μm thick Zn interlayer, completing the interdiffusion between the base material and the interlayer in a shorter time.

[0068] Table 1

[0069]

Claims

1. A diffusion bonding method based on diffusion followed by film rupture suitable for preparing aluminum alloy laminated structures, characterized in that... The diffusion connection method is performed according to the following steps:

1. The surfaces of the aluminum alloy and Zn foil are mechanically ground and polished, and then placed in an acetone solution to remove and dry them, thus obtaining a pretreated aluminum alloy and Zn intermediate layer.

2. Lay out aluminum alloy and Zn interlayer in a manner that places a Zn interlayer between two adjacent aluminum alloys, as a pre-welded part. Pressurize the pre-welded part to 2-5 MPa and heat it to 350-370℃ for holding. The number of aluminum alloys is greater than 2. The thickness of the aluminum alloy is 0.1-10 mm. The Zn interlayer is pure Zn or a Zn-Al based alloy, in the form of metal foil, mixed solder paste or metal powder. The thickness of the Zn interlayer is 10-300 μm. The pressurization pressure is 3-4 MPa, and the holding time is 10-30 min.

3. Heat to 390-410 ℃ and apply ultrasonic vibration to the upper side of the base material for 0.1-5 s to remove the oxide film; the ultrasonic vibration time is 0.1-1 s and the ultrasonic electrode output amplitude is 1~20μm; 4. After the ultrasonic treatment, the temperature is lowered to 350-370℃ and held; then cooled to room temperature to complete the low-temperature diffusion welding of the aluminum alloy and obtain a high-strength welded joint; the holding time is 30-60 min.

2. The diffusion bonding method for preparing aluminum alloy laminated structures based on diffusion followed by film breaking, as described in claim 1, is characterized in that... The aluminum alloy mentioned in step one is a 1-series aluminum alloy, a 2-series aluminum alloy, a 3-series aluminum alloy, a 5-series aluminum alloy, a 6-series aluminum alloy, or a 7-series aluminum alloy; or, the aluminum alloy is a fine-grained strengthened ultrafine-grained aluminum alloy.

3. The diffusion bonding method based on diffusion followed by film breaking, suitable for preparing aluminum alloy laminated structures according to claim 1, is characterized in that... Step 3 describes applying ultrasound to either the lower or upper substrate.

4. The diffusion bonding method for preparing aluminum alloy laminated structures based on diffusion followed by film breaking, as described in claim 1, is characterized in that... The heating and temperature rise methods described in steps two and three are resistance heating, high-frequency induction coil heating, infrared heating, or hot gas heating.

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