A method for connecting Al2O3 ceramic and foam aluminum sandwich panels

Abstract

The present invention provides a method for connecting an Al2O3 ceramic to an aluminum foam sandwich panel. The method comprises the following steps: placing an AgCuInTi foil brazing filler metal on the aluminum foam sandwich panel, then covering the AgCuInTi foil with Al2O3 ceramic, and then folding the aluminum foil over the aluminum foam sandwich panel and the Al2O3 ceramic. The material is then placed in a tube furnace under an argon atmosphere at 680-710°C for 10-20 minutes, followed by cooling at a rate of 5-15°C / min to room temperature, thereby completing the connection between the Al2O3 ceramic and the aluminum foam sandwich panel. This method requires minimal equipment and is relatively low cost. Furthermore, it is simpler and more convenient than metallizing ceramics.

Description

Technical Field

[0001] The invention belongs to the field of connecting two heterogeneous materials, and in particular relates to the connection of Al2O3 ceramic and foam aluminum sandwich panels. Background Art

[0002] With the continuous advancement of military weaponry, guns, cannons, and missiles are the spear, while bulletproof armor is the shield. High-performance bulletproof armor often plays a crucial role in warfare. Due to its low density, high hardness, and high strength, bulletproof ceramics are widely used in armor protection. The most common bulletproof ceramic materials are silicon carbide, boron carbide, and aluminum oxide. Al2O3 bulletproof ceramics are used in personal and vehicle combat, critical parts of aircraft and helicopters, and mine explosion protection.

[0003] When a bullet strikes, the front side of the ceramic shatters, while the remaining energy is absorbed by the soft, reinforced material on the back side. This back side material must be able to support both the ceramic fragments and the bullet itself. This requires the support panel behind the bulletproof ceramic to have sufficient energy absorption properties. Aluminum foam sandwich panels meet this requirement because they not only have the good plasticity of aluminum metal, but also have a unique pore structure that absorbs energy and reduces the weight of the armor, thus avoiding the energy and physical loss caused by excessive armor weight.

[0004] Because ceramic and aluminum foam sandwich panels are made of two dissimilar materials, compounding them is quite difficult. Epoxy resin is typically used to bond ceramic and aluminum foam sandwich panels together. However, this method suffers from low interface strength and low service temperatures, making it prone to interfacial debonding and resulting in less than ideal connection performance.

[0005] Another way to connect Al2O3 ceramic and foam aluminum sandwich panels is welding. However, due to the significant differences in the physical and chemical properties of ceramic and foam aluminum sandwich panels, welding these two heterogeneous materials is somewhat difficult. Usually, direct copper plating or Ni plating is used on the surface of Al2O3 ceramics. Alternatively, active brazing filler metal can be used in a vacuum greater than 3×10 -3 Active metallization of the Al2O3 ceramic surface in a vacuum brazing furnace at Pa can produce a dense metal layer on the Al2O3 ceramic surface. This metal layer on the Al2O3 ceramic surface is then connected to the foam aluminum sandwich panel, transforming the process into metal-to-metal welding, reducing the difficulty of welding. However, this connection method is complex, inefficient, and has certain equipment requirements, resulting in high costs. The low connection strength between the Al2O3 ceramic and the surface metal layer can also lead to the Al2O3 ceramic and foam aluminum sandwich panel falling off.

[0006] Another method is to use AgCuTi active brazing filler metal to directly braze Al2O3 ceramics and metal in a vacuum brazing furnace, ensuring the vacuum degree is 3×10 -3 Pa or above, the vacuum degree has high requirements on equipment. Although the process is simpler than surface metallization, the brazing temperature of AgCuTi solder is around 850℃-900℃. Welding at this temperature will cause the collapse of the foam aluminum sandwich panel, so it is not suitable for welding foam aluminum sandwich panels. Summary of the Invention

[0007] The present invention aims to address the service temperature issues of epoxy resin bonding and the high equipment requirements of vacuum bonding in current technology by providing a method for joining Al2O3 ceramic and aluminum foam sandwich panels. This method involves placing an AgCuInTi foil brazing filler metal between the ceramic and aluminum foam sandwich panels, then wrapping them with aluminum foil. The brazing is then completed under argon at 680°C-710°C. This method requires minimal equipment requirements and is relatively low cost. It is also simpler and more convenient than metallizing ceramics.

[0008] The technical solution of the present invention:

[0009] A method for connecting an Al2O3 ceramic and aluminum foam sandwich panel, the method comprising the following steps:

[0010] (1) Place the AgCuInTi foil solder on the foam aluminum sandwich plate, then cover the AgCuInTi foil solder with Al2O3 ceramic, and then fold the aluminum foil to cover the foam aluminum sandwich plate and Al2O3 ceramic;

[0011] (2) The material obtained in the previous step is placed in a tube furnace at 680-710°C under an argon atmosphere, kept warm for 10-20 minutes, and then cooled at a rate of 5-15°C / min to room temperature, thus completing the connection between the Al2O3 ceramic and the foam aluminum sandwich plate.

[0012] The foam aluminum sandwich plate is polished and cleaned; the Al2O3 ceramic is cleaned;

[0013] The AgCuInTi foil solder is preferably Ag 43.6 -Cu 29.1 -In 24.3 -Ti3, thickness is 0.1~0.2mm.

[0014] The foam aluminum sandwich panels and Al2O3 ceramics were cleaned by ultrasonic cleaning with alcohol and then dried.

[0015] The polishing is performed using 60-mesh, 240-mesh and 480-mesh sandpaper in sequence.

[0016] In the argon atmosphere, the flow rate of argon in the furnace is 500ml / min-800ml / min.

[0017] The essential features of the present invention are:

[0018] 1. The melting point of the aluminum foam sandwich panel is relatively low, so the sample is placed into the furnace chamber just before the tube furnace temperature reaches 690°C. If the sample heats up with the furnace for a long time, the porous structure of the aluminum foam sandwich panel will cause it to collapse when the temperature exceeds 660°C. If the holding time is too short, it will not fully react with the base material and will fall off at a force of only 0.5-1.5MPa, thus failing to achieve a good connection. In the present invention, however, the sample is placed in the furnace at 690°C and held for 14-16 minutes, ensuring that the aluminum foam sandwich panel does not collapse and achieving excellent welding results.

[0019] 2. This invention utilizes AgCuInTi foil-like solder for bonding. The active element Ti, protected from oxidation by a protective atmosphere, reacts with the Al2O3 ceramic to form a dense bonding layer. The Ag-Cu eutectic reacts with the aluminum foam sandwich panel to form a solid solution. The addition of In lowers the melting point of the Ag-based solder, preventing the Al2O3 ceramic and aluminum foam sandwich panels from softening and collapsing when held at 690°C-710°C for 10-20 minutes.

[0020] Compared with other methods for connecting ceramics to metals, the method of the present invention has the following beneficial effects:

[0021] 1. Brazing or diffusion welding of ceramics and metals using active solder is performed under vacuum conditions, which has high costs and equipment requirements. However, in the present invention, by wrapping the sample with aluminum foil and using argon as a protective atmosphere, vacuum equipment is not required, which reduces the equipment requirements and equipment costs, and the process flow is simple.

[0022] 2. Unlike alloys, foam metals are prone to collapse and deformation due to their unique pore structure as the furnace heats up. However, the present invention introduces the sample at 690°C, protects it with argon gas, and insulates it for 13-16 minutes. This ensures that the foam metal does not collapse while also maintaining a connection strength of at least 20 MPa. Using vacuum equipment not only places high demands on the equipment, but also forces the furnace to heat up to maintain vacuum, making the foam aluminum sandwich panels susceptible to softening and collapse. The present invention's use of ceramics and porous metals for connection is also significantly different from most alloy-ceramic connections. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1This is a sample picture of the connection in Example 1;

[0024] Figure 2 is a side view of the connected sample of Example 1;

[0025] Figure 3 This is the microscopic morphology of the connection interface of the sample of Example 1 (the upper part is Al2O3 ceramic, and the lower part is foam aluminum sandwich plate);

[0026] Figure 4 This is a microscopic morphology of the connection interface of the sample in Example 2. DETAILED DESCRIPTION

[0027] The following are examples given by the inventors, but the present invention is not limited to these examples.

[0028] In the present invention, the AgCuInTi foil solder is a commercially available material with a solidus temperature of about 540°C and a liquidus temperature of about 640°C; specifically, the AgCuInTi foil solder is from Changsha Tianjiu Metal Materials Co., Ltd., a silver-based solder, Ag 43.6 -Cu 29.1 -In 24.3 -Ti3, but not limited to this;

[0029] The foam aluminum sandwich panel is a well-known material. Specifically, the foam aluminum sandwich panel has aluminum panels on the front and back surfaces, the panel thickness is about 1-3 mm, and the middle is a foam aluminum sandwich layer with a porous structure. The thickness of the middle core layer is about 18-14 mm.

[0030] Example 1

[0031] The method for connecting Al2O3 ceramic and aluminum foam sandwich panels described in this embodiment is carried out according to the following steps:

[0032] a. Polish the surface of the aluminum foam sandwich panel with 60-, 240-, and 480-grit sandpaper, then ultrasonically clean it and the Al2O3 ceramic in alcohol. Then, dry it in a vacuum drying oven. Stack the Al2O3 ceramic and aluminum foam sandwich panels on top of each other, placing AgCuInTi foil brazing filler metal in the middle. Securely wrap the panels with aluminum foil, especially at the interface, to ensure a good seal.

[0033] b. The size of the aluminum foam sandwich plate used is 20 mm × 20 mm × 10 mm, the size of the Al2O3 ceramic is 10 mm × 10 mm × 1 mm, and the size of the AgCuInTi foil solder is 10 mm × 10 mm × 0.1 mm.

[0034] c. Start heating the tube furnace at a rate of 8°C / min to 400°C and keep warm for 15 minutes; heat to 600°C at a rate of 5°C / min and keep warm for 10 minutes; then heat to the connection temperature of 690°C at a rate of 5°C / min and keep warm for 15 minutes.

[0035] When the temperature reaches the connection temperature, use a hexagonal screwdriver to open the furnace door and start to pass argon at a capacity of 500ml / min-800ml / min (so that the concentration (volume fraction) of argon reaches 55%-65%), place the sample at the argon inlet position in the furnace, close the furnace door and keep warm.

[0036] Keep the temperature at 690℃ for 15 minutes, then cool to 300℃ at a rate of 10℃ / min, and then cool to room temperature along with the furnace to complete the connection between the Al2O3 ceramic and the foam aluminum sandwich panel. Figure 2 The microscopic morphology of the connection interface is shown in Figure 3 As shown in the figure, it can be seen that the solder connects the two together and the connection interface is dense, indicating that this method has a better connection effect.

[0037] Use the cut aluminum foil to wrap the ceramic and foam aluminum sandwich panels, especially the interface joints. This will not only fix the Al2O3 ceramics, but also minimize the degree of oxidation of the brazing material, so that the connection between the Al2O3 ceramic and the foam aluminum sandwich panels has a certain strength.

[0038] The obtained samples were subjected to a pull-out test on a pull-out test bench. The ceramic sheet was glued with glue, and then the foam aluminum sandwich panel was fixed. Tensile force was applied in front of the ceramic. As the tension increased, until both of them fell off in whole or in part, the measured force divided by the force-bearing area was the final strength data (this method was used for testing because the foam aluminum sandwich panel has a unique porous structure. If the interface bonding strength is tested in the form of shear, at a force of 15MPa-20MPa, the interface between the two has not even debonded, and the foam aluminum sandwich panel itself has collapsed and deformed, making it impossible to accurately evaluate its interface bonding strength).

[0039] The composite material obtained in this example was partially detached at the corners under a force of 28.13 MPa.

[0040] Example 2

[0041] The method for connecting Al2O3 ceramic and aluminum foam sandwich panels described in this embodiment is carried out according to the following steps:

[0042] a. Polish the surface of the Al2O3 ceramic and foam aluminum sandwich panel, then ultrasonically clean it in alcohol and dry it in a vacuum drying oven. Apply AgCulnTi solder paste evenly on the Al2O3 ceramic and foam aluminum sandwich panel and securely wrap it with aluminum foil, especially at the interface to ensure good sealing.

[0043] b. The size of the aluminum foam sandwich panel used is 20mm×20mm×10mm, and the size of the Al2O3 ceramic is 10mm×10mm×1mm.

[0044] c. Start heating the tube furnace at a rate of 8°C / min to 400°C and keep warm for 15 minutes; heat to 600°C at a rate of 5°C / min and keep warm for 10 minutes; then heat to the connection temperature of 650°C at a rate of 5°C / min and keep warm for 15 minutes.

[0045] When the temperature reaches the connection temperature, use a hexagonal screwdriver to open the furnace door and start to pass argon at a capacity of 500ml / min-800ml / min. Place the sample at the argon inlet position in the furnace and close the furnace door for insulation heating.

[0046] The connection temperature is kept at 650℃ for 15 minutes, then cooled to 300℃ at a rate of 10℃ / min, and then cooled to room temperature along with the furnace to complete the connection between the Al2O3 ceramic and the foam aluminum sandwich panel.

[0047] The obtained samples were subjected to a pulling test on a pulling test bench, and the results showed that the Al2O3 ceramic and foam aluminum sandwich panel partially fell off under a force of 21.74 MPa.

[0048] Compared with Example 1, Example 2 which was kept at 650°C for 15 minutes had lower strength, indicating that the most suitable temperature is 680-710°C.

[0049] Example 3

[0050] The other steps were the same as in Example 1, except that the flow rate of argon was changed to 350 mL / min;

[0051] The final connector fell off under a force of 0.35 MPa;

[0052] Comparison between Example 1 and Example 3 shows that when the argon concentration (volume fraction) reaches 55%-65%, good connection strength is achieved. If the argon concentration is lower, the connection strength is only 0.1-0.5 MPa, and the connection effect is not ideal.

[0053] Example 4

[0054] The other steps are the same as those in Example 1, except that the temperature is kept at 700° C. for 30 min;

[0055] The final foam aluminum has completely collapsed, the sample morphology is completely destroyed, and it has no use value.

[0056] Example 5

[0057] The other steps are the same as those in Example 1, except that the temperature is kept at 700° C. for 15 min;

[0058] The resulting connector partially fell off under 30.53 MPa;

[0059] Comparing Example 5 with Example 4, it is shown that keeping the temperature at 690° C.-710° C. for 14-16 minutes is a necessary condition to ensure a good connection effect.

[0060] From the above examples, it can be seen that the present invention uses an argon protective atmosphere, 680°C-710°C, and AgCuInTi solder for welding, which reduces the requirements for equipment and has wider applicability. Previously, stainless steel metal with a higher melting point was selected for direct brazing with ceramics (patent number: CN 108546095 A), or ceramics were surface metallized and diffusion brazed with aluminum alloys (literature number: Materials and Design 86 (2015) 328-337). However, the present invention directly brazes foam aluminum sandwich panels with a lower melting point and does not require metallization of the ceramics, which is simpler and more convenient.

[0061] Matters not covered by the present invention are known technologies.

Claims

1. A method for connecting Al2O3 ceramic and foam aluminum sandwich panels, characterized in that the method comprises the following steps: (1) Place the AgCuInTi foil solder on the foam aluminum sandwich plate, then cover the AgCuInTi foil solder with Al2O3 ceramic, and then fold the aluminum foil to cover the foam aluminum sandwich plate and Al2O3 ceramic; (2) Place the material obtained in the previous step into a tube furnace at 690-710°C under an argon atmosphere, keep the temperature for 14-16 minutes, and then cool it down at a rate of 5-15°C / min to room temperature, thus completing the connection between the Al2O3 ceramic and the foam aluminum sandwich plate; In the argon atmosphere, the volume fraction of argon in the furnace is 55% to 65%; The foam aluminum sandwich plate is polished and cleaned; the Al2O3 ceramic is cleaned; The AgCuInTi foil solder is Ag 43.6 -Cu 29.1 -In 24.3 -Ti3, thickness is 0.1~0.2mm.

2. The method for connecting Al2O3 ceramic and foam aluminum sandwich panels as described in claim 1, characterized in that the polishing is performed using 60 mesh, 240 mesh, and 480 mesh sandpaper in sequence.

3. The method for connecting Al2O3 ceramics and foam aluminum sandwich panels as claimed in claim 1, wherein the foam aluminum sandwich panels and Al2O3 ceramics are cleaned by ultrasonic cleaning with alcohol and then dried.

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