Vacuum Brazing of Aluminum Alloys and Brazing Materials

Aluminum steel or aluminum-iron composite panels combine the advantages of aluminum alloys such as light weight, good corrosion resistance and thermal conductivity, and high strength of steel or iron. They can be used in automobile manufacturing, power station air cooling equipment, aerospace thruster heat pipe and duct structures, gas heat reflection covers, etc. field, and the composite plate can transform the problem of welding of dissimilar materials between aluminum alloy and steel or iron into the problem of welding of the same materials of aluminum alloy and aluminum alloy steel and steel, thereby avoiding the problem of welding of aluminum alloy and steel or iron during the direct welding process. Mutual reaction. During the vacuum brazing process of aluminum alloys and aluminum alloys, when the brazing temperature is close to or even higher than the heat treatment strengthening temperature of the base metal, it is easy to cause the strengthening phase to redissolve and reduce the mechanical properties. Therefore, AI-Si materials are used to weld aluminum alloys. The choice of base metal is limited and energy is consumed. It is usually only suitable for furnace brazing and vacuum brazing. Thin-film aluminum-iron composite panels use AI-Si fiber material and can be brazed with pure aluminum in the furnace. The Zn-Al needle material liquidus temperature range is 382~400C. The eutectic brazing material has a tensile strength of about 170 MPa, which is suitable for medium-temperature welding of aluminum alloys. However, ZnAl fiber material has poorer fluidity and corrosion resistance than AI-Si fiber material and requires the use of flux during the welding process. However, it is difficult to develop a suitable flux, and the flux cannot be completely removed for complex components, resulting in potential corrosion. Problem. At the same time, the welding process usually needs to be carried out in vacuum or inert gas protection.

Using ultrasonic-assisted vacuum brazing method and Zn-Al brazing filler metal, high-strength and reliable connection of 5A06 aluminum alloy and thin-film aluminum-iron composite panels was achieved. The brazing temperature is 420C, the dissolution of the aluminum layer is easy to control, no flux is used in the welding process, the oxide film is completely broken, and there are no intermetallic compounds at the aluminum-iron interface. In the shear test, the fracture occurred at the interface between the aluminum film and the matrix, and the strength was 70 MPa.

Ultrasonic waves can effectively break the oxide film and control the dissolution and diffusion of the aluminum layer. A-Al, m-Zn, eutectoid structure and two eutectic structures were observed in the weld.
Using AI-Si material 1100 pure aluminum and composite plate for brazing, the temperature is high, the aluminum layer is completely dissolved in a short time, there is an intermetallic compound layer at the interface between the brazing material and the iron matrix, and the shear strength is about 20 MPa.

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