Aluminum alloy forging will also be corroded after long-term use, and the common manifestations are pitting corrosion, galvanic corrosion, crevice corrosion, intergranular corrosion, filiform corrosion, etc.
1. Pitting corrosion is a very localized form of corrosion that produces needle-like, spot-like and porous morphologies on metals. Pitting corrosion is a unique form of anodic reaction and autocatalytic process. The pitting corrosion limit is related to the dielectric alloy, and the substances that promote the cathodic reaction must also be present;
2.Galvanic corrosion is also a unique form of aluminum corrosion. The spontaneous potential of aluminum is very low. When aluminum is in contact with other metals, aluminum is always on the anode, which accelerates aluminum corrosion. The more serious the galvanic corrosion is, almost all aluminum alloy profiles cannot avoid galvanic corrosion;
3. Crevice corrosion occurs when the aluminum alloy profile itself or aluminum is in contact with other materials. Due to the different actions of the pneumatic battery, the corrosion in the crevice is accelerated while there is no corrosion outside the crevice. Sediment corrosion is a form of crevice corrosion;
4.The cause of intergranular corrosion is related to improper heat treatment. Alloying elements or intermetallic compounds are precipitated along the grain boundary, and the corrosion cell is formed by the anode relative to the grain boundary, which accelerates the intergranular corrosion;
5. Filiform corrosion is a kind of underwater corrosion that occurs under the worm-like membrane. This kind of film can make the paint film and other layers, generally not lower than the anodic oxide film. Filiform corrosion is related to alloy composition, pre-coating treatment of aluminum alloy profiles and environmental factors such as humidity, temperature, chloride, etc.;
What are the factors that affect the deformation resistance of aluminum alloys?
Sensitive to temperature As the temperature decreases, its high temperature deformation resistance increases rapidly, faster than carbon steel. It can be seen that the ultimate growth rate of high temperature strength is faster than that of carbon steel when it is dry. Aluminum alloys, especially those with a high degree of alloying, cannot be forged at low temperatures. Therefore, the forging temperature range of aluminum alloys is narrow, and the operation should be rapid. The deformation resistance of aluminum alloys in the die forging process determines the strength limit of the material itself, the processing conditions and the complexity of the forgings.