Analysis And Treatment Of Deterioration Of Aluminum Alloy

The inhomogeneity of the ingot structure affects the performance of the ingot in a concentrated manner. The ingot used for forging, rolling and extrusion is particularly undesirable to reduce the columnar structure of the alloy process plasticity. Generally, alloys with a fine grain structure, fine grain internal structure, and uniform distribution of excess phase have the best cast properties and the highest press workability. Measures such as increased cooling rate, low-temperature casting (the term “pouring” is provided by the industry encyclopedia), ultrasonic oscillation casting, electromagnetic casting, etc. are conducive to obtaining the above ideal organization. Processing is the fundamental means to adjust the ingot structure.

  1. Overview of deterioration treatment
    The so-called metamorphic treatment is the process of changing the microstructure of the as-cast alloy under the action of a small amount of special additives (modifiers) to improve the dispersion of the metal or alloy structure. At present, the technical terminology of this processing method is not uniform, some are called thinning processing, and some are called gestation processing. The classification of metamorphic treatment is also different. Some people divide metamorphic treatments into three categories according to the final structural change characteristics of metals and alloys: the treatment of changing the size of primary dendrites and other primary crystals is called the first type of metamorphism, and the treatment of changing the internal structure of primary dendrites is called the second type Metamorphism treatment is called the third type of metamorphism treatment. Others classify the physical and metallurgical effects on crystallized alloys. Obviously, the boundaries between these concepts are difficult to distinguish. This manual understands the metamorphism treatment as the improvement of the metal and alloy ingot microstructure dispersion.
    At present, there are various theories that explain the process of metamorphism. Among them, there are famous nucleation theory, carbide theory, peritectic reaction theory, atomic structure theory, etc., but none of them can fully explain process. This is because, first, the metamorphism treatment process is very complicated, which is related to both smelting conditions and casting conditions; second, uncontrollable impurities have an effect, and the interaction of certain elements in the aluminum alloy also has an effect, they strengthen Or weaken the effect of grain refinement.
    According to the theory of crystal nucleation, the grain refinement is due to the presence of crystal nuclei, and the melt begins to crystallize on the crystal nuclei. These particles may be carbides, borides and aluminides of transition metals, and their lattice constants are similar to those of aluminum solid solutions (4.04A). According to this theory, additives added as modifiers should meet the following requirements: ① The chemical composition does not change at high temperature and there is sufficient stability in the aluminum melt; ② The melting point of the additive should be higher than that of aluminum; ③ The additive and aluminum The lattice should be compatible in structure and size; ④ form a strong and strong adsorption bond with the melt atoms to be processed.
    At present, in addition to aluminum sheet and aluminum foil production enterprises still using aluminum-titanium additives, domestic deformed aluminum alloy material manufacturers generally use aluminum-titanium-boron additives (wire or cake) for modification treatment. In addition, newly developed aluminum-titanium-boron-rare earth modifiers and aluminum-titanium-carbon modifiers have also been promoted.