The sensitivity of 2A12 alloy is lower than that of 2A11 alloy. The biggest factor affecting the cracking tendency of the alloy is the content of two impurities, that is Fe and Si. At the same time, the content of Mn and Mg also has a certain effect.
The tendency of 2a12 aluminum to form hot cracks increases with the increase of Si content. At the same time, the more impurities Fe and Si in the alloy, the lower the casting process performance of the alloy.
In order to eliminate the cracks in the ingot, the Si content should be controlled to be less than 0.35% in composition, and the Fe content should be 0.05-0.10% higher than the Si content.
The content of Mn and Mg in 2A12 aluminum plate should be appropriately controlled to be at a low level. Because with the increase of Mn content, the solubility of Cu, Mg, and Si in the alloy in aluminum decreases.
When the content of Mg in the alloy increases, it not only reduces the casting process performance of the alloy, but also increases the alloy's sensitivity to notches, thereby increasing the tendency of the ingot to crack.
The Mg content is controlled lower than the middle limit, and the total amount of Cu and Mg is less than 6.3%, to prevent the increase of the hard and brittle phase volume fraction leading to an increase in the tendency of cracks.
After the aluminum alloy is aged, the phenomenon of aging strengthening will occur. If the low-temperature-aged alloy is heated for a short time at a relatively high temperature (but lower than the solution treatment temperature) and quickly cooled, its hardness will immediately drop to almost the same as when it was just quenched. This phenomenon is called regression.
After 2A12 aluminum plate is naturally aged, it is heated for a short time at 200-250℃ and then rapidly cooled, then it can be naturally aged again.
Original Source:https://www.aircraftaluminium.com/a/effect-of-element-control-of-2a12-aluminum-on-hot-cracking.html
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