Effect of Directional Solidification Conditions on the Structure and Rollability of 2024 Aluminum Alloy

The 2024 aluminum alloy slab is usually produced at industrial scale with precise control on the solidification parameters using modern machines and undergoing extrusion process after casting in to eliminate the casting structure and increase the quality of the slab. The purpose of this research is to provide directional solidification in the 2024 aluminum alloy slab to control the mushy solidification and improve the rollability. For this reason directional solidification is used to eliminate the casting defects and to obtain thermal gradient between the riser and chiller. After studying on the effect of solution treatment T4 on the microstructure of the produced slab the possibility of avoiding rolling defects such as alligator cracking was studied and was optimized using simulation. The obtained results showed that with the feeder/sample ratio of 0.35 and the use of a suitable chiller, the directional solidification of Al2024 alloy can be obtained with minimum casting defects. Also study on the macrostructure and microstructure before and after solution treatment showed that a significant difference in the increase of the homogenization can be obtained by applying the applied thermal treatment. Furthermore the hardness of the solution treated sample is 30 percent less than of the as-cast sample which is due to the grain growth after thermal treatment and the elimination of the intermetallic phases of higher hardness. Also it was shown that the possibility of improving the rollability and avoiding rolling defects specially alligator cracking is possible using the suitable conditions of directional solidification and thermal solution.