Influence of Thermomechanical Processing on the Microstructure and Tensile Behavior of Solution-Treated Al-18%Si-4.5%Cu Alloy

The precipitation behavior during equal-channel angular pressing (ECAP) performed at 400°C in an Al-Si-Cu alloy has been investigated. Meanwhile, grain refinement and tensile properties of solution-treated A390 Al alloy have been studied under various ECAPed passes. Microstructural results showed that during the solution treatment, the high volume fraction of intermetallic compounds (IMCs) such as Al₂Cu and Al₆₅Cu₂₀Fe₉Mn₆ were dissolved into the α-Al phase and the eutectic silicon particles were dramatically modified. The dynamic precipitation of the second phase particles occurred into the aluminum matrix during the first pass of high-temperature ECAP processing. The postponing occurrence of the DRX process in the first two ECAP passes can be attributed to releasing the stored energy by precipitation process before recrystallization and hindering dislocation movement by fine precipitates interior the grains. Further ECAP passes increased the roundness of second phase particles such as primary silicon particles and IMCs. The ultimate tensile strength increased after solution treatment due to dislocation strengthening and solid solution strengthening. ECAP process in high temperature led to improve the ductility of solution-treated A390 Al alloy due to eliminating the shrinkage porosities, refining the Al grains, and modifying the second particles.