Relation between mechanical properties and microstructure of cast aluminum alloy AlSi9Cu3

One common material for engine applications is the AlSi9Cu3 alloy. This alloy has a good castability, excellent machinability, medium strength, and low specific weight. The study was focused on the investigation of the effect of the solution heat treatment on the microstructure and mechanical properties of the alloy (strength-Rm, hardness-HBS). The temperatures of the solution heat treatment were 505°C, 515°C, and 525°C ± 5°C and the solution time ranged from 0 to 32 h (0, 2, 4, 8, 16, and 32 h). Alloy AlSi9Cu3 contained α-matrix, eutectic silicon, and other Fe-and Cu-rich phases with different morphology (needle-like, Chinese script, skeleton-like, blocky, etc.). The results obtained revealed the relation between the mechanical properties and the morphologies of the eutectic silicon and the predominant copper-rich phase Al-Al2Cu-Si during the solution treatment.