Copper content and cooling rate effects over second phase particles behavior in industrial aluminum-silicon alloy 319

This study was done choosing, the automotive aluminum alloy 319, to know how copper content act over Si, Cu and Fe particles versus applied different loads (stress) and cooling rate. This was done to know which particles fracture according to the morphology and size. This analysis was carried out has been using samples with different secondary dendrite arm spacing (SDAS) values (similar to 27 to similar to similar to 46 mu m). After applying solution and overageing heat treatment for 485 degrees C for 5 h, then quenched in water at 25 degrees C and 230 degrees C for 3 h and 20 min, after they cooled out of furnace. The tensile stage consisted of applying different stresses, start from 150, 200, 250 and finally 300 MPa on every batch of specimens for each condition. The particle fractures were also analyzed on the polish surface by optical microscope and image analyzer to quantitative metallography. SEM was used to identify and EDX to confirm the fracture of particles on the polished section. Cast Al-Si-Cu-Mg alloys may contain interdendritic phases, including Si, Fe and Cu bearing particles and it is necessary to know how SDAS, heat treatment and copper content affect the mechanical properties and this has been illustrated and discussed in this study. (c) 2005 Elsevier Ltd. All rights reserved.