The role of damage on the deformation and fracture of Al-Si eutectic alloys

An experimental study has been conducted on an aluminum silicon alloy to evaluate the effects of microstructural damage on the overall ductility of the alloy. The alloy contained two populations of brittle phases, i.e. silicon particles and iron rich intermetallics. The morphology of the silicon second phase was varied from a fine fibrous to a fully spherodized structure. Microstructural damage was introduced by cold rolling. To separate the effect of strain on damage from its effect on work hardening behavior, the aluminum matrix was recrystallized after cold rolling. Damage of the second phase was observed by metallographic observations and quantified by changes in material density. It was observed that the tensile ductility was strongly dependent on the nature of the iron rich intermetallic phase. Cold reduction was found to be highly beneficial to the overall ductility, primarily as a result of damage to the iron rich phase. It was, therefore, concluded that the effect of microstructural damage on ductility requires a careful consideration of the nature of the damage and its effect on subsequent deformation behavior. Finally, density measurements suggested that some of the microstructural damage could be reduced during annealing of the alloy. (C) 2002 Elsevier Science B.V. All rights reserved.