THE ROLE OF Sr ON MICROSTRUCTURE FORMATION AND MECHANICAL PROPERTIES OF Al-Si-Cu-Mg CAST ALLOY

摘要

The aim of this paper is to assess the role of Sr modification on eutectic Si, Fe-rich intermetallic phases and porosity and their responses to the mechanical properties of a commercial high pressure die cast alloy Al-Si-Cu-Mg with Fe level up to 1%. Tensile test samples with a variety of coarsenesses, containing different Sr levels were cast using the gradient solidification technique, that enables a study of the solely influence of Sr on microstrucrure and tensile properties. The modification altered the morphology and size of eutectic silicon, while did not make a significant change on morphology of Fe-rich intermetallic and volume fraction distribution of porosity. The tensile test results indicate that eutectic Si modification is not a guarantee for improved mechanical properties due to the presence of a variety of intermetallics that tend to have a larger role on initiating and propagating cracks leading to premature failures in these commercial alloys.