AlTiSi intermetallics: morphology and its role on nozzle blockage during semi-continuous casting

Abstract

It is shown that the addition of small percentages of Ti to A356 Al-Si alloys results in the formation of AITiSi intermetallics with two distinct morphologies; flake and blocky. Higher cooling rates and lower Ti contents favor flake formation while the reverse is true for blocky particles. On further reheating, the flakes undergo morphological changes due to spheroidization and coarsening and convert into large blocks which may result in confusion as to which morphology is more detrimental toward the blockage of casting nozzles. This paper is a further elaboration of the previous reports to not only emphasize the effect of Ti content and cooling rate on the formation of either ATT iSi intermetallic morphologies, but also to identify the morphology that becomes problematic for semi-continuous or continuous casting operations.