Prediction of solidification paths in Al-Si-Fe ternary system and experimental verification: Part II. Fe-containing eutectic Al-Si alloys

Abstract

The effects of Fe content and cooling rate on the solidification path and formation behavior of the Al5FeSi (β) phase in Fe-containing eutectic Al-Si alloys were studied based on thermodynamic analysis and pertinent experiments. To predict solidification path in Fe-containing eutectic Al-Si alloys, the thermodynamic calculations in the Al-Si-Fe ternary system, including the high Fe region, were systematically performed using the Thermo-Calc program and updated database. To experimentally verify the predicted results, designed two eutectic Al-Si alloys with different Fe levels were solidified under slowly-and rapidly-cooled conditions, respectively. The cooling curves of the solidified alloys were recorded by thermal analysis. Microstructures of the casting samples were studied by the combined analyses of optical microscopy (OM) and scanning electron microscopy (SEM). For the slowly-cooled condition with the high Fe level, the primary β phase was mainly formed by the quasi-peritectic reaction of L + γ → α + β (656°C). For the rapidly-cooled condition with high Fe level, the primary β phase was mainly formed by the reaction of L → β (583∼649°C). © 2011 The Japan Institute of Metals.