Effect of melt flow on macro- and microstructure evolution during solidification of an Al-4.5% Cu alloy

Melt flow plays a significant role in structure formation and redistribution of solid phase in liquid during solidification processes. The effect of melt flow along the solidification front on macro- and microstructure of an aluminium alloy is investigated. An electromagnetic pump is used as a tool to create the controlled forced flow of liquid metal. The experiments are performed on an Al-4.5% Cu alloy in a wide range of melt flow velocities and temperatures. Simulations of melt flow and solidification using "computational fluid dynamics" software are applied to clarify the structure formation and to obtain the temperature gradient along the solidification front. It is observed that the constant melt flow influences the structure formation, growth direction and grain size during solidification, i.e. the grain morphology changes from equiaxed under no-flow conditions to columnar under constant flow. The effect of melt flow on dendrite arm spacing is more complex. (c) 2005 Elsevier B.V. All rights reserved.