The solidification behaviour of undercooled Al-Cu alloys in contact with the primary phases

Abstract

The near eutectic Al-Cu liquid is undercooled in contact with both α-Al and θ -Al₂ Cu phase by entrained droplet technique to study and understand the evolution of solidification microstructures at different undercoolings and for different substrates. Four different types of microstructures could be observed in droplets in contact with α-Al and two distinct morphologies could be observed in the droplets in contact with θ -Al₂ Cu. The results can be qualitatively explained with the help of an extrapolated metastable phase diagram and present understanding of solidification in undercooled melt. Finally the knowledge gained is extended to analyse the solidification behaviour of Al-Cu eutectic melt pool obtained by pulsed laser processing.