Rapid solidification and decomposition of a hypomonotectic Al-Cd alloy

Abstract

Rapid solidification of Al-1.5at % Cd alloy can lead to a wide variety of morphologies. The sequence of the morphologies with increasing foil thickness is single phase → elongated cell → hexagonal cell → dendrite. Monotectic reaction ahead of the solid-liquid interface leads to a unique distribution of the cadmium particles. Models are proposed to explain the genesis of the distribution of these particles. The study of the decomposition behaviour confirms the existence of a preprecipitation stage. The G.P. zones are found to be spherical and lead to a precipitate-free zone near grain/cell boundaries. The coarsening of the precipitates at liquid temperatures takes place by the migration and coalescence of the droplets.