Studies on directional and rapid solidification of Al‐B‐Cu composites

Abstract

The present work studies the effect of directional and rapid solidification on the distributions of borides reinforcements and mechanical properties of Al-B-Cu composites. To analyze the influence of these two manufacturing methods, samples of Al alloys with copper levels between 1 and 5 wt % and boron between 1 and 5 wt% were prepared in an arc-melting furnace and via directional casting. The characterization techniques used included optical microscopy, scanning electron microscopy (SEM), differential thermal analysis (DTA) and Vickers microhardness. From directionally solidified samples, cooling curves were recorded and parameters as local solidification times, front (solid and liquid) velocities, among others were determined. The results allowed identifying AlB2 particles in samples obtained from directional solidification and the coexistence of AlB2 lamellar and AlB12 reinforcements in rapid solidification samples, depending on the amount of input energy. Dendritic structures were presented in both methods and θ phases tended to locate in the grain boundaries. The particles’ role as nucleant agents was discussed and the main differences were established between both processing methods.