Melting and solidification in microgravity of sintered aluminum powder alloys.

Results of melting and solidification experiments in μ-g of sintered aluminum powder alloys (with 4 pct and 7 pct of A1O) are presented. Thin oxide films have been used as tight containers which remain adherent during melting and solidification. Convective motion in melted metals in μ-g are indicated from observations of the oxide particle distribution after melting and solidification. Effects of Marangoni convection are always observed in relatively large cylindrical samples, 5 mm diameters, melted and solidified in μ-g. Thin disc-shaped samples do not present evidence of convective motions in μ-g. Even in the absence of convective motion in the thin samples, some particle aggregation occurs, depending on the interactions with the solidification front and conditioned by diffusion controlled critical radii for capture in the solid. [ABSTRACT FROM AUTHOR]