GLASS-FORMATION BY CONTAINERLESS SOLIDIFICATION OF METALLIC DROPLETS IN DROP TUBE EXPERIMENTS

The authors investigated the glass-forming ability of Cu-Zr and Pd-Cu-Si alloys. Container wall-induced nucleation was eliminated by solidification of small droplets during free fall in a drop tube. The droplets were analyzed in terms of the fraction which solidified as a glass as a function of droplet size D (50 μm62Zr38, Cu58Zr44 and Pd77.5Cu6Si16.5 are obtained. The critical cooling rate for solidification are up to 20 times smaller than those which are required in splat cooling. The analysis of the microstructure enables the density of nuclei to be determined; this depends essentially on the alloy concentration and the temperature from which the melt is cooled.