Design and microstructure analysis of globules in Al-Co-La-Pb immiscible alloys with an amorphous phase

Abstract

An immiscible alloy with an amorphous phase, Al-Co-La-Pb, was designed by the combination of empirical rules, prediction of phase diagrams based on ab initio calculations, and thermodynamic calculations. The solidification microstructure of rapidly solidified Al-Co-La-Pb melt-spun ribbons was investigated. Liquid-phase separation and the formation of an amorphous phase occurred simultaneously in the Al-Co-La-Pb alloy, resulting in the formation of Pb globules embedded in the Al-Co-La–based amorphous matrix. The particle size distribution of the globules and the formation of Pb nanoglobules were explained by the multistep liquid-phase separation. STEM observation clarified the microstructure of oxygen-enriched globules with double shell layers in the Al-Co-La-Pb alloy.