Design and Characterization of Al-Co-La-Bi Multicomponent Immiscible Alloys with Liquid Phase Separation and an Amorphous Phase Formation

An immiscible alloy with an amorphous phase, Al-Co-La-Bi, was designed by the combination of the empirical alloy parameters of the mixing entropy, the predicted ground state diagram constructed by Materials Project for the database of ab initio calculations, and thermodynamic calculations using FactSage software and FTlite database. The solidification microstructure of rapidly solidified melt-spun ribbons of Al-Co-La-Bi alloy was investigated focusing on the distribution of Bi and liquid phase separation behavior. Liquid-phase separation and the formation of an amorphous phase occurred simultaneously in the Al-Co-La-Bi alloy, resulting in the formation of Bi–La intermetallic globules embedded in the Al-Co-La-based amorphous matrix. STEM observation clarified the microstructure of oxygen-enriched globules with double shell layers in the Al-Co-La-Bi alloy.