General role of rare earth elements in dynamic characteristic of series of FeB-based bulk-glass-forming liquids

Abstract We investigated the viscosities of several series of FeB-based bulk-glass-forming melts with rare earth element additions. The viscosity discontinuity generally exists in the melts. With the rare earth element addition, such dynamic transition becomes indistinct. By the concept of superheated liquid fragility, the addition of rare earth elements significantly reduces the degree of the dynamic transition F from larger than 1 to less than 1. A generally negative correlation between F and GFA has been demonstrated. By conducting the ab initio molecular dynamics simulations, the competition between the formations of square antiprism structures and the stable rare-earth-contained polyhedra around B atoms have been found to determine the F value, as well as the GFA of FeB-based liquids. This work demonstrates the mechanism underlying which the glass-forming ability of alloys is greatly improved by rare earth elements, and provides a novel route to obtain bulk-size Fe-based glasses.