Fragility of superheated melts and glass-forming ability in Pr-based alloys

The kinetic viscosity (η) of superheated melts, thermal properties (Tx, Tm, TL) and X-ray diffraction analysis on the Pr-based bulk metallic glasses (BMG) are reported and discussed. A new refined concept, the superheated fragility defined as M′  = ESδx/kB, has been developed based on common solidification theory and the Arrhenius equation. The interrelationship between this kind of fragility and the glass-forming ability (GFA) is elaborated on and evaluated in Pr-based BMG and Al-based amorphous ribbon alloys. Using viscosity data of superheated melts, it is shown, theoretically and experimentally, that the fragility parameter M′ may be used as a GFA indicator for metallic alloys.