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

The kinetic viscosity (eta) of superheated melts, thermal properties (T-x, T-m, T-L) 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' = E-s delta(x)/k(B), 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. (c) 2005 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.