Correlation between thermal expansion coefficient and glass formability in amorphous alloys

The dilatometric and thermal behaviors such as the thermal expansion coefficient (α) and the liquidus temperature (Tl) of Al-Ni-RE (RE = Y, Ce, Gd and Er) amorphous alloys were investigated by a conventional dilatometer and differential scanning calorimetry (DSC). Results show that αexp/Tl (defined by θ) has a good positive correlation with glass forming ability (GFA) in Al-based amorphous alloys, where αexp is the average linear thermal expansion coefficient. A similar phenomenon is also found in Gd- and Cu-based amorphous alloys. Based on the free volume model, it is found that the amorphous alloy which exhibits better GFA contains less free volume. Consequently, the parameter θ can be applied to predict the GFA in the system with same main element.