Investigation of glass forming ability of Al-based metallic glasses by measuring vaporization enthalpy.

The analysis of the enthalpy changes for vaporization (ΔHvap) of Al-based metallic glass (MG) can provide insight into the origin of the MG's glass forming ability (GFA). The ΔHvap of three Al-based MGs, Al84.5 ± x(Y10Ni5.5)15.5 ± x, Al85 ± x(Y8Ni5Co2)15 ± x, and Al86 ± x(Y4.5Ni6Co2La1.5)14 ± x, (hereafter referred to as AYNx, AYNCx, and AYNCLx, respectively), is analyzed by measuring their weight losses below their glass transition temperatures. The relationship between ΔHvap and aluminum concentration exhibit minimum values in the range of 83-85 at.% of Al, and the ΔHvap increases, becoming saturated at 320-350 kJ/mol, as the percentage of Al deviates from this range. The depth of the enthalpy well, referring to the bottom of the parabolic graph of ΔHvap against the Al concentration, is proportional to the viscosity of clusters showing liquid-like behavior. The amount of weight loss is proportional to the concentration of these clusters. The cluster viscosity and concentration influences the overall viscosity of the MGs, and thus determines the GFA.