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

The analysis of the enthalpy changes for vaporization (ΔH_vap) of Al-based metallic glass (MG) can provide insight into the origin of the MG's glass forming ability (GFA). The ΔH_vap of three Al-based MGs, Al_{84.5 ± x}(Y₁₀Ni_5.5)_{15.5 ± x}, Al_{85 ± x}(Y₈Ni₅Co₂)_{15 ± x}, and Al_{86 ± x}(Y_4.5Ni₆Co₂La_1.5)_{14 ± x}, (hereafter referred to as AYN_x, AYNC_x, and AYNCL_x, respectively), is analyzed by measuring their weight losses below their glass transition temperatures. The relationship between ΔH_vap and aluminum concentration exhibit minimum values in the range of 83-85 at.% of Al, and the ΔH_vap 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 ΔH_vap 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.