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)(Y(10)Ni(5.5))(15.5 ± x), Al(85 ± x)(Y(8)Ni(5)Co(2))(15 ± x), and Al(86 ± x)(Y(4.5)Ni(6)Co(2)La(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.