We studied the glass forming ability of Ni–Nb binary alloys and found that some of the alloys can be prepared into bulk metallic glasses by a conventional Cu-mold casting. The best glass former within the compositional range studied is off-eutectic ${\mathrm{Ni}}_{62}{\mathrm{Nb}}_{38}$ alloy, which is markedly different from those predicted by the multicomponent and deep eutectic rules. The glass formation mechanism for binary Ni–Nb alloys was studied from the thermodynamic point of view and a parameter ${\gamma }^{*}$ was proposed to approach the ability of glass formation against crystallization.

In the study of metallic glasses, it is vitally important for us to understand glass formation and glass forming ability (GFA). This letter presents a thermodynamic model for evaluating glass formation in metallic glasses. An expression has been derived from considering both the stability of amorphous phases and the resistance to the formation of crystalline intermetallic phases. This equation is very useful for identifying alloy compositions with good GFA in binary and other alloy systems. The prediction of this equation has been verified by the experimental study of glass formation and glass forming ability in the Zr–Cu system.