A conceptual approach to evaluate glass-forming ability for various glass-forming systems has been proposed from a physical metallurgy point of view. It was found that the glass-forming ability for noncrystalline materials was related mainly to two factors, i.e., 1/(Tg + Tl) and Tx (wherein Tx is the onset crystallization temperature, T g the glass transition temperature, and Tl the liquidus temperature), and could be predicated by a unified parameter γ defined as Tx/(Tg +Tl). This approach was confirmed and validated by experimental data in various glass-forming systems including oxide glasses, cryoprotectants, and metallic glasses.

Recent advancement in bulk metallic glasses, whose properties are usually superior to their crystalline counterparts, has stimulated great interest in fabricating bulk amorphous steels. While a great deal of effort has been devoted to this field, the fabrication of structural amorphous steels with large cross sections has remained an alchemist’s dream because of the limited glass-forming ability (GFA) of these materials. Here we report the discovery of structural amorphous steels that can be cast into glasses with large cross-section sizes using conventional drop-casting methods. These new steels showed interesting physical, magnetic, and mechanical properties, along with high thermal stability.