Modeling the atomic structure of amorphous steels using crystalline approximants

Using the pair density function analysis of pulsed neutron diffraction data, the local topology of Fe-based metallic glasses with good glass forming ability was investigated upon alloying with transition metal ions of Y, Zr, or Mo. Distinct short and medium range atomic order with common characteristics in all the glasses is observed. The local order is well described by a geometrical model constructed from superposition of "crystalline approximant" phases which is different from Frank-Kasper polyhedra clustering or dense random packing models. The mechanism responsible for the structure in the glass phase might involve a frustration-induced structural disorder of the crystalline approximant phases as they are driven away from stable stoichiometric compositions.