Role of Mo in the local configuration and structure stabilization of amorphous steels, a Synchrotron X-ray diffraction and Mössbauer study

Amorphous steels are promising materials with potential structural applications. The glass-forming ability (GFA) and mechanical properties of metallic glasses are intimately related to the local structure. In Fe-based alloys, Cr and Mo content seem to play a key role in stabilizing the amorphous atomic-level structure. Here we present a study on the effects of changing Mo content in Fe72−xC7Si3.3B5.5P8.7Cr2.3Al2Mox amorphous steels. We study the local structure of these alloys by Synchrotron X-ray diffraction and Mössbauer spectroscopy. The results show how the amorphous phase evolves from a ferromagnetic Fe-rich structure to a structure with predominance of paramagnetic environments with the increase of Mo content. The changes in the distribution of magnetic environments cannot be attributed only to the Fe–Mo substitution but to a change of local configuration in the amorphous phase.

► Mo substitution of Fe atoms stabilizes structure in amorphous steels.
► Mössbauer spectroscopy evidences two distinct Fe atoms environments in the amorphous structure of the Mo containing glassy alloys.
► Structural relaxation before crystallization produces homogenization of the Fe environments reducing population of sites with low hyperfine fields.