Amorphous phase partitioning in FeCo-based metallic glass alloys

There are evidences in the literature of a short-range order concerning B and Si metalloids in the FeCo-based alloys. The existence of chemical preferences leading B–Fe and Si–Co pairs seems to be the origin of this short-range order. In this work amorphous and crystalline FeCo-based alloys were analyzed regarding their crystallization process. The alloy compositions were chosen in order to present super-cooled liquid region prior crystallization. Ribbons of Fe36Co36Nb7Si10B11, Fe36Co36Nb6Cu1Si10B11 and Fe36Co36Zr7Si10B11 alloys were extensively analyzed by X-ray diffraction, differential scanning calorimetry and transmission electron microscopy in amorphous state, after annealing below the crystallization temperature and after annealing at the crystallization temperature. The TEM revealed an interconnected and textured structure suggesting amorphous phase partitioning prior crystallization. The textured amorphous structure produced by spinodal decomposition could trigger the crystallization process leading to nanometer sized crystals.