Role of starting phase of boron on the mechanical alloying of FeNbB composition

Mechanical alloyed Fe75Nb10B15 systems, prepared with crystalline or commercial amorphous boron and a similar composition with the same Fe/Nb ratio but no boron, have been studied as a function of milling time in the aim of enhancing the homogenization of boron and determining its role on the mechanical alloying process. Neither boron addition nor boron phase used affect the developed microstructure at very early stages. After 4 h milling at 350 rpm, the formation of an amorphous phase was observed for boron containing compositions while for the boron-free alloy a supersaturated solid solution was found in the final microstructure. The alloy prepared using commercial amorphous boron showed a larger fraction of amorphous phase than that prepared using crystalline boron for the same milling time, suggesting that amorphous boron accelerates the formation of the amorphous phase during mechanical alloying.

► Boron addition is needed to produce amorphous alloy in the studied Fe/Nb ratio. ► Amorphous boron facilitates the incorporation of this element to the matrix. ► The use of amorphous boron enhances the formation of amorphous Fe–Nb–B phase. ► Crystalline inclusions of almost pure boron remain even after long milling times. ► The incorporation of Nb to Fe matrix can be followed from the variation of low field contributions to Mössbauer spectra.