The amorphous phase of Co₆₇Si₂₃B₁₀ alloy produced by mechanical alloying

ABSTRACT

In this work, the evolution and formation of the amorphous phase during the preparation of amorphous Co₆₇Si₂₃B₁₀ (at.%) powder by mechanical alloying (MA) under an argon atmosphere were studied. The grinding time of 15 h had a profound effect on the phase transformation, microstructure, morphology development, and thermal and magnetic behavior of the powders. These effects were studied by X-ray diffraction (XRD), EDX scanning electron microscopy (SEM), thermal analysis (TGA/DTA), N₂ texture analysis (BET/BJH) and, magnetic measurements (VSM). The results show that the evolution of the amorphous phase in the early stage of milling consists of nanocrystalline α-Co₂B and β-Co₂Si phases, which are diluted and coexist with the amorphous phase. After 15 hours of ball milling, the amorphous phase became the main phase with a proportion of 98.1%, which is relatively high compared to the 1.9% of the nanocrystalline phases α-Co₂B and β-Co₂Si. The results obtained indicate that amorphization develops with higher thermal stability than a small fraction of the nanocrystalline phase diluted in the amorphous phase. This behavior suggests the presence of the amorphous phase coexisting with the nanocrystalline phase in a small fraction with overlapping crystallization and recrystallization at a temperature of around 924.42°C.

Keywords:
amorphous phase; Co₆₇Si₂₃B₁₀ powder; mechanical alloying (MA)