Evaluation of relaxation process in FeMo₁₄C₁₅B₆Er_x (x = 0–2) bulk metallic glass by valence electron energy loss spectroscopy

Relaxation processes during heating of both ribbon and bulk FeMo₁₄C₁₅B₆Er_x(x = 0∼2) metallic glasses were examined using valence electron energy loss spectroscopy (VEELS). The plasmon energy was decreased with increasing temperature due to thermal expansion and chemical reordering in the glasses. The chemical reordering stimulates a specific solute cluster formation; M₂₃(CB)₆ solute clusters began to form above about 200 °C in both ribbon and bulk FeMo₁₄C₁₅B₆Er_x (x = 0, 0.5, 1) metallic glasses. The M₂₃(CB)₆ solute clusters were only formed above 400 °C in the ribbon FeMo₁₄C₁₅B₆Er₂ metallic glass, indicating inhibition of the M₂₃(CB)₆ formation occurred owing to the Er-(C, B) complexes/clusters formation. The Er-(C, B) complexes/clusters were formed in the cooling process of the sample fabrication. In contrast to the ribbon sample, the M₂₃(CB)₆ formation did not occur in the bulk FeMo₁₄C₁₅B₆Er₂ metallic glass during heating. The amount of the Er-(C, B) complexes/clusters in the bulk sample was larger than that in the ribbon sample because of the slow cooling rate in the bulk sample fabrication. Because the solute carbon and boron atoms were mostly consumed by forming Er-(C, B) complexes/clusters in the bulk FeMo₁₄C₁₅B₆Er₂ metallic glass, the M₂₃(CB)₆ formation was suppressed.