Direct imaging of structural heterogeneity of the melt-spun Fe85.2Si2B8P4Cu0.8 alloy

A structural heterogeneity of the melt-spun Fe85.2Si2B8P4Cu0.8 alloy has been studied by spherical aberration (Cs) corrected high-resolution transmission electron microscopy. Hollow-cone illumination imaging revealed that the density of coherent scattering regions in the as-quenched Fe85.2Si2B8P4Cu0.8 alloy is much higher than that in the Fe76Si9B10P5 bulk metallic glass. According to the Cs-corrected TEM, crystalline atomic clusters, typically of ∼1 nm in diameter, are densely distributed in an amorphous matrix of Fe85.2Si2B8P4Cu0.8 alloy. Observation of four-fold and six-fold atomic arrangements of these clusters implies existence of Fe clusters with the body centered cubic structure. These Fe clusters must be responsible for the formation of ultrahigh-density α-Fe nanocrystals produced by post-annealing.