Ultra-fine grained FeNi-based amorphous and nanocrystalline alloys with medium-range structural order

In this study, Fe 40 Ni 38 Ga 8 B 14 amorphous alloys were prepared through the melt spinning process, and the crystallization behavior and non-isothermal crystallization kinetics were investigated. Unlike the crystallization process in Finemet alloys where α-Fe precipitates using Cu clusters as nucleation sites, the Fe 40 Ni 38 Ga 8 B 14 amorphous alloy contains numerous pre-existing clusters that directly grow to form medium-range structural order. When the crystallized volume fraction of the alloy is below 0.25, some medium-range structural order continue growing into long-range structural order, specifically the γ-(Fe, Ni, Ga) phase. When the crystallized volume fraction exceeds 0.25, atomic diffusion become significantly suppressed. This results in a unique microstructure where medium-range structural order with varying degrees of atomic ordering coexist with long-range structural order approximately 5 nm in size. Consequently, the alloy exhibits excellent soft magnetic properties. The medium-range structural order and the novel type of nucleation site discovered in this work suggest new research directions for further refining the grain size of amorphous and nanocrystalline soft magnetic alloys.