Nanocrystalline Fe(Co)ZrMoBCu soft magnetic alloys: A transmission electron microscopy study of the microstructures

Nanocrystalline Fe ₈₁Zr ₇Mo ₂B ₉Cu ₁ and Fe _40.5Co _40.5Zr ₇Mo ₂B ₉Cu ₁ alloy ribbons were prepared by annealing the as-quenched amorphous alloys at their first exothermic peak temperature. The primary crystallization phases of Fe ₈₁Zr ₇Mo ₂B ₉Cu ₁ and Fe _40.5Co _40.5Zr ₇Mo ₂B ₉Cu ₁ consisted of nanoscale body-centered cubic α-Fe and α-FeCo grains, respectively _. The microstructures and compositions were analyzed via transmission electron microscopy (TEM) and scanning transmission electron microscopy (STEM), and area maps were obtained through energy-dispersive spectroscopy (EDS). The addition of Co decreased the mean grain size ( D ) and broadened the grain-size distribution (σ). The effect of the addition of Co on the Cu clusters and element distribution was studied in detail. Scanning transmission electron spectroscopy combined with energy-dispersive spectroscopy revealed that both alloys contained Cu clusters; the Fe _40.5Co _40.5Zr ₇Mo ₂B ₉Cu ₁ alloy exhibited a Cu-cluster density similar to that of the Fe ₈₁Zr ₇Mo ₂B ₉Cu ₁ alloy. Both alloys contained relatively less Fe in their residual amorphous phases than in their nanocrystals, with the nanocrystals in Fe _40.5Co _40.5Zr ₇Mo ₂B ₉Cu ₁ containing less Co than in the residual amorphous phase. Fe _40.5Co _40.5Zr ₇Mo ₂B ₉Cu ₁ exhibited higher specific saturation magnetization ( M _s ), specific remanent magnetization ( M _r ) and larger coercivity ( H _c) than Fe ₈₁Zr ₇Mo ₂B ₉Cu ₁.