Influence of partial substitution of Ge on crystallization kinetics, microstructure and magnetic property of Fe_(44)Co_(44-x)Zr_7B_5Ge_x alloys

摘要

Partial substitution of Ge for Co in Fe_(44)Co_(44)Zr_7B_5 amorphous alloy is found to have a large influence on crystallization kinetics and magnetic property of the alloy. Activation energy of nanocrystallization of FeCo phase (primary crystallization) decreases by 90 kj/mol with 4at.% Ge substitution, while that of precipitations of Zr-type phase from a residual amorphous phase (secondary crystallization) increases by 106 kj/mol. The suppression of the secondary crystallizations stabilizes the FeCo nanocrystals embedded in the residual amorphous phase for the Fe_(44)Co_(44-x)Zr_7B_5Ge_x until higher temperatures. It is proposed that the stabilization mechanism is attributed to preferential partitioning of Ge in the residual amorphous phase revealed by scanning transmission electron microscopy analysis. Microstructure and coercivity for the annealed alloys are also presented in combination with the effect of the Ge substitutions.