Influence of partial substitution of Ge on crystallization kinetics, microstructure and magnetic property of Fe44Co44−xZr7B5Gex alloys

Partial substitution of Ge for Co in Fe44Co44Zr7B5 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 4 at.% 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 Fe44Co44−xZr7B5Gex 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.

Research highlights▶ Partial substitution of Ge for Co in Fe44Co44Zr7B5 is found to have a large influence on crystallization kinetics of the amorphous alloy and magnetic property. The activation energy of the desirable primary crystallization of the FeCO phase decreases while that of the undesirable secondary crystallization increases.▶ The suppression of the secondary crystallizations stabilizes the FeCo nanocrystals embedded in the residual amorphous phase for the Fe44Co44Zr7B5 until higher temperatures. ▶ The stabilization mechanism is attributed to preferential partitioning of Ge in the residual amorphous phase, which is revealed by scanning transmission electron microscopy analysis.