Compositional Effect on the Crystallization Behavior of Co–Fe–Si–B Amorphous Alloys with Zero Magnetostriction

抄録

Compositional dependence on crystallization behavior was examined for (Co_0.94Fe_0.06)_100−x−ySi_xB_y and Co_70.5−xFe_4.5M_xSi₁₀B₁₅ (M=transition metal) amorphous alloys with nearly zero magnetostriction. The crystallization occurs through one exothermic peak in the limited range of 26 to 27%(Si+B) and 0.5 Si/(Si+B) and two exothermic peaks in the other range. The onset temperature of the first exothermic peak (T_x1) increases with an increase of Si and B contents and a decrease of Si/(Si+B) from 0.7 to 0.5. The decrease of T_x1 with an increase of Si/(Si+B) is due to an easier precipitation of Co₂Si as compared with Co₃B. The heat of crystallization (ΔH_x) decreases with an increase of Si and B contents and shows a minimum value near 0.5 Si/(Si+B) for the alloys with the same metalloid content. The replacement of Co by Nb or Ta gives rise to a remarkable increase of T_x1. The Co–Fe–M–Si–B amorphous alloys containing 2 at% Nb or Ta crystallize through a simultaneous precipitation of crystalline phases and the crystalline structure is very fine because of the degradation of growth due to the dissolution of Nb or Ta. The two types of alloys exhibit smaller ΔH_x at compositions having larger glass-forming capacity. The tendency is interpreted by the assumption that the short-range atomic configuration in the amorphous alloys with large glass-forming capacity is similar to the corresponding equilibrium compounds.