Influence of Crystallization on Magnetic Properties in Co₆₆Fe₄Mo₂Si₁₆B₁₂ Amorphous Alloy

The annealing effects on the magnetic properties and structures of Co₆₆Fe₄Mo₂Si₁₆B₁₂ amorphous alloy were studied by means of ballistic method and x-ray diffraction technique respectively. During the isothermal annealing at T_a = 460°C, the initial permeability μ_i of the sample increased at first, then decreased with the annealing time t_a and exhibited a maximum at about t_a = 45 min. Meanwhile, it was found that magnetostriction λ_s changed with t_a and ran through zero at about t_a = 45min. The x-ray diffraction results showed that the sample was still in an amorphous state in the whole 460°C isothermal annealing process ( t_a = 0-120min). After the annealing temperature increased to 480°C, α-Fe(Co,Si) phase began to precipitate, then, Co₃Mo crystallites and other phases were formed subsequently at 500°C. The results of magnetic measurement indicated that the formation of any crystalline phases should lead to the deterioration of magnetic properties.