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Microstructural defects of Fe-based Amorphous and Nanocrystalline Soft Magnetic Alloys Investigated by Doppler Broadening Positron Annihilation Technique

Wei LU*, Biao YAN, Renjian Tang

 

Abstract

The structural defects in Fe-based amorphous and nanocrystalline soft magnetic alloy has been investigated by Doppler broadening positron annihilation technique. Amorphous alloys (Type I) which can form a fixed microstructure with amorphous and nanocrystalline phases after traditional annealing have more defects than alloys (Type II) which cannot form this microstructure after the same heat treatment Also, the nanocrystallized Finemet alloy has more defects than the as-quenched state and the nanocrystallization process introduce more defects. The change of line shape parameter S with annealing temperature in Finemet alloy is mainly due to the structural relaxation, the pre-nucleation of Cu nucleus and the nanocrystallization of α-Fe (Si) phase during annealing. In addition, Nanocrystalline Finemet alloy has good thermal stability at temperature range of 500°C~580°C and good aging stability at room temperature.

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