Nanocrystallization and magnetostriction coefficient of Fe52Co34Hf7B6Cu1 amorphous alloy treated by medium-frequency magnetic pulse

The Fe₅₂Co₃₄Hf₇B₆Cu₁ amorphous alloy ribbons were prepared by single-roller-quenching method and then treated by medium-frequency magnetic pulse. The microstructural changes of specimens before and after magnetic pulse treatment were observed by TEM and Mössbauer spectroscopy techniques. The magnetostriction coefficient of specimens before and after the medium-frequency magnetic pulse was measured by homemade magnetostriction coefficient measurement system. The results showed that the specimens were nano-crystallized after treated by medium-frequency magnetic pulse. The crystalline phase was α-FeCo which dispersed in the residual amorphous matrix phase to form the two-phase nanocrystalline alloys. The magnetostriction coefficient of specimens after treated by medium-frequency magnetic pulse was composed of the positive magnetostriction coefficient of amorphous matrix phase and the negative magnetostriction coefficient of nanocrystalline phase. With the increase of the crystallization volume fraction, the magnetostriction coefficient λ decreased. And accompanied with the increase of the applied DC magnetic field intensity H, the magnetostriction coefficient λ firstly increased and then decreased.