Nanocrystallisation of Soft Magnetic Fe-Co-Zr-Cu-B Alloys

In the present study, Fe$\text{}_{41}$Co$\text{}_{41}$B$\text{}_{10}$Zr$\text{}_{7}$Cu$\text{}_{1}$ alloy has been investigated in order to evaluate its thermal stability and structure after heat treatment, as well as the impact of heat treatment on magnetic properties. X-ray diffractometry, differential scanning calorimetry, chemical composition microanalysis, transmission electron microscopy, and magnetic hysteresis loop measurement techniques were employed. The crystallisation temperature of the as-quenched alloy is 490ºC (continuous heating at 5ºC/min). The melt-spun ribbon having 27μm in thickness was annealed for 1 hour at temperatures from 400 to 700ºC. The alloy after treatment at about 550ºC underwent primary crystallisation, with the average size of crystals under 20 nm. This specimen shows the coercive field of 38 A/m, as compared to about 160 A/m reported for a similar alloy (Fe$\text{}_{44}$Co$\text{}_{44}$B$\text{}_{4}$Zr$\text{}_{7}$Cu$\text{}_{1}$) with a similar structure, annealed at 600ºC.