The influence of the casting parameters and of the surface quality on magnetic and magnetoelastic properties of the amorphous Co21Fe64B15 alloy

The influence of the casting parameters and of the surface quality upon DC hysteresis loops J(H) and field dependence of the Youngʹs modulus E on the applied field H was studied for 6 mm wide ribbons of the Co21Fe64B15 amorphous alloy. Five ribbons were prepared by melt-spinning technique with the different thermal history of the melt. The as-cast ribbons exhibited different levels of quenched-in stresses and different surface topology, as determined by surface profiling and optical microscopy. A correlation was found between the thermal history of the melt and the surface topology of the ribbons. The as-quenched ribbons were stress-relieved at 263 °C × 2 h in vacuum and after the stress-relief DC J(H) and E(H) curves were measured. The coercivity and the magnitude of ΔE-effect increased and the initial susceptibility decreased with increasing surface roughness. There was, however, found no correlation between surface roughness and saturation magnetostriction of the stress-relieved samples. The annealing in transverse magnetic field (265 °C × 2 h × 358 kA m−1 in vacuum) removed almost all differences between materials, excepting the material with the worst surface quality.