Correlation between magnetic and mechanical properties of devitrified glass-coated Fe71.8Cu1Nb3.1Si15B9.1 microwires

The effects of the thermal treatment on the coercivity and mechanical behaviour of glass covered Fe71.8Cu1Nb3.1Si15B9.1 microwires have been investigated. Variations of the coercivity, Hc, with the annealing are attributed mainly to the devitrification process in this kind of microwires. The annealing temperature dependencies (300-700 deg. C) of Hc exhibit some peculiar differences with respect to that of the classical Finemet ribbon, especially in the temperature range of 400-500 deg. C (very beginning of the nucleation of the nanocrystallization process) and at 650-700 deg. C (magnetic hardening owing to the iron borides segregation). Correlation of coercivity with the tensile strength after annealing has been observed. Character of the fracture studied by the scanning microscopy changes significantly with annealing.