Rapid heating of ferromagnetic amorphous alloys

Fe-base and Ni-base ferromagnetic amorphous alloys become brittle after conventional furnace annealing. It is a serious problem for practical applications. The purpose of the research is to use rapid heating processes to improve the magnetic properties and avoid the annealing embrittlement of Fe-base amorphous alloys. The results show that ac Joule heating and pulsed high current heating are suitable techniques to improve the soft magnetic properties and to retain the ductility of Fe-base and Ni-base amorphous ribbons.;We supposed that the mechanisms in rapid Joule heating could be considered as follows: (1) Improving the soft magnetic properties by (a) rapid heating to relieve the quenched-in stress of as-cast; amorphous ribbons. (b) fast impulse on magnetic domain pinning in amorphous ribbons. (2) Improving the annealing embrittlement by avoiding the time dependent structural relaxation of amoprhous ribbons.;Our results showed that the above supposition is reasonable. A summary of our results are: (1) The improvement of the soft magnetic properties has a good correlation with the stress relief in ferromagnetic amorphous alloys. (2) Annealing embrittlement of Fe-base amorphous alloys is induced by the structural relaxation which is time dependent. (3) The stress relief rate in rapid Joule heating is much faster than that in conventional furnace annealing. (4) The kinetics of the stress relief in rapid Joule heating satisfies the relation of ;A detailed investigation of the above is discussed in this thesis.