Structural relaxation and irreversible changes of electrical resistivity of Fe-Ni-Mo-B amorphous alloys

Abstract

The structural relaxation of Fe-Ni-Mo-B alloys with different Mo content is studied through electrical resistivity measurements between the room temperature and the glass transition temperature Tg. The observed behavior of the resistivity during isothermal annealing treatments gives evidence for the presence of competing processes of compositional and topological short-range ordering, whose nature and role are discussed. The variation of the temperature coefficient of resistivity, α, observed after annealing of ribbons, is related to the variation of the degree of topological short-range order, and interpreted on the basis of the theories describing the electrical resistivity and the structural relaxation of amorphous metals. A simple relation between the variation of α after annealing, and the reduction of the alloys’s free volume, is derived and discussed.