Resistometric detection of short-range ordering in the metallic glasses Cu50Ti50and Ni35Ti65

Abstract

The potentialities of combined electrical resistivity measurements and quench experiments to follow the evolution of local order and infer atom jump frequencies in short-range ordering alloys are recalled. Application to two amorphous alloys, Cu₅₀Ti₅₀ and Ni₃₅Ti₆₅, is presented. In either case, a reversible variation of the resistivity with quench temperature could be discriminated from an irreversible evolution linked to the metastability of these materials with respect to the 'ideal' glass. The reversible term is thought to be reflection of the thermodynamic equilibrium state of chemical short-range order. This effect is discussed in the light of recent neutron diffraction and EXAFS studies, which have produced clear evidence that the metal atoms have a preference for unlike neighbours in both alloy glasses considered. From the observed pattern of the resistivity ordering curves, the existence of ordering domains each characterised by a specific relaxation rate and evolution degree of short-range order, was inferred. Atom jump rates were also derived.