Electrical transport during phase transformation in metallic glasses

Electrical resistivity measurements have been used as a primary tool to study relaxation phenomena and high temperature structural transformations in metallic glasses. The author correlates, throughout this work, the resistivity behavior with structural measurements from high and low angle x-ray scattering, transmission electron microscopy, Moessbauer experiments, and low temperature superconductivity measurements to get a better understanding of the scattering mechanism during the phase transformation. He distinguishes between topological relaxation and chemical relaxation and in this latter case, phase separation is emphasized. Three systems are discussed extensively: amorphous Cu/sub 100-x/Zr/sub x/ around the equiatomic composition, (Mo/sub 0.6/Ru/sub 0.4/)/sub 100-x/B/sub x/ for boron concentrations ranging from x = 14 to x = 22, and (Zr/sub 1-x/Hf/sub x/)62Ni38. Upon annealing above 3000C, Cu50Zr50 phase separates into two amorphous phases of concentration close to CuZr2 and Cu10Zr7. In Mo-Ru-B alloys, the nonlinear behavior in resistivity is correlated with the presence of a peak in the small angle x-ray intensity and is explained in term of spinodal decomposition caused by the diffusion of boron in the amorphous matrix. In (Zr/sub 1-x/Hf/sub x/)62Ni38, an exothermic transformation which gives rise to an increase in resistivity but no resolvable Bragg peaks in the high angle x-ray pattern is investigated in detail. The applicability of the Ziman formalism to successfully explain the behavior of the resistivity in all these cases is questioned, and an alternative approach based on d-band conduction, is proposed