Structural relaxation in metallic glasses

Structural relaxation in several transition metal based metallic glasses has been studied using differential scanning calorimetry (DSC), X-ray diffraction (XRD), electrical resistivity, acoustic emission and Mossbauer spectroscopy techniques. Annealing of metallic glass below the crystallization temperature gives rise to discontinuous changes in electrical resistance. These changes are accompanied by acoustic emissions. The latter process provides an indication for the viscous flow in the matrix. In diverse alloy compositions, it has been observed that changes in electrical resistivity which begin instantly with the onset on isothermal annealing do not follow diffusion kinetics. Mossbauer experiments also show that neither long range diffusion nor the formation of a new phase occurs as a result of annealing. It is concluded that viscous flow is the mechanism for structural relaxation induced by isothermal annealing and short range ordering during this process is also a consequence of the viscous flow process.