Dynamic tensile measurements for below the calorimetric glass transition temperature

Abstract

Dynamic tensile measurements have been carried out on a ternary metallic alloy, , below and close to the calorimetric glass transition temperature. The storage and loss tensile moduli, as well as the complex and dynamic tensile viscosity, are found to obey the time-temperature superposition principle in this temperature range. Structural relaxation times were measured from the position of the maximum in the loss modulus and from the limiting low-frequency value of the complex viscosity and its real component. The three quantities display Arrhenius temperature dependences with similar activation energies and indicate that the metallic alloy has an intermediate fragility strength in the general classification scheme for glass-forming liquids. The master curves obtained by scaling the measured dynamic properties by the appropriate relaxation time reflect a very broad distribution of microscopic relaxation times. A discrete spectrum of relaxation frequencies has been calculated from the master curve for the storage modulus assuming a superposition of intrinsic exponential responses. The resulting distribution is broad and skewed towards high frequencies, a characteristic feature of heterogeneous relaxation. It is found that the high-frequency end of the relaxation spectrum controls the amplitude, whereas the low-frequency end determines the width of the overall macroscopic response. The results presented here indicate a very high degree of dynamic heterogeneity in the tensile relaxation process for supercooled .