Relook on fitting of viscosity with undercooling of glassy liquids

Abstract

The present approach is on the modification of viscosity fitting of undercooled liquid as a function of undercooling. The method consists of finding analytical solution of three arbitrary constants of the Vogel–Fulcher–Tamman (VFT) equation by choosing three viscosity data at three critical temperatures for an undercooled liquid. Three critical temperatures are liquidus temperature (T l), crystallization onset temperature (T x) and glass transition temperature (T g). The experimental viscosity data at or very near to these three critical temperatures (depending on the availability in literature) have been utilized to achieve the analytical solution. The analytical solution of VFT equation is further examined by selecting the experimental data points away from the critical temperatures in order to check their (T l,T x and T g) significance towards the solution. Total absolute error (TAE) and total squared error (TSE) values obtained from the present method with respect to the experimental viscosity data in the temperature range between T l and T g are very much comparable and in most of the cases lower than that of existing ‘best-fit’ cited in the literature for a number of glassy alloys. Moreover, this method interestingly enables us to find the fragility parameters for a number of glassy alloys and convincingly explain their true glass forming abilities (GFA).