Gibbs free energy for the crystallization of metallic glass-forming alloys from an undercooled liquid

摘要

A novel expression has been obtained for the Gibbs free-energy change (Delta G) during the crystallization of an undercooled liquid. The expression for Delta G has been derived assuming that the specific heat difference Delta C-p is constant over a wide temperature range. Calculations based on the expression show that the Delta G values obtained for a variety of bulk glass-forming alloys (La55Al25Ni20, La55Al25Ni15Cu5, Cu47Ti34Zr11Ni8) are in excellent agreement with experimental values, with a maximum deviation of similar to 3% up to a chosen temperature as low as the Kauzmann temperature, T-K. However, for systems like Pd40Cu30Ni10P20, which possess excellent glass-forming ability, the constant-Delta C-p assumption is not appropriate and another similar expression for Delta G has been derived that uses a hyperbolic temperature variation of Delta C-p. The Delta G values for Pd40Cu30Ni10P20 obtained under this assumption lie very close to the experimental ones.