Calculation of the glass forming range in binary metallic systems using thermodynamic models

The volume fraction of crystallized material formed during continuous cooling of Ni-Ti melts is calculated as a function of cooling rate and alloy composition. The thermodynamic driving force for the transformation is calculated from a thermodynamic model for the liquid and solid phases of the Ni-Ti system. A numerical integration of the transformation kinetics equation is used to calculate CCT curves as a function of alloy composition, x. These results are used to calculate the temperature T'(x,ζ, dT dt) for the formation of a volume fraction ζ of crystalline material during cooling at the constant rate dT dt. Defining a critical value of ζ for the retention of the amorphous (liquid) structure and with the measured crystallization temperature curve Tx(x), we predict the glass forming range for the Ni-Ti system which is in good agreement with experiment. These calculations are summarized in a T' - Tv. criterion which states that the GFR of a binary alloy system is determined by the intersections of the T'(x) curves and the T(x) curve. This criterion considers explicitly transformation kinetics, unlike the earlier T0 - Tx criterion which considers only thermodynamics. © 1988.