Features of the Use of Equilibrium State Diagrams for Description of Crystal Growth from Metastable Melts

Abstract

The crystallization of metastable metal alloys is characterized by a high rate of the crystallization front, which leads to the effect of "impurity capture" and deviation from the local equilibrium near the surface of the growing crystal. To calculate the growth rate of the crystalline nuclei, a method was developed for prediction of deviation of the components’ concentration near the crystal surface from the equilibrium values. A crystal nucleus was considered to be growing from the initial multicomponent phase, due to interphase transition of the components through its surface. It became possible to distinguish the equilibrium and non-equilibrium effect of the nucleus growth rate by decomposing the molar rate of the product formation near equilibrium, as a function of the molar concentration of the components in the Taylor series and limiting with the linear members. The practical calculations were carried out for the crystallization of the amorphous alloy Fe73,5Cu1Nb3Si13,5B9 of the FINEMET type. The local deviations were investigated for the silicon concentration from the equilibrium values at the surface of the growing crystal.