Decomposition of crystal-growth equations in multicomponent melts

•A new variational method describing crystal growth has been developed.•The equations can be applied to crystal growth out of supercooled, multicomponent melts.•The model was applied to the process of crystal growth when annealing amorphous tapes of the FINEMET® alloy Fe73.5Cu1Nb3Si13.5B9.

Using a variational approach, the macroscopic laws of the growth of a new-phase, multicomponent particle are compared to the physicochemical laws of processes in the “new phase – initial melt” system. A suitable equation-based method has been developed to calculate the growth of a new-phase particle under the conditions of diffusion growth and non-equilibrium solute trapping by the quickly growing front of a new phase. The laws of crystal growth have been studied while annealing the amorphous alloy FINEMET® Fe73.5Cu1Nb3Si13.5B9.