CRYSTALLIZATION KINETICS AND MICROSTRUCTURE PARAMETERS OF Mg65Cu25Y10 ALLOY, OBTAINED BY QUENCHING FROM THE LIQUID STATE

Annotation. Purpose. Calculation analysis of the interrelationships of the thermal regime of the quenching from the liquid state with the crystallization kinetics and the microstructure parameters of the Mg65Cu25Y10 alloy. Methodology. The concerted numerical solution of the heat conduction equations and mass crystallization kinetics for melt layers with a thickness from 10-6 to 2·10-2 m, solidifying in contact with a semi-infinite heat-conducting substrate or walls of a metal ingot. Findings. It is shown that a wide range of structural states are fixed in products of rapid quenching of different thickness l: from polycrystalline to truly amorphous, including intermediate composite structures, which differ in the fraction of crystallized volume xe, bulk density Ne and crystal sizes Re . The intervals of values of l and melt cooling rates  m are determined. Within this intervals the types of structures identified by calculations are fixed. It has been established that the main reason for the predisposition of the Mg65Cu25Y10 alloy to complete suppression of crystallization is a substantial slowdown of the crystal nucleation with increasing of the melt cooling rate due to the effect of a nonstationary distribution of heterophase fluctuations in sizes. Originality. A classification scale of the structural states that are fixed by cooling the layers of the Mg65Cu25Y10 melt at rates from 6 to 3·108 K/s is constructed for the first time by a generalization of the obtained calculated data array. The proofs of the principle possibility of complete suppression of the crystallization of the investigated alloy are obtained and the corresponding values of the thickness and cooling rate of the melt layers are determined. Practical value. The proposed algorithm of calculating analysis of thermal regimes and crystallization kinetics will be useful as a tool for predicting the structure of materials of different classes, the production of which is associated with using of accelerated melt cooling technologies.