Influence of modification of the cast metal structure by solid phase particles on the nucleation of crystallization centers and their stability

Abstract

The inoculation method has wide possibilities for improving the mechanical and operational properties of cast metal, which makes it possible to create artificial centers of crystallization due to the direct introduction of dispersed refractory particles into the melt. The efficiency of such particles serving as crystallization centers is due to the presence of an activated transition layer on their surface. In this regard, it is promising to use complex modification, in which activating additives are introduced into the melt together with dispersed refractory particles, which form a transition layer with the desired properties on the particles. At the same time, the features of the interaction of particles with activating additives have not been sufficiently studied. A theoretical assessment of the influence of dispersed particles on the nucleation of crystallization centers and their stability was carried out on the basis of a study of the phenomena of wetting, adsorption, and dissolution using the relationship between the critical size of additional nuclei, their wetting angle, and supercooling of the melt. It is shown that if between the particle and the cladding layer the difference in chemical potentials of the contacting phases will exist throughout the entire process, and on the surface of the complex it will have a low value of surface tension, then such a particle will be stable, which takes place during adsorption of a surface-active component from a melt. Therefore, the efficiency of melt heterogenization and modification of the cast metal structure is determined by the thermodynamic activity of the substance of the transition layer to the material of the solid phase particle. The obtained conclusions make it possible to select the composition of complex modifiers that allow controlling the structure of castings in the process of their crystallization.