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a substance added to a metal or alloy in small quantities, causing a significant change in its structure and properties. The effect of such treatment is called inoculation.
According to the classification of P. A. Rebinder, inoculants are divided into two groups. The first group includes surface-active substances, which are adsorbed on the nuclei that form on crystallization centers and retard their growth, resulting in the appearance of a large number of new nuclei, whose growth becomes possible as the concentration of the inoculant on their surfaces decreases.
Inoculants of the second type facilitate the formation of crystallization centers, such as colloidal particles, which affect the nucleation of crystals of the metallic phase during hardening. Upon the appearance of a large number of such centers, there is increased formation of fine granules of the principal phase or fine inclusions of other phases. Phases that otherwise would not be formed in the material sometimes crystallize on such centers.
Inoculants of both groups disintegrate granules (inclusions), but inoculants of the first group enhance the supercooling of melts during crystallization, and those of the second group reduce supercooling.
REFERENCERebinder, P. A., and M. S. Lipman. “Fiziko-khimicheskie osnovy modifikatsii metallov i splavov malymi poverkhnostno aktivnymi primesiami.” In Issledovaniia v oblasti prikladnoi fiziko-khimii poverkhnostnykh iavlenii. Moscow-Leningrad, 1936.
A. A. ZHUKOV