Electronic theory for the refinement mechanism of ultrafine steel

The model of 1/2110 edge dislocation in austenite phase was set up with comp uter programming. The environmentsensitive embedding energy (ESE) of C, N and alloy elements in grains or in the area of edge dislocation was calculated by us ing recursion method. The enrichment and interaction of C, N and alloy elements in the area of dislocation were discussed. Calculation results show that: discre te light impurities C and N tend to aggregate in the dislocation area, forming C aldwell air mass above the edge dislocation; the alloy element is liable to dist ribute in perfect austenite grains. Ti, V, Nb and Cr, which are strong or middli ng strong elements for carbide formation, are easy to aggregate in the edge disl ocation area. They can also form the Caldwell air mass above the edge dislocatio n like C or N. But Ni, which is non_carbide formation element, aggregates below the dislocation line or distributed in the perfect grains. The light impurity ca n enforce the aggregation of strong carbide forming elements in the edge disloca tion area. When the temperature is decreased, and when the concentration of C, N and alloy elements reach the high limit of concentration, the C, N compound of alloying elements will precipitate from the matrix in the edge dislocation area of austenite in the steel. These compounds can act as heterogeneous nuclei of au stenite phase in the course of recrystallization, leading to the refinement of a ustenite grains.