Influence of the equilibrium dislocation substructure on the structure component morphology in the heterogeneous phase transformations in polycrystalline metallic alloys

Theoretical analysis of the dislocation subgrain boundary (DSB) influence on the microstructure formation at the equilibrium heterogeneous polymorphic phase transformations in polycrystalline alloys has been carried out. Based on the disloca-tion structure of the DSB and its tendency of reaching equilibrium, evolution of the internal state for the various types of DSB (twisting and tilting) and corresponding elastic strain fields has been considered. Redistribution is shown to develop during the transformation of the crystal elastic energy from the twist to the tilt DSB formed, respectively, by screw and edge dislocations. Localization of the elastic energy on the tilt DSB in the equilibrium crystal state is shown due to the dislocation reactions development between screw dislocations within the corresponding mutually crossing arrays. Taking into account the crystalline lattice elastic distortions around solute atoms and interaction of the atoms with grain boundaries (GB), the analogous chemical element space distributions are shown to appear on DSB and GB. Forming of structure components of specific morphology resulting from the distribu-tions is shown. The possibility to form homogeneous space distributions of atoms as well as dispersed structural constituents under optimal thermal treatment has been stated. Metallographic investigations were conducted using alloy steels of various chemical compositions. Main conclusions of the theoretical analysis have been confirmed by the experimental results