Peculiarities of deformation localization in additive material with structural-phase heterogeneity

Creation of compounds of dissimilar metals is one of the priority areas in the field of obtaining special structural materials with a unique combination of properties. In connection with development of new production processes, the question arises about the influence of structural-phase heterogeneity of multilayer materials on deformation behavior. In particular, an important scientific problem is the localization of plastic flow. The digital image correlation (DIC) method was used to analyze the nature of localized plastic deformation in the bimetallic composite austenitic stainless steel/low-carbon steel manufactured by additive beam technology. It was found that in all layers of the bimetal, plastic deformation develops locally in each layer of the studied composite according to the loading stages. It is shown that during deformation of a bimetallic compound, the appearance of the yield plateau stage ( n = 0) and, accordingly, the Lüders deformation is suppressed, despite the significant content of a low-carbon steel layer in the bimetal. In the parabolic section with the hardening index n = 0.5, the components of local elongations ε xx form a stationary periodic distribution of localized deformation zones. With the onset of the stage with n ≤ 0.5, a high-amplitude deformation zone is observed in the transition layer, which coincides with the place of future sample fracture. In this case, the growth of the amplitude of localized deformation in this zone begins at the parabolic stage of the loading diagram. Structural heterogeneity at the interface in the bimetallic composite austenitic stainless steel/low-carbon steel is the source of the initiation of a fracture crack in the austenitic steel layer. Apparently, the initiation of the destruction zone in the transition layer is associated with the formation of a brittle carburized layer, which occurs due to the diffusion of carbon through the interface low-carbon steel – stainless steel.