Features of deformation of a bimetallic plate

The features of macroscopic localization of plastic flow during uniaxial tension of a flat bimetallic plate are discussed. The extension axis of the sample was oriented normally to the direction of rolling. The studied bimetal "low-carbon steel - stainless steel" is used in chemical engineering for the manufacture of reaction columns, autoclaves, reactors, and heat exchangers. The plastic flow curve of the bimetal after the yield point in the area of large plastic deformations is located between the curves for its components - austenitic stainless steel (AISI 304) and low-carbon steel (ASTM A414 grade A). The visualization of localized plastic deformation bands and registration of the kinetics of their movement were carried out on the working part of the sample by the method of digital speckle photography. It has been established that at the yield plateau, plastic deformation in the form of Lüders fronts originates at the interface between the cladding layer and the base bimetal layer and propagates in the base layer of low-carbon steel, while the less plastic cladding layer of stainless steel deforms elastically. Then, together with the base one, the cladding layers also begin to plastically deform in the form of the propagation of Portevin - Le Chatelier fronts. The process of failure of a bimetal also begins with the localization of plastic deformation near structural inhomogeneities and stress concentrators in the area of contact between layers of two dissimilar metals. The stress concentrators formed at the early stages of plastic flow in this region initiate the formation of a high-amplitude peak of strain localization, which is a precursor to the formation of a neck in the sample and further ductile failure of the bimetal.