Development Kinetics of the Plastic Wave Front at the Metal Interface
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Russian Physics Journal, Vol. 63, No. 5, September, 2020 (Russian Original No. 5, May, 2020)
DEVELOPMENT KINETICS OF THE PLASTIC WAVE FRONT AT THE METAL INTERFACE S. A. Barannikova and Yu. V. Li
UDC 669.539.381.296
The paper considers an inhomogeneous development of plastic strain at the Chernov–Lüders band front in the bimetal consisting of carbon and austenitic steel layers. It is found that in the low carbon steel basal layer, the distribution of localized deformation at the yield point represents two zones similar to the Chernov–Lüders band. In the austenitic steel coating layer, the distribution of localized deformation at the yield point represents two plastic wave fronts similar to the Portevin–Le Chatelier effect. The paper proposes a mechanism of nucleation of localized deformation bands in the frame of the model of the solid fracturing. Keywords: plasticity, deformation, localization, bimetal, Lüders bands.
INTRODUCTION On the scale of the specimen size, macroscopic inhomogeneity and instability of plastic strain manifests itself in the form of the mutual stress-strain dependence σ(ε) and localized strain patterns [1]. According to works [2–4], localized plastic strain during tension of metal alloys is realized in the form of either the Chernov–Lüders bands (also known as slip bands) at the yield point or the Portevin–Le Chatelier (PLC) effect during a discontinuous plastic strain [5]. The development kinetics of the Chernov–Lüders and PLC band fronts indicates both the similarities and differences between these phenomena [4]. As the similarity is concerned, it should be noted that the slip and the PLC band fronts represent macroscopic localizations of plastic strain in the form of narrow moving zones, in which plastic strain concentrates. The kinetics of the band evolution is similar, viz. in both cases the nuclei of localized plastic strain occur on the specimen lateral side and then grow across the whole cross-section. Significant differences in these phenomena are observed at a stage of developed localized plastic strain caused by the slip bands and the PLC effect [4]. Further investigations of these phenomena include the combined behavior of both slip and PLC band fronts during the tension of bimetal consisting of the carbon and austenitic stainless steels. Known models of strength physics and fracture mechanics used to describe the deformation and fracture of the solid material and individual components of laminated materials [6], do not allow estimating plastic strain localization and fracture at the layer interface. The purpose of this work is to analyze the macroscopic localized plastic strain under uniaxial tension of this bimetal [7].
LOCALIZED PLASTIC STRAIN OF BIMETAL AT THE YIELD POINT The laminated metal consisting of carbon steel with the BCC crystal system and the austenitic stainless steel with the FCC crystal system were used in this experiment in the as-delivered condition [7]. The ASTM A414 grade A (st3sp) low carbon steel was used as a basal layer ~6.7 mm thick. The thickness of
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