Influence of hydrogen on the localization of plastic strain in low-carbon steel

Abstract

The localization of plastic strain in the extension of 08ps low-carbon steel is compared after hot rolling and after electrolytic saturation with hydrogen by means of a three-electrode electrochemical cell. Analysis of the strain curves shows that they include a plasticity region, a stage of linear strain hardening, and a stage of parabolic strain hardening (Taylor hardening). Double-exposure speckle photography is used to visualize the localized strain zones. On that basis, the quantitative deformation characteristics may be obtained. In other words, the displacement-vector field in a plane sample under extension may be determined, and then the components of the plastic distortion tensor (the local elongation ε_xx, shear ε_xy, and rotation ω_z) may be calculated. The basic types of plastic flow localization are identified at different stages of strain hardening, and their parameters are determined.