Localization of plastic deformation in alloyed γ-iron single crystals electrolytically saturated with hydrogen

Abstract

On chromonickel γ-iron single crystals with $\left[ {\bar 111} \right]$ orientation and low packing-defect density, the plastic-flow localization during electrolytic saturation with hydrogen within a three-electrode electrochemical cell is investigated, with constant controllable cathode potential. On the plastic-flow curve for the extension of single crystals in the initial state (without hydrogen), beyond the transition from elasticity to developed plastic flow, linear strain hardening and then parabolic (Taylor) strain hardening may be observed. The plastic-flow curve for single crystals of austenitic steel saturated with hydrogen includes a small projection and a flow trough, stages of linear strain hardening and parabolic strain hardening, and a prefailure stage. Saturation of $\left[ {\bar 111} \right]$ single crystals with hydrogen reduces the yield point, increases the plasticity to failure by a factor of 1.3, and suppresses necking in crystals oriented for multiple slip. By double-exposure speckle photography, the basic types of plastic flow location at different stages of strain hardening may be identified, in the presence and absence of hydrogen, and the corresponding parameters may be determined. Hydrogenation of chromonickel γ-iron single crystals intensifies the localization of deformation and leads to considerable changes in the characteristic distances between the plastic-shear bands and the localized-strain zones.