Plastic deformation of nitrogen-containing austenitic stainless steel single crystals with low stacking fault energy

Abstract

On single crystals of austenitic stainless steel with nitrogen C N =0-0.5 wt.% the stages of stress-strain curves, work-hardening coefficient, deformation mechanism - slip and twinning, the developing of dislocation structure in dependence on crystal tensile axis orientation, test temperature, nitrogen concentration have been investigated. The type of dislocation structure (cellular or planar) and deformation mechanism (slip or twinning) have been shown to determine by the value of matrix stacking fault energy, by the level of friction forces due to solid solution hardening with nitrogen atoms and by the crystal orientation. It has been established that the contribution of mechanical twinning to the plastic deformation of steel crystal increases with nitrogen content, and in high-strength states at concentration of interstitial atoms C>0.5 wt.% mechanical twinning develops from early stages of deformation and determines work-hardening coefficient. The achievement of high level of deformation stresses due to the solid solution hardening with nitrogen atoms in combination with low values of γ 0 results in twinning in [001] orientations.