Slip and twinning in single crystals of austenitic stainless steels with nitrogen

Single crystals of austenitic stainless steels (Fe-26% Cr-32% Ni-3% Mo, Fe-18% Cr-12% Ni-2% Mo) are used to study the dependences of stacking fault energy γ0, dislocation structure type (cellular and planar), plastic deformation mechanisms (slip and twinning) on nitrogen atom concentration CN, tension axis orientation, test temperature T. It is shown that γ0 decreases with T and with a growth of CN. In low-strength steel crystals with CN ≤ 0.3 mass % the type of dislocation structure is determined not only by the value of γ0 but by the crystal orientation as well. In high-strength steels at CN > 0.3 mass % the planar dislocation structure and mechanical twinning are progressing in <111>, <001> orientations early in the deformation. The dislocation criterion of transition from cellular structure to planar one is proposed which takes into account the effects of the value of stacking fault energy, the level of stresses, the crystal orientation on processes of dislocation cross slip