オーステナイト系ステンレス鋼の転位組織に及ぼす窒素添加量および変形温度の影響

Nitrogen-added austenitic stainless steels exhibit excellent work-hardenability due to planar slips of dislocations. Two mechanisms of the planar slip have been proposed so far: glide plane softening mechanism and stacking-fault energy (SFE) reduction mechanism, which are thought to be dependent on nitrogen content and deformation temperature. In this study, conventional TEM, STEM-EDS and HR-STEM characterizations were carried out to clarify the influences of deformation temperature and nitrogen content on the dislocation characteristics of austenitic stainless steels. In the case of the nitrogen-added steel, the dislocation configurations became planar at a high temperature, 973 K. HR-STEM analysis revealed that SFE decreased with N addition and increased with temperature increase. Weak-beam TEM and HR-STEM analyses revealed that the planar dislocations were composed of 60° mixed-dislocations and SFs at room temperature, and edge-dislocation and SFs at 973 K. These results suggested that the edge components of defects interacted elastically with N and N-Cr pairs and contributed to the origin of the planar slips.