SEM/EBSD法を用いたオーステナイトステンレス鋼のクリープひずみ評価

Abstract

Changes of misorintation in grains were studied by Scanning Electron Microscopy and Electron Back Scattering Diffraction (SEM/EBSD) for austenitic stainless steel, SUS 316 that were crept under 100 MPa at 973K. Misorientation of the specimens was calculated by Kernel Average Misorientation (KAM), Grain Average Misorientation (GAM) and Grain Orientation Spread (GOS). The values calculated by KAM, GAM and GOS increased with the strain increasing linearly during the transient creep stage. The tendency corresponded to the changes in total dislocation density estimated by Transmission Electron Microscopy (TEM). In the transient creep stage, good linearity between geometrically necessary (GN) dislocation estimated from KAM values and dislocation density by TEM was revealed. Compared the increments among misorientations calculated by KAM, GAM and GOS, one of GOS was the highest and the others were almost the same. Increments of KAM values were lower than those reported in the previous papers. Because data was obtained from the crept specimens in this study but data were obtained from specimens deformed in room temperature or moderate temperature. It was suggested that the increment of GN dislocation become lower due to dynamic recovery during creep test in this study. When the pitches in the EBSD measurement were taken account into, the increment of GAM values in this study was equal to one reported in the previous paper where the data was obtained from the crept specimens of stainless steel with the similar grain size.