PSI - Issue 23

Ivo Šulák et al. / Procedia Structural Integrity 23 (2019) 161–166 Author name / Structural Integrity Procedia 00 (2019) 000 – 000 5 dislocation density running parallel to ( 1̅ 11 ) can be recognised from Fig. 5 d. The PSBs cut both γ matrix and γ  precipitates. The average spacing of PSBs varies from grain to grain but nevertheless corresponds to the spacing of PSMs detected on the surface of fatigued superalloy. 165

Fig. 4 SEM and AFM (CPEM) micrographs documenting characteristic features of surface relief evolution and fatigue crack initiation in grain of superalloy MAR-M247 cyclically strained with the total strain amplitude ε a = 0.5% for (a) 300 cycles, (b, c) 600 cycles, (h) 1200 cycles.

Fig. 5 Cyclic strain localization in grain of superalloy MAR-M247 cyclically strained with ε a = 0.5% to 20% of N f . (a) SEM overview of PSM morphology, (b) topography of PSMs in 3D as obtained by AFM from the area indicated by a blue square in (a), (c) profile across PSMs along section indicated by a blue arrow in (b), (d) bright field STEM micrograph of dislocation arrangement.