Fig. 1 Heat-treated microstructures of γ/γʹ phases along the cross sections in a [001], b [011], c [111] specimens

Fig. 2 Stress rupture lives and elongations of [001], [011] and [111] specimens

Fig. 3 γ/γʹ morphologies of three oriented samples tested at 1100 °C/150 MPa: a interrupted at 30 h and b after rupture of [001] specimens on (100) plane; c interrupted at 30 h and d after rupture of [011] specimens on (100) plane; e interrupted at 30 h and f after rupture of [111] specimens on ($0 1 {\bar{{1}}}$) plane. Loading direction of all figures is along the vertical direction as marked in a

Fig. 4 Fracture morphologies and longitudinal sections of a-d [001], e-h [011], i-k [111] specimens; l longitudinal surface of a [111] specimen

Fig. 5 Interfacial dislocation networks in a, b [001], c, d [011], e, f [111] specimens. Beam is [001] for [001] specimens; beam is [011] for [011] specimens; beam is close to e$[\bar{1}\bar{1}{2}]$ and f [111] for [111] specimens

Fig. 6 Superdislocations in [001] specimens: aa<110>superdislocations, B = [001]; ba[100] superdislocations, B = [100]; c superdislocation node, B = [001], d schematic illustration of the node

Fig. 7 Superdislocations in [011] specimens: aa<110> superdislocations in γʹ phase, ba[100] superdislocations viewed along [100] direction, c, d magnified figures of a[100] superdislocations in b. All images were taken close to the [100] zone axis

Fig. 8 Superdislocations in [111] specimens: a, b superdislocation arrays viewed along the cross (B = [111]) and longitudinal sections (B = $[\bar{1}\bar{1}{2}]$), respectively, c, d superdislocation networks in γʹ phase, B = $[\bar{1}\bar{1}{2}]$

Fig. 9 TEM micrographs of superdislocation 1-11 under six two-beam conditions in [111]-oriented specimens: ag = ${\bar{1}}{11}$, bg = $0 2 {\bar{{2}}}$, B = [211]; cg = ${\bar{{2}}{02}}$, dg = $1{\bar{1}}{1}$, B = [121]; eg = $2 {\bar{{2}}{0}}$, fg = $11 {\bar{{1}}}$, B = [112]. Foil normal is close to [111] direction

Fig. 10 Schematic illustration of the alignment of micropores and crack propagation paths in a [001], b [011], c [111] specimens

Fig. 11 Effects of different rafts on dislocation movement: a slip and climb of dislocations are hindered by N-type rafts in [001] specimens; b dislocations can easily glide and climb along the ± 45° rafts in [011] specimens; and c dislocations are piled up at the joints of regions A and B in [111] specimens

Fig. 12 Dislocations are piled up at the joints of regions A and B, in [111] ruptured specimens, B = $[\bar{1}\bar{1}{2}]$