Fig. 1. (a) Schematic diagram of the ECF apparatus; (b) Schematic showing the electrically assisting creep age forming conditions; (c) Temperature history of the specimens under three conditions and a magnification box on the left of temperature curves clearly showing the temperature rise when electropulsing was applied; (d) The arc-shaped TEM sample was prepared in order to confirm the relationship between pulsed direction and dislocation distribution.

Fig. 2. Comparison of creep strain curves of three samples during the early ageing stage of 0.6 h (a) and the whole creep ageing of 24 h (d). Comparison of creep strain (b) and creep strain rate (c) for three samples at the same time of 0.6 h, showing a greatly increased creep strain due to electropulsing. (e) Stress-strain curves of the creep aged sample for 24 h under different processing conditions.

Fig. 3. EBSD maps (colored with reference to RD direction) showing the microstructure of the samples after different heat processing; (a) sample of beginning creep tests; (b) ICF sample for 0.6 h; (c) NICF sample for 0.6 h; (d) the ECF sample for 0.6 h. ND is the normal direction.

Fig. 4. Comparison of dislocation morphology of the samples at the different given conditions. (a, b) Bright-field TEM micrograph of the sample of creep ageing initiation; (c) the ICF sample after creep aged for 0.6 h. The NICF sample aged for (d) 5 min, (e) 18 min and (f) 0.6 h. The ECF sample aged for (g) 5 min, (h) 18 min and (i) 0.6 h. (g1) A single dislocation structure in the ECF sample for 5 min. (h1-h3) Those evolved dislocation structures in the ECF sample for 18 min.

Fig. 5. A series of weak-beam bright field micrographs (a)-(c), captured using several g-vectors. From the g?b invisibility criterion, the helical dislocation has a Burgers vector of 1/2[$0\bar{1}\bar{1}$]. (d) showing the direction of the Burgers vector b (insert a diffraction pattern of [112] zone axis).

Fig. 6. Schematic diagram of the kinematics for a helical dislocation in the NICF and ECF samples, respectively. The climb plane PN is normal to the Burgers vector b.

Fig. 7. HAADF images and corresponding EDX STEM-Mapping of the three samples: (a) ICF sample aged for 0.6 h; (b) NICF sample aged for 18 min and (c) ECF sample aged for 5 min.

Fig. 8. Schematic illustration of dislocation configuration during evolution for the NICF and ECF samples, respectively.