EBSD study of the effect of electropulsing treatment on the microstructure evolution in a typical cold-deformed Ni-based superalloy

Abstract

Evolution of grain structure and grain boundary character distribution in a cold-deformed Ni-based superalloy during the electropulsing treatment (EPT) was investigated by EBSD technique. Compared with the conventional heat treatments (CHT), the nucleation and growth of SRX grains were significantly accelerated by EPT, which was mainly attributed to the high mobility of dislocations and solute atoms, and the efficient energy transfer under the effect of EPT. Especially, with the introduction of electric current, the activation energy of dislocation motion could be reduced by generating additional energy near the dislocation line, which made the motion of dislocation easy to start. The dislocations would also be easy to move in the form of slipping and climbing, under the effect of electron wind force. On the other hand, most of Σ3 boundaries were newly formed through growth accidents in the form of coherent Σ3 boundaries during EPT, and the mutual interactions between different Σ3n (n = 1, 2, 3) boundaries were rather limited. In addition, EPT could indirectly promote the formation of Σ3 boundaries by accelerating the SRX process, but the formation of Σ9 and Σ27 boundaries was inhibited at the temperatures higher than 700 °C. Moreover, the connectivity of random boundaries in the cold-deformed alloy treated by EPT was also discussed.