Microstructure characterization and thermal behavior around crack tip under electropulsing

Abstract

Electropulsing treatment is a practical method to arrest crack propagation. The microstructure characterization and research on the forming mechanism are difficult due to the small affected area (0.01-1 mm 2 ), high-temperature gradient (10 2 K/mm) and change rate (10 4 -10 7 K/ s). In this paper, the 1045 steel plate with a preexisting crack subjected to high-voltage pulses was investigated. The surface morphologies and microstructure around the crack tip were observed using optical microscopy and scanning electron microscopy. Experimental results showed that the material around the tip melted, splashed and blunted under electropulsing treatment. The microstructure around the molten hole was divided into four distinct regions. An electro-thermal coupled model considering material ejection, cavity formation, current oscillation and temperature-dependent material properties was proposed to investigate the dynamic formation process of molten hole and gradient microstructure. The uneven temperature distribution, high cooling rate and insufficient carbon diffusion led to the formation of gradient microstructure.

Self-healing of damage inside metals triggered by electropulsing stimuli

“…Of course, there are restrictions on the scale of defects. In previous reports 25 – 28 , for instance, using the electric current to a plate with the artificial cracks (its magnitude reached up to millimeter level), melting of metal could be caused by the strong detour effect, and a molten hole may be formed in the melting area. In this case, cracks cannot be healed, only is arresting or retarding crack propagation.…”