Abstract
In the present paper, the multiple applications of high-density pulsed electric current (HDPEC) with current densities between 100 and 200 A/mm2 made fatigue crack growth (FCG) slow, in which a current density of more than 150 A/mm2 provided high efficiency to refrain from FCG. The application of multiple HDPECs under the current density of 200 A/mm2 showed a significantly reduced fatigue crack growth rate (FCGR). The fracture surfaces without the HDPEC effect showed signs of FCG along the crystal structure elongated in the rolling direction, on the other hand, a series of welded joints were formed at the crack tips due to the effect of applying multiple HDPECs, which provided different patterns of FCG leading to crack arrest. When initial HDPEC is applied in a short crack under the same HDPEC condition, it shows partial welding at the crack tip, while more concentrated welding at the crack tip by moderate Joule-heating is shown as fatigue progresses and the fatigue crack length increases. Elemental analysis by energy-dispersive X-ray spectroscopy and crystallographic analysis by electron backscatter diffraction also provided the microstructure features at the crack tip subjected to the application of multiple HDPECs. It is most efficient to perform in a short crack with multiple applications, and applying multiple manners as the crack progresses contributes to the accumulated improvement of fatigue properties by slowing the FCGR based on each application.
