Effects of Pulsed Current on Microstructure and Properties of Crack Tip in Remanufacturing Blank

A high energy pulsed current impacting device was used to treat 316 austenitic stainless steel containing prefabricated unilateral fatigue crack aiming for remanufacturing. The influence of high density pulsed current on the microstructure at crack tip was investigated by metallographic microscope, X-ray diffraction, electron backscattered diffraction (EBSD) and transmission electron microscope (TEM). And the evolution of microstructure during melting treatment was analyzed. Results show that the structure at crack tip is obviously refined after the pulsed current processing, and the gradient structure including the columnar crystal area, recrystallization zone and matrix is observed. Due to the rapid heating and cooling, the generation of high-speed electronic wind and electrically induced plasticity effect reduce the thermodynamic barrier of recrystallization or phase change. Thus, the rate of nucleation is increased, and the grain growth process is inhibited. Therefore the grain size of recrystallization zone is smaller than that of the matrix, and hence the mechanical properties of materials are improved.