Effect of pulsed current frequency on electroplasticity in plain carbon steel : an experimental study

Abstract

This research investigates the impact of the electroplasticity phenomenon on the mechanical behavior of two plain carbon steel samples with different carbon contents (0.09wt.% and 0.39wt.%) under uniaxial tensile loading combined with low-frequency high amplitude electrical pulses. Prior to the tensile tests, all samples underwent normalization heat treatment. The experimental results demonstrate a progressive decrease in yield stress accompanied by an improvement in ductility as the pulse frequency increases, up to a frequency of 0.83 Hz. These findings suggest a positive influence of the electroplasticity effect on the tensile properties of plain carbon steels. However, beyond 0.83 Hz, despite further reduction in yield stress, a gradual decline in ductility is observed until a frequency of 1.64 Hz, primarily attributed to enhanced strain localization and induced defects resulting in premature fracture. Microstructural analysis reveals that the fracture surfaces of samples tested under electrical current exhibit intermediate grain sizes between non-deformed samples and deformed samples tested without current. Additionally, the presence of characteristic dimples on the fractographs further supports the observed variation in ductility with pulse frequency. Notably, the combination of a pulse frequency of 0.83 Hz and an effective current of 777.8 A yields a significant enhancement in formability.