Electroplastic phenomenon has been demonstrated by that the elongation increases remarkably during deformation under electric current without significant temperature rise due to Joule heating. Since the 1960s, the electroplasticity has been actively investigated; however, full explanation of electroplasticity mechanism has been lacking. In this presentation, the origin of electroplasticity is elucidated based on numerical and experimental approaches. Ab-initio calculations show that a charge imbalance near defects weakens drastically atomic bonding. In addition, the weakening of atomic bonding was confirmed by measuring elastic modulus under electric current, which is inherently related to bond strength. As a result, the weakening of atomic bonding near defects may enhance the kinetics on various microstructural change under electric current.

As a fundamental example of the electric current induced kinetic enhancement, we investigated the effect of electric current density on recrystallization kinetics of ultra-low carbon steel through the microstructure characterization and mechanical property analysis. A single pulse treatment (SPT) with different electric current densities and appropriate durations was utilized to achieve a target peak annealing temperature. The experimental results show that the degree of recovery, recrystallization, and grain growth tend to decrease with increasing the electric current density and then increase above a certain current density. The athermal effect of electric current was examined by comparing the recrystallization fractions obtained in the SPT with those measured in a conventional furnace heat treatment. The increase of the recrystallization fraction by the athermal effect was quantitatively calculated using Johnson-Mehl-Avrami-Kolmogorov (JMAK) equation adopting the additivity rule. The result of calculation confirms that the athermal effect becomes prominent as the current density increases. The dependence of the athermal effect in the SPT recrystallization on the current density was elucidated by introducing effective activation energy and effective temperature.

As one of the challenging applications of electroplasticity, in addition, we utilized sub-second electric pulsing, which could enhance the kinetics of microstructural change to infinitely reset the damaged microstructure as a non-autonomous self-healing method. The principle of microstructure resetting is explained based on three categories of resetting cores: phase transformation, and dislocation recovery. Microstructure resetting assisted infinite reuse was successfully realized using SUS301L and NiTi alloys, which are applicable materials of the resetting core. This is a new concept combining extreme simplicity, rapidness, and infinite repetition, which cannot be achieved by conventional methods. In addition, various application examples such as electric current assisted joining, sintering and deformation will be introduced in this presentation.