| Abstract Scope |
Electroplastic phenomenon has been demonstrated by that elongation increases remarkably during deformation under electric current without significant temperature rise due to Joule heating. Since 1960s, 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.
Then, we investigated the effect of electric current density on recrystallization kinetics of ultra-low carbon steel. 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 result confirms that the dependence of athermal effect in recrystallization on the current density was quantified by introducing effective activation energy and effective temperature.
In the last part of the presentation, I introduce the mechanical shaping of brittle amorphous silica at nanoscale via electron-matter interactions without heating. We observed a ductile superplastic deformation of amorphous silica under a focused scanning electron-beam with low acceleration voltages from a few to tens of kilovolts during in-situ compression studies, with unique dependencies on the acceleration voltage and beam current. By simulating the electron-matter interaction, we show that the deformation of amorphous silica depends strongly on the volume where inelastic scattering occurs. The excess electrons introduced via electron-matter interaction alter the Si–O interatomic bonds, enabling the high temperature deformation behavior of amorphous silica and even crystalline silica to occur athermally. These findings will deepen our understanding of electron–matter interactions and can be extended to new glass forming and processing technologies at nano-scale. |