Effect of pulse current and its application direction on the size effect of nanocrystalline nickel foil

Abstract

In order to gain a deeper understanding of the effect of pulsed current on the mechanical properties and size effect of nanocrystalline Ni foils, nanocrystalline Ni foils with different grain thickness-to-grain size ratios (λ) were prepared using pulsed electrodeposition in this paper and unidirectional tensile experiments were carried out at room temperature with different currents and their applied directions. The experimental results show that the nanocrystalline Ni foil produces an obvious electroplasticity effect after applying the current field, and when 300< λ <1100, the current weakens the size effect of nanocrystalline Ni foils to a certain extent, and the angle between the current direction and the deformation direction also affects the mechanical response of nanocrystalline Ni foils, and when the angle between the current direction and the deformation direction is 0°, electroplasticity effect is the best, and the current has the most significant effect of abating the size effect of the material. The mechanism of unidirectional tensile deformation of nanocrystalline Ni foils under the effect of pulsed current was analyzed using TEM and TKD. It was found that the applied pulse current increased the activity of the nanocrystalline boundaries, promoted the movement of dislocations, and reduced the tendency of dislocation entanglement. The higher the peak current density and the smaller the angle between the direction of the current and the direction of deformation, the smaller the grain boundary orientation difference, the more dispersed the grain orientation, and the lower the density of geometrically necessary dislocations (GND) in the deformed nanocrystalline foil, the more significant the effect on material plasticity improvement.

Keywords

nanocrystalline Ni foil / size effect / electroplasticity effect / current direction

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Central South University