Plastic deformation mechanism transition with solute segregation and precipitation of 304 stainless steel foil induced by pulse current

Abstract

Stainless steel ultra-thin strip has become a hotspot because of its high added economic value. Reducing the deformation resistance during rolling is an effective and economical way to break through the minimum thickness limit of foil strips. And the dynamic softening effect of electroplastic effect provides a possible solution. However, the influence mechanism of electric pulse on stainless steel foil needs to be fully explored. In this work, the effects of pulse current with various peak current densities on the mechanical properties and deformation mechanism of 304 stainless steel foil were investigated. Compared with the conventional tension, the flow stress and elongation of steel foil are reduced during electro-pulsing assisted (EA) tension. The current causes the stress-strain curve to fluctuate in a serrated manner. The above changes can be attributed to the promotion of dislocation slip and the solute precipitation induced by coupling effect of deformation and pulse current. Besides, the pulse current suppresses the transformation from austenite to martensite and promotes the dynamic recrystallization (DRX), leading to reduction of deformation resistance. However, the severe solute segregation forms hard and brittle CrC intermetallic compound, which enhances the grain boundary strengthening, worsens the grain boundary properties and induces the generation of crack sources, resulting in the drastic diminishment in the ductility and toughness of steel foil. But this phenomenon can be avoided by controlling the current density and the treatment time during the deformation process.