Flow characteristics and microstructural evolution in pulsed current assisted micro-scaled compression of stainless steel sheet

Electrically assisted (EA) microforming has pervasive benefits for the fabrication of highperformance microproducts. In this research, the coupled effect between the microstructural size effect and pulsed current on the flow characteristics of 304 stainless steel sheets along thickness direction was explored by using EA micro-compression tests. The results revealed that the strain hardening rate and the deformation stress of 304 stainless steel decreases during the EA deformation, especially when the current density exceeds 57.16 A/mm(2). Besides, the effect of grain size on the micro-scaled compression is gradually weakened with the augment of current density and plastic strain. The electron backscatter diffraction (EBSD) results showed in the perspective of microstructure that the decrease of flow stress and strain hardening rate with the rise of pulsed current density is related to the reduction of dislocation density and texture strength due to the dynamic recrystallization during EA deformation. The pulsed current suppresses the grain refinement of finegrained material and promotes that of coarse-grained material, and the recrystallization rate of EA deformation increases with the decrease of initial grain size. In addition, the recrystallization texture induced by the pulsed current can promote grain deflection and weakens the effect of twins in coarse-grained material. That can explain the reason for the weakening of the grain size effect. The findings in the research have important guiding significance for understanding the coupled mechanism of electroplastic and grain size effect on the flow characteristics of difficult-to-deform material, and further promoting the application of EA micro-rolling of high-strength materials. (C) 2021 The Author(s). Published by Elsevier B.V.

Automated summary

Electrically assisted microforming has widespread benefits for high-performance microproducts. This research explores the coupled effect of microstructural size and pulsed current on flow characteristics of 304 stainless steel sheets. The findings suggest that strain hardening rate and deformation stress decrease during EA deformation, especially when current density exceeds 57.16 A/mm². Additionally, the impact of grain size on micro-scaled compression weakens with higher current density and plastic strain.