Overcoming the trade-off between strength and ductility in austenitic stainless steel using a high-density pulsed electric current

Abstract

This paper presents a method to overcome the trade-off between the strength and ductility in metals and clarifies its mechanism via a crystal structure analysis on type 316 austenitic stainless steel subjected to high-density pulsed electric current (HDPEC) treatment. Because of the HDPEC treatment, the fractions of low-angle grain boundaries (LAGBs) and high-angle grain boundaries (HAGBs) increased, while those of ∑ 3 twin boundaries (TBs) decreased significantly. An increase in the number of HAGBs and the formation of new LAGBs, which leads to achieving refined grains, was achieved by virtue of the change of misorientation angles and dislocation formation. Furthermore, the dissolution of Cr-rich precipitates occurred in the grain surroundings, which led to an increase in ductility of the material. The dislocation density, measured by the mean kernel average misorientation values, decreased because of the dislocation motion induced by HDPEC. The strengthening of the material was attributed to the grain refinement, and the increased ductility was attributed to the decreased dislocation density and decreased content of Cr-rich precipitates, which prevented precipitation hardening. The combination of these advantages contributed to overcoming the trade-off between strength and ductility.