Electrically enhanced plastic deformation of duplex stainless steel UNS S32750

It is well known that increasing the temperature softens the materials and increases formability. This could be done in many ways, one of which is by joule heating. In the late fifties it has been observed an enhancement of formability for certain alloys when heated by electrical current, compared to traditional heating method. This led the researcher to investigate the effect of electrical current on the plastic flow of metallic materials discovering a new effect called Electroplastic Effect (EPE). EPE is used in the so called Electrically Assisted Manufacturing processes (EAM). The stacking fault energy (SFE) describes the dislocation dynamics of metallic materials and it has been hypothesized an a-Thermal effect which is caused by direct interaction between dislocations and electrical current. High SFE materials show an increase of formability while low SFE materials reach the fracture prematurely. In this work, duplex stainless steel (DSS) UNS S32750 has undergone uniaxially tested with the aid of continuous and pulsed electrical current in order to study the EPE of a metallic material that presents two different phases, high SFE (ferrite) and low SFE (austenite). Different current densities (continuous and pulsed) were tested while to separate the EPE from the effect of temperature some thermal tensile counterpart tests has been conducted. The DSS was then characterized through optical microscopy, scanning electron microscopy and x-ray diffraction. The DSS tested shows an increase in the elongation at rupture, either for the continuous current set-up and much more evident in the case of the pulsed current compared to the thermal tests, while the ultimate tensile strength and the yield strength were barely affected.