Gennari Claudio, Pezzato Luca, Simonetto Enrico, Gobbo Renato, Forzan Michele, Calliari Irene
Department of Industrial Engineering, University of Padua Via Marzolo 9, 35131 Padova PD, Italy.
Department of Industrial Engineering, University of Padua Via Venezia 1, 35131 Padova PD, Italy.
Materials (Basel). 2019 Jun 13;12(12):1911. doi: 10.3390/ma12121911.
Since the late 1950s, an effect of electrical current in addition to joule heating on the deformation of metals called the Electroplastic Effect (EPE) has been known. It is used nowadays in the so-called Electrically Assisted Forming (EAF) processes, but the understanding of the phenomenon is not very clear yet. It has been found that EPE increases the formability of high stacking fault energy (SFE) materials, while low SFE materials reach fracture prematurely. Since Duplex Stainless Steels (DSSs) possess a microstructure consisting of two phases with very different SFE (low SFE austenite and high SFE ferrite) and they are widely used in industry, we investigated EPE on those alloys. Tensile tests at 5 A/mm, 10 A/mm and 15 A/mm current densities along with thermal counterparts were conducted on UNS S32101, UNS S32205, UNS S32304 and UNS S32750. The DSS grades were characterized by means of optical microscopy, X-ray diffraction and their mechanical properties (ultimate tensile strength, total elongation, uniform elongation and yield stress). An increase in uniform elongation for the electrical tests compared to the thermal counterparts as well as an increase in total elongation was found. No differences were observed on the yield stress and on the ultimate tensile strength. Un uneven distribution of the current because of the different resistivity and work hardening of the two phases has been hypothesized as the explanation for the positive effect of EPE.
自20世纪50年代末以来，人们就知道电流除了焦耳热之外，对金属变形还有一种效应，称为电塑性效应（EPE）。如今它被用于所谓的电辅助成形（EAF）工艺中，但对这一现象的理解还不是很清楚。已经发现，电塑性效应提高了高堆垛层错能（SFE）材料的成形性，而低SFE材料则过早断裂。由于双相不锈钢（DSS）具有由两种具有非常不同SFE的相（低SFE奥氏体和高SFE铁素体）组成的微观结构，并且它们在工业中广泛使用，我们对这些合金的电塑性效应进行了研究。在UNS S32101、UNS S32205、UNS S32304和UNS S32750上进行了电流密度为5 A/mm、10 A/mm和15 A/mm的拉伸试验以及热模拟试验。通过光学显微镜、X射线衍射及其力学性能（极限抗拉强度、总伸长率、均匀伸长率和屈服应力）对双相不锈钢等级进行了表征。与热模拟试验相比，电试验的均匀伸长率有所增加，总伸长率也有所增加。在屈服应力和极限抗拉强度方面未观察到差异。由于两相的不同电阻率和加工硬化导致电流分布不均匀，这被认为是电塑性效应产生积极影响的原因。
