%0 Journal Article
%T An Investigation on Dislocation Density in Cold-Rolled Copper Using Electrochemical Impedance Spectroscopy
%A Elyas Rafiee
%A Mansour Farzam
%A Mohammad Ali Golozar
%A Ali Ashrafi
%J ISRN Corrosion
%D 2013
%R 10.1155/2013/921825
%X Variation of electrochemical impedance with dislocation density was investigated using electrochemical impedance spectroscopy (EIS). For this purpose, EIS measurements were carried out on 10, 20, 30, 40, and 50% cold-rolled commercially pure copper in 0.1£¿M NaCl (pH = 2) solution. Nyquist plots illustrated that the electrochemical reactions are controlled by both charge transfer and diffusion process. Increasing dislocation density, the magnitude of electrochemical impedance of samples was decreased. Decreasing magnitude of impedance at intermediate frequencies indicated increasing double-layer capacitance. Charge transfer resistance decreased from value 329.6£¿£¿cm2 for annealed sample to 186.3£¿£¿cm2 for sample with maximum dislocation density ( £¿ ). Phase angles were lower for samples that contained more dislocation density, indicating more tendencies to loss of electrons and releasing atoms into electrolyte. 1. Introduction It has been reported that after deformation of a metal more than yield limit, hardening occurs which is due to multiplication and rearrangement of dislocations and the more severe the cold deformation, the more generation of dislocations [1¨C4]. Tensile properties of metals such as yield strength, ultimate tensile strength, and ductility depend heavily on density of dislocations. Also, dislocation density plays a significant role on brittle to ductile transition, fatigue, hardness, work hardening, and plastic behavior of metals and alloys [5¨C8]. Furthermore, dislocations have considerable effect on physical properties of metals such as density [9¨C12], thermal conductivity [13, 14], and electrical resistivity [9, 13, 14]. In this respect, some researchers [5, 15, 16] have investigated density of dislocations by ultrasound waves and have proposed some relationships between dislocation density and changes in the speed of elastic waves propagation. Sablik and Landgraf [17, 18], Kobayashi et al. [19], and Yaegashi [20] reported some relationships between dislocation density and magnetic properties. Kikuchi et al. [21] investigated the relation between AC permeability and dislocation density in pure iron as well. Also, other researchers tried to correlate dislocation density with stored energy and critical transformation temperatures using differential scanning calorimetry [4, 7, 22] and high-resolution dilatometry [23], respectively. The strain field and energy of dislocation line intersects with metal surface increase the susceptibility of the metal to corrosion [24¨C26]. Since corrosion is an electrochemical degradation, electrochemical
%U http://www.hindawi.com/journals/isrn.corrosion/2013/921825/