Papers by Author: Zhong Ze Du

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Authors: Qing Juan Wang, Zhong Ze Du, Xiao Yan Liu, Ludvík Kunz
Abstract: The fatigue life, cyclic deformation behavior and microstructure of ultra-fine grained (UFG) copper produced by equal-channel angular pressing (ECAP) were tested and observed in present work. Development of surface relief and fracture surfaces were observed by means of scanning electron microscopy. The results show that the higher tensile strength UFG copper has lower ductility and its strain controlled cyclic properties are worse while comparing with those of lower strength CG counterpart. All the ECAP specimens display obvious cyclic softening behavior under the applied strain range. The cyclic softening ratio increases with increasing strain amplitude. The cyclic hysteresis loops of UFG Cu shows the tension and compression peak stresses decreased gradually with number of cycles. The formation of SBs and grain boundary sliding is the main factor causing crack nucleation as well as premature failure.
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Authors: Qing Juan Wang, Y.C. Wang, Zhong Ze Du, Xiao Yan Liu
Abstract: The corrosion behavior of ultra-fine grain (UFG) copper bulk prepared by equal channel angular pressing (ECAP) was studied in 3.5% NaCl solution. The effect of ECAP deformation on the copper corrosion is controversial in the literature, and worth to verify by means of various experimental techniques. Corrosion performances of UFG copper were investigated in comparison with that in recrystallized coarse grain (CG) copper by polarization curves, Tafel extrapolation method, electrochemical impedance spectroscopy(EIS). The shape of polarization curves and type of corrosive attack remains the same in the UFG and the coarse-grain state. UFG copper exhibited a lower corrosion current and high self-corrosion potential in comparison with CG copper. Electrochemical experimental results showed that UFG copper increased in resistance to corrosion compared with CG copper. This decrease in corrosion resistance was mainly attributed to the more compact corrosion film of UFG copper. The compact passive film led to decrease of the diffusion capability of ions within the corrosion film and corrosion rate.
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