Iranian Journal of Materials Science and Engineering

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In this research accumulative roll bonding process as sever plastic deformation process was applied up to 8 cycles to produce the ultrafine grain copper. Microstructure of cycle 1, cycle 4 and cycle 8 investigated by TEM images. By analyzing TEM images the grain size measured below 100 nm in cycle 8 and it was with an average grain size of 200 nm. Corrosion resistance of rolled copper strips in comparing with unrolled copper strip was investigated in acidic (pH=2) 3.5 wt. % NaCl solution. Potentiodynamic polarization and EIS tests used for corrosion resistance investigations. The corrosion morphologies analyzed by FE-SEM microscopy after polarization test and immersion for 40 hours. Results show that the corrosion resistance decreased up to cycle 2 and increased after rolled for forth time. The corrosion degradation was more intergranular in cycle 2 and unrolled counterpart. It was more uniform rather than intergranular type in cycle 8. Corrosion current density in unrolled sample (2.55 µAcm -2 ) was about two times of that in cycle 8 (1.45 µAcm -2 ). The higher corrosion rate in cycle 2 in comparison with others was attributed to unstable microstructure and increase in dislocation density whereas the uniform corrosion in cycle 8 was due to stable UFG formation

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In the present study, the effect of post-rolling annealing heat treatment on the formation of intermetallic compounds between Al-Cu strips, in the presence of nickel coating on the Cu strips, was investigated. In addition, the effect of post-rolling annealing and intermetallic compounds on the bond strength of Al-Cu strips was evaluated. In order to prepare samples, Cu strips were coated with nickel by electroplating process. After surface preparing, Cu strips were placed between two Al strips and roll bonded. This method is used for producing Al-Ni-Cu composites. Then the samples were annealed at 773K for 2 h. The formation of intermetallic compounds was studied using energy dispersive spectroscopy (EDS) and X-ray diffraction (XRD). Also, in order to investigate bond strength of Al-Cu after post-rolling annealing heat treatment, samples were produced using nickel powder and nickel coating. Then bond strength of strips was investigated using peeling test. The results revealed that by post-rolling annealing of layers, the bond strength between Al-Cu strips decreases dramatically.