Iranian Journal of Materials Science and Engineering

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Metal porous foams have been eliciting much interest in recent years due to their high capacity of energy absorption. The characteristics of the pores in these materials play an important role on their energy absorption capability and other properties. This study reports the fabrication of aluminum closed-cell foams by accumulative roll-bonding (ARB) technique using calcium carbonate (CaCO3) as the blowing agent. Calcium carbonate is an inexpensive material and imparts relatively high porosity to the produced foam. The effects of heating rate foaming temperature and time on porosity have been investigated. The results show that increasing the foaming temperature and time results in improvements in the foaming process. It is also shown that the heating rate does not affect the porosity. The shape and structure of pores are spherical and regular with CaCO3 as blowing agent. With TiH2 blowing agent the sample should be heated up abruptly from decomposition temperature of TiH2 to foaming temperatures in order to produce high porosity foam. It is found that increasing the numbers of accumulative rolling cycle causes uniform distribution of calcium carbonate powder and increases porosity in the final foam by up to 55%.

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Accumulative roll-bonding process (ARB) is an important severe plastic deformation technique for production of the ultrafine grained, nanostructured and nanocomposite materials in the form of plates and sheets. In the present work, this process used for manufacturing Al/SiO 2 nanocomposites by using Aluminum 1050 alloy sheets and nano sized SiO 2 particles, at ambient temperature. After 8 cycles of ARB process, the tribological properties and wear resistance of produced nanocomposites were investigated. The wear tests by abrasion were performed in a pinon-disc tribometer. Results show that by increasing ARB cycles and the amount of nano powders, the friction coefficient of produced nanocomposites decreases.

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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 work, accumulative roll bonding (ARB) was used as an effective method for processed of nano/ultrafine grained AA6063 alloy. Microstructural characteristics indicate considerable grain refinement leading to an average grain size of less than 200 nm after 7 ARB cycles. Texture analysis showed that 1-cycle ARB formed a strong texture near Copper component ({112}<111>). However, texture transition appeared by increasing the number of ARB cycles and after 7-cycle of ARB, the texture was mainly developed close to Rotated Cube component ({100}<110>). The results originated from mechanical properties indicated a substantial increment in strength and microhardness besides a meaningful drop of ductility after 7 ARB cycles.