Papers by Keyword: Accumulative Roll Bonding Process

Abstract: In this study, the effect of stacking fault energy on the grain size of aluminum, copper, and brass fabricated via accumulative roll bonding (ARB) process was investigated. Evolution of microstructure of the samples was investigated by transmission electron microscopy (TEM). It was found that occurrence of the recrystallization (both continuous and discontinuous) in the copper and brass led to the formation of nanograins with mean size of 80, and 40 nm, respectively; while, the mean grain size of aluminum was 250 nm. Differences in microstructural evolution during processing of aluminum, copper, and brass was related to their stacking fault energies (SFEs). When the SFE decreased, grain refinement occurred more easily and the measured grain size was smaller.

Abstract: The 3-layers accumulative roll bonding process (ARB) has been attempted to increase the strength of copper alloy (Cu-0.02wt.%P) by refining grain size. The 3-layers accumulative roll bonding was conducted up to 7 cycles at room temperature without lubrication. Microstructural evolution of the copper alloy with the number of the 3-layers ARB cycles was investigated by optical microscopy (OM), transmission electron microscopy (TEM), and electron back scatter diffraction (EBSD). The average grain size has been refined from 20 μm before ARB to 170 nm after 7 cycles of 3-layers ARB. More than 70% of ultrafine grains formed by 3-layers ARB were composed of high angle grain boundaries. The average misorientation angle of ultrafine grains was 30.7 degrees in the center of the specimen. Tensile strength after 7 cycles of 3-layers ARB was 605 MPa, which is about 3.2 times higher than the initial value.

Abstract: Aluminum based metal matrix composite (MMC) was processed by accumulative roll bonding (ARB) for ultra grain refinement and high strengthening. The ARB process up to 4 cycles was performed for the composite with 5vol.%SiC at ambient temperature under unlubricated conditions. The ARB of unreinforced aluminum powder compact was also performed for comparison. The tensile strength of the composite increased with the number of ARB cycles, and reached a maximum of 375MPa at the 3rd cycle, which is 1.8 times higher than that of the initial material. An increment of the strength per cycle was much larger in the composite than that in the unreinforced 6061 aluminum powder compact. The elongation of the composite decreased gradually with the number of ARB cycles, became almost zero after 4 cycles. TEM observation revealed that the composites fabricated by 1 to 3 cycles showed a dislocation cell structure, but after 4 cycles it showed an ultra-fine grained structure with mean grain size below 500nm. The ultra-fine grains developed at lower cycles in the composite than in the unreinforced one.