چكيده به لاتين
In recent years, the use of fine-grained metal materials has been highly regarded due to its desirable physical and mechanical properties. Therefore, severe plastic deformation methods are of great importance for the production of ultra-fine crystal structure. One of its newest methods is the bonding of sheets with the help of accumulative rolling process, which is considered for its mass production capability as well as economical cost. In this process, sheets of higher strength, better ductility and structure with fiber and uniform graining are obtained. In this investigation, thin aluminum foils with a thickness of two hundred microns were produced using accumulative roll bonding method in five passes without lubricant, without heat treatment between passes and at ambient temperature. After manufacturing samples, mechanical properties and microstructure of the fracture surface were investigated using uniaxial tensile test, micro hardness and electron microscope. Also, in this study, the formability of aluminum foil rolled in 5 passes was investigated experimentally by Nakazima test. According to the results, by increasing the number of accumulative roll bonding passes, the thickness of the layers decreases and the microstructure becomes more homogeneous. At the first pass of the process, the tensile strength is greatly increased and the percentage of elongation increases dramatically. Thereafter, with the increase in the number of cumulative rolling passes, the tensile strength and the percentage of elongation decrease with increasing slope, respectively. Thereafter, with the increase in the number of accumulative rolling passes, the tensile strength and the percentage of elongation increase and decrease respectively with low slope. The best mechanical properties were obtained in the fifth pass of the process where the ultimate tensile strength increased by 5.9 times that of the initial sample to 393.5 Mpa and the elongation percentage increased by 1.7 times to 3.05%. Micro hardness also increases with increasing number of process passes, which It was very high in the first pass, and then with a low slope, an increasing trend and after the 4th pass with the same low slope, the hardness decreases. The highest amount of micro hardness was in the fourth pass, reaching 81 Vickers. Also, the trend of changes of FLD0 is quite similar to the sample elongation percentage, which reached its maximum value equals 0.064 in the fifth pass, which is 46% lower than the original sample.
