چكيده به لاتين
Abstract:
In recent decades have been wide improved the use of metal materials with fine grain structure because of the remarkable physical and mechanical properties of these materials. ARB process is considered as a novel method due to economic efficiency and mass production capability. Through the ARB process are achieved multi-layered sheets with the suitable combination of high strength, acceptable ductility and uniform ultra-fined structure. In this study, multi-layered Al/Al and multi-layered composite Al/Cu in seven and five passes produced by ARB process. To produce Al/Cu composite, for the first used Aluminum alloy that followed achieved the best mechanical properties, for produced samples compared with previous similar studies. After producing production samples, mechanical properties, micro structure and fracture surface were studied by using uniaxial tensile testing, micro, optic and electron microscope, respectively. Also in this investigation, is studied for the first time, formability of ARBed sheets through drawing forming limit diagrams and using Nakazima test for Al/Al, experimentally. According to the results, it was found that for both samples, with increasing the number of ARB cycles, the thickness of each layer is reduced and the microstructure is more uniform and homogeneous. Also by increasing the number of ARB cycles, and after first cycle, for the two samples, value of elongation decreased and tensile strength increased and FLD for Al/Al decreased, sharply and in the next pass elongation and the forming limit diagram with low rates increases and the tensile strength increases at a lower rate than the first cycle. The best mechanical properties of Al/Cu composite sample was obtained in the fifth pass that values of elongation and strength achieved 9.61 and 566.5 MPa, respectively, that this results were more best mechanical properties for Al/Cu composite compared with previous studies. For Al/Al elongation after seventh pass arrived to the maximum amount that compared to annealed samples 77% reduced. Also trend of FLD0 and variation elongation was similar and at last cycle, FLD0 was 13% and compared to annealed samples 44% decreased and tensile strength at seventh pass arrived maximum value that compared to annealed samples 241.5% improved. For two samples, the value of micro hardness increased by increasing the number of ARB cycles so that at the end of the primary cycle rises more rate and the end of the final cycle is nearly constant and compared to initial samples improved more than twice.
Keywords: SPD, ARB, mechanical properties, microstructure, fractugraphi, FLDs
