چكيده به لاتين
Accumulative roll bonding (ARB) is one of the severe plastic deformation methods (SPD), which is used to produce metal matrix composites. ARB process has been studied by many researchers. In this study, the ARB process is used to produce the layer composites, made from two dissimilar aluminum, AA2024 and AA7075 alloys performing at room temperature. The purpose of this study, is to study the feasibility of ARB process on the microstructure and the mechanical properties of the used alloys. In order to microstructural study of the generated composites, the scanning electron microscopy (SEM) and the X-ray diffraction (XRD) were used. The interface junction of the alloys in different Passes of ARB process were studied by optical microscopy and SEM. Dislocation densities were calculated using Williamson-Hall method and X-ray diffraction patterns. The calculations of determining the Dislocation densities showed the highest Dislocation densities have been obtained after the third pass and will be decreased by increasing the passes, due to dynamic recovery during the deformation. To evaluate the mechanical properties, the tensile and the micro-hardness tests have been used. The results showed, after one ARB pass, the hardness have been increased greatly, while continuing the process until 4 passes, increases the hardness with a lower rate. According to the tensile test in the first pass, the yield strength have been increases 128 percent compared to the annealed sample. Moreover, Investigation of Work hardening properties showed the ARB process greatly decreases the work hardening ability compared to the annealed sample. Increase in the dislocation densities and decrease in the grain size are found as the factors of the reduction in work hardening ability. After the tensile test, the fracture surface of samples were studied by SEM. By investigating the Fracture morphologies of samples after ARB process, show that the average dimple size gradually decreases with increasing number of ARB passes, which lead to fracture type changes from ductile to brittle.
