چكيده به لاتين
Due to their high strength to weight ratio, excellent corrosion resistance, good mechanical properties, malleability, and low cost, aluminum-based composites are considered as a candidate in the industries such as aerospace and automotive industries. In this research, the fabrication of 2024 aluminum alloy matrix composite reinforced with graphene through Accumulative Roll Bonding (ARB) was performed. Generally due to the significant difference in the surface energy of the reinforcing phase and the aluminum substrate, the wettability is weak, and this is intensified through nanometric size of these phases resulting in lack of proper distribution of the reinforcing phase in matrix and agglomeration of particles is promoted. For this reason, the combined method of mechanical alloying and molecular level mixing (MLM) was used to improve the distribution of graphene in the aluminum matrix. The results of XRD, FTIR and FESEM tests on the synthesized powders showed no agglomeration of graphene layers and homogeneous distribution of CuO and Cu nanoparticles on them. Mechanical alloying were carried out at stirring speed of 300 rpm, combined ball size of 5 and 10 mm, ball to powder weight ratio of 10:1 at the presence of 2% weight of stearic acid as PCA and milling time of 10 hours. the ARB rolling process was performed at the rolling speed of 12 rpm. For this, the samples were preheated at 360°C for 15 minutes in the first cycle and for 2-3 minutes in the remaining cycles up to 7 cycles, and 50% thickness reduction per cycle. XRD test confirmed the presence of Al2Cu phase in the structure of nanocomposites. The evaluation of the mechanical properties showed that the tensile properties increased with the addition of RGO. In this regard, at the presence of 0.1 percent by weight, RGO in 2024 aluminum matrix provided a significant improvement about 18.5% (of 79 to 93.63HV), 60% (from 78 to 125 MPa) and 24.5% (from 125 to 155 MPa) respectively for micro-hardness, yield strength and ultimate strength compared to that of the rolled base alloy. The Investigation of strengthening mechanisms in this nanocomposite showed that the strengthening caused by grain refining has the greatest contribution to improving the mechanical properties of the produced nanocomposite. by performing the heat treatment on AA2024/0.1%Y nanocomposite, it was observed an increase in hardness, yield strength, and ultimate tensile strength by 20%, 17%, and 10.5%, respectively.
