چكيده به لاتين
Aluminum and its alloys are one of the most important materials used in the aerospace, military and automotive industries due to their properties such as low density, precipitation hardening and corrosion resistance, high conductivity and high thermal conductivity. In this research, graphene reinforced aluminum matrix nanocomposites have been produced using a combination of mechanical alloying and molecular level mixing (MLM), which is followed by spark plasma sintering (SPS) process. As a common method, the Hummer method was used for the synthesis of graphene oxide in this project. The results of XRD, FTIR, AFM, Raman and FESEM tests of synthesized graphene showed that few layers graphene oxide was produced. MLM was used as a novel method for synthesizing CuO/GO and Cu/RGO nanocomposites powder. The results of FTIR, XRD, FESEM, and TEM tests on fabricated powders showed no agglomeration of graphene layers as well as homogeneous distribution of CuO and Cu nanoparticles on the layers. The optimal conditions for mechanical alloying were achieved at the blending speed of 300 rpm, a combination of ball size 5 and 10 mm, BPR of 20 to 1, a total powder weight of 10 g, 2 wt.% benzene as PCA, and ball milling time of 10 hours. The results of the XRD test showed that copper in the absence of RGO is completely soluble in aluminum during the mechanical alloying time of 10 hours, while in the presence of RGO, the copper dissolution in aluminum is limited. The temperature, pressure and maintaining time for SPS process was achieved to be 500°C and 50 Mpa and 10 minutes, respectively. A relative density above 99% for sintered specimens showed a high consolidation of the produced nanocomposite. Microstructural studies of the samples with the X-ray diffraction and Raman test showed the formation of Al2Cu nanoparticles as well as no formation of the Al4C3 phase during the SPS process. These results showed low damage applied on graphene during the synthesis process and thus helped improve the mechanical properties of fabricated nanocomposites. By studing of the mechanical properties of the produced nanocomposite in the presence of graphene, the properties were improved by increasing the graphene weight percent. In this regard, in the presence of 1 % wt. RGO, significant improvement in microhardness, yield strength and ultimate strength of Al-4Cu / RGO nanocomposites 44% (78 to 125 HV), 78% (78 To 139 MPa) and 49% (from 215 to 320 MPa) were achived, respectively. Investigation of the strenghtening mechanisms of the nanocomposites showed that the grain riefinment strengthening has the greatest contribution on the mechanical properties improvement of the produced nanocomposite.
Keywords: Nanocomposite, aluminum, spark plasma sintering (SPS), mechanical properties, and microstructure
