Investigation On Preparation And Properties Of 2024-Al Network Composites Reinforced With CNTs And SiCw

Conventional aluminum matrix composites are usually fabricated with homogeneous distribution of reinforcements in the matrix. This structure does not display the best ductility because the integrity of the matrix is compromised.To solve this problem, a new structural material with network distribution was designed and prepared. In this paper, CNTs and Si Cw with network distribution reinforced 2024 Al matrix composites were fabricated by powder metallurgy. Then the optimal sintered composites was selected to hot extrusion deformation and aging treatment, with the purpose of increasing the density and mechanical properties. The microstructure and interface phase of the sintered, extruded and aged composites were analysised by the OM, SEM, XRD and TEM respectively.Ambient and high temperature tensile experiments were performed to investigate the mechanical properties of different state. The strengthening and toughening mechanism of the network reinforcement were also explored. Wear rate and friction coefficient of different state were test at the ambient respectively.Combined with grinding crack surface morphology, the wear mechanism was explained.The homogeneous distribution of CNTs was achieved by mixing acid. Then CNTs 、 Si Cw and Al power were mixed evenly through mechanical agitation.Different volume fraction of composites of sintered state were fabricated by hot pressing sintering. The result showed that with the increasing of volume fraction,the network structure became more apparent, but cluster was serious. Then hot extrusion was conducted to materials. Microstructure observation results showed that hot extrusion could make reinforcements distribute along the extrusion direction, eliminate defects and enhance the combination of reinforcement and matrix. The results after aging treatment showed that aging treatment led to grain refinement of the matrix and most generated Cu Al2 distributed around the sub-boundary.The tensile experiments showed that the sintered system of 1%CNTs+5%Si Cw had the highest strength of 218 MPa. The strength and elongation of extruded composites increased to 338 MPa and 6.1%. After aging strength increased to426 MPa and elongation decreased slightly. High temperature tensile experiments of extruded and aged composites showed that the tensile strength reduced slowly before 250℃, but when reached 300℃, the strength rapidly declined and plasticityincreased. As the temperature increased, the effect of improving the strength by aging became worse.Friction and wear tests of sintered composites and 2024 Al alloy were conducted respectively. It was found that, under different loads, the composites displayed lower wear rate compared to the 2024 Al alloy. Compared with sintered state, the wear rate of extruded state reduced and friction coefficient increased. Under 12 N load, there was no serious adhesive. After aging the wear rate further reduced.