Microstructure And Properties Of Aluminum Matrix Composites Prepared By Lost Foam Method

In this paper,conventional alloy smelting method and lost foam casting method were used to prepare pure silicon(brand name Al99.90)as the base silicon carbide(SiC)particles,carbon nanotubes(CNTs)as the reinforcement,and 2297 alloy as the matrix silicon carbide(SiC)particles,carbon nanotubes(CNTs)are four aluminum-based composites of reinforcement.Metallographic observation(OM),scanning electron microscopy(SEM),X-ray diffractometry(XRD)and energy spectrum analysis(EDS),microhardness tester,electronic universal tester and conductivity test system were used.The microstructure and properties of as-cast,extruded and annealed state were studied.The microstructure,mechanical properties and electrical properties of the composites were investigated.The effects of the enhancement of silicon carbide particles and carbon nanotubes on the mechanical and electrical properties of aluminum matrix composites were discussed,which provided ideas and references for the further development of aluminum matrix composites.The as-cast,extruded and annealed microstructures of the experimentally prepared aluminum matrix composites show that the as-cast microstructure of Al99.90 is mainly composed of ?-Al,and the grain shape is approximately equiaxed.The size is uniform,and the grain boundary is clear and the crystal grains are intact.The aluminum matrix composite with 2297 alloy as matrix has a large amount of unresolved non-equilibrium eutectic structure and continuous coarse phase near the grain boundary.The dendrite spacing is large and the segregation is obvious.The obvious change of the microstructure of the extruded composite material is changed from the equiaxed shape of the original as-cast shape to the elongated shape elongated in the extrusion direction.After the extruded sheet is annealed at 410 ° C for different time,the composite material is obtained.Recrystallization occurs,and the crystal grains are transformed into fine crystal grains from the elongated strip after extrusion.Through the microhardness analysis of the as-cast microstructure of composite materials,the microhardness of the composites is higher than the microhardness of the matrix materials,and the microhardness growth is not obvious.It is possible that the content of SiC particles or CNTs is too low.The microhardness of the prepared composites showed a downward trend in the 1h-3h period by the effect of annealing the extruded composite materials at 410 °C for different time.The recrystallization process was a The process of eliminating deformation and returning to the matrix by nucleation and growth is a completely softening process.After more than 3h,it showed a downward trend in the 3h-6h time period.As the homogenization time prolonged the solute atoms in a large number of non-equilibrium tissues and dissolved back into the aluminum matrix,it could strengthen the role,leading to the trend of increasing hardness.The tensile strength,yield strength,and electrical conductivity of the 1h-3h annealing period gradually increased,while the elongation decreased gradually.The tensile strength,yield strength,and electrical conductivity gradually decreased during the annealing period of 3h-6h,while the extension The rate is gradually rising.