Microstructure And Mechanical Properties Of SiCp/2014Al Composite After Hot Extrusion

The aluminum matrix composites was developed more than30years, many researchesstill have performed on it during this period. Low density, high strength, high modulus ofelasticity and other excellent properties of SiCp/2014aluminum composite are attractiveleading to its prevalent usage, from electronic packaging substrate to auto parts. Nevertheless,the problem of homogeneous distribution of particles in the matrix and the interfacialbonding strength between particles and matrix alloy are still detailed investigated with moreresearchers.Due to low cost flexible operation of strirring casting, in this thesis, SiCp/2014aluminum composites were fabricated by semi-solid stirring technique. The effect of the hotextrusion process was investigated on the homogeneous distribution of SiCp particles in thematrix alloy and the interfacial bonding mechanism between particles and matrix alloy. Theeffects of solution heat treatment and the hot extrusion processing parameters on themicrostructures of SiCp/2014aluminum composites with existence of casting defects such aspores and shrinkages cavities and on the distribution behavior of SiCp were investigated forputting forward reasonable extrusion processing. Also, in order to further increasingmechanical properties of SiCp/2014aluminum composites, the effects of age hardening onthe microstructures and mechanical properties of SiCp/2014aluminum composites after hotextrusion. The main results are follows:(1) It was found that hot extrusion can eliminate casting shrinkage and shrinkage cavitydefects, reduce the SiC particles reunion phenomenon, improve the distribution of SiCparticles in the matrix and the interface bonding between particles and matrix alloy of SiCp/2014Al composites.(2) It was found that different heat treatment processes have important influence onimproving the organization of SiCp/2014Al composites before extrusion. Low melting pointeutectic phases Al2Cu of SiCp/2014Al composite were dissolved to matrix alloy by solidsolution treatment which improving the distribution of SiC particles in the matrix andbenefiting the deformation of matrix alloy.(3) The effects of extrusion processing parameters(extrusion ratio, extrusiontemperature and extrusion holding time)were investigated on the final microstructure andmechanical properties of the SiCp/2014Al composites through the hot extrusion process,concluded that lower extrusion temperature, higher extrusion ratio, suitable extrusionholding time have a great effect on the microstructure and mechanical properties ofSiCp/2014Al composites. The relatively excellent extrusion process: extrusion temperatureis510℃, holding timeis30min, extrusion ratio is19:1. With this extrusion process, thehomogeneous distribution of particles in the matrix was improved, the casting defects suchas pores and shrinkages cavities were decreased and providing favorable conditions toimprove the interfacial bonding strength between particles and matrix alloy.(4) In studying aging treatment on the precipitated phase precipitation behavior and themicrohardness of SiCp/2014Al composite, conclusion that optimization parameters of agingtreatment for SiCp/2014Al composite was aged at165℃for8h.(5) Extrusion processing can greatly improve the mechanics performance ofSiCp/2014Al composite. The tensile strength is24.95%higher than as-casting(384.7MPa)while solid solution treatment of SiCp/2014Al composite after extrusion and aging heattreatment(480.7MPa), the elongation is17.25%higher. The tensile strength is11.3%higherthan as-casting(384.7MPa) while homogenization treatment of SiCp/2014Al composite afterextrusion and aging heat treatment (428.2MPa), the elongation is21.5%higher.