Preparation And Characterization Of Aluminum Matrix Composites Reinforced By Micro/Nano Al₂O₃ Particles

Particle reinforced Al matrix composites are attractive materials for automotive and aeronautic applications due to their high strengths, good wear resistance, low thermal expansion coefficient and good mechanical properties. In this paper, two different methods preparing composites were adopted, the mechanical stirring method manufacturing nano-Al₂O₃/7075 and hot extrusion method manufacturing Al₂O₃/Al composites reinforced with bimodal sized Al₂O₃ particles. And metallurgical microscope, Brinell hardness tester, X-ray diffraction?XRD?, Electronic universal tensile testing machine, Cold field emission scanning electron microscope?FESEM? were used to analyze the microstructure, hardness, phase composition, mechanical properties and tensile fracture morphology of the composites.The results indicated that??? Using the mechanical stirring casting technique to prepare the nano-Al₂O₃/7075 composites, when the content of Al₂O₃ particles increased from 0 to 1.5wt%, the microstructure of the composites was refined and the hardness and the tensile strength were improved.But once the weight fraction of Al₂O₃ exceeds 1.5%, the grain size of the composites began to grow and the strength began to decrease;??? Using the hot extrusion technique to prepare the composites reinforced with nono-sized Al₂O₃ and micro-sized Al₂O₃ particles, the tensile strength of the 4wt%nanoparticle+10wt% microparticle/Al composites was remarkably improved to174 MPa. And the SEM results showed that with the increase of mixed particles,the agglomeration was observed. But the tensile fracture morphology was no obvious difference with the particle changing and increasing.In conclusion, the Al₂O₃ particles play an important role in refining the grain and improving the mechanical properties of the composites. Also, bimodal sized Al₂O₃ particles were more effective in improving the mechanical properties than unimodal sized particles.