The Preparation And Solidification Microstructure Control Of In-situ Aluminum Matrix Composites

(Al₃Zr+Al₂O₃)p/Al, (Al₃Zr+Al₂O₃)p/Al-4Cu and (Al₃Zr+Al₂O₃)p/A356 composites have been successfully prepared by in-situ melt reaction technique.Optical microscopy (OM), scanning electron microscopy (SEM), electron probe microanalyzer (EPMA) and X-ray Diffractometer (XRD) were used to analyze the influence of different synthesizing parameters on the microstructure of aluminum matrix composites. The technology parameters were optimizedThe mechanical properties of in-situ (Al₃Zr +Al₂O₃) particulate reinforced aluminum matrix composites were investigated. The inter-reaction mechanism between reinforcement particles and the second phases was studied. The strengthening mechanism was discussed.The XRD and EPMA analysis results show Al₃Zr and Al₂O₃ reinforcement phases synthesized by in-situ molten reactions from ZrOCl₂ and Al, Al-4Cu and A356, respectively, were obtained. The shapes of Al₂O₃ (<2μm in size) and Al₃Zr(2-5μm in size)are circular and polyhedral (lath), respectively.The optimal parameters for in-situ reaction technology in the Al-ZrOCl₂ system are as follows: the initial reaction temperature is 850℃, reaction time 15 minutes.The solidification microstructure of (Al₃Zr+Al₂O₃) p/A356 synthesized with the above parameters is the optimum.The analysis of the solidification microstructure of the composites fabricated under magnetic field shows that the reinforcement particle is diminished in size and uniformed in distribution with the increase of current intensity and magnetic intensity under 100-300A and 10HZ conditions.Under the magnetic field conditions , the dendrite structures of the matrix is refined.The analysis of the effect of rapid solidification on the microstructure of composites shows rapid solidification not only make the Al₃Zr particle mainly distribute in spherical shape not in lath shape, promote the shape of metastable phase...