5th International Conference on Advances in Solidification Processes (ICASP-5) 5th International Symposium on Cutting Edge of Computer Simulation of Solidification, Casting and Refining (CSSCR-5)

Metal matrix composites (MMCs) can be tailored to produce various combinations of stiffness and strength and have found a wide range of applications where existing materials are not suitable for use in automotive and aerospace industries and many other areas. Stir casting is commonly used for fabricating large quantity of primary MMCs, in comparison to liquid metal infiltration and powder metallurgy, which are methods for making near net-shape MMC components or small quantity MMCs. Stir casting is cost-effective but suffers from severe particle agglomeration, particularly when the size of reinforced particles is down to nanoscale. The present work was carried out to investigate the effect of high shear treatment on the distribution of reinforcing particles in the fabrication of magnesium and aluminium alloy matrix particulate nanocomposites. An Mg-2Zn-0.5Ca alloy and commercially pure aluminium was selected as the matrix. Hydroxyapatite nanoparticles (~50nm, spherical, 1-5wt%) were added to the magnesium alloy as reinforcing elements and alumina nanoparticles (~30nm, spherical, 1-3wt%) to aluminium. The high shear treatment was employed after the admission of reinforcing particles by mechanical stir and performed with a rotor-stator device at a speed of ~5000rpm. Experimental results showed that the high shear treatment effectively reduced particle agglomeration for both Mg/HA and Al/Al2O3 nanocomposites, although the features of particle segregation are different, probably due to difference in wettability between the matrix and reinforcing elements in these two systems. The as-cast Mg/HA and Al/Al2O3 nanocomposites were deformed by hot extrusion and cold rolling respectively. The microstructure and mechanical properties of the material were characterized and the effect of processing parameters was studied.