Comparing addition of ZrO2 particles in micron and nano scale on microstructure and mechanical behavior of aluminum-matrix composites produced by vortex route

Aluminum matrix composites are important engineering materials in automotive, aerospace and other applications because of their low weight, high specific strength and better physical and mechanical properties compared to pure aluminum. ZrO2 particles as reinforcement were selected to add aluminum with micron and nano size. Al/ZrO2 composites were produced by direct incorporation (vortex method) in different temperatures and 5 volume percents of ZrO2 particles. Microstructure of the samples was studied by scanning electron microscopy (SEM). Chemical composition of the phases was studied by XRD. Hardness, and density of these composites were also measured. The microstructure and mechanical properties tests of composites and study the effect of particle size, resulted the better properties compared to matrix aluminum. Homogeneous dispersion of the reinforcement particles in the matrix aluminum was observed. The results show enhancing the composites properties for all samples compared to the monolithic alloy. However there are some differences in results because of particle size of ceramics and therefore differences between particles surface area. Maximum volume percent that can be added to A356 aluminum alloy is 5 vol.%, for nano ZrO2 particles, but it seems that is more than 5 vol.% for micron particles. Increasing of viscosity, porosities and much more defects are caused by increasing volume percents and using smaller particles. The casting processing is difficult in these conditions. Furthermore, optimum temperatures of casting for micron and nano zirconia particles are not the same.