Investigating the Influence of Type and Amount of Reinforcement Particles and Processing Parameters on the Micro Structure and Mechanical Properties of Aluminum Matrix Composites

Al-12%Si metal matrix composites reinforced with 6-25 vol% of Al2O3, TiC and B4C reinforcement particles, were fabricated by stir casting. The microstructure, density, porosity, micro-hardness, tensile strength of composites were evaluated. Microstructure and mechanical properties characterization showed uniform reinforcement distribution and increasing of hardness and tensile strength of composites samples with increasing of Al2O3 (25 vol%), TiC (18 vol%) and B4C (10 vol%). For Al-5% Al2O3, various parameters of stir casting processing such as temperature of molten metal, rate and time of stirring, Type of agitator, were investigated. The results show that fabrication of composites in condition of 700- 750 rpm for agitator, 17 minutes of agitation for alumina and 6 min for carbides particlrs, using of zirconia- coated agitator with blades in angle of 30° in relation to rotation axis, adding of ceramic particles with speed of 0.375-1.2 gr/sec, temperature of casting of 700-750°C give the optimum reinforcement distribution, wetting and quantity of porosity.