Among all metal matrix composites, aluminum matrix composites are one of the applicable kinds of composites in vehicle manufacturing, aerospace and military industries due to their high strength, wear and oxidation resistance and low thermal expansion coefficient. In Situ method is one of the new routes for aluminum composites' manufacturing in which reinforcement phase is formed within the matrix through chemical reaction between elements or other compounds with elements. In this case, small size reinforcement particles with an appropriate dispersion in the matrix are obtained. The most important advantage of In Situ method is the suitable wettability of reinforcement particles by the melt. In this research, zinc oxide and copper oxide powders were utilized as additive materials to aluminum melt for In Situ synthesis of Al-Al2O3 composite. For this purpose, activated aluminum-zinc oxide Powder mixture was combined with copper oxide powder and injected to aluminum melt. After finishing of the injection process, cast composite slurry was solidified in a high pressure squeeze casting system. By the chemical reaction of metallic oxides with aluminum melt, in addition to the formation of alumina particles, zinc and copper elements were formed and dissolved in the matrix which resulted to synthesis of alloyed matrix. In order to detection of the ignition temperature of aluminothermy reaction of zinc oxide and copper oxide in activated powder samples and multi powder mixture in comparison with the similar quantity in non activated samples, differential thermal analysis(DTA) technique was employed. The result showed the considerable reduction for ignition temperature of aluminothermy reaction in activated and multi powder mixture samples. Effective parameters in casting process of composite materials were determined through obtained results from phase analysis of slag and chemical analysis of primary samples. In order to evaluation of size and dispersion of alumina particles, scanning electron microscopy was employed. Scanning electron microscopy micrographs showed the more appropriate dispersion and bigger size of alumina particles obtained from reaction of aluminum with multi powder mixture in comparison with those particles obtained from reaction of zinc oxide solely. In order to mechanical properties evaluation of composite samples, a corresponding monolithic sample with similar chemical composition related to each composite sample was fabricated and hardness, compression and tensile tests were applied to both monolithic and composites samples. Comparative results revealed the higher tensile and compression strength and lower elongation for composite samples in comparison with monolithic samples. Key Words: Metal Matrix Composite, In Situ, Aluminothermy reaction, Squeeze Casting, Microstructure
