Al-ni <sub> 2 </ Sub> O <sub> 3 </ Sub> Aluminum Matrix Composites, Microwave Synthesis Study

Microwave synthesis is an efficient and energy conservation method for material preparation. In this paper, the Al-Ni2O3 system of aluminum matrix composites were prepared by microwave and conventional synthesis method respectively, with Al and Ni2O3 powders as raw material. The reaction process and the production of the Al-Ni2O3 system were analyzed by many modern methods. The temperature-time curves of microwave heating process were tested by the self-developed software, which used to study the processing and mechanism of microwave synthesis.The reaction process of the Al-Ni2O3 system followed in two steps. Al reacted with Ni2O3 firstly and formed Al2O3 and active Ni atoms. Then Al reacted with active Ni atoms and resulted in Ni2Al3.When volume fraction increased from 20% to 100%, the amount of reactive activation energy increased from 139.963 kJ/mol to 331.320 kJ/mol.When 20% reinforcement volume fraction material solidified,Ni2Al3 grew up, NiAl3 separated out from the liquid phase. The production was consisted of Al matrix and three reinforcements:fine particle of Al2O3,massive Ni2Al3, shredded NiAl3.When 50% reinforcement volume fraction material cooled to a certain centigrade, peritectic reaction happened with Ni2Al3 in liquid state and resulted in NiAl3.Compared with conventional synthesis, the initiation temperature of microwave synthesis reduced more than 134℃,the reactive speed increased evidently, the total time reduced to 1/20. The production's structure was dense, dispersion was uniform, and crystalline grain was fine. The tensile strength of the composites was higher than the matrix, and elongation reduced. The tensile strength of 10% reinforcement volume fraction material was 145.3MPa, elongation was 8%, fracture contained many dimples, belong to gliding fracture. The tensile strength of 20% reinforcement volume fraction material was 126.1MPa, elongation was 1.75%, fracture contained massive blocks clearly, belong to brittle rupture. The coefficient of linear expansion was reduced 2.11% and 8.05% respectively. Add rare earth, can improve the tensile strength of the material and reduce the coefficient of thermal expansion.