Fine particle reinforced composites obtained with suspension method

In the production of composites by the suspension method (mechanical stirring) may be used, ceramic particles, which are wetted by the liquid metal such SiC, Al₂O₃ or glassy carbon. However, to obtain a stable suspension with the use a particle size below 10 μm is extremely difficult. Phenomena related i.a. with agglomeration of particles, convection currents over molten metal surface make practically impossible to obtain composite material. One possibility to obtain fine reinforced composite is the use of in situ methods, in which the reinforcing phase is formed by the reaction between the aluminum and the reactive powder oxides such FeO, TiO₂, SiO₂, NiO, Nb₂O₅ or Fe₂O₃. Such reactions are exothermic (aluminothermic) and their kinetics dependent on the dispersion of the reactants, the quantitative phase composition and temperature. The technological solution involving the formation of a suspension with particles (chemically active with aluminum) is one of the promising solutions to obtain batch material for the synthesis of composites reinforced with Al₂O₃ and intermetallic phases. The aim of this study is to evaluate the suitability of suspension technology to obtained in situ fine reinforced composite.