Development of Spontaneous Infiltration-<I>in situ</I> Production Process for Fabrication of Particulate Reinforced Aluminum Composites

The spontaneous infiltration of liquid pure aluminum into the mixture of raw materials is used to synthesize particulate reinforced aluminum composites with the in situ process. The addition of powder of a column IVa element (Ti, Zr) or a column Va element (Nb, Ta) into the raw carbide particles of Al4C3, SiC or B4C allows liquid pure aluminum to infiltrate into the mixture spontaneously and subsequently in situ formation of the carbide particles of column IVa and Va elements occurs in the melt. It is revealed from macroscopic and SEM observations that liquid aluminum completely infiltrates into the mixture independently of the kind of atmosphere used in the experiment, nitrogen or argon. However, processing under nitrogen gas, which can react with the aluminum melt, is effective in prohibiting pores from remaining in the composite. The rate of in situ reaction of the (Ti+B4C) system is somewhat high compared to those of (Ti+SiC) and (Ti+Al4C3) systems. Very fine TiC and TiB2 particles simultaneously synthesized through the decomposing reaction of B4C are dispersed in the aluminum matrix. As soon as liquid aluminum begins to infiltrate, the melt temperature increases drastically not only in (Ti+raw carbide) systems but also in a (Ti+Al2O3) system. Hence, it seems that the spontaneous infiltration of liquid aluminum is attributed to the exothermic formation of Al3Ti.