TiC particulate-reinforced Al–20Si–5Fe composite fabricated by melt in situ reaction spray forming

A novel technique in which TiC particulates are fabricated by an in situ reaction in molten aluminum is introduced for producing TiC/Al–20Si–5Fe composite. In order to reveal the characteristics of the technique, in this paper the formation mechanism of TiC particulates obtained by this method is studied. Both theoretical and experimental results have shown that the TiC particulates are formed by a diffusion mechanism when the molar fraction of aluminum in the preform is greater than 20.02%. Contrarily, the TiC particulates are formed by a solution-precipitation mechanism when the fraction is less than 20.02%. An unwanted needle-like phase is always present in the spray-formed alloys. Experimental results have shown that the amount of the brittle phase decreases in spray-formed Al–20Si–5Fe preforms with increase in the TiC content, and that the brittle phase can be eliminated completely by adding more than 3 wt.%TiC particulates to the alloy. Moreover, another major problem of coarsened silicon particulates, often encountered in hyper-eutectic Al–Si alloy has also been solved by using the technique.