Al-TiC particulate composite produced by a liquid state in situ process

An in situ process was used to produce fine TiC particulates in a molten aluminium alloy. In this approach, a carbonaceous gas is introduced into an Al melt containing Ti to form the TiC particulates, and the carbide volume fraction is determined by the initial Ti content. The melt containing the carbides was cast and subsequently extruded for microstructure and property evaluation. As-cast microstructure of the in situ processed composites reveals a relatively uniform distribution of TiC particles with an average size of a few microns. No preferential particle segregation to the dendritic cell boundaries was observed. In this paper, several aspects associated with evolution of the microstructure including phase formation sequence, TiC formation mechanism and particle distribution during solidification are discussed. The observation of particle entrapment is also compared with the existing models for predicting particle trapping/rejection during solidification. In addition, comparisons of properties such as tensile strength, elastic modulus and fracture toughness of the extruded composites with those of the baseline alloy are presented.