Microstructure evolution and high-temperature oxidation behaviour of selective laser melted TiC/TiAl composites

In this work, TiC ceramic particle reinforced TiAl-based composites were synthesized by selective laser melting (SLM) by using Ti, Al, and TiC multi-component powder. The results showed that a plenty of TiC dendritic crystals formed during the solidifying process. It was found that TiC dendrites exhibited three different modes of nucleation and growth, corresponding to the dissolution-precipitation of fully melted fine TiC particles, the epitaxial growth along the margin of partly melted TiC particle, and the recrystallization growth based on stress-induced nonequilibrium melting. Subsequently, the influence of laser energy density on microstructure evolution and high-temperature oxidation behaviour of SLM fabricated TiC/TiAl composites were investigated. At a high laser energy density of 189 J/mm3, the relatively full dense SLM-fabricated part was obtained, accompanying the formation of a variety of TiC dendrites with the coarsening structure, which made a contribution to the elevated high-temperature oxidation resistance with a low oxidation kinetics constant of 1.32 × 10−5 mg 6 cm−12 h−1.