Characterization of In-situ Titanium Matrix Composites Prepared by Laser Melting Deposition

Preliminary characterization of microstructure and mechanical properties of (TiB+TiC)/TC4 and TiC/Ti60 in-situ titanium matrix composites prepared by laser melting deposition is reported in this paper. The results indicate that in-situ reaction occurred during laser melting deposition of coaxially fed mixed powders from TC4 and B(4)C with formation of form TiB and TiC reinforcement. For TiC/Ti60 composites, there are some un-melted TiC particles and re-solidified TiC particles appeared as discontinuous chain-like morphology. Reinforcements of TiB and TiC with fraction about 25 vol% were formed with feeding 5 wt% B(4)C. The morphology of TiB tended to be needle-like and prismatic, while TiC appeared as granular. Small amount of un-reacted B(4)C with reduced size remained within the composites. A thin skull of reaction product formed around the un-reacted B(4)C weakened its interface bonding with the titanium alloy matrix, thus resulting in less outstanding properties of the composites. Under 600 C, the ultimate tensile strength of the TiC(p) (5wt%)/Ti60 composites was 60 MPa higher than that of Ti60 alloy, following with decreased elongation.