In situ transformations during SLM of an ultra-strong TiC reinforced Ti composite.

This work demonstrates a successful in situ method capable of producing an ultra-strong novel Ti composite without aluminium and vanadium. In this method, selective laser melting is used to conduct in situ alloying and reinforcing of a Ti/10.5 wt% MoC powder mixture. It is shown that this leads to a metastable β-Ti matrix homogeneously reinforced by high aspect ratio, 50-200 nm wide and up to several micrometre long TiC whiskers. The transformations of the phases are controlled by decomposition, dissolution, diffusion, and reformation of constituents. The whisker morphology of in situ formed TiC particles is associated with directional crystal growth along the TiC direction. The developed TiC reinforced β-Ti alloy combines a hardness over 500 HV, a Young's modulus of 126 GPa, and an ultimate compressive strength of 1642 MPa. Improving the ductility of this composite is the subject of another work.