Tuning the size of TiC plates in additive manufactured titanium matrix composites by laser heat input and its effect on strengthening effect

Reinforcement size plays a crucial role in fabricating high-performance metal matrix composites. Due to the high chemical reactivity of Ti[sbnd]C, TiC is prone to coarsening in titanium (Ti) matrix composites (TMCs). The TiC dimensions of the reported TiC/Ti are concentrated in the micron scale, and the preparation of ultrafine TiC reinforcement is difficult, so that the strengthening efficiency of TiC in TMCs is limited. In this study, we proposed a facile lase additive manufacturing (AM) strategy to utmost refine TiC to nanoscale in TMCs by adjusting laser heat input using the powder mixture of nano-sized carbon black and pure Ti. The results showed that the average thickness of plate-shaped TiC decreased from 140 nm to 55 nm while maintaining high relative density over 99 % with decreasing the laser volume energy density from 152 J/mm³ to 52 J/mm³. Consequently, the uniformly dispersed superfine in-situ TiC reinforced TMCs achieved high strengthening efficiency of 119.6, which exceeded almost all of the AM TMCs reinforced by TiC or TiB in literature. It was further revealed from the strengthening analysis that refining TiC improved contributions of grain refinement, thermal mismatch and Orowan strengthening mechanisms. The results are expected to provide guidance for optimizing the microstructure of TMCs by controlling AM parameters.