Influence of in situ ceramic reinforcement towards tailoring titanium matrix composites using laser-based additive manufacturing.

Increasing performance requirements of advanced components demands versatile fabrication techniques to meet application-specific needs. Composite material processing via laser-based additive manufacturing offers high processing-flexibility and limited tooling requirements to meet this need, but limited information exists on the processing-property relationships for these materials as well as how to exploit it for application-specific needs. In this study, Ti/B4C+BN composites are developed for high-temperature applications by designed-incorporation of ceramic reinforcement (5 wt% total) into commercially-pure titanium to form combined particle and in situ reinforcing phases. We combine both B4C (limited reactivity with matrix) and BN (high reactivity with matrix) reinforcements to understand the processing characteristics, in situ phase formations, and combinatorial effect of the multiphase microstructures on thermomechanical properties and high-temperature oxidation resistance. Combined reinforcement in this new composite material leads to superior yield strength and wear resistance in comparison to the other compositions and matrix, as well as comparable oxidation characteristics to commercially-developed high temperature titanium alloys, alleviating the need for multiple rare-earth alloying elements that significantly raises costs for manufacturers. Tubular structures are fabricated to demonstrate the ease of site-specific composition and dimensional tolerancing using this method. Our results indicate that tailored ceramic reinforcement in titanium via laser-based AM could lead to significantly enhanced engineering structures, particularly for developing higher temperature titanium-based materials.