Fundamental study of in-situ strengthening and formation of continuous gradient titanium alloys via laser directed energy deposition

Current heterostructured materials have significant potential for improving the strength-ductility trade-off, but the interfacial bonding capabilities are limited. In this research, composites with TiN/Ti6Al4V interlayer structure were in-situ synthesized by atmospheric remelting using laser directed energy deposition (LDED). The elemental diffusion, microstructure, and mechanical properties of TiN/Ti6Al4V interlayer structure composites were investigated. The mechanical properties of the composites were improved after nitrogen remelting due to the strengthening of internal TiN ceramic particles. The microhardness of TiN/Ti6Al4V composites increased by up to 209.8% to 1141 HV0.2, ultimate tensile strength by 6% and elongation by 34.5% to 1071.4 MPa and 15.6%, respectively. This research demonstrates that a flexible combination of the LDED process and reaction atmosphere can synthesize new periodic layered ceramic/metal composites with excellent mechanical properties. This research offers the groundwork for the fabrication of in-situ strengthening continuous gradient materials.