In-situ synthesis of high-performance TiN/TC4 sandwich structures via nitrogen-controlled laser directed energy deposition

Laser Directed Energy Deposition (LDED) additive manufacturing offers a versatile approach for fabricating composite materials, encompassing a wide range of heterogeneous and transition materials, known for their exceptional mechanical properties. In this study, we focus on the synthesis of TiN/TC4 sandwich structural materials in atmospheres characterized by varying nitrogen-to-argon ratios. This study includes the in-situ synthesis, microstructural evolution, and mechanical characteristics of these TiN/TC4 sandwich structures during the LDED process. Through this process, TiN was formed in-situ by the interaction of Ti and N atoms, exhibiting in robust metallurgical bonding with the TC4 matrix. Notably, the microhardness of the TiN/TC4 sandwich structures exhibits periodic variations along the deposition direction, ranging between 314.4 HV0.2 and 661.5 HV0.2. The tensile strength of the TiN/TC4 sandwich structures experiences significant enhancement, while maintaining toughness due to the laminate structure and reinforced with ceramic particles inside. The resulting sandwich composites demonstrate outstanding ultimate tensile strength, which can achieve 1123.3 ± 29.7 MPa. This represents a notable improvement of 20.3% over the TC4 deposited in a pure Ar environment, with a corresponding plastic strain of 2.5 ± 1.7%. This study demonstrates that layered heterogeneous materials with superior mechanical strength can be synthesized in-situ through flexible integration of LDED process and reaction atmospheres.