Wire arc additive manufacturing NiTi/Nb bionic laminated heterogeneous structure: Microsturcture evolution and mechanical properties

In the aerospace industry and the medical field, there is a demand for materials that combine the functional properties of NiTi with the excellent ductility of Nb. However, creating high-strength interfaces between these two materials has been difficult due to their inherent differences in physical and chemical properties. In this study, a laminated heterogeneous structure (LHS) combining NiTi and Nb was prepared using wire arc additive manufacturing (WAAM) with different layer thickness ratios. The resulting microstructure of the NiTi/Nb LHS components consisted of a large amount of NiTi and β-Nb eutectic structures. This was due to the metallurgical bonding between the NiTi and Nb layers. The NiTi/Nb LHS components exhibited excellent compressive strength, measuring at 2607.6 ± 31 MPa. Additionally, the interface strength of the NiTi/Nb LHS component was remarkable, showing an ultimate tensile strength of 789.3 ± 8 MPa. The enhanced strength of the NiTi/Nb LHS component can be attributed to the gradient microstructure of the NiTi layer, which promoted heterogeneous plastic deformation generation. Furthermore, this study unveiled the relationship between the formation mechanism of the heterogeneous eutectic microstructure and the strength-ductility synergistic mechanism. As a result, this study provides an innovative approach for additive manufacturing in the strengthening of laminated multi-material interfaces.