A Study on Microstructure and Mechanical Properties of Electron Beam Welded Joint of Nb/Selective Laser-Melted TC4 Dissimilar Alloys

In this work, high-quality welding of two dissimilar Nb/TC4 and Nb/SLMed TC4 alloys is performed via electron beam welding. The precise control over orthogonal parameter optimization built strong mechanical performance of Nb/SLMed TC4 welded joints. The optimal conditions for attaining the highest tensile strength of 314.1 MPa are 62 kV of acceleration voltage, 10 mA of welding beam current, and 4.5 mm/s of scanning rate. The tensile strength of Nb/TC4 joint can be modulated by applied welding beam current, followed by acceleration voltage and scanning rate. Welded surfaces are investigated for crystal phase and microstructure analysis. Notably, no intermetallic compounds are formed in the fusion zone (FZ), and a dendritic zone of Ti-rich phase and an island zone of Nb-rich phase are observed for all welded joints. Results confirmed that composition segregation occurs in the Nb/TC4 and Nb/SLMed TC4 dissimilar joints.