Joints of TiBw/Ti6Al4V composites- Inconel 718 alloys dissimilar joining using Nb and Cu interlayers

Abstract

Dissimilar joining of TiBw/Ti6Al4V composites to Inconel 718 superalloys were explored using interlayers of Nb and Cu. It was difficult to gain good joints by using Nb interlayer. High thermal conductivity of Nb and particular assembly mode made more heat concentrated between Nb interlayer and Inconel 718 base metal, thus the connection between Nb and TiBw/Ti6Al4V composite was poor. While joints with good appearance and excellent mechanical properties could be obtained with Cu interlayer, and Ti-Cu, Ti-Ni-Cu and Ti-Ni intermetallic compounds could be found. The shear strength of the joints would be greatly improved in joints with Cu interlayer of 0.2 mm, because retained Cu-based solid solution in the joints could relieve the residual stress to a certain extent, and the maximum shear strength was 616 MPa (90 A, 100 mm/min, 0.2 mm). The formation of joints mainly depended on the formation of intermetallic compounds and solid solutions during welding. In addition, TiB whisker (TiBw) in TiBw/Ti6Al4V composites played a role in promoting the formation of intermetallic compounds in the joint reaction layer.