Effect of Ta/Ni dual-interlayer on the microstructure and properties of high strength titanium alloy and steel composite plate

The combination of ultra-high-strength Ti-6Al-4V (TC4) titanium alloy and 30CrNiMoNb (6211) steel was achieved by adding Ta/Ni dual-interlayer and rolling at 950 °C through welding a symmetrical blank sleeve with a vacuum electron beam. In order to unveil the metallurgical bonding mechanism and the interfacial structure, SEM, XRD, and compression-shear performance tests were used. The results revealed the presence of thin-film brittle TiC, TiFe, and TiFe₂ compounds at the TC4/6211 interface, resulting in an increased risk of interface mismatch and brittle fracture along the matrix phase interface, and the average interfacial bonding strength was tested at 323 MPa. In contrast, the TC4-Ta interface and the 6211-Ni interface in the TC4/Ta/Ni/6211 composite plate displayed good solid solution formation. The strengthening mechanism of the Ta/Ni dual-interlayer interfacial bonding was analyzed using selected area electron diffraction (SAED), revealing that the Ta-Ni diffusion region consisted of Ni₃Ta and Ni₂Ta. The addition of the Ta/Ni dual-interlayer prevented the aggregation of Ti and Fe atoms to form Ti-Fe compounds. The malleable intermetallic compounds of Ni₃Ta and Ni₂Ta effectively coordinated deformation, leading to an average interfacial bonding strength of 469 MPa, which was 45.2 % higher than the composite plate without Ta/Ni dual-interlayer.