Hot-pressing sintering diffusion bonding of a high-toughness titanium alloy and an ultra-high-strength steel with Ta/Ni dual-interlayer

Abstract

The powder metallurgy forming of ultra-high-strength steel (UHSS) G33 and its combination with high toughness titanium alloy Ti–7Al–1Mo-0.5V-0.1C were achieved through the application of Ta/Ni dual-interlayer in a hot-press sintering diffusion bonding (HPSDB) process, conducted at 970 °C, 50 MPa, and a duration of 3 h. The resulting bonding strength proved excellent, with a high shear strength of 485.5 MPa. The interface structure, precipitated phases, and element diffusion behavior were investigated through scanning electron microscopy (SEM), transmission electron microscopy (TEM), and energy-dispersive X-ray spectroscopy (EDS). Notably, no intermetallic compounds (IMCs) precipitated in the Ti–Ta diffusion zone or the Ni-G33 diffusion zone, underscoring the effectiveness of the metallurgical bond. Selected area electron diffraction (SAED) and phase diagram calculation were employed to elucidate the mechanisms contributing to the robust bonding strength of the joint with Ta/Ni dual-interlayer. The results revealed that the diffusion zone primarily comprised NiTa2, Ni2Ta, and Ni3Ta with high shear modulus and excellent ductility. Near the bonding interface, Ni3Ta grains exhibited approximate low-angle torsional grain boundaries, effectively impeding dislocation movement. Moreover, the bonding strength was further enhanced by the precipitation of nanoscale tetragonal-Ta dispersed within the Ni2Ta matrix.