Bonding Interface Evolution Characteristics of Laser Depositing Ti₂AlNb Intermetallic Compound on the Near-α Titanium Alloy Plate

Gradient titanium alloys are more conducive to meeting the requirements of large temperature and stress gradients than single homogeneous titanium alloy components used only within specific temperature and stress ranges. In this study, the near-α high-temperature titanium alloy and Ti₂AlNb intermetallic compound were combined by laser deposition technology to attempt to prepare a gradient titanium alloy that can be used in a broader temperature and stress range. The evolution characteristics of the bonding interface between the two alloys were deeply analyzed. Results show that a good metallurgical bonding interface without defects was formed after laser depositing Ti₂AlNb powders on the forged near-α titanium alloy plate. The very narrow heat-affected band (HAB) and fine-grain zone were formed at the bonding interface under different laser parameters, which lead to higher microhardness than that of both sides. The chemical composition homogenization difference within and without the bonding interface should be responsible for the formation of HAB, and the solid-state transformation induced by the complex thermal history of the laser deposition process is also an essential factor. The bonding interface evolution can be generalized as the variation of phase from the substrate to the deposition zone, which is α + β→α + α’+β→β/B2. Directly laser depositing Ti₂AlNb powders on the forged near-α titanium alloy plate results in the discontinuous transition of microstructure and property at the bonding interface. Graphical Abstract: [Figure not available: see fulltext.]