Synergistically engineered Ti-based interlayer for high-strength pulsed-current diffusion bonding of TiAl/Ti2AlNb joints at ambient and elevated temperatures

Abstract

Reliable joining of TiAl and Ti₂AlNb alloys, pivotal for high-temperature aerospace applications, remains challenging due to their structural and chemical disparities, which often result in brittle interfacial phases and degraded mechanical performance. This study introduces a synergistically engineered Ti-based interlayer for pulsed-current diffusion bonding (PCDB), enabling high-strength joints with exceptional stability across ambient and elevated temperatures. The interlayer, featuring a metastable β matrix and multi-element solid solution, which promotes the formation of a gradient interfacial structure: a dual-phase α₂ + B2 layer and a single phase α₂ layer on the TiAl side, and a B2-dominant structure on the Ti₂AlNb side. Optimal bonding at 900 °C yields uniform diffusion layers, balancing elemental interdiffusion and microstructural stability to achieve peak tensile strengths of 684.1 MPa at room temperature (fracturing in the TiAl substrate) and 587.9 MPa at 700 °C—surpassing conventional interlayer-based joints. Strengthening arises from synergies between solid-solution, intracrystalline defects (dislocation walls and nanotwins), and gradient interfacial structures, demonstrating a breakthrough in joining dissimilar TiAl intermetallics for high-performance engineering applications.