Current-assisted versus furnace diffusion bonding of TA15 - TiBw/Ti65 composites: Interfacial evolution and mechanical properties

This study systematically presented a systematic comparison conventional furnace heating diffusion bonding (FHDB) and electric current-assisted diffusion bonding (EADB) for joining TA15 titanium alloy and a TiB whisker-reinforced Ti65 (TiBw/Ti65) composite, elucidating the respective mechanisms governing interfacial evolution and mechanical properties. The primary focus was on the acceleration mechanism and performance advantages by the current-assisted process. Diffusion bonding was performed on the rolled sheets in a vacuum hot press. The interfacial bonding behavior was examined under furnace heating (875–950 °C for 60 min) and electric current-assisted heating (925 °C for 15–60 min). The microstructure, elemental interdiffusion, recrystallization, and dislocation evolution were characterized using a multi-scale approach. The mechanical integrity of the joints and laminates was assessed through room-temperature shear and tensile testing, and fracture mechanisms were analyzed by fractography. The results showed that full interfacial densification via FHDB required a minimum temperature of 925 °C. The width of the interdiffusion zone (IDZ) increased from 1.5 μm to 3.5 μm with increasing temperature. In contrast, EADB at 925 °C achieved a defect-free interface within only 30 min, yielding a peak shear strength of 739 MPa after 60 min. This enhancement is attributed to the synergistic effect of Joule heating and athermal effects. The TiBw reinforcements exhibited exceptional thermal stability, effectively suppressing grain growth on the composite side through the Zener pinning effect. Tensile tests on the laminate bonded for 60 min with current assistance revealed that the fracture path deviated from the interface. The EADB process, by leveraging electro-thermo-mechanical multi-field coupling, effectively suppresses overheating of the matrix while substantially reducing the processing time. This approach successfully produces a high-strength, high-toughness metallurgical bond at the TA15-TiBw/Ti65 dissimilar interface, offering a novel strategy for the efficient fabrication of high-performance titanium-based laminated structures.