Insights into the bonding and strengthening mechanism of Nb/Al2O3 heterostructure by AlNbNi phase and eutectic structure

To meet the demand for a reliable Nb/Al 2 O 3 heterostructure in nuclear high-temperature applications, TiNi filler was employed to achieve a high-strength bond. The effects of brazing temperature and holding time on the microstructure evolution and mechanical properties of the Nb/Al 2 O 3 heterostructure was analyzed, with a focus on the bonding and strengthening mechanisms. It was found that the TiNi-Nb eutectic reaction is crucial for the reliable bonding of Nb/Al 2 O 3 heterostructure. The AlNbNi phase precipitation significantly improves the lattice match at the brazing seam/Al 2 O 3 interface, while the (Ti, Nb)Ni-(Nb, Ti)ss eutectic structure mitigates residual stress from mismatched thermal expansion coefficients through its micro composite and gradient properties. At the optimized process of 1200°C/10 min, the shear strength of Nb/Al 2 O 3 heterostructure reached 53 MPa, with fracture behavior closely related to stress concentration at the brazing seam/Al 2 O 3 interface. This research offers a vital theoretical and experimental foundation for the design and performance control of high-reliability ceramic-metal heterostructures.