An efficient method to engage oxide ceramics in low-temperature interfacial reactions: Microstructure evolution and kinetics behaviors based on supercooling in a transient liquid phase bonding joint

Ductile transient liquid phase (TLP) bonding joints reinforced by multiple precipitates were produced us-ing novel pre-sintered coatings and Au-Si fillers; therefore, the highest strength of NiTi/sapphire joints brazed at 460 degrees C for 30 min reached 72 MPa. The pre-sintering process improved the surface-active of sapphire by forming metastable Ti3O and non-stoichiometric Al2O3. The typical brazing seam consisted of O-rich compounds, TiSi2, and Ti-Ni-Si, wherein the O-rich phase featured different crystallinity depending on the oxygen content. The sapphire/seam interface was either a nanoscale diffusion region or a Si-rich amorphous layer. The breakdown of the Stokes-Einstein relation (SER) occurred, and the deviation from SER increased with a higher cooling rate. The influence of coating thickness was reflected in (i) the su-percooling related to the viscosity and fractional exponent of liquids and (ii) the microstructural change of the joint related to the driving force for crystal growth. This work presented a new strategy for joining ceramics to metals at lower temperatures but using the joint at higher temperatures; furthermore, gave an insight into the microstructure evolution and kinetics behaviors based on supercooling in a transient liquid phase bonding joint.(c) 2023 Published by Elsevier Ltd on behalf of The editorial office of Journal of Materials Science & Technology.

Automated summary

Ductile transient liquid phase (TLP) bonding joints with multiple precipitates were successfully produced using pre-sintered coatings and Au-Si fillers. The pre-sintering process improved the surface activity of sapphire and created metastable Ti3O and non-stoichiometric Al2O3. The brazing seam consisted of O-rich compounds, TiSi2, and Ti-Ni-Si, with the O-rich phase showing different crystallinity depending on the oxygen content. The breakdown of the Stokes-Einstein relation (SER) occurred, and the influence of coating thickness on supercooling and microstructural change of the joint was observed.