Evaluation of biocompatible NiTi/ZrO₂ joint brazed with AuSi fillers: Interfacial evolution, mechanical properties, and corrosion resistance

Reliable NiTi/ZrO₂ joints with superior corrosion resistance were fabricated through a two-step process: Pre-metallization of ZrO₂ ceramics with NiTi filler, followed by brazing with an AuSi eutectic filler. The interfacial microstructure of the metallization layer and NiTi/ZrO₂ joints were thoroughly characterized. The influence of temperature on the interfacial microstructure, mechanical properties and corrosion resistance was more significant. As the temperature rose, the NiSiTi nanocrystalline layer went through three stages: formation, thickening, and decomposition. During this process, the amount of Si decreased, and the Ni₄₉Si₃₇Ti₁₄ particle phase became more evenly dispersed, and some Au(s,s) transformed into Au₂Ti. Collectively, these changes in the Au(s,s) contributed to the enhancement of the joint strength. Moreover, at 460 °C for 10 min, the Au(s,s) had the least amount of phase, leading to the formation of the least amount of primary cells, and the NiTi/ZrO₂ joint exhibited the best corrosion resistance. The findings indicated that AuSi fills hold great potential for achieving high corrosion resistance in implantable devices.