Wetting of AlN by molten Sn-xSc (x=1, 2 and 3 at.%) alloys at 700–800°C

This study addresses the challenges of poor wettability and insufficient interfacial activity of active elements in the brazing of AlN ceramics with metals. By proposing the substitution of traditional Ti with Sc as the active component, we systematically investigated the wetting behavior of Sn- x Sc ( x =1∼3 at.%) filler alloys on AlN ceramics at 700–800 °C. Improved sessile drop experiments combined with interfacial characterization revealed that Sc significantly enhances wettability, reducing the contact angle of Sn-3Sc/AlN from an initial 123.0° to 37.1° at 800 °C, outperforming the Sn-3Ti/AlN system (∼85°) under equivalent conditions. Interfacial analysis demonstrated that Sc accumulates at the solid/liquid interface in the form of Sn-Sc intermetallic compounds. Thermodynamic calculations confirmed the unlikely spontaneous formation of ScN, indicating that the wettability improvement primarily stems from the interfacial adsorption effect of Sc. Spreading dynamics showed that at low temperatures or with low Sc concentrations, the process is limited by Sn 5 Sc 3 decomposition, whereas at high temperatures, it transitions to Sc diffusion dominance (Diffusion coefficient D ≈1.19×10 -10 –1.39×10 -9 m 2 /s). This research provides a novel filler alloy design strategy for low-temperature, high-efficiency joining of AlN ceramics.