Wetting Kinetics of AgCu/Polished TC4 Substrate System with Different Temperatures

The effects of temperature on wetting kinetics of AgCu filler metal over polished TC4 substrate under a high-purity argon atmosphere were investigated by the sessile drop technique. The results showed that the elevation of temperature obviously promoted the wettability and interfacial reaction. When the spreading processes of AgCu over TC4 substrate were similar at 1103 and 1133 K, the entire spreading process could be divided into four stages: initial stage; rapid spreading stage; limited spreading stage; asymptotic stage. When temperature was 1213 K, the chemical reaction was more drastic and the spreading rate of AgCu over TC4 substrate rose distinctly, the entire spreading process became three stages: initial stage; rapid spreading stage; asymptotic stage. In the case of 1103 and 1133 K, interface structure of brazed joint consisted of Ag-rich phase of residue filler metal/Ti₃Cu₄ phase/mixture of Ti-rich and Ti₂Cu phase/TC4 substrate, while a layer-structure of Ag-rich phase/Ti₃Cu₄ phase/Ti₂Cu phase/the mixture of Ti-rich and Ti₂Cu phase/TC4 substrate was captured at 1213 K. The thickness of layer increased and Ag-rich phase decreased with temperature increasing. Wetting kinetics of AgCu/polished-TC4 followed power law of Rⁿ~t, and value of n changed with temperature.