Reactive wetting of AgCuTi filler metal on the TiAl-based alloy substrate

Reactive wetting of the AgCuTi over a TiAl substrate was investigated by hot stage microscopy in real-time in situ, under a high purity argon atmosphere at an elevated temperature (∼1270 K level). The results show: wetting process of the AgCuTi alloy on both polished and rough surfaces feature similar kinetics. Three stages were identified, (i) initial stage upon the onset of melting characterized with triple line essentially stationary or contracting, (ii) middle stage featuring almost linear spreading kinetics, and (iii) asymptotic stage with kinetics with diminishing spreading rate. Wetting kinetics within the main spreading stage features the power law of Rn ∼ t (n = 1). During spreading, Ag-based solid solution and Al–Cu–Ti ternary intermetallics were formed along the interface within the joint zone. Therefore, the spreading of AgCuTi filler over TiAl is highly reactive and the topographical modification of the base metal surface may have a minimal impact on wetting process.