Wetting of liquid aluminum alloys on pure titanium at 873-973 K

The wetting behaviour of Al alloys (i.e., 6061 Al and 4043 Al alloys) on the surface of pure titanium was studied by sessile drop method at temperatures of 873–973K under high vacuum with ˜10−4 Pa. All wetting processes were divided into two stages: in the nonlinear stage, the formation of a compact intermetallic layer (Ti7Al5Si12) blocked the mass transfer at solid/liquid (S/L) interface and deteriorated wetting, while the formation of loose phase (Al3Ti) at triple line region can removed the oxide film and improved wettability. The wetting activation energy (56kJ/mol for a 6061Al/Ti system, and 71kJ/mol for a 4043Al/Ti system) corresponded to the sum of the difference in surface energy per molar area between α-Ti and TiO2 (27.2kJ/mol), and the Gibbs energy of formation for Al3Ti (30kJ/mol) or the decomposition energy for Ti7Al5Si12 (48kJ/mol). In the near-linear stage, the droplet spread on the surface of intermetallic compound (IMC). The spreading dynamics for 6061 alloy satisfied the Jiang’s empirical equation, and for 4043 alloy satisfied the viscous dissipation-limited model. The interfacial reaction had little effected on a droplet spreading, while the viscous friction drove the spread of 4043 alloy on precursor film in the near-linear stage.