Wetting of liquid copper on TC4 titanium alloy and 304 stainless steel at 1273–1433 K

The wetting behaviour of pure copper on the surface of TC4 titanium alloy and 304 stainless steel plates was studied by the sessile drop method at temperatures of 1273–1433 K under high vacuum. The FeO oxide film limited the solid/liquid interfacial mass transfer in a Cu/304ss system, but the TiO oxide film was not a limiting factor in a Cu/TC4 system. The potential spreading model was judged by the Rn-t relationship, in which n was close to 4 in a Cu/TC4 system, which confirmed the presence of diffusion-limited wetting. For Cu/304ss, 4 ≤ n ≤ 10: this indicated behaviour between that of the diffusion-limited reactive control model and the hydrodynamic model. At the Cu/304ss joining side, the wetting activation energy (55.1 kJ/mol) corresponded to the sum of the diffusion activation energy for Fe in liquid Cu (10 kJ/mol) and the difference in surface energy per molar area between Fe and FeO (44.9 kJ/mol). At the Cu/TC4 joining side, the wetting activation energy (23.6 kJ/mol) corresponded to the diffusion activation energy for Ti in liquid Cu (21 kJ/mol). The diffusion of Ti and Fe in molten Cu caused variations in capillary force, which were attributed to changes in the micro-grooves. Keywords: Wetting behaviour, Diffusion, Activation energy, Ti-Cu-steel