Influences of Si and Ti on the wettability and reactivity of Al/graphite system at 900 °C

Abstract The effects of Si and Ti alloying elements and their concentrations on the wettability and reactivity of the Al/graphite (Al/Cg) system at 900 °C were studied by improved sessile-drop methods combined with thermodynamic and kinetic analyses. The Al/Cg system was not wettable, with an initial contact angle of 132°. However, the subsequent interfacial reaction to generate Al4C3 improved the wettability, despite the rate was relatively slow. The Si addition weakened the formation of Al4C3 at the interface, thus slightly worsening the wettability when its addition amount was less than 12 wt.%; whereas, when the Si addition reached 20 wt.%, the interfacial reaction product transformed from Al4C3 to SiC and a SiC + Al4C3 composite layer was formed at the triple line, resulting in substantial improvement in the wettability. On the other hand, a continuous composite layer of TiCx + Al4C3 covering the triple-line region was formed when 1–3 wt.% Ti was alloyed with Al. With the increase in the Ti content, the proportion of TiCx product in the composite layer increased and the wettability improved significantly. The reaction and spreading kinetics of the Al–Ti/Cg system were mainly controlled by the diffusion of Ti from the drop bulk to the triple line.