Effect of Ta, Nb, and V on the Interfacial Interaction of Al-Ti Alloys with an Oxide Melt

The surface properties and the density of melting products significantly influence the separation of metallic and slag phases in a metallothermic process and correspondently influence the formation of a final alloy as an ingot. There are poor data in the literature on surface and interfacial properties of aluminum-titanium alloys containing rare refractory metals. The aim of this work is to study the surface and volumetric properties of contacting phases using experimental and computational methods and to analyze the revealed dependences. The interaction of a base Al-Ti alloy containing tantalum, niobium, and vanadium up to 4 at % with an oxide slag. The surface tension and the density of a metallic melt are determined by the sessile drop method. These properties in oxide melts are studied using the maximum pressure in a gas bubble. The interfacial tension between the metal and the slag is estimated using an equation, which takes into account the experimental values of the surface tension of the contacting phases and the contact angle. Our calculations and measurements show that the surface tension and the density of Al-Ti-(1.5-3) at % Nb and Al-Ti-(0.6-1.2) at % Ta alloys decrease as temperature increases. According to the experimental data, the interfacial tension between the metal and the slag is 922-1035 mJ/m(2), which implies good separation of the metallic and slag phases in combination with a significant difference in the densities of these phase (from 5 to 6 g/cm(3)). The revealed tendency in changing the interfacial tension and the adhesion indicates a positive influence of Ta, Nb, and V on the separation of the metallic and oxide phases when these elements are introduced into a Ti-Al alloy. The data obtained in this work allow us to conclude that, in the case when a base Al-Ti alloy containing up to 4 at % tantalum, niobium, and vanadium is melted, a metallic phase will form at the crucible bottom and will be well separated from an oxide phase and the crucible material.