Effects of solute trapping on solidification path in Ta-rich Ta-Al-Fe ternary alloys under rapid freezing

The solidification sequence of Ta-rich Ta-Al-Fe alloys was examined under rapid freezing processes, arc melting and splat cooling techniques. It is found that loss of interfacial equilibrium results in an extended solubility of Al (up to 15 at. %) and a lower Fe content in primarily Ta phase (A2) in arc melted samples. Trapping of Al in the primary phase leads to a deviation of the solidification path from equilibrium prediction. When Al content is less than 10 at. % Al and Fe content is less than 4 at. % in the primary phase, the peritectic reaction, L + A2 → σ, is suppressed and instead the eutectic reaction, L → A2 + μ takes place following primary freezing. It is also found that under splat cooling conditions extended solute solubility occurs in μ phase formed via a eutectic reaction.