Derivation of the liquidus surface projection for the Al-Pt-Ru system from as-cast samples

The liquidus surface projection for the Al-Pt-Ru ternary system has been determined based on the microstructural characterisation of arc-melted alloys. The liquidus surface is dominated by the ∼RuAl phase, and slopes down to the Al-rich corner. Two new ternary phases ∼Ru12Pt15Al73 and ∼Ru18Pt28Al64 were observed near the Al-corner. The ∼Ru12Pt15Al73 phase has a primitive cubic structure, lattice parameter of ∼0.7721 nm, and is stable to room temperature. The ∼Ru18Pt28Al64 phase is a high-temperature phase, and decomposes to form ∼Ru12Pt15Al73 and ∼PtAl2. There is a ternary eutectic near 23 at.% Al, 55 at.% Pt and 22 at.% Ru, whereas most of the other reactions were identified from their microstructures as being peritectic in nature. ∼RuAl was found to contain at least 27 at.% Pt and the ∼PtAl2 phase exhibited up to 11 at.% solubility for ruthenium. ∼RuAl6 showed solubility of at least 10 at.% platinum. Most of the other phases showed more limited solubilities for the ternary element: ∼RuAl2, ∼Pt2Al3 and ∼PtAl contained only about 2 at.% of the third component. ∼Ru4Al13 has less than 1 at.% solubility for platinum.