On the constitution of the ternary system Al–Ni–Ti

The constitution of the ternary system Al–Ni–Ti is investigated. Phase equilibria at 1000 °C and 900 °C are clarified confirming the stability of the four ternary phases τ1 to τ4 already described in the literature. An additional ternary phase τ5 occurs as an equilibrium phase in the Al-rich corner. The composition of this phase is Al65Ni20Ti15. The ternary phases τ3 and τ4 melt congruently at 1289 °C and ∼1500 °C, respectively. The ternary phases τ1, τ2 and τ5 are found to melt incongruently at 1347 °C, 1225 °C, and 1107 °C, respectively. Two ternary eutectics occur: E1 (τ4 + Ni3Al + TiNi3) at 1269 °C and E2 (τ3 + τ4 + NiAl) at 1221 °C. The composition reported for E1 in the literature is corroborated. The composition for the newly discovered E2 is determined to be 43 at%Al, 31 at% Ni, and 26 at% Ti. The section NiAl–NiTi is pseudobinary, but NiTi melts incongruently into L + τ4 rather than congruently as binary NiTi. The section Ni3Al–Ni3Ti is eutectic, but not pseudobinary. By adding aluminium apparently all invariant equilibria of the binary system Ni–Ti are shifted to higher temperatures.