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

Abstract

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 τ 1 to τ 4 already described in the literature. An additional ternary phase τ 5 occurs as an equilibrium phase in the Al-rich corner. The composition of this phase is Al 65Ni 20Ti 15. The ternary phases τ 3 and τ 4 melt congruently at 1289 °C and ∼1500 °C, respectively. The ternary phases τ 1, τ 2 and τ 5 are found to melt incongruently at 1347 °C, 1225 °C, and 1107 °C, respectively. Two ternary eutectics occur: E 1 (τ 4 + Ni 3Al + TiNi 3) at 1269 °C and E 2 (τ 3 + τ 4 + NiAl) at 1221 °C. The composition reported for E 1 in the literature is corroborated. The composition for the newly discovered E 2 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 + τ 4 rather than congruently as binary NiTi. The section Ni 3Al–Ni 3Ti is eutectic, but not pseudobinary. By adding aluminium apparently all invariant equilibria of the binary system Ni–Ti are shifted to higher temperatures.