The Al-rich region in the Y–Ni–Al system: microstructures and phase equilibria

The Al-rich region of the Y–Ni–Al ternary system has been investigated mainly by using different micrographic techniques. In the range 60<at% Al<100 the 500°C isothermal section has been partially defined. The compound Y4Ni6Al23 and its role in phase equilibria have been highlighted. The YNi3Al16 phase previously suggested has not been confirmed. Two ternary tie-triangles in this region have also been defined: Al+NiAl3+Y4Ni6Al23 and Al+YAl3+Y4Ni6Al23. Two ternary eutectic equilibria: E1, Ni-rich: at about 96.5 at% Al, 2.6 at% Ni, 0.9 at% Y and E2, Y-rich: at about 96.0 at% Al, 1.0 at% Ni, 3.0 at% Y have been identified. The crystallization behaviour of the Al-rich alloys is described and typical micrographic appearances presented.