An investigation of the Al–Ni–Rh phase diagram between 50 and 100 at% Al

Abstract

The Al-rich part of Al–Ni–Rh was studied between 800 and 1080 °C. The Al 9Rh 2 phase was found to contain up to 8 at% Ni. The orthorhombic Al–Rh ɛ 6-phase extends up to 17.5 at% Ni, high-temperature cubic C-Al 5Rh 2 up to about 10 at% Ni while low-temperature hexagonal H-Al 5Rh 2 extends up to 4 at% Ni. The Al 7Rh 3 phases contained up to 3 at% Ni. The solubility of Rh in Al 3Ni is up to 3 at% and in Al 3Ni 2 up to 5 at%. The isostructural binary AlNi and AlRh phases probably form a continuous β-range of the CsCl-type solid solutions. A ternary hexagonal phase similar to Al 28Ir 9 ( a = 1.213 and c = 2.626 nm) was found to be formed between Al 76Ni 4Rh 20 and Al 76Ni 13Rh 11. The formation of the high-temperature stable decagonal phase was confirmed. Another ternary phase, whose structure is not yet clarified, was revealed around Al 70Ni 11Rh 19. Partial 1080, 1000, 900 and 800 °C isothermal sections of the Al–Ni–Rh phase diagram are presented.