An investigation of the Al–Rh–Ru phase diagram above 50 at.% Al

Partial 1100, 1000, 900 and 700 °C isothermal sections of the Al–Rh–Ru phase diagram were determined. The isostructural binary AlRu and AlRh phases probably form a continuous β-range of the CsCl-type solid solutions. The Al9Rh2 and C-Al5Rh2 dissolve up to 4.5 and 13 at.% Ru, while Al13Ru4 and Al2Ru dissolve up to 14.5 and 8 at.% Rh, respectively. A ternary orthorhombic structure (Pbma, a = 2.34, b = 1.62 and c = 2.00 nm) related to the Al–Rh ɛ-phases was revealed at the extension of the Al–Rh ɛ-phase area at compositions up to Al77Rh15Ru8.

► The Al–Rh–Ru phase diagram was studied for the first time between 50 and 100 at.% Al at 700–1100 °C.
► C-Al5Rh2 dissolves up to 13 at.% Ru and Al13Ru4 up to 14.5 at.% Rh.
► A ternary orthorhombic structure related to the Al–Rh ɛ-phases is formed at the extension of the Al–Rh ɛ-phase area at ∼Al77Rh15Ru8.
► The formation regions of the similar phases in the Al–Rh–Ru and Al–Pd–Ru alloy systems are compared.