An investigation of the Al-rich region of the Al-Cu-Ir phase diagram

Chem. Met. Alloys 2 (2009) 30-33

https://doi.org/10.30970/cma2.0083

D. KAPUSH, B. GRUSHKO, D. PAVLYUCHKOV, T.Ya. VELIKANOVA

The Al-Cu-Ir alloy system was studied in the range above 35 at.% Al. Partial 900 and 540°C isothermal sections were determined. Congruent equiatomic AlIr extends at approximately constant Al concentration up to 30 at.% Cu. Cubic C-Al_2.7Ir (C-phase) dissolves up to 12 at.% Cu, Al₃Ir up to 8.5 at.% Cu, Al₂₈Ir₉ (χ-phase) and Al₄₅Ir₁₃ (φ-phase) up to 3 at.% Cu, and Al₉Ir₂ up to 2.5 at.% Cu. Increase of the Cu concentration results in a decrease of the Al concentration of these phases. The Al-Cu є₁-phase dissolves up to 3 at.% Ir, while the solubility of Ir in θ and η₂ is below 0.5 at.%. Close to the high-Cu limit of the C-phase region an fcc C₂-phase (Fm3, a = 1.53928 nm) structurally related to the C-phase is formed. A stable decagonal phase (D₁-phase) is formed below 1002ºC in a compositional range extending from Al_61.5Cu₂₀Ir_18.5 to Al₅₉Cu_25.5Ir_15.5. A ternary orthorhombic ε₆-phase (a = 2.34 nm, b = 1.65 nm, c = 1.24 nm) was found below ~1200ºC in a compositional range extending from Al_71.5Cu₆Ir_22.5 to Al₆₈Cu_12.5Ir_19.5. An additional ternary ω-phase (P4/mnc, a = 0.6414 nm, c = 1.4842 nm) forming around the Al₇₀Cu₂₀Ir₁₀ composition below 683ºC was revealed.

Partial isothermal section at 900°C. The compositions of the studied samples are shown by spots. Provisional tie-lines are shown by broken lines. L is liquid. The compositional region marked by (?) was not studied.

Keywords

Phase diagram / Intermetallics / Quasicrystals