A contribution to the Al–Pd–Cr phase diagram

Abstract

The Al–Pd–Cr alloy system was investigated in the compositional range above 50 at.% Al. The binary Al–Cr phases θ, η, μ, ν and γ 2 extend up to about 1, 2, 1, 1 and 3 at.% Pd, respectively. The binary Al–Pd ɛ, δ and β-phases dissolve up to 3, 4 and at least 10 at.% Cr, respectively. Five ternary structures were revealed in a quite small compositional range adjusting to that of the Al–Cr μ-phase. One, resembling the high-temperature Al 3Mn phase (T-phase, orth. a = 1.47, b = 1.24 and c = 1.25 nm), is formed in a small region around Al 77Pd 7Cr 16 composition. A hexagonal structure with a = 1.77 and c = 1.25 nm resembling Al–Ni(Cu)–Cr ζ-phase was revealed around Al 81.5Pd 1.5Cr 17 and another hexagonal structure with very close lattice parameters around Al 73Pd 11Cr 16. A ternary -phase resembling that in Al–Ni–Cr (orth., a = 1.24, b = 3.46 and c = 2.04 nm) was found at 970 °C around the Al 77.5Pd 1.5Cr 21 composition. An additional orthorhombic phase with a = 2.48, b = 3.87 and c = 2.04 nm was found to be formed between about Al 80Pd 4Cr 16, Al 73Pd 8Cr 19, Al 77Pd 4Cr 19 and Al 77Pd 6Cr 17. Partial 930, 970, 990 and 1020 °C isothermal sections are presented.