FOUR TERNARY STRUCTURES IN THE Al-Cu-Ru SYSTEM. C. Freiburg, U. Lemmerz, W. Reichert Zentralabteilung für Chemische Analysen, Forschungszentrum Juelich, D-52425 Juelich

The structures of (Al,Cu)₁₃Ru₄ (C2/m), Al₇Cu₂Ru (P4/mnc), Al₅₈Cu₃₀ Ru₁₂ (Pm3), and Al Ru(Cu) (Pm3m) have been determined from 2-phase powder mixtures by X-ray diffraction and Rietveld refinements. The Al-Cu-Ru system also has an icosahedral phase Al₆₅Cu₂₀Ru₁₅ (FCI) [1], so it is important to investigate its neighbourhood. Many alloys with different nominal compositions were prepared by inductive melting in a water cooled copper crucible under Ar-atmosphere and annealed for different times and temperatures. Two powdered alloys each with two of the above thermodynamically stable phases, were chosen for the final structure determinations with a suitable Rietveld program [2].

The first alloy had a nominal composition Al_70.3Cu₁₉Ru_10.3, it was annealed for 1630h at 650⁰C, and it consisted of 13 vol% of the 1^st above mentioned structure and 87% of the 2^nd. The second alloy had a nominal composition of Al₅₆Cu₃₁Ru₁₃, it was annealed for 600h at 8000C, and it consisted of 73 vol% of the 3rd structure and 27% of the 4th. The first two structures are homeotypic to (Al, Cu)₁₃ Fe₄ [3] and Al₇Cu₂Fe [4]. The 3^rd structure is also adjacent to the FCI-phase and homeotypic to -Al Mn Si [5], the 4^th is of the CsCl-type and has an unexpected concentration range.

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[3] Freiburg, C., Grushko, B, Melchers, M., Reichert, W.: Mater. Sci. Forum, 166-169, 455 (1994)

[4] Bown, M. G.; Brown, P. J.: Acta Cryst. 9, 911 (1956)

[5] Shield, J. E., Chumbley, L. S., Mc Callum, R. W.; Goldman, A. I.: J. Mater.Res., 8, 44 (1993)