Regensburg 2004 – scientific programme

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M: Metallphysik

M 31: Quasikristalle II

M 31.2: Talk

Thursday, March 11, 2004, 16:45–17:00, H16

Formation and stability of the Al-Cu-Ru icosahedral phase — •Benjamin Grushko and Shaobo Mi — IFF, Forschungszentrum Juelich, D-52425 Juelich

The Al-Cu-Ru icosahedral (I) phase is formed in a wide compositional range elongated between about Al61Cu26Ru13 and Al70.5Cu12.5Ru17. The powder X-ray diffractograms only revealed some variation in the intensities of the lines as a function of the composition but no their apparent shift. The I-phase is formed by a peritectic reaction at 1057 C, its stability was confirmed down to 600 C. At lower temperatures the equilibration of the relevant samples is difficult. Extrapolated towards lower Cu the I-region clearly reaches the binary composition of about Al78-80Ru20-22. At close compositions a similar I-phase has also be reported to form in rapidly solidified alloys. The elongated geometry of the stability region is consistent with a suggestion that the ternary Al-Cu-Ru I-phase is a solid solution of Cu in a metastable binary Al-Ru I-phase. The shape of the I-region corresponds to an approximately constant electron-to-atom ratio.