Bauer, Birgitta; Gille, Peter
Crystal Growth of Al-Rich Complex Metallic Phases in the System Al-Cr-Fe Using the Czochralski Method.
In: Zeitschrift für Anorganische und Allgemeine Chemie, Vol. 637, Nr. 13, SI: S. 2052-2058
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Complex metallic phases in the Al-Cr-Fe system are considered to beinteresting because of their enhanced resistance against corrosion.Single crystal growth of the Al(4)(Cr,Fe) and Al(13)(Fe,Cr)(4) phases,which is a prerequisite for detailed studies is presented herein for thefirst time. Along with their binary end members Al(4)Cr and Al(13)Fe(4)growth of cm(3)-size crystals was achieved by using the Czochralskimethod from Al-rich solutions at temperatures of approximately 1000degrees C. Special emphasis is put on the refinement of the Al-richcorner of the ternary phase diagram in determining the 1000 degrees Cequilibria between the incongruent melts and the corresponding ternarysolid solutions. Our findings confirm earlier data on the existenceregion of Al(13)(Fe,Cr)(4), but significantly differ from those withrespect to the so called Al(4)(Cr, Fe) phase. It is shown that theexistence region of Al(4)(Cr,Fe) decomposes into four regions ofstructurally different phases depending on the Cr/Fe ratio. Binarymu-Al(4)Cr crystallizes in the hexagonal space group P6(3)/mmc and candissolve only up to about 1 At-\% iron. More Fe-rich alloys crystallizein the orthorhombic space group Cmcm (about 2 At-\% iron) or Immm(containing between 3 and about 6 At-\% iron). For crystals containingabout 7 At-\% iron the structure belongs to the space group R (3) overbar. The grown single crystals were characterized by electron probemicroanalysis revealing only weak segregation effects. The structuralperfection of the orthorhombic phase was studied using X-ray topographywith the Lang technique. Significant anisotropic properties of thisphase allow to discuss structural similarities with decagonalquasicrystals.