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Crystal Growth of Al‐Rich Complex Metallic Phases in the System Al–Cr–Fe Using the Czochralski Method
Author(s) -
Bauer Birgitta,
Gille Peter
Publication year - 2011
Publication title -
zeitschrift für anorganische und allgemeine chemie
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.354
H-Index - 66
eISSN - 1521-3749
pISSN - 0044-2313
DOI - 10.1002/zaac.201100290
Subject(s) - orthorhombic crystal system , ternary operation , crystallography , materials science , metal , phase (matter) , phase diagram , crystal (programming language) , electron probe microanalysis , solid solution , group (periodic table) , crystal structure , chemistry , metallurgy , electron microprobe , organic chemistry , computer science , programming language
Complex metallic phases in the Al–Cr–Fe system are considered to be interesting 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 the first 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 Czochralski method from Al‐rich solutions at temperatures of approximately 1000 °C. Special emphasis is put on the refinement of the Al‐rich corner of the ternary phase diagram in determining the 1000 °C equilibria between the incongruent melts and the corresponding ternary solid solutions. Our findings confirm earlier data on the existence region of Al 13 (Fe,Cr) 4 , but significantly differ from those with respect to the so called Al 4 (Cr,Fe) phase. It is shown that the existence region of Al 4 (Cr,Fe) decomposes into four regions of structurally different phases depending on the Cr/Fe ratio. Binary μ‐Al 4 Cr crystallizes in the hexagonal space group P 6 3 / mmc and can dissolve only up to about 1 At‐% iron. More Fe‐rich alloys crystallize in the orthorhombic space group Cmcm (about 2 At‐% iron) or Immm (containing between 3 and about 6 At‐% iron). For crystals containing about 7 At‐% iron the structure belongs to the space group R $\bar{3}$ . The grown single crystals were characterized by electron probe microanalysis revealing only weak segregation effects. The structural perfection of the orthorhombic phase was studied using X‐ray topography with the Lang technique. Significant anisotropic properties of this phase allow to discuss structural similarities with decagonal quasicrystals.