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Formation of micrometer sized quasicrystals in slowly cooled Zr–Ti–Nb–Cu–Ni–Al alloys
Author(s) -
Kühn U.,
Eckert J.,
Mattern N.,
Schultz L.
Publication year - 2005
Publication title -
physica status solidi (a)
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.532
H-Index - 104
eISSN - 1862-6319
pISSN - 1862-6300
DOI - 10.1002/pssa.200520079
Subject(s) - quasicrystal , materials science , alloy , icosahedral symmetry , phase (matter) , volume fraction , microstructure , metallurgy , copper , crystallography , analytical chemistry (journal) , composite material , chemistry , organic chemistry , chromatography
Abstract The solidification behavior of copper mold cast Zr 60 Ti 6 Nb 2 Cu 14 Ni 9 Al 9 and Zr 60 Ti 2 Nb 6 Cu 14 Ni 9 Al 9 alloys has been investigated. The phase formation of the alloy with a ratio of Ti:Nb = 3:1 depends very sensitively on changes of the cooling conditions, exhibiting three competing phases: a glassy, an icosahedral quasicrystalline ( i phase) and a crystalline phase, which are arranged very closely in the part of the sample with the highest cooling rate. Decreasing the cooling rate leads to a fully crystalline microstructure. In contrast, the alloy with a ratio of Ti:Nb = 1:3 forms predominantly an i phase and presents only a low volume fraction of a residual glassy phase at the interfaces of the quasicrystals. Besides a specific cooling rate a content of Cu + Ni + Al of about 32 at% and a content of Ti + Nb of about 8 at% is required for the formation of an as‐cast i phase in these Zr‐based alloys, because of a decrease of their glass‐forming ability linked with more pronounced icosahedral short‐range ordering in the melt. (© 2005 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)