Formation of micrometer sized quasicrystals in slowly cooled Zr-Ti-Nb-Cu-Ni-Al alloys
✍ Scribed by Kühn, U. ;Eckert, J. ;Mattern, N. ;Schultz, L.
- Publisher
- John Wiley and Sons
- Year
- 2005
- Tongue
- English
- Weight
- 275 KB
- Volume
- 202
- Category
- Article
- ISSN
- 0031-8965
No coin nor oath required. For personal study only.
✦ Synopsis
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)