Quasicrystal-Enhanced Nucleation During the Solidification of fcc Metallic Alloys: A Tentative Thermodynamic Approach
- 137 Downloads
This short contribution is an extended abstract which summarizes a recent discovery we have made regarding the nucleation of fcc grains during the solidification of metallic alloys. While trying to analyze the effects of minute solute additions to the directional solidification of aluminum alloys, we observe that 200 ppm of Cr added to Al-20 wt.%Zn alloys induced a change of the primary trunk growth direction from 〈100〉 to 〈110〉. Such a change of growth directions, so-called dendrite orientation transition (DOT), has been evidenced in the Al-Zn system when the zinc composition is increased from about 25 to 55 wt.%.[2, 3, 4] It has been attributed to a change of the solid-liquid interfacial energy anisotropy, since zinc is a highly anisotropic element which has a very high solubility in aluminum at high temperature. In the present case, it seems that a few hundreds ppm of Cr produce the same effect for Al-Zn alloys having a composition at the lower limit of the DOT.
KeywordsPeritectic Transformation Icosahedral Quasicrystal Fivefold Symmetry Equiaxed Solidification Interfacial Energy Anisotropy
- 1.G. Kurtuldu, “Influence of Trace Elements on the Nucleation and Solidification Morphologies of fcc Alloys and Relationship with Icosahedral Quasicrystal Formation,” Ph.D. Thesis #6057, EPFL, Lausanne, Switzerland, 2014Google Scholar
- 7.M. Hubert Protopopescu and H. Hubert, Aluminium-Chromium-Zinc, Ternary Alloys, VCH, 1991, 4, p 449-454Google Scholar