Post-solidification Effects in Directionally Grown Al-Ag\(_2\)Al-Al\(_2\)Cu Eutectics
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The post-solidification reactions that take place behind the growth front in directionally solidified ternary eutectic Al-Ag-Cu alloys have a marked influence on the observed room temperature microstructure, obscuring many aspects of the solidification morphology present at the growth front. Quantifying these solid-state processes is necessary for proper interpretation of ex-situ microstructure as an indicator of growth dynamics and operating point selection. In this study, the directional growth structure and phase compositions are quantified as a function of distance from the growth front to describe microstructural changes that occur during cooling in the solid state. The solubility of Ag in the Al(fcc) phase decreases rapidly below the eutectic point, and the excess Ag is accommodated by growth of the Ag2Al(hcp) phase, mainly by motion of the Al(fcc)-Ag2Al(hcp) interface. These structural changes are quantified, and compared to the coupled morphology at the solidification front. A cellular automaton method is proposed here to mimic either the forward or reverse solid-state changes, providing a means to estimate many features of the directional growth morphology based on sampling the structure at some known distance from the front.
Keywordscoupled growth solid-state effects ternary eutectics
The research reported here was supported by the National Aeronautic and Space Administration (NASA), under Grant Number NNX10AT61G, within the Microgravity Research Program.
- 2.D.A. Pawlak, Metamaterials and Photonic Crystals-Potential Applications for Self-organized Eutectic Micro-and Nanostructures. Sci. Plena 4(1), 1-12 (2008)Google Scholar
- 3.D.A. Pawlak, S. Turczynski, M. Gajc, K. Kolodziejak, R. Diduszko, K. Rozniatowski, J. Smalc, I. Vendik, How Far Are We from Making Metamaterials by Self-organization? The Microstructure of Highly Anisotropic Particles with an SRR-Like Geometry. Adv. Funct. Mater. 20(7), 1116-1124 (2010)CrossRefGoogle Scholar
- 4.K.A. Jackson, J.D. Hunt, Lamellar and Rod Eutectic Growth. Trans. Metall. Soc. AIME 236(8), 1129-1142 (1966)Google Scholar
- 10.R. Kraft, Crystallography of Equilibrium Phase Interfaces in Al-CuAl\(_2\) Eutectic Alloys. Trans. Metall. Soc. AIME 224(1), 65 (1962)Google Scholar
- 14.T. Himemiya, Three-Phase Planar Eutectic Growth Models with Rod+Hexagon or Semi-regular Structure for a Ternary Eutectic System. J. Wakkanai Hokuseigakuen Jr. Coll. 13, 77-102 (1999)Google Scholar
- 17.W. Kurz, D.J. Fisher, Fundamentals of Solidification (Trans Tech Publications Ltd., Aedermannsdorf, 1986), p. 244Google Scholar
- 18.E. Monberg, Handbook of Crystal Growth (North-Holland, Amsterdam, 1994), p. 51-97Google Scholar
- 19.R.N. Grugel, A. Anilkumar, P. Luz, L. Jeter, M.P. Volz, R. Spivey, G. Smith, P.A. Curreri (2001) NASA Marshall Spaceflight Center, Huntsville, AL http://exploration.nasa.gov/programs/station/PFMI.html
- 20.A.L. Genau, L. Ratke, IOP Conference Series-Materials Science and Engineering, vol. 27 (Iop Publishing Ltd., Bristol, 2012)Google Scholar
- 22.D.J.S. Cooksey, J.A. Hellawell, The Microstructures of Ternary Eutectic Alloys in the Systems Cd-Sn-(Pb, In, Tl), Al-Cu-(Mg, Zn, Ag) and Zn-Sn-Pb. J. Inst. Met. 95, 183-187 (1967)Google Scholar