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One commonly used system to study morphology development in multi-phase, multi-component alloys is directionally solidified ternary eutectic Al - Ag 2 Al - Al 2 Cu . One challenge in studying this system is a relatively large solubility shift of the chemical element Ag in the Al -phase after solidification, which significantly affects the observed phase fractions. The effects of this change on the microstructural patterns are not yet understood. To study these effects, directionally solidified samples of ternary eutectic Al - Ag 2 Al - Al 2 Cu were quenched, sectioned and subjected to systematic annealing. This allowed the microstructure evolution at the quenched solid-liquid interface to be recorded in cross section and quantitatively analyzed. The results show that the phase fraction changes in the micrographs are in good accordance with theoretical predictions from the thermodynamic Calphad database. Different microstructural patterns show distinct responses to the annealing. For a more highly ordered chain-like structure, the pattern is preserved even after 32 h at more than 96% of the melting temperature, as determined by the constant number and size of the intermetallic rods in the micrographs. For a less ordered cross-type structure, coarsening of the microstructure is observed, resulting in a pattern change. The outcomes underline the importance of considering post-solidification effects during the investigation of ternary eutectic Al - Ag 2 Al - Al 2 Cu and help to improve the understanding of the microstructure arrangement in complex eutectic alloys. |
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