Thermal stability of Al–Fe–Ni alloy at high temperatures

Abstract

The Al–Fe–Ni eutectic alloy was produced by gravity cast, and the thermal stability of this eutectic alloy was studied for the first time in this work. The phase composition was characterized by X-ray diffraction, and the morphology evolution of eutectic phase was analyzed by differential scanning calorimeter and scanning electron microscopy. According to the microstructure evolution of the eutectic phase exposed to different temperatures, three stages can be divided to distinguish coarsening behaviors of the eutectic phase, including the stable stage, transient coarsening stage and fully coarsening stage. In each stage, the coarsening behavior of eutectic phase was studied. Firstly, it was found that the stable stage can be maintained up to at least 673 K. Subsequently, the eutectic phase should go through coarsening and spheroidization in the transient coarsening stage. Among this stage, both the shape change and diffusion factors have played the vital roles in affecting the coarsening rate and spheroidization process. Finally, in the fully coarsening stage, the volume fraction of eutectic phase was deemed to be the main reason accounted for the difference between the results given in literature and this work. Keywords: Al–Fe–Ni eutectic alloy, Thermal stability, Coarsening, Ostwald ripening, Spheroidization