Solidification paths and phase equilibria at 873 and 673 K in the Al-Er-Zr system

Highlights: • Phase equilibria of Al-Er-Zr system at 873 and 673 K were experimentally studied. • The temperature effect is not obvious for the phase equilibria at 873 and 673 K. • Ten primary phases were experimentally revealed. • The solubilities of Er in Al-Zr and Zr in Al-Er binary compounds are noticeable. -- Abstract: In the literature, there is only one publication on the experimental isothermal section at 773 K in the Al-Er-Zr system, and no information is available on solidification microstructure in this system. Solidification paths and phase equilibria of the Al-Er-Zr ternary system at 873 and 673 K were thus investigated by means of 14 alloys using X-ray diffraction (XRD), scanning electron microscope (SEM) and electron probe micro analysis (EPMA). Ten primary phases were revealed and two isothermal sections at 873 and 673 K were established in this work. There are fourteen ternary-phase regions at two temperatures and the topology of phase relations is identical at both temperatures. It is found that the maximal solubilities of Er in Al₃Zr, Al₂Zr, Al₃Zr₂, AlZr, Al₃Zr₄, Al₂Zr₃, AlZr₂ and AlZr₃ are 2.2 ± 0.1, 4.5 ± 0.2, 9.8 ± 0.5, 11.8 ± 0.6, 8.6 ± 0.3, 6.8 ± 0.3, 4.8 ± 0.2 and 4.4 ± 0.2 at%, respectively. In addition, there are also noticeable solubilities for Zr in Al-Er binary compounds (i.e., Al₃Er, Al₂Er, AlEr, Al₂Er₃ and AlEr₂), and the maximal solubility of Zr in Al₂Er₃ is up to 18.0 ± 0.9 at% at 673 K. The phase equilibria and solidification paths in the Al-Er-Zr system determined in the present work provide new experimental data for a future thermodynamic assessment of this system.