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

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.