Experimental investigation and thermodynamic assessment of the Al–Er system

Abstract

The phase equilibria of the Al–Er binary system have been investigated through both experiments and CALPHAD assessment. The phase relationship in the compositional range of 0–50 at. % Er was experimentally redetermined using scanning electron microscopy (SEM) with Energy Dispersive Spectroscopy (EDS), electron probe micro analysis (EPMA) with wavelength dispersive spectrometer (WDS), X-ray diffraction (XRD) and differential scanning calorimetry (DSC). The results confirmed the existence of the Al3Er phase (Al3Ho-type structure) with limited homogeneity range in the Al–Er system. It was formed through the peritectic reaction L + Al2Er ↔ Al3Er at 1105.3 ± 2.4 °C. While the Al17Er2 phase was proved to be metastable in the present work. A full thermodynamic optimization of the Al–Er binary system has been carried out by utilizing the current experimental data as well as all available results in the previous publications. A set of self-consistent thermodynamic parameters for the Al–Er system was established. The calculated phase diagram and thermodynamic properties agree well with the available data. The artificial inverted liquid-liquid miscibility gap at high temperature in the previous evaluation is removed.