Microstructural Characterization of the As-cast AZ91 Magnesium Alloy with Rare Earth Elements

Microstructural analysis of as-cast Mg-9Al-0.9Zn-xRE (x = 0, 1, 2, 3, 5 wt.%) magnesium alloys is presented. Light microscopy (LM) and scanning electron microscopy (SEM+EDX) were used to characterized the obtained material. The results revealed that the as-cast AZ91 alloy consists of α – Mg matrix, binary eutectic α + γ (where γ is Mg17Al12). While rare earth elements were introduced to the Mg-Al-Zn alloy new Al11RE3 phase was formed. Additionally, in the experimental alloys instead of Al-Mn phase, ternary Al-Mn-RE compound was observed. What is more, the influence of RE addition on the area fraction of eutectic and needle-like phase was analysed. With increasing addition of RE, the amount of γ phase decreased, but the amount of Al11RE3 phase increased