Effects of Ce-rich RE additions and heat treatment on the microstructure and tensile properties of Mg-Li-Al-Zn-based alloy

Research highlights: → Adding Ce-rich RE leads to the formation of Al2RE/Al3RE phases in LAZ532 alloy. → Ce-rich RE additions improve the tensile properties of the alloy. → The tensile properties of alloys processed by heat treatment are increased greatly. → Adding RE changes the fracture pattern of the alloy. - Abstract: As-cast Mg-5Li-3Al-2Zn-xRE (x = 0-2.5 wt.%) alloys were prepared under the ambient of pure argon, and the effects of Ce-rich rare earths (RE) and heat treatment on the microstructure and mechanical properties of Mg-Li-Al-Zn-based alloy were investigated. The results show that the main phase compositions of Mg-5Li-3Al-2Zn (LAZ532) alloy consist of α-Mg and AlLi. With the addition of RE, Al-RE precipitate forms, and increases gradually, whereas AlLi phase decreases. The room temperature tensile test reveals that the addition of RE could clearly improves the mechanical properties of alloys which are further improved after heat treatment. In more detail, excellent tensile strength and ductility are obtained in 1.5 wt.% RE containing alloy in as-cast state. After heat treatment, the 1.0 wt.% RE containing alloy attains superior tensile strength. The differences in tensile strength are related to the morphology, distribution of second phases and solid-solution strengthening in different alloy systems. In addition, the fracture pattern of the alloy is predominantly brittle cleavage and tends to be quasi-cleavage with RE addition.