Investigation on microstructure characterization and property of rapidly solidified Mg–Zn–Ca–Ce–La alloys

Rapidly solidified (RS) Mg–Zn–Ca–Ce–La (wt.%) alloys have been produced via atomizing the alloy melt and subsequent splat-quenching on the water-cooled copper twin-rollers in the form of flakes. Microstructure characterization, phase compositions and thermal stability of the alloys have been systematically investigated. The results showed that with addition of RE (Ce and La) to the Mg–6Zn–5Ca alloy, the stable intermetallic compounds i.e. the MgxZnyREz phase with a few Ca (about 3 at.%), shortened as the T′ phase, were formed at the expense of the binary Mg–Zn and Ca2Mg6Zn3 phases, which was possibly beneficial to the enhanced thermal stability of the alloy. In the Mg–6Zn–5Ca–3Ce–0.5La alloy, the composition of the T′ phase in the grain interior was different from that at the grain boundaries, in which the segregation of the La elements was found, and the atomic percentage ratio of Zn to Ce in the T′ phase within the grains was close to 2. Moreover, the stable Mg2Ca phases were detected around the T′ phases at the grain boundaries in the alloy.

Research Highlights
► The phase constitution of RS Mg–6Zn–5Ca alloy can be improved by RE additions.
► In the Mg–Zn–Ca–Ce–La alloys, the MgxZnyREz phase with a few Ca (T′ phase) is formed.
► The formation of the T′ phase leads to the loss of the Mg–Zn and Ca2Mg6Zn3 phases.
► The composition of the T′ phase differs from the grain interior to the grain boundary.