Microstructural evolution in twin-roll strip cast Mg–Zn–Mn–Al alloy

A study has been made on the microstructural evolution in strip cast Mg–6 wt.% Zn–1 wt.% Mn–1 wt.% Al (ZMA611) alloy. The as-cast ZMA611 alloy strip shows equiaxed α-Mg dendritic structure throughout the thickness of the strip. Quasicrystalline phase and primary Al8Mn5 particles are formed in interdendritic region. During solution treatment at 330 °C, the interdendritic quasicrystal phase is rapidly replaced by equilibrium Φ-phase (Mg21(Al,Zn)17), which gradually disappears within α-Mg. In addition, fine secondary Al8Mn5 dispersoids precipitate from supersaturated as-strip cast α-Mg and these dispersoid particles act as effective nucleation sites for precipitation of MgZn2 phase during aging treatment.