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-castZMA611 alloy strip shows equiaxed alpha-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 degrees C, the interdendritic quasicrystal phase is rapidly replaced by equilibrium (D-phase (Mg-21(Al,Zn)(17)), which gradually disappears within a-Mg. In addition, fine secondary Al8Mn5 dispersoids precipitate from supersaturated as-strip cast alpha-Mg and these dispersoid particles act as effective nucleation sites for precipitation of MgZn2 phase during aging treatment.close363