As-cast microstructure and phase structure of ZnAl10Cu2 alloy

The as-cast microstructure and phase structure of ZnAl10Cu2 alloy were observed and analyzed by optical microscopy(OM),scanning electron microscopy(SEM),energy dispersive X-ray spectroscopy(EDS),and X-ray diffraction(XRD).The formation mechanism of the structures was also studied.It is shown that the solidification of cast ZnAl10Cu2 alloy is consisted of primary α₁ dendrites and rod-like eutectic(α₂ + β) surrounding primary α₁ dendrites.There occur eutectoid reactions in primary α₁ phase and α₂ phase in the eutectic structure during the subsequent cooling process,and lamellar(α + η) eutectoid organization forms.The retained α₁ and α₂ phase precipitate discontinuously and form granular precipitates in room temperature aging.The primary α₁ is the Al-rich(Al forms solid solution with Zn) and strengthening phase,with the crystal structure of a face-centered cubic lattice.And for β,the crystal structure of the Zn-rich phase is a hexagonal lattice.