Nanophase decomposition of a Zn-Al based alloy Zn₆₈Al₁₀Cu₂₂

The nanostructural evolution and phase transformation of the films of a Zn-Al based alloy (Zn68Al10Cu22in wt pct) have been studied by using X-ray diffraction and scanning electron microscopy. Nanostructural thin films of the Zn-Al based alloy were produced by using an electron beam deposition technique. It was found that a nanocrystalline phase η'nhad a strong preferred crystal orientation at (0002) crystal planes in the as-deposited films. During ageing at 220°C, the decomposition of nanophase η'nstarted with clustering to form Z-zones, and transitional phase, which was accompanied by an eutectoid decomposition of the η'nphase: η'n→β'eut+T'. Decomposition, such as clustering and the formation of the Z-zones, and the transitional phase etc. were observed in the nanophase β'eut. The formation and the decomposition of the transitional phase of micrometers in size were involved in the decomposition of the main nanophase η'n. The mechanism of the Z-zones formation and the stability of nanophases were discussed.