Zn-Al and Zn-Al-Cu-Mg alloys containing Al 3.6 to 27.0%, Cu 0.7 to 2.3% and Mg 0.06 to 0.4% were tested. Microsegregation in the dendritic
β-phase is promoted and consequently the cored structure in which Al is extremely condensed at the center is formed when the Al content increases. When dendritic
β-phase transforms to
α+
β´ eutectoid structure, it is always surrounded by granular
β´ crystals. Nonequilibrium eutectic phases disappear by solution treatment. Homogenizing of the microsegregation zone delays as Al content increases. Cu addition results in the precipitation of
ε-phases and hardens the
α-phases in Zn-Al alloys. A large amount of Zn-Al-Cu-Mg particles precipitate in the alloys containing an excess amount of Mg. These particles are held at the grain boundary by solution treatment. The hardness of Zn-Al alloys is remarkably raised when increasing amount of Mg is added.
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