The Restraint of Underside Shrinkage of Zn-High Al Alloys by Increasing the Cu-Content

The shrinkage is produced at the underside of cast Zn-high Al alloys and their hardness is greatly decreased during the solidification in the sand mold, due to their age-softening. We have developed new types Zn-high Al alloys, Z1610 (Zn-16 Al-10 Cu-0.02 Mg) and Z2520 (Zn-25 Al-20 Cu-0.02 Mg), which solve the problems, such as Underside-Shrinkage and age-softening, of the existing alloys. Higher Cu-content makes the solidification range narrower, consequently raising of their primary phases is restrained. So the new alloys produce less Underside-Shrinkage and further show less age-softening by crystallizing intermetallic compounds of CuAl and CuAl2