Effects of Zn and Mg on machinability of Al-Zn-Mg casting alloys

Abstract

The alloys containing Zn+Mg 4.5, 6.0 and 7.5% at different Mg/(Zn+Mg) ratios were examined. The alloys containing a constant amount of Zn+ Mg at Mg/(Zn+Mg) ratio 0.3 show the best surface finish. The reason is that the built-up edge formation and the tool-chip contact length of the alloys are remarkably decreased with increasing the ratio less than about 0.3 and are increased with increasing the ratio more than about 0.3. The finished surfaces of the alloys with the ratio 0.3 are superior to those of Al-Mg alloys which are equivalent to those of Al-Zn-Mg alloys with the ratio 1.