The primary liquid demixing ceases when the curves ‘‘1”
arrive at the lines of double saturation, L0 + L00 + (Al),
where the crystallization of (Al) starts at 450 C. The large
solid solution range of Zn in (Al), shown clearly in the binary
system in Fig. 1, requires a tracking of its composition
variation. Thus, three curves labeled ‘‘2” display the composition
paths during this second step in the solidification