ABSTRACT
Figure 30 displays the M g - D y phase diagram in the whole concentration range. It is
redrawn from [85] with correction of the Mg-r i ch part according to investigation of Ba ikov
Institute of Metallurgy [97, 106]. The main features of the M g - D y phase diagram as a
whole are formation of five binary compounds, one eutectic equilibrium on the M g side and
one eutectoid equilibrium connected with the existence of two allotropic forms of
dysprosium. Three compounds, M g 2 4 D y 5 , M g 2 D y and M g D y are formed from the l iquid
phase peritectically. The compound M g 3 D y is formed from M g 2 4 D y 5 and M g 2 D y by the
peritectoid reaction. In the phase diagram [85] the phase M g ^ D y is shown as supposed
where x is more than 2. The phase with the same crystal structure (partial disordered type
NaTl ) was observed also in [128]. Its formation mechanism and exact composition were
not established. Existence of the compound M g ^ D y is doubtful because, in addition to the
noticed uncertainties, a phase of such type was not observed in the systems of magnesium
with the neighbouring rare earth metals, terbium and holmium. The crystal structure of the
compounds is described in Table 17. X-ray determination of the lattice parameters showed
Table 17. Crystal structure of the M g - D y binary compounds.
