ABSTRACT
Figure 42 shows M g - L u phase diagram reproduced from the reference book [139] with
insignificant amendments. The assessed phase diagram takes into account the firmly
established existence of the compounds M g 2 4 L u 5 , M g 2 L u , M g L u and the phase p with
body-centred cubic lattice without ordering [23, 83, 128, 167]. Formation of the compound
M g L u is established to be according to the peritectic reaction [23]. In that work, the phase
P was considered to be the solid solution of the high temperature allotropic form of L u [23],
but as the existence of this allotropic form of L u is now refuted, (3 is assumed to be an
independent phase. The phase P decomposes eutectoidly into M g L u and Lu-base solid
solution. The solubility of M g in solid L u is assumed according to [83]. The M g - r i c h side
of the M g - L u phase diagram was constructed in [139] taking into account the study by the
Baikov Institute of Metallurgy [101]. It is characterised by the extended M g solid solution
and eutectic equilibrium. Moreover, equilibrium in the solid state is suggested. In [139] the
equilibrium in the solid state is supposed to be the eutectoid decomposition of the unknown
solid phase M g ^ L u ^ with y/x > 24/5 stoichiometry (-17 at. % Lu) . Meanwhile , [139]
believe that the existence of this phase and its stability range remains to be established. The
other details of the M g - L u phase diagram were proposed in [139] assuming its similarity
with that of the M g - G d system. Table 21 contains characteristics of the intermediate
Table 21. Crystal structure of the M g - L u intermediate phases.
