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Ye et al. J Mater Inf 2023;3:15 https://dx.doi.org/10.20517/jmi.2023.08 Page 23 of 37

Table 11. Temperatures of formation reaction for Fe-RE intermetallic compounds
Systems Fe RE 2 Fe RE 6 Fe RE 5 Fe RE Fe RE
17
23
3
17
2
Fe-La — — — — —
P P
Fe-Ce 1344.6 — — — 1205.6
P
Fe-Pr 1383.0 — — — —
P P
Fe-Nd 1490.0 — 1071.0 — —
P P P
Fe-Sm 1557.0 — — 1287.0 1174.0
Fe-Gd 1604.0 P 1556.0 P — 1429.0 P 1354.5 P
C C P P
Fe-Tb 1587.5 1561.1 — 1486.0 1462.7
Fe-Dy 1651.0 C 1567.4 P — 1576.4 C 1545.5 P
C C P C
Fe-Ho 1615.6 1605.2 — 1567.6 1565.0
Fe-Er 1625.1 P 1602.7 P — 1615.0 P 1640.4 C
P P P C
Fe-Tm 1573.4 1544.6 — 1552.5 1572.6
Fe-Lu 1590.1 P 1560.9 P — 1580.4 P 1619.6 C
C C C P
Fe-Y 1650.1 1603.0 — 1605.5 1421.0
C: Congruent; P: peritectic.

Figure 13. Calculated enthalpies of formation of the Fe-Er intermetallic compounds at 298 K with the experimental data [44,54,103] and the
calculations [19,110-112,140,141] .

Fe RE only exists in the Fe-Nd binary system, and Fe RE is stable in the Fe-RE (apart from Fe-La) binary
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2
5
17
systems.
The types and temperatures of the invariant reactions for the formation of the Fe-RE (e.g., Fe RE , Fe RE,
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2
3
Fe RE, and Fe RE ) intermetallic compounds are demonstrated in Figure 28 and Table 11. As can be easily
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6
2
seen in the Fe-RE (RE = Ce, Pr, Nd, Sm, Gd, Er, Tm, and Lu) binary systems, Fe RE is produced through
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2
the peritectic reaction, but by the congruent reaction in the Fe-RE (RE = Tb, Dy, Ho, and Y) binary systems;
Fe RE is produced by the congruent reaction in the Fe-RE (RE = Tb, Ho, and Y) binary systems, but by
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6
peritectic reaction in the Fe-RE (RE = Gd, Dy, Er, Tm, Lu, and Y) binary systems; Fe RE is produced by the
3