Mg-RE (Rare Earth) Alloy Systems

Rare earth (RE) elements are especially important to the mechanical properties of many series of magnesium alloys.

Among the 102 ternary systems currently assessed in TCS Mg-based Alloys Database (TCMG) starting with version 6 (TCMG6), 43 systems are RE (rare earth) containing, which is about 42 % of the total number.

This section presents a few simple examples for phase equilibria calculations and solidification simulations in Mg-RE alloys. In fact, most precipitation hardenable magnesium alloys are RE-containing. All stable precipitates and important metastable ones are modeled.

The designations are not consistent. Taking the Mg-Nd system as an example, the typical sequence is: β'' (D019) > β'(Mg7Nd) >> β1 (D03) >> β (Mg12Nd) >> βe (Mg41Nd5). Translational precipitates between β' and β'' are sometimes designated as β''' (Mg3-7Nd).

Gd-Mg-Y

Calculated solidus and solvus of the (Mg) solution in the Gd-Mg-Y system.

Figure 1: Calculated solidus and solvus of the (Mg) solution in the Gd-Mg-Y system [2007Guo].

Mg-Nd

Figure 2 shows the calculated (Mg) solvi, relative to various stable and metastable precipitates in the Mg-Nd binary system.

Calculated solvi of the (Mg) solution in the Mg-Nd binary system, relative to various stable and metastable precipitates

Figure 2: Calculated solvi of the (Mg) solution in the Mg-Nd binary system, relative to various stable and metastable precipitates [2020Che].

Mg-8Gd-0.6Zr-3(Nd, Y) Alloys

Scheil solidification calculations of the Mg-8Gd-0.6Zr-3(Nd, Y) alloys.

Figure 3: Scheil solidification calculations of the Mg-8Gd-0.6Zr-3(Nd, Y) alloys.

References

[2007Guo] C. Guo, Z. Du, C. Li, A thermodynamic description of the Gd–Mg–Y system. Calphad. 31, 75–88 (2007).

[2020Che] H.-L. Chen, Modeling Mg-RE (rare earth) metastable precipitates in TCMG6, Thermo‑Calc Software (2020).