Applications for Magnesium
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Application Examples
Predicting Secondary Phases Formed during Casting of AZ91
AZ91 is a series of the most important die casting Mg alloys. The typical microstructures of the solidified AZ91 alloys usually consist of (Mg) grains and mainly the Al12Mg17 phase at the grain boundaries [Kabirian and Mahmudi, Metall Mater Trans A 40, 2190–2201 (2009) and Wang et al, Acta Mater. 54, 689–699 (2006)]. Similar microstructures are observed in other AZ series alloys [Wu et al, Trans. Nonferrous Met. Soc. China. 21, 784–789 (2011)].
The Scheil Solidification Simulation Calculator in Thermo-Calc can predict the phases formed during solidification under both rapid cooling (non-equilibrium) and slow cooling (equilibrium) conditions. The figure shows the total fraction of all solid phases as a function of temperature for AZ91, where the solid line corresponds to the non-equilibrium Scheil calculation and the dashed line to equilibrium. As can be seen, the calculation predicts the formation of three Al-Mn compounds, Al8Mn5, Al11Mn4, and Al4Mn, in addition to the experimentally observed phases, hcp_A3-(Mg) and Al12Mg17.
Improving High-temperature Properties of Mg-based Alloys for Hot Component Applications
Improving high-temperature properties of Mg-based alloys is crucial for hot component applications. Among these, Mg–Sn–Sr alloys show strong potential for enhanced creep resistance. Sr and Sn can combine to form MgSnSr, which is a thermally stable intermetallic phase. Rare earth element additions such as Ce, Y, and Gd can further improve mechanical properties. Yang et al., 2014 found that adding 1% Ce, Y, or Gd to Mg–3Sn–2Sr (all wt.%) refined coarse MgSnSr phases, enhancing tensile and creep performance. Moreover, Ce provided the highest tensile strength, and RE-specific intermetallics—Mg₁₂Ce, MgSnY, and GdMgSn—were observed.
The figure shows the equilibrium phase fraction for the Mg–3Sn–2Sr–1Ce (wt%) alloy, calculated using the Equilibrium Calculator and Magnesium-based Alloys Database in Thermo-Calc. The existence of all predicted phases is confirmed by Yang et al., 2014.
Predicting Metastable Phases in Mg-Rare Earth Alloys to Improve Strengthening
The Mg–Gd system is an important part of Mg–rare earth (Mg–RE) based engineering alloys, where Gd significantly enhances strength through precipitation hardening. To accurately model precipitation kinetics and optimize heat treatments in Mg–Gd alloys, it is necessary to understand the metastable precipitation sequence and the solubility of alloying elements in the relevant phases. The Thermo-Calc Magnesium-based Alloys Database (TCMG) addresses this by providing thermodynamic descriptions of all metastable phases in the system, enabling prediction of phase stability and precipitation sequences during processing.
As an example of the first step, the figure shows calculated phase boundaries for the β-series metastable phases in equilibrium with the hcp-Mg solid solution in the Mg–Gd system, calculated using the Equilibrium Calculator. The results reveal the metastable precipitation sequence βʺ (Mg₃Gd, D0₁₉) >> βʹ (Mg₇Gd) >> β₁ (Mg₃Gd, D0₃) >> β (Mg₅Gd), illustrating how Thermo-Calc provides a thermodynamic basis for understanding phase evolution during alloy processing.
Learn more about Applications to Mg-based Alloys
A new magnesium sheet alloy with high tensile properties and room-temperature formability
