Discovery of Mg₃Zn₂ Intermetallic Phase in the Mg-Zn System Enabled by Neuroevolution Potentials

Area of Science:

• Materials Science
• Computational Materials Science
• Alloy Development

Background:

• Magnesium-zinc (Mg-Zn) alloys gain mechanical strength from intermetallic compounds.
• Structural resolution in Mg-rich and intermediate Mg-Zn compositions is limited, hindering phase stability understanding.
• Accurate phase diagrams are crucial for optimizing Mg-Zn alloy performance.

Purpose of the Study:

• To develop a high-accuracy computational method for exploring the Mg-Zn phase space.
• To identify previously unknown stable and metastable intermetallic phases in Mg-Zn alloys.
• To establish structure-property relationships for enhanced microstructural strengthening.

Main Methods:

• Development of a neuroevolution potential (NEP) for the Mg-Zn system.
• Integration of active learning with the CALYPSO structure-search method.
• NEP-assisted systematic exploration of configurational phase space with near-first-principles accuracy.

Main Results:

• Reproduced all known experimental Mg-Zn intermetallic phases.
• Predicted a new thermodynamically stable Mg3Zn2 phase (P42/mnm symmetry).
• Identified a metastable I4/mcm-Mg2Zn phase and confirmed Mg3Zn2's thermal robustness and superior mechanical properties compared to MgZn2.

Conclusions:

• Neuroevolution potential-assisted structure prediction effectively resolves hidden intermetallic phases in complex alloy systems.
• The newly discovered Mg3Zn2 phase is a promising constituent for Mg-Zn alloys due to its thermal stability and mechanical strength.
• This approach enables systematic establishment of structure-property relationships for advanced alloy design.