Solute co-segregation mechanisms at low-angle grain boundaries in magnesium: A combined atomic-scale experimental and modeling study
Plain Language Summary
Researchers studied how different alloying elements arrange themselves at the internal boundaries between crystal grains in magnesium metal, which is used in lightweight structural applications like cars and aircraft. Using a powerful technique that maps individual atoms in three dimensions, combined with computer simulations, they found that calcium, zinc, and aluminum atoms all cluster at these boundaries, but in distinct ways based on their size. Larger calcium atoms are drawn to regions where the crystal is being pulled apart, while smaller zinc and aluminum atoms prefer compressed regions, and calcium atoms show a particularly strong tendency to pair up with other calcium atoms. These atomic-scale interactions turn out to be important because the way solute atoms arrange themselves at grain boundaries directly influences how strong and workable the final metal is. The findings give materials scientists a clearer roadmap for designing better magnesium alloys by carefully choosing which elements to add and in what amounts.
Abstract
Solute segregation at low-angle grain boundaries (LAGBs) critically affects the microstructure and mechanical properties of magnesium (Mg) alloys. In modern alloys containing multiple substitutional elements, understanding solute-solute interactions at microstructural defects becomes essential for alloy design. This study investigates the co-segregation mechanisms of calcium (Ca), zinc (Zn), and aluminum (Al) at a LAGB in a dilute Mg-0.23Al-1.00Zn-0.38Ca (AZX010) alloy by combining atomic-scale experimental and modeling techniques. Three-dimensional atom probe tomography (3D-APT) revealed significant segregation of Ca, Zn, and Al at the LAGB, with Ca forming linear segregation patterns along dislocation arrays characteristic of the LAGB. Clustering analysis showed increased Ca–Ca pairs at the boundary, indicating synergistic solute interactions. Atomistic simulations and elastic dipole calculations demonstrated that larger Ca atoms prefer tensile regions around dislocations, while smaller Zn and Al atoms favor compressive areas. These simulations also found that Ca–Ca co-segregation near dislocation cores is energetically more favorable than other solute pairings, explaining the enhanced Ca clustering observed experimentally. Thermodynamic modeling incorporating calculated segregation energies and solute-solute interactions accurately predicted solute concentrations at the LAGB, aligning with experimental data. The findings emphasize the importance of solute interactions at dislocation cores in Mg alloys, offering insights for improving mechanical performance through targeted alloying and grain boundary engineering.
Solute co-segregation mechanisms at low-angle grain boundaries in magnesium: A combined atomic-scale experimental and modeling study.