Grain Boundary Segregation in Metallic Alloys

Grain boundary segregation in metallic alloys describes the selective enrichment or depletion of solute atoms at the interfaces between crystalline grains. This phenomenon alters interfacial chemistry and structure, thereby influencing mechanical strength, embrittlement resistance and high-temperature stability. The driving forces for segregation include differences in atomic size, electronic interactions and elastic strain, while kinetics are governed by diffusion along grain boundaries. Control of segregation through alloy design and thermal processing has emerged as a powerful tool to tailor properties such as creep resistance, corrosion performance and nanocrystalline stability. Insights into atomistic segregation mechanisms underpin the development of alloys for demanding applications in energy, transport and structural engineering.

Research from Nature Portfolio

Recent studies have revealed that certain high-angle boundaries in body-centred cubic alloys exhibit incommensurate atomic structures, characterised by non-periodic arrangements of icosahedral clusters at the grain boundary core. Combined experimental imaging and theoretical calculations demonstrate that these reconstructed interfaces possess unique energy minima and enhanced stability compared with their commensurate counterparts, challenging long-standing assumptions about boundary periodicity.

Investigations into co-segregation of interstitial impurities have shown that carbon and boron preferentially occupy sites at specific tilt boundaries in iron-aluminium alloys, leading to local depletion of aluminium by repulsive interactions. Atomic-resolution microscopy and first-principles modelling indicate that impurity co-segregation disrupts structural motifs within the boundary, thereby modifying cohesion and emphasising the importance of multi-solute interactions in controlling interfacial chemistry.

Grain Boundary Segregation in Metallic Alloys publication trend

The graph below shows the total number of articles in grain boundary segregation in metallic alloys across all publications each year (not limited to Nature Index journals).

Technical terms

Grain boundary: The interface between two crystalline grains in a polycrystalline material.

Segregation: Preferential enrichment or depletion of solute atoms at defects such as grain boundaries.

Interstitial impurity: An atom that occupies a space between the regular lattice sites of a host crystal.

Substitutional solute: An atom that replaces a host atom at a lattice site.

Cohesion: The energy required to separate adjoining grains along their boundary.

Embrittlement: Reduction in ductility or toughness due to chemical or structural changes at interfaces.

References

1. Incommensurate grain-boundary atomic structure. Nature Communications (2023).
2. Aluminum depletion induced by co-segregation of carbon and boron in a bcc-iron grain boundary. Nature Communications (2021).
3. Interstitial Segregation has the Potential to Mitigate Liquid Metal Embrittlement in Iron. Advanced Materials (2023).
4. Effect of Grain Size on Grain Boundary Segregation Thermodynamics of Phosphorus in Interstitial-Free and 2.25Cr-1Mo Steels. Metals (2017).
5. New Cr‐Ni‐Base Alloy for High‐Temperature Applications Designed on the Basis of First Principles Calculations. Advances in Condensed Matter Physics (2018).