Grain Boundary Engineering in Alloy Systems
Summary
Grain boundary engineering (GBE) seeks to tailor the character and connectivity of interfaces between crystalline grains in alloys to enhance mechanical performance, corrosion resistance and thermal stability. By promoting the formation of low-energy, “special” boundaries—most notably coherent Σ3 twin boundaries—and disrupting the network of high-angle random boundaries, GBE optimises the microstructural pathways that govern properties such as ductility, fatigue life and intergranular degradation. Control is exerted through thermomechanical processing sequences—cold work, annealing and recrystallisation—to induce boundary migration, twin formation and selective boundary annihilation. Key descriptors include the grain boundary character distribution (GBCD), twin-related domain (TRD) size and triple-junction connectivity. This approach has been demonstrated across a wide range of alloy systems, from stainless steels and nickel-based superalloys to emerging high-entropy alloys. Practical applications span nuclear reactors, aerospace components and biomedical implants, where extended service life and resistance to environmental attack are critical.
Research from Nature Portfolio
Recent studies on equiatomic CoCrFeMnNi and related subsystems have revealed that a single-step recrystallisation can markedly increase the fraction of Σ3 twin boundaries and twin density. Electron backscatter diffraction analyses demonstrate that the increment in special boundary fraction is governed primarily by grain boundary velocity, whereas twin density correlates more closely with the relative energies of grain and twin boundaries. Among the alloys analysed, FeCoNi exhibits the highest special boundary fraction and twin density following recrystallisation, underscoring the influence of composition on boundary migration kinetics and twinning propensity.
Grain Boundary Engineering in Alloy Systems publication trend
The graph below shows the total number of articles in grain boundary engineering in alloy systems across all publications each year (not limited to Nature Index journals).
Technical terms
Grain boundary engineering (GBE): A set of processing techniques aimed at increasing the proportion of low-energy grain boundaries to improve material performance.
Σ (Sigma) boundary: A designation from the coincidence site lattice model denoting the degree of lattice site coincidence across a boundary; Σ3 typically corresponds to coherent twin boundaries.
Grain boundary character distribution (GBCD): The statistical representation of boundary types (e.g., Σ3, random high-angle) within a microstructure.
Twin-related domain (TRD): A cluster of grains interconnected by successive twin (Σ3) boundaries, influencing network connectivity and property pathways.
Recrystallisation: The nucleation and growth of new, strain-free grains during annealing, leading to changes in boundary character and microstructure.
References
- Effect of one-step recrystallization on the grain boundary evolution of CoCrFeMnNi high entropy alloy and its subsystems. Scientific Reports (2016).
- Microevolution of grain boundary character distribution in Hastelloy C-276 during the annealing process. Journal of Materials Research and Technology (2022).
- Twin-Related Grain Boundary Engineering and Its Influence on Mechanical Properties of Face-Centered Cubic Metals: A Review. Metals (2023).
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