Segregation-induced ordered superstructures at general grain boundaries in a nickel-bismuth alloy.

Area of Science:

• Materials Science
• Solid-State Physics
• Metallurgy

Background:

• Alloying elements and impurities at grain boundaries significantly alter material properties.
• Solute segregation at high-symmetry boundaries in bicrystals can form ordered atomic patterns.
• The existence of superstructures at general grain boundaries in polycrystals remains largely unknown.

Purpose of the Study:

• To investigate the occurrence of grain boundary superstructures at general grain boundaries in polycrystalline materials.
• To determine the driving forces behind these segregation-induced reconstructions.
• To assess the implications for the performance of engineering alloys.

Main Methods:

• Utilized bismuth-doped polycrystalline nickel as a model system.
• Examined randomly selected general grain boundaries.
• Analyzed the atomic structures and segregation patterns at these boundaries.

Main Results:

• Discovered ordered, segregation-induced grain boundary superstructures at general grain boundaries.
• Found that these reconstructions are primarily driven by the orientation of the terminating grain surfaces.
• Demonstrated that lattice matching between grains is not the sole determinant of superstructure formation.

Conclusions:

• Adsorbate-induced superstructures are not confined to special grain boundaries.
• Superstructures can form at a variety of general grain boundaries in polycrystals.
• The findings have significant implications for understanding and controlling the properties of polycrystalline engineering alloys.