Twin Boundary Superstructures Assembled by Periodic Segregation of Solute Atoms

Abstract

Twinning is a common deformation mechanism in metals, and twin boundary (TB) segregation of impurities/solutes plays an important role in the performances of alloys such as thermostability, mobility, and even strengthening. The occurrence of such segregation phenomena is generally believed as a one-layer coverage of solutes alternately distributed at extension/compression sites, in an orderly, continuous manner. However, in the Mnfree and Mn-containing Mg−Nd model systems, we reported unexpected three-and five-layered discontinuous segregation patterns of the coherent {101̅ 1} TBs, and not all the extension sites occupied by solutes larger in size than Mg, and even some larger sized solutes taking the compression sites. Nd/Mn solutes selectively segregate at substitutional sites and thus to generate two new types of ordered two-dimensional TB superstructures or complexions. These findings refresh the understanding of solute segregation in the perfect coherent TBs and provide a meaningful theoretical guidance for designing materials via targeted TB segregation.

Unveiling of interstice-occupying dopant segregation at grain boundaries in perovskite oxide dielectrics for a new class of ceramic capacitors

“…Notable advances in scanning transmission electron microscopy (STEM) at atomic resolution have made a key contribution to unveiling many unexpected structures and composition distributions at GBs. Recent discoveries of GB structural transformation in Cu, 9 periodic arrays of solute atoms and the formation of superstructures at GBs in Cu, 1,24 Mg, 6,[25][26][27] Ni, 7,19,28 MgO, 5 and Al 2 O 3 , 4,17 and space-charge-driven interface segregation in oxides 8,29,30 are noteworthy examples demonstrating the critical role of atomic-level direct probing.…”

Synthesis of Rhenium-Doped Copper Twin Boundary for High-Turnover-Frequency Electrochemical Nitrogen Reduction

“…Such a deposition mode enables the synthesis of nanotwin crystal structures (Figure S2). Previous studies have shown that heteroatoms can segregate at grain boundaries after annealing treatment, resulting in a local concentration surge of ∼4 orders of magnitude. − Given the nearly zero solubility of Re in Cu, Re can be easily separated from Cu, facilitating its segregation at TBs upon high-temperature annealing following the Brunauer–Emmett–Teller (BET) theory; meanwhile, the adsorption of Re dopants can significantly reduce the corresponding grain boundary energy . After pulsed electrodeposition, the sample was subsequently annealed at 400 °C to obtain the Re-doped Cu TB (Re/TB-Cu-400).…”