Interstitial solute segregation at triple junctions: Implications for nanomaterialsand a case study of hydrogen in palladium

N Tuchinda and M Wagih and CA Schuh, PHYSICAL REVIEW MATERIALS, 9, 056002 (2025).

DOI: 10.1103/PhysRevMaterials.9.056002

At very fine grain sizes, grain boundary segregation can deviate from conventional behavior due to triplejunction effects. While this issue has been addressed in prior work for substitutional alloys, here we develop aframework that accounts for interstitial sites in the grains, grain boundaries, and triple junctions of model Pd(H)polycrystals. This approach allows computation of interstitial segregation spectra separately at both defect types,which permits an understanding of segregation at all grain sizes via a size-scaling spectral isotherm. The sizedependencies of dilute Pd(H) are found to be influenced not only by the triple junction content, but also by grainsize-dependent lattice strains; the latter effect is evidenced by size dependencies of individual grain boundaryand junction subspectra. The framework proposed here is applicable to interstitial alloys in general and mayserve as a basis for interfacial engineering in interstitial nanocrystalline alloys. As an example, we show thatusing the dilute limit isotherm, hydrogen density can triple in nanocrystalline vis-& agrave;-vis microcrystalline Pd dueto hydrogen adsorption at intergranular defect sites.

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