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Grain boundary segregation in Ni–Sb alloy polycrystals
Author(s) -
Lejček Pavel,
Rar Andrei,
Hofmann Siegfried
Publication year - 2002
Publication title -
surface and interface analysis
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.52
H-Index - 90
eISSN - 1096-9918
pISSN - 0142-2421
DOI - 10.1002/sia.1320
Subject(s) - grain boundary , antimony , annealing (glass) , crystallite , materials science , crystallography , alloy , enthalpy , atmospheric temperature range , analytical chemistry (journal) , condensed matter physics , metallurgy , thermodynamics , microstructure , chemistry , physics , chromatography
Abstract In order to compare the grain boundary segregation of antimony and sulphur in bi‐ and polycrystals, the chemical composition of grain boundaries was studied by AES on fracture surfaces of polycrystalline Ni–Sb alloy (0.485 at.% Sb, 0.003 at.% S) samples annealed in the temperature range 773–1173 K. In contrast to the previously studied {133} bicrystals, dominant antimony segregation was observed at the grain boundaries of samples annealed in the above temperature range. By quantification of the AES results, the temperature dependence of grain boundary composition was determined and correlated with the Guttmann model of interfacial solute segregation in multicomponent systems. Consideration of various levels of grain boundary saturation and mutual interactions enabled the determination of the values of segregation enthalpy $(\Delta H^{0}_{Sb} = - 63\,\hbox{kJ mol}^{-1}, \Delta H^{0}_{S} = - 70\,\hbox{kJ mol}^{-1})$ and entropy $(\Delta S^{0}_{Sb} = - 20\,\hbox{J } (\hbox{mol}^{-1}\hbox{K}^{-1}), \Delta S^{0}_{S}= +12\,\hbox{J } (\hbox{mol}^{-1}\hbox{K}^{-1}))$ of both segregants. Extraordinarily high values of antimony concentration were detected at grain boundaries of bicrystals as well as polycrystals after annealing at high temperatures. It is highly probable that an extended two‐dimensional precipitation of nickel antimonides at grain boundaries occurs during the corresponding heat treatment. Copyright © 2002 John Wiley & Sons, Ltd.