Open AccessPhase configuration and stability in the nanocrystalline Sm-Co system
Author(s) -
Wei Xu,
Xiaoyan Song,
Erdong Li,
Jun Wei,
Lingmei Li
Publication year - 2009
Publication title -
wuli xuebao
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.199
H-Index - 47
ISSN - 1000-3290
DOI - 10.7498/aps.58.3280
Subject(s) - nanocrystalline material , materials science , thermodynamics , alloy , gibbs free energy , phase (matter) , grain boundary , phase transition , phase boundary , metallurgy , microstructure , chemistry , nanotechnology , physics , organic chemistry
A thermodynamic model that describes the thermal properties of the compound phases in the nanocrystalline NC alloy systems has been developedwhich provides quantitative predictions on the stabilities and transition features of different phases. By using the NC Sm-Co alloy system as an examplethe temperature dependence of the mole Gibbs free energy of the NC alloy phases with different excess volumes in the nano-grain boundary regions were provided. Based on the model calculationsthe relative stability of different phases and the phase transition rules in the NC Sm-Co system were analyzed. It was shown by the calculation results that near the room temperaturesome of the NC alloy phaseswhose mole Gibbs free energy values change from negative to positive due to the decrease of the nano-grain sizewill transform into stable NC alloy phases. This is distinctly different from the phase transformation features in the coarse-grained alloy systemswhose thermodynamic properties are only dependent on the temperature. The experimental results on the phase configuration and the phase stability obtained from the prepared NC Sm-Co alloy confirmed the theoretical predictions of the present thermodynamic model.