It was recalled that the grain boundary excess free volume, together with the surface tension, determined the major thermodynamic properties of grain boundaries. The excess free volume largely controlled the evolution and stability of polycrystals. Unfortunately, knowledge concerning the excess free volume was completely restricted to data generated by computer simulations, which were strictly limited to grain boundaries in the vicinity of special misorientations. A special technique was developed that made it possible to measure the excess free volume for almost any grain boundary and provided a means for estimating the excess free volume, for grain boundaries of various classes, to high accuracy. A knowledge of the excess free volume of fine-grained and nanocrystalline systems offered new possibilities for designing their physical properties and microstructures.

Grain Boundary Excess Free Volume - Direct Thermodynamic Measurement. L.S.Shvindlerman, G.Gottstein, V.A.Ivanov, D.A.Molodov, D.Kolesnikov, W.Łojkowski: Journal of Materials Science, 2006, 41[23], 7725-9