Size Effects in Formation of Segregation and Grain-Boundary Decomposition in Nanocrystalline Alloys

The effect of finite grain size on the formation of grain boundary segregations, and on the morphology of precipitates during decomposition, is studied. It is shown that in dilute solid solutions there are critical grain sizes at which decomposition is suppressed, both at the grain boundaries and in the bulk. A generalized phase-equilibrium diagram is constructed that considers the size factor, and a classification of the morphologies of precipitates during grain-boundary decomposition is suggested.