Abstract
The phase-decompositions of super-saturated solid solutions are drived through two decomposition mechanisms, “Nucleation-Growth” and “Spinodal Decomposition”. This review is concerned with thermodynamics and kinetics of the latter mechanism and with morphologies of microstructures produced by the spinodal decomposition. When the supersaturated solid solutions are held inside the spinodal region of phase-diagram, specified sinusoidal composition waves, which are theoretically given, increase so rapidly in soluteconcentration that the natures of waves become to dominate over the microstructural morphologies. If the lattice strain between the conjugating mixtures and elastic anisotropy of the crystals are large, the specified directional decomposition, mainly along <100> cube directions, becomes larger than that of the other directions and then the modulated structure is formed, while if either the lattice strain or the elastic anisotropy is small, the microstructure results in “a mottled structure”. The review is also drived on the coarsening behaviours of precipitates in the alloys spinodally decomposed.
