Theory of discontinuous precipitation: importance of the elastic strain Original Research Article

In the framework of the approach developed in our previous paper, E.A. Brener and D.E. Temkin, Acta Materialia, 1999; 47, 3759, we consider discontinuous precipitation taking into account elastic effects. Elastic stresses arise because of the sharp concentration change ahead of the transformation front. The interface kinetics is assumed to be very fast and the process is controlled by interfacial diffusion along all interfaces. We show that the inclusion of elastic effects removes unphysical restrictions on material parameters required for steady-state solutions to exist. As usual in theories of the steady-state growth of periodic structures, the continuous spectrum of solutions with one free parameter exists. We calculate the growth velocity and the lamellar spacing as functions of the supersaturation, assuming that the dimensionless parameter, related to Cahn’s parameter, is approximately a constant close to 1 in a wide range of supersaturations. This nontrivial assumption, which does not follow directly from theory, is supported by experimental observations and allows to obtain α unique solution. The calculated dependencies agree with the experiments.