Lamellar decomposition far from thermodynamic equilibrium

Abstract

We use phase field modeling to investigate far-from-equilibrium lamellar decomposition mechanisms. To that end, we develop a free energy function that allows us to vary the specific free energy of the parent phase without altering the specific free energies of the product phases. By performing simulations across a wide range of layer thicknesses and the parent phase specific free energies, we construct a complete map of lamellar decomposition mechanisms for this model. In addition to confirming several previously reported decomposition mechanisms, our investigation also reveals new ones: layer retraction, front reorientation, isolated layer creation, layer refinement, and spontaneous decomposition. The last two are inherently far-from-equilibrium processes that occur when the parent phase can no longer coexist with the product phases. Our work stands to advance understanding of lamellar decomposition from a metastable parent phase that is not near any eutectic or eutectoid point.