Nonequilibrium phase transformations in alloys with stacking faults. Long-period structures

Equilibrium and nonequilibrium distributions of stacking faults appearing in alloys under martensitic transformations in quenching processes are investigated. Various stacking-fault distributions are represented through the quasi-spin variables. The free energy of an alloy contains both the surface stacking-fault energy and the energy of stacking-fault interactions. Based on the Landau-Khalatnikov equation for an order parameter, the kinetic equations describing a change of stacking-fault distribution are obtained. Computer simulation of phase transformation is carried out. As shown, the formation of imperfect structures with a long period of packing is possible. Such structures may be proved even within the framework of the model, which is taking into account the short-range interactions between the stacking faults. Between long-period structures, one may dis-tinguish the kinetic structures (which are arisen at an initial stage of transformation and disappeared after terminating of transformation) and the kinematical structures (which are formed owing to the kinematical restriction on the arrangement of stacking faults).