On the nature of plasticity upon polymorphic transformations

The deformation occurring in iron and iron-nickel alloys with nickel contents up to 20 % on cyclic α→γ→α transformations under light compressive load is investigated by the method of dilatometry. At constant loads a heating rate decrease results in a threefold increase of dilatometric effect of α→γ transformation (from one third on rapid heating up to its total value on slow one). Iron alloying with nickel induces a decrease of deformation on transformation. It is noted that anomalous plasticity during polymorphic transformation is associated with the fact that external stresses remove spatial degeneration and form the direction of dimensional changes conditioned by volumetric effect of transformation