A statistical thermodynamic theory of pre-martensitic tweed structure

Abstract

After a phenomenological understanding of the second-order-like martensite transformations, which are associated with pre-martensitic phenomena, the tweed structure is treated by a statistical thermodynamics theory as a stable heterogeneous configuration containing small embryos of the martensite phase. In the free-energy expression of this heterogeneous state, the entropy of cluster mixing and the strain energy moderated by lattice softening play important roles, and thereby the appearance of tweed structure far above the transformation temperature M s and the second-order-like transition are explained.