ABSTRACT
Martensitic transformations, and displacive transformations in general, remain the only mechanism for the manufacture of bulk nanostructured materials for engineering applications. During martensitic transformation, the pattern in which the atoms in the parent crystal are arranged is deformed into that appropriate for martensite, there must be a corresponding change in the macroscopic shape of the crystal undergoing transformation. The phenomenological theory of martensite crystallography explains all the observed features of the martensite crystallography. The orientation relationship is predicted by deducing the rotation needed to change the Bain strain into an invariant-line strain. The habit plane does not have rational indices because the amount of lattice-invariant deformation needed to recover the correct macroscopic shape is not usually rational. The theory predicts a substructure in plates of martensite (either twins or slip steps) as is observed experimentally.
