The bain strain, lattice correspondences, and deformations related to martensitic transformations

The contribution of E. C. Bain in identifying the correspondence and pure strain involved in ferrous martensitic transformations is reviewed, together with later work which has confirmed Bain’s hypothesis. Modern crystallographic theories of martensitic transformations have their origin in Bain’s recognition that a pure strain by itself would produce a major accommodation problem between the parent and product phases; thus, additional lattice invariant processes have been introduced. Some aspects of the crystallographic theories are considered and attention is drawn to the increased number of factorizations of a total strain that become possible when sequences of three (or more) strains are considered instead of the usual two. Some implications of the recent double shear theory (and double interface mechanism) and plastic accommodation model are examined. The nucleation of martensitic transformations with respect to the Bain strain is considered briefly.