  From our previous models of martensitic transformation, the continuous
matrices of atomic displacements and lattice deformations from
face-centred-cubic (fcc) to body centred-cubic (bcc) phases are calculated in
agreement with different possible final orientation relationships, such as
Bain, Pitsch and Kurdjumov-Sachs (KS). The angular distortion introduced in the
calculations appears a natural order parameter of transition. The distortion
corresponding to KS is the only one that respects the parallelism of a dense
direction and of a dense plane of both the fcc and bcc phases. This paper gives
an alternative to the classical crystallographic theories and shear concepts
associated to martensitic transformations.

Materials Science