Crystallographic Theory of Martensitic Transformations

A crystallographic theory of martensitic transformations has been developed, which adequately describes their real mechanisms. A mathematical description of real processes occurring during martensitic transformation has been obtained as a product of four matrices: P1 = R1PB1Г, where Г is the shear deformation of the austenite lattice, В1 is additional “pure” deformation, the main axes of which coincide with the shear direction, with the normal to the shear plane and, accordingly, with the transverse direction, Р is the deformation of the lattice martensite with an invariant lattice, and R1 is a slight rotation of the martensite plate to obtain an invariant plane (relaxation rotation). All four processes occur almost simultaneously, but in the specified sequence. Crystallographic analysis of eight alloys based on the theory allowed obtaining a number of important results. A relaxation rotation has been detected during martensitic transformations. A relationship has been found between the relaxation rotation and martensite texture scattering. The mechanism of packet structure formation during polymorphic transformation in a zirconium single crystal has been established. The real mechanisms of deformation during martensitic transformations in these alloys have been established.