The martensitic transformations at presence of an external not hydrostatical mechanical stress are the specific mechanism of convertible (martensitic) deformation in which basis motion of the martensitic boundary lays, that is cooperative transition of atoms from an initial phase in final. Such deformation is convertible return of deformation is carried out during return martensitic transformation. The acoustic emission accompanying the martensitic transformations reflects habits of deformation behaviour of an alloy at the martensitic transformations.