Instability of the FCC lattice, dislocations and their part in realization of martensitic gamma<->epsilon- and gamma->alpha-transformations

On the basis of direct observation of gamma <-> epsilon- and gamma --> alpha-transformations and literature data, it was concluded that features, which are reflecting instability of the f.c.c. lattice of austenite under premartensite condition, are following: 1) a beginning of ''working'' of dislocation source which generate ''newly'' mode dislocations; 2) a splitting of these dislocations on partial owes at condition of lowered stacking-faults' energy inside the nucleus inhomogeneous concentration areas. It was concluded that dislocations can not be the epsilon- and alpha-phase nucleation centre. At determined conditions only, dislocations facilitate the nucleation and accommodation lattice processes due to their ability to split and to move.