Superlattice dislocations and antiphase boundaries in Fe₃Si

Abstract

TEM investigations of DO₃-ordered Fe₃Si reveal dislocations belonging to the slip system (100){001}. The glissile superlattice dislocations consist of two superlattice partial dislocations with Burgers vector b = ^a ₀/₂(100) which are linked together by an antiphase (APB_NNN) which changes the next nearest neighbour. The dissociation width is of the order of 100nm. The TEM observations are analysed by means of thermodynamics. The state of order of the undisturbed crystal and the free energy of the APB using the concept of thermodynamic relaxation of an antiphase boundary are calculated. The behaviour of the APB in the vicinity of a phase transition of the first and second kind is studied. It is shown that the APB can be seen as the B2 nucleus during phase transition DO₃→B2 below the Curie temperature.