NUCLEATION ON THE CRACK TIP AND TRANSFORMATION TOUGHNESS IN CRYSTALS UNDERGOING STRUCTURAL PHASE-TRANSITIONS

Stress-induced local phase transition on both motionless and moving cracks is considered. The asymptotically exact solution describing a small nucleus of a new phase on a crack tip is obtained. The nucleation temperature value is determined and nuclei phase diagram is constructed on the background of a phase diagram of bulk transition. It is demonstrated that nucleation is possible only during slow subcritical crack growth. The exact solution of the phase boundary equilibria equation is obtained for the case of a large nucleus. It is shown that fracture toughness has a maximum near the transition point.