A DISLOCATION MODEL OF PARENT-MARTENSITE INTERFACES

摘要

Interfaces separating parent and product phases are modelled using dislocation theory. Glissile interfaces are partially coherent structures; a network of dislocations and disconnections accommodates the coherency strains, and lateral motion of the disconnections across the interface effects the transformation. The short and long-range distortion fields of static interfaces are defined. The long-range strains disappear for ideal solutions, but small rotations may persist, depending on the constraints imposed. Plastic transformation strains are expressed as the combined strains due to the motion of disconnections and dislocations. The topological model of {575} lath martensite habits formed in ferrous alloys are described, and shown to be consistent with experimental observations. A range of solutions is found with orientation relationships varying from Nishiyama-Wasserman to Kurdjumov-Sachs; quantifiable degrees of sessile constraint and residual coherency strain arise for non-ideal solutions.