Dislocation and twin interactions with polytwin interfacesin L10-ordered FePd

The frequent polytwin (PT) interfaces present in L10-phases after appropriate heat treatments strongly influence the properties and behavior of this interesting class of intermetallics. The interactions of dislocation glide and twinning with the PT-interfaces has been studied through crystallographic and geometric analyses for {101}-conjugated PT-L10-phases. The most suitable boundary reactions for the shear transfer of hard dislocation glide and microtwinning across {101}-conjugated PT-interfaces in L10-phases have been determined. Defect-interface interactions in lightly deformed PT-FePd, which exhibits {101}-conjugated PT-interfaces, have been documented by experimental observations using transmission electron microscopy (TEM). A model for the defect-interface interactions in PT-FePd, based on the most suitable boundary reactions identified through theoretical analyses, has been proposed and is consistent with the experimental TEM observations. This model enables a micro-mechanism based rationalization of the plastic flow behavior typical of polycrystalline PT-FePd. Defect-interface interactions in PT-L10-FePd and their role for the deformation behavior have been discussed.